For organizations that must report emission figures, the definition is only the start. The next question is how to get those figures: use default values that others have already calculated, or measure them yourself? And if you measure them yourself, what kind of instrument do you need?

This article covers which gases are involved, which ones work in Thailand actually deals with, the principles of the two most widely used measurement techniques, and how to choose the one that fits your work.

Which gases count as greenhouse gases

Organizational reporting generally counts seven gases: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride and nitrogen trifluoride.

A common misconception is that the most abundant gas is the most important one. In fact, each gas traps a different amount of heat per molecule. A gas present in the air at very low concentrations can therefore still carry real weight in an emissions inventory.

In practice, the three gases most often encountered in Thai industry and agriculture are carbon dioxide, methane and nitrous oxide. Methane is linked to waterlogged areas and the management of organic waste. Nitrous oxide is linked to nitrogen management in soil and in treatment systems.

How Scope 1, Scope 2 and Scope 3 differ

Organizational emissions reporting is divided into three scopes.

Scope 1 covers emissions from sources the organization owns or directly controls, such as fuel combustion in production processes and in company vehicles.

Scope 2 covers indirect emissions from purchased energy. These emissions occur at the power plant, not at your own factory.

Scope 3 covers all remaining emissions in the value chain, both upstream and downstream.

Scope 3 is the hardest to measure because most of the data is not in your hands. It has to be requested from business partners, and each partner collects data differently and at a different level of detail. Many organizations therefore start with generic average values and replace them with measured data later.

Direct measurement usually makes the clearest difference for activities that have both a high share of emissions and high uncertainty. When deciding where to invest in measurement, start from these two conditions, not from what is easiest to measure.

The two main measurement techniques and how they differ

1. NDIR (Non-Dispersive Infrared)

The first technique is NDIR, short for Non-Dispersive Infrared. It measures how much infrared light the gas absorbs. The design is simple, it stands up well to field use, and it gives good results for carbon dioxide in typical concentration ranges.

It works by passing infrared (IR) light through a cell that holds the sample gas. Each gas (for example CO₂, CH₄ or CO) absorbs IR light at its own characteristic wavelengths. A detector at the far end measures how much light is left. The higher the gas concentration, the more light is absorbed.

Strengths: a simple design, robust in the field, easy to use, low maintenance and lower cost.

Limitations: moderate sensitivity (readings in % or ppm), possible signal drift over time, and interference from humidity and temperature.

2. CRDS (Cavity Ring-Down Spectroscopy)

The second technique is CRDS, short for Cavity Ring-Down Spectroscopy. A laser beam is sent into a cavity lined with high-reflectivity mirrors, and the instrument measures how fast the light signal decays. Because the light bounces back and forth many times, the effective path length is very long. This makes CRDS better at detecting gases at low concentrations, and it can also measure isotope ratios.

It works by sending a laser beam into a cavity with very high-quality mirrors (reflectivity above 99.99%) at both ends. The light bounces back and forth tens of thousands of times, so the distance it travels through the sample gas is equivalent to a tube several kilometers long. The system then switches the laser off and measures the time it takes for the light intensity to decay (the ring-down time).

Strengths: very high precision and sensitivity, easily measuring gases at ppb (parts per billion) or ppt (parts per trillion) levels. It can also distinguish molecular isotopes (for example, telling rainwater from groundwater) and is little affected by temperature.

Limitations: higher cost, a more delicate construction, maintenance by specialists, and mirrors that must be kept absolutely clean.

Two soil gas flux systems from the same product line show the difference clearly.

The LICA PS-9000 uses the NDIR principle. It measures carbon dioxide from 0 to 6,000 ppm and water vapor from 0 to 60,000 ppm, with accuracy of less than 1% of reading and precision of less than 1 ppm. It operates from -20 to 60 °C and weighs 7.3 kg including the battery.

The LICA PS-9600 uses the CRDS principle and measures methane, carbon dioxide and water vapor at the same time. Methane precision is no more than 1.2 ppb at a 10-second averaging time and no more than 0.6 ppb at 100 seconds. The methane measurement range is 0 to 100 ppm.

The measurement principle explains the difference between these two sets of figures. NDIR reports in ppm, which is sufficient for carbon dioxide work. CRDS reports in ppb, which is necessary when you need to measure methane or nitrous oxide, whose atmospheric concentrations are much lower.

How to choose the right technique for your work

Choose NDIR if you need to monitor air quality in factories, buildings or ventilation systems, or detect toxic gases for safety, where ppm-level readings are enough. For biogas measurement, mainly carbon dioxide, or work that means moving the instrument often, NDIR already meets the need.

Choose CRDS if you do research, collect environmental data or measure flux and need the highest precision. For continuous data collection at multiple points, some systems support several chambers on a single instrument, such as the LICA SF-9000, which connects to 1–18 chambers, and the SF-3500, which measures carbon dioxide, nitrous oxide, methane and ammonia, as well as isotopes, and is controlled through an Android app. CRDS is also the choice in high-tech industries (such as semiconductor manufacturing), where even a trace of contaminant gas can cause damage, or when you need isotope ratio data to identify where a gas comes from. Picarro provides complete systems to support this work, along with standard methods ready to use.

If your work focuses specifically on measurements from soil and agricultural land, we cover that in a separate article.

What to prepare besides the instrument

Calibration standard gases that match the concentration range you will actually use.

Chambers and mounting bases suited to the surface, if you are measuring flux.

A data logging system and power supply, especially for setups left running continuously.

Control of moisture and condensation in the gas sample lines, which is the most common cause of problems in the field.

A plan for calibration and for performance checks between calibration cycles.

Frequently asked questions

How many greenhouse gases are there, and which matters most for industry?

Organizational reporting generally counts seven gases. In Thai industry and agriculture, the three most common are carbon dioxide, methane and nitrous oxide. Importance does not depend on quantity alone. It also depends on how much heat each molecule can trap.

How do I choose between NDIR and CRDS?

If you measure carbon dioxide at typical concentrations and need portability, NDIR is sufficient and better value. If you need to measure methane or nitrous oxide at ppb levels, measure several gases at once, or need isotope data, you need CRDS.

What is the difference between measuring concentration and measuring flux?

A concentration measurement tells you how much gas is in the air at that spot. A flux measurement tells you the rate of exchange between the surface and the atmosphere per unit area per unit time. It requires a chamber and measurement of how the concentration changes over time.

What should I use to calibrate a gas analyzer?

Use standard gases with known, traceable concentrations, chosen to cover the range you actually work in. As with other types of analyzer, you should also run performance checks between calibration cycles.

If my budget is limited, where should I start?

Start by pinning down which gas you need to measure, at roughly what concentration, at how many points, and whether you need data over set periods or continuously. These four points will narrow your options more than starting from the budget, and they help you avoid buying an instrument that is more sensitive than you need or not capable enough.

PPWR is Regulation (EU) 2025/40, the Packaging and Packaging Waste Regulation, which applies from 12 August 2026. The PFAS requirements for food-contact packaging are in Article 5(5) and are set in three tiers: 25 ppb for individual PFAS, 250 ppb for the sum measured by targeted analysis, and 50 ppm for total PFAS, including polymeric PFAS.

This article sets out to explain why these three tiers cannot all be measured with the same method. The reason lies in sample preparation, not in the analytical instrument.

What PPWR is, and why goods made before the deadline are not exempt

PPWR is the European Union regulation on packaging and packaging waste. It was published in February 2025 and applies from 12 August 2026. Read this point carefully: 12 August 2026 is the date the rules start to apply, not the publication date. The time between those two dates was the preparation period, and it has already passed.

What sets this regulation apart from others you may have dealt with is that there is no transitional provision for existing goods. Packaging made before August 2026 cannot be sold on the EU market if its PFAS levels exceed the limits. Existing stock is therefore not an exception.

In practice, for Thai exporters, this means the question has changed from “when do we need to start?” to “what are our levels right now?” That question has to be answered with analytical results, not with documents.

The three tiers in Article 5(5), and why each tier needs a different measurement

Tier one, 25 ppb, applies to any single PFAS. It is measured by targeted analysis and does not include polymeric PFAS.

Tier two, 250 ppb, applies to the sum of PFAS measured by targeted analysis, and also does not include polymeric PFAS.

Tier three, 50 ppm, applies to total PFAS, including polymeric PFAS.

The first two tiers are familiar to labs that already run PFAS work. Target compounds are measured one by one by LC-MS/MS, and both the individual values and the sum are reported. Tier three is a different job. PFAS bound to polymers will not show up in the extract if the extraction step does nothing to the polymer.

Put another way, if one sample preparation method is used to measure all three tiers, the result may pass tier three with a clean-looking number. That does not mean the item is actually clean. It means the method cannot see what it should see.

Another point is often confused. If total fluorine in packaging exceeds 50 mg/kg, the manufacturer must, on request, provide evidence of what proportion of the measured fluorine is PFAS. This does not mean the packaging fails as soon as the value is exceeded, and it is separate from the 50 ppm limit in tier three. Many secondary sources mix these two points up. If you quote figures, quote them directly from the text of Article 5(5).

Packaging is a different matrix from soil and tissue

The PFAS work Thai labs know best is water, soil and tissue, which we covered in article B-02 in September. This article covers a different matrix: the packaging itself.

A single food package is rarely one material. Coated paper, multilayer film, grease- and moisture-resistant coatings, printing inks and adhesives are all combined in one item. How much PFAS an item contains therefore depends on which layer is extracted and how much can actually be extracted from it.

A substance often found in this group is side-chain fluorinated polymer, used as a grease-resistant coating. Its structure is a polymer chain with fluorinated groups attached along the side. These substances are not released as free molecules if the sample is simply soaked in solvent.

Contamination control for equipment and consumables is important in every PFAS job, whatever the matrix, and we also covered it in our September article.

EN 17681-1:2025 and alkaline hydrolysis — extraction is the deciding step

EN 17681-1:2025 was published by CEN on 30 April 2025. Its full title is Textiles and textile products — Per- and polyfluoroalkyl substances (PFAS) — Part 1: Analysis of an alkaline extract using liquid chromatography and tandem mass spectrometry

To be clear from the start, this is a textile standard, not a packaging standard. Many labs adapt it for packaging because there is not yet a clearly specified sample preparation method for packaging, and the principle behind it matches the problem packaging presents.

The key difference is that the 2022 edition extracts with methanol, which only detects free PFAS. The 2025 edition switches to alkaline hydrolysis, which breaks down side-chain fluorinated polymers and releases the bound substances. As a result, the new edition detects polymer-bound PFAS and the old edition does not.

This is the whole reason why PPWR tier three, set at 50 ppm including polymeric PFAS, cannot be checked with a simple methanol extraction. The method you choose decides whether the figure reflects reality. It is not only a question of instrument sensitivity.

A point to watch: if a lab reports results citing only EN 17681-1, without stating the edition year, the recipient has no way to know whether the figure already covers the polymer-bound fraction. Stating the edition year is therefore not only a paperwork detail. It also changes what the result means.

How EPA Method 1633 and 1633A differ

The search term “epa 1633 vs 1633a” is one people really use, because many older documents still cite only 1633.

EPA 1633A is a revised version of EPA 1633. It keeps the same principles for PFAS analysis but incorporates error corrections and refinements to technical details, so the procedure is clearer and more standardized.

The version actually in use today is 1633A, which EPA released in December 2024. It covers 40 PFAS in water, soil, sediment, biosolids and tissue, analyzed by LC-MS/MS.

Under EPA 1633A, the difference that shows up most clearly in practice is the sample preparation each matrix needs. For water samples it is simply weigh, add standards, adjust the pH, then straight onto WAX SPE.

Solid samples start with weighing the sample, adding standards and adding solvent, then vortexing, shaking and sonication, then centrifugation to collect the supernatant for GCB cleanup, then concentration, pH adjustment and finally WAX SPE. This sequence has several points where things can go wrong if the preparation is all done by hand.

For packaging work, packaging itself is not directly on the 1633A matrix list. Some labs that take on packaging work adapt alkaline hydrolysis extraction based on the principle of EN 17681-1:2025.

Where automated SPE and concentrators matter if you need to reach ppb and ppt levels

Method 1633A does not require evaporation for water samples. In practice, however, labs often modify the SPE step to add evaporation in two cases: when a lower detection limit is needed, and when working with less than 1 milliliter of methanol.

When the target is at ppb and ppt level, both cases apply at the same time. The step that decides whether the analysis reaches the limit is therefore usually not the LC-MS/MS instrument, but the extraction and concentration steps before it.

The problem with doing these two steps by hand is consistency. Flow rates through the SPE column differ from sample to sample, and evaporation temperature and time are not controlled equally, so recovery swings from batch to batch. That is a major issue when the limits are at ppb and ppt level.

Systems that take over these three steps can be grouped by function. CEM EDGE PFAS handles extraction from solid samples, Detelogy iSPE-216/864 handles automated SPE for many samples at once, and Detelogy FV64/80UP handles concentration by nitrogen gas evaporation.

Before deciding, consider the number of samples per run you actually need to process, the matrices the system supports, and the connection to the results recording system you already use.

What to prepare besides the instrument, and support in Thailand

PFAS work has stricter requirements than general work for materials that touch the sample, which we covered in our September article. What packaging work adds is the procedure for preparing test portions: which part of the package to cut from, how to cut it without mixing layers, and what weight the results are reported against.

Another thing to agree with the downstream buyer from the start is the list of compounds to report. Targeted analysis can only report compounds on the list that has been set. If your list and the buyer’s list do not match, the results you send will not answer their question.

In Thailand, the bottleneck is usually not the instrument itself but consumables and spare parts that have to be ordered. We state this here so expectations are set correctly before any work is agreed.

Frequently asked questions

When does PPWR start to apply, and can goods made before then still be sold in the EU?

PPWR, or Regulation (EU) 2025/40, applies from 12 August 2026. It was published in February 2025, and there is no transitional provision for existing goods. Packaging made before that date cannot be sold on the EU market if its PFAS levels exceed the limits.

How do the 25 ppb, 250 ppb and 50 ppm limits differ?

All three values are in Article 5(5) of PPWR, for food-contact packaging. The 25 ppb limit applies to any single PFAS measured by targeted analysis, not including polymeric PFAS. The 250 ppb limit applies to the sum of PFAS measured by targeted analysis, also not including polymeric PFAS. The 50 ppm limit applies to total PFAS, including polymeric PFAS. This is the tier that needs a different kind of extraction before it can be measured.

Does Thailand have legal requirements on PFAS in packaging yet?

Not yet. PPWR is an EU rule, not Thai law. Thai businesses are affected when they ship packaged goods to the EU market, because those goods must meet these limits. Businesses that sell only in Thailand therefore have no legal requirement on this yet.

How do EPA Method 1633 and 1633A differ?

EPA 1633A is a revised version of EPA 1633. It keeps the same principles for PFAS analysis but incorporates error corrections and refinements to technical details, so the procedure is clearer and more standardized. If you need to cite it in a report, state clearly that it is version A.

Why use alkaline hydrolysis when EN 17681-1:2025 is a textile standard?

Because there is not yet a clearly specified sample preparation method for packaging, and the principle of the 2025 edition matches the problem packaging presents. Side-chain fluorinated polymers used as grease-resistant coatings do not release the bound substances if extracted with methanol as in the 2022 edition. Labs therefore adapt this principle, and the report should state clearly which method was used and which edition year is cited.

Does total fluorine above 50 mg/kg mean the packaging fails?

No. The requirement states that when total fluorine exceeds 50 mg/kg, the manufacturer must, on request, provide evidence of what proportion of the measured fluorine is PFAS. This is separate from the 50 ppm limit in tier three, which covers all PFAS. Many secondary sources mix these two points up.

This article does not set out to copy the table of standard limits for you yet again, since it is easy to find. Instead, it looks at a side people often overlook. The notification in force does not only set how high each value may be. It also sets which method must be used to measure it, and that is what decides which instruments your lab needs.

The notification in force, and what it sets out

The general standard for wastewater discharge from factories is the Ministry of Industry notification setting standards to control wastewater discharge from factories, 2017 (B.E. 2560).

This notification always sets out two things side by side: the standard limit for each parameter, and the test method referenced for that parameter.

The main parameters to be reported are BOD, COD, suspended solids, TKN, oil and grease, sulfide, cyanide, phenolic compounds, free chlorine and heavy metals, together with color, which is limited to no more than 300 ADMI.

As examples of how the main parameters are measured: BOD is incubated at 20 °C for 5 days and taken as the difference in dissolved oxygen, COD uses chemical digestion followed by measurement, suspended solids are filtered and weighed dry, and the nitrogen and phosphorus group uses a color-forming reaction followed by an absorbance measurement. The point to check is whether the method your lab uses matches the method the notification references, because a result that is numerically correct but produced by a different method is not the same thing.

A practical tip: open the notification that applies to your type of business, and always read the test-method column alongside the limit column. Some types of business have their own specific notifications with requirements that differ from the general one.

BOD takes the most time and the most staff effort

BOD, or biochemical oxygen demand, is the amount of oxygen that microorganisms use to break down organic matter in water. It shows how dirty our effluent is and how much pollution it puts on the receiving water body.

What sets BOD apart from other parameters is that it is not an immediate measurement but a biological test that has to wait for the microorganisms to work. The sample is diluted into the measurable range, a microbial seed is added, and dissolved oxygen is measured on day one. The bottle is then sealed and incubated in a temperature-controlled cabinet at 20 °C for 5 days before it is measured again. The result is the difference between the two readings.

So the real time sink is not the measurement but getting the sample dilution into the right range. If the dilution is wrong, the result falls outside the valid range, and you only find out 5 days later. The whole batch then has to start again.

An automated BOD system therefore does not shorten the 5-day incubation. What it changes is that preparation, dilution, measurement and recording no longer depend on someone being there on schedule. It also lowers the chance of losing a whole batch because of one missed step.

How COD differs from BOD, and why the two are reported together

COD, or chemical oxygen demand, measures the oxygen used to oxidize organic matter with chemicals rather than with microorganisms. Results therefore come within a few hours instead of 5 days.

COD is usually higher than BOD in the same sample, because COD covers all the organic matter that can be oxidized chemically, both the part microorganisms can degrade and the part they cannot, while BOD counts only the part microorganisms can degrade.

The ratio between the two is therefore more useful than either number alone. An unusually low BOD-to-COD ratio means the water contains a lot of material that microorganisms cannot break down. That is a sign the biological treatment system may not be able to cope, and you should look upstream at what is entering the system.

In practice, many labs track COD daily because results come quickly, and use BOD as the value reported each reporting period. Having both is not duplication. It is the same picture seen at two different speeds.

Nitrogen and phosphorus: where automation pays off most

This group includes ammonia, nitrate, nitrite, orthophosphate, total phosphorus and TKN. Most are analyzed with a color-forming reaction followed by an absorbance measurement.

This group gains the most from automation because the time-consuming step is not the measurement. It is pipetting sample and reagents to exact volumes, mixing, and waiting for the full reaction time. This work is repeated the same way every time, and it is where human error happens most often.

Two main families of instruments handle this work. The first is the Discrete analyzer, where each sample reacts in its own reaction well. It suits labs where each sample batch needs a different set of tests, because the test list is easy to switch.

The second is the Continuous Flow Analyzer of the Segmented Flow type, where sample and reagents flow continuously through tubing, separated into segments by air bubbles. It suits high sample numbers with a fairly fixed test list, and it can handle in-line sample preparation steps such as continuous distillation or digestion.

One Discrete analyzer used in environmental work is the SEAL AQ400. It uses 3 to 500 microliters of sample and 10 to 600 microliters of reagent per test, depending on the method selected. This matters when sample volume is limited, for example water from sites that are hard to sample, or samples that have already been through several preparation steps.

Parameters we confirm can be run on the AQ400 in Thailand are alkalinity, ammonia, chloride, hexavalent chromium, color, cyanide, nitrate, nitrite, ortho-phosphate, silica, sulfate and total phosphate.

The AQ400 can also be used as a benchtop spectrophotometer for COD. This works differently from the color-forming tests, where the instrument automates the whole process. It is worth discussing the details with our team before deciding whether to run COD on the same instrument or separately.

Summary: which parameters are worth automating

The clear case is parameters measured with a color-forming reaction and optical detection: ammonia, nitrate, nitrite, phosphate, cyanide and color. The instrument takes over all of the pipetting and mixing.

BOD pays off in a different way. The instrument does not shorten the incubation time, but it means staff do not have to keep watch over the incubation schedule, and it reduces errors between steps.

For parameters that are run infrequently or have few samples, look at the workload first. Investing in automation may not yet pay off compared with doing them by hand.

So the question to answer before deciding is not which brand is best. It is how many samples you have per month, how many parameters you must report, how low the values you must report go, and at which step time is currently being lost.

What to prepare besides the instrument

Reagents and consumables matched to the number of parameters and your actual workload.

Reference materials for checking performance between calibration rounds.

Space for the instrument and ventilation suited to the reagents used.

Purified water of consistent quality, which directly affects blank values.

A calibration and routine maintenance plan, including parts that wear with use, such as pump tubing and seals.

User training, and connection to the results recording system you already use.

Support after installation in Thailand

Analyzers in this group are not finished on installation day. Parts in contact with reagents wear with use, and drifting results almost always start with these parts.

Thai Unique supports this work with a team that understands the chemistry behind the analytical methods, not just which buttons to press. This lets the team tell whether a deviation comes from the instrument, the reagents or the sample preparation.

Most on-site issues can be resolved within Thailand. The real limitation we see is that some spare parts have to be ordered in, not technical capability. We state this here so expectations are set correctly from the start.

Frequently asked questions

How do BOD and COD differ, and why is COD usually higher?

BOD measures the oxygen that microorganisms use to break down organic matter, while COD measures the oxygen used in chemical oxidation. COD therefore covers substances that microorganisms can and cannot degrade, so it is usually higher in the same sample.

COD is unusually high. Where should we start looking for the cause?

Start by checking whether a new type of waste is entering the system, then compare the BOD-to-COD ratio. If the ratio has dropped, the incoming material is hard to break down biologically, and you should look at the upstream process rather than only adjusting the treatment system.

What can cause high ammonia in water?

Common causes are incomplete nitrification in the treatment system, more nitrogen-rich waste entering the system than it was designed for, and changed conditions that reduce microbial activity, such as temperature or pH.

If we have to report daily, at what volume does it pay to buy our own instrument?

There is no single figure that applies everywhere. It depends on the number of parameters per sample, how often you report, and the labor currently spent on preparation. The most direct approach is to count your actual samples and parameters over one month, then let us help you assess where the break-even point is.

Once we have bought an instrument, who services and calibrates it in Thailand?

Thai Unique has a service team in Thailand that covers installation, user training, scheduled calibration and on-site troubleshooting. We also service instruments in the chromatography, flow analyzer and spectrophotometer groups, even if they were not bought from us. The limitation we have is some spare parts, not technical capability.

Thai Unique provides this support with a team of PhD-level specialists based in Thailand.

Calibration, performance checks and preventive maintenance: what is the difference?

These three terms are lumped together so often that many labs buy the wrong service, then only realize it when their analytical results start to show problems. All three are necessary and none can replace another, because each one answers a different question.

The most common mistake is to assume that an instrument that passed calibration is good for the whole year. In fact, calibration only shows the instrument’s condition on the day it was done. An instrument with deteriorating parts, such as pump tubing, seals or the light source lamp, will drift out of specification sooner than the planned calibration cycle.

So a plan that works in practice includes all three in one schedule, rather than choosing only one of them.

How often should you calibrate?

The standard answer is at least once a year, but the right frequency really depends on three factors. Labs that set their cycle based on these three spend less than labs that set it out of habit.

1. How often the instrument is used

An instrument that runs every day all year wears faster than one used only a few times a month. Using the same cycle for both means one is calibrated more often than needed and the other not often enough.

2. How critical the reported results are

Results submitted to regulators, results used to decide whether a product passes or fails, and results used internally to watch trends do not carry the same cost of error. Work where an error causes more damage should be checked more often.

3. The requirements of the lab’s quality system

If the lab works under a quality system that sets a calibration interval, treat that as the minimum. Then decide whether to calibrate more often based on the first two factors.

Between calibrations, check performance with reference materials at regular intervals. The reason is not paperwork, but damage that can be prevented. If you cannot tell at the next calibration when the instrument started to drift, you will have to re-check all the results from that whole period, which costs far more than checking between calibrations.

Signs an instrument will drift out of specification before its calibration is due

In our field service work, instruments usually give warning signs before they produce clearly wrong results. You can read these signs from data the lab already has, with nothing extra to buy.

• The standard curve is no longer linear — check r², which shows how linear the curve is. If r² is below 0.98, the cause usually traces back to how the standard solutions or reagents were prepared, not to the instrument itself.
• The baseline is higher in every measurement — in colorimetric analyzers, this usually comes from deposits in the cuvette or flow cell.
• LOD and LOQ rise without any change in method — a common cause is a light source lamp nearing the end of its life. As light intensity falls, the absorbance of both the samples and the standard curve shifts together, and noise increases.
• Results for the same sample are no longer repeatable — if the same set of control samples gives values that differ more and more, that is a systematic signal, not chance.
• Dispensed volumes are no longer consistent — worn pump tubing causes errors in the aspirating and dispensing rate, which distorts the curve and the analytical results. Pump tubing is a consumable that should have a clear replacement schedule.

If you see two or more of these signs at the same time, do not wait for the annual calibration. While you wait, results that have already been reported may later need to be re-checked.

3 questions to ask before choosing a service provider

There are many calibration service providers, and their quotations often look so similar that they are hard to compare. These three questions show the differences fastest.

1. Does the team that comes on site really understand the instrument’s technique?

This is not the same as knowing how to run through a calibration procedure. Someone who understands the technique can tell you what is causing a deviation and where it should be fixed, rather than just issuing a pass or fail certificate. A simple test is to describe a problem you have had and see whether they can analyze it.

2. Are spare parts and consumables ready to ship?

This determines how long the instrument will be out of action when something goes wrong. A provider that has to order parts every time something fails will always leave the lab down for longer than expected.

3. When the instrument has a problem, is there a team in the country that can fix it?

This is different from asking whether there is a local representative, because having a sales representative is not the same as having people who can actually solve technical problems. Ask directly which kinds of cases require the instrument to be shipped abroad.

What Thai Unique’s team can do for you

Thai Unique’s instrument support does not start when an instrument breaks down. It starts while the lab is still choosing its analytical method, and continues through installation, scheduled calibration, user training and condition checks between calibrations. All of this is done by a team based in Thailand.

What makes a service different is not replacing parts by the manual, but being able to tell whether a symptom comes from the instrument, the reagents or the sample preparation. Our team are PhD-level specialists who work directly with these analytical techniques. We can discuss problems with users at the level of the analytical method, not just the instrument, and we can often identify the cause on the first site visit.

Instrument groups we support

The instruments we support fall into three main groups: sample digestion and extraction systems, automated water analyzers, and gas analyzers. We also support chromatography instruments, both LC and GC, as well as flow analyzers and spectrophotometers, even if they were not bought from us.

Most work can be completed in Thailand. Only cases where the main structure or a specialized component is damaged still need to be sent back to the manufacturer’s factory for repair. The more common limitation is therefore not technical capability, but spare parts for brands we do not represent, which may take longer to source.

What to prepare before the service engineer arrives

Preparing these two things in advance lets the job be finished in a single visit, instead of needing a second appointment.

• A list of the consumables you have on hand — so the team knows in advance what else to bring and does not waste a trip because something is missing.
• Any reference materials or standards you want checked in particular — if you have doubts about a parameter, prepare the material and tell us in advance, so the team can plan checks that cover it from the start.

It also helps a lot to write down the symptoms you have seen beforehand, together with what you have already checked yourself. This information greatly shortens the diagnosis and helps us judge more quickly what needs to be replaced.

Beyond service, analytical instruments, spare parts and consumables for the brands we represent are also available in Thailand through Thai Unique.

If you would like us to assess an instrument’s condition or plan a calibration schedule for you, contact us: Tel. 0-2629-0191-6 · customer.service@thaiunique.com

Frequently asked questions

How often should instruments be calibrated?

Generally at least once a year, but the right frequency depends on how often the instrument is used, how critical the reported results are, and the requirements of the lab’s quality system. Between calibrations, check performance with reference materials at regular intervals. That way you know early when the instrument starts to drift, instead of finding out at the next calibration and having to re-check a whole year of results.

What is the difference between calibration and preventive maintenance?

Calibration checks how closely the instrument’s readings match the reference values. Preventive maintenance replaces parts that wear out according to their service life, such as pump tubing, seals or the light source lamp. Both are necessary and neither can replace the other, because an instrument with deteriorating parts will drift out of specification sooner than the planned calibration cycle.

Is there a calibration team in Thailand, or do instruments have to be sent abroad?

We resolve more than 95% of the problems we encounter within Thailand. Only cases involving damage to the main structure or a specialized component need to be sent back to the manufacturer’s factory for repair. Contact us: Tel. 0-2629-0191-6 · customer.service@thaiunique.com

How are calibration service fees calculated?

Fees depend on the type of instrument, the number of points to be calibrated, the reference materials required and the location. We therefore quote case by case. When you contact us, tell us the instrument model, the number of instruments and the province where they are installed, and we will prepare a service plan that fits how your lab uses them.

We bought our instrument elsewhere. Can you still support it?

Yes. Thai Unique’s team of PhD-level specialists calibrates and supports chromatography instruments (LC, GC), automated water analyzers of the flow analyzer / CFA type, and spectrophotometers, even if they were not bought from us. The most common limitation is not technical, but spare parts and consumables for brands we do not represent, which may take longer to source. The fastest way forward is to send us the brand, model and symptoms so we can assess them first.

What types of automated water analyzers are there, and how do they differ?

Automated water analyzers based on colorimetric analysis fall into two families. The difference is not only speed. It lies in how the sample and reagents react, which affects the volume of reagents used, the detection limit, and how flexibly you can switch between parameters.

A discrete analyzer keeps the reaction of each sample separate. Each test takes place in its own vessel, with no mixing. Its strengths are lower sample and reagent use per test and fast parameter switching without reconfiguring the system. This makes it a good fit for labs that must report many parameters but do not run very many samples per parameter, such as service labs that handle a wide range of work, or factory labs that monitor both the water they use and their wastewater.

A segmented flow analyzer lets reagents and samples flow into the instrument continuously, with air bubbles separating each segment to prevent carryover between samples. Because the reaction has time to go to completion, it stands out for low detection limits and accuracy in work that analyzes large numbers of samples repeatedly for the same parameters, such as seawater analysis or water quality monitoring where samples are collected from the same sites every month. The trade-off is that it uses larger volumes of reagents and samples than a discrete analyzer.

In short: if your situation is “many parameters, not many samples per parameter”, start by looking at a discrete analyzer. If it is “only a few parameters, but a very large number of samples and low values that must stay stable”, start by looking at a segmented flow analyzer.

5 things to include when you request a quotation

Quotations for water analyzers often need several revisions. This is not because suppliers are deliberately stalling. It is because the starting information is incomplete, so the specification has to be guessed first. If you provide these 5 items together from the first round, you will get offers that can genuinely be compared across suppliers.

1. Number of samples per day, and your busiest period

Not just the average. An instrument that fits a normal day may not keep up in months when clients send in samples all at once. The most useful figures are “how many samples on a normal day, and how many on the busiest day”.

2. Parameters you must report

List them all: those you run now and those you expect to add in the next 2-3 years. The number of parameters determines both the instrument model and the number of reagent positions required.

3. Standard methods you must use

This matters more than many people think. The notifications of the Thai authorities you report to often specify reference analytical methods as well, not just the limit values you must meet. Open the notification that applies to your business, check which methods it specifies, and include them in your request.

4. Type of water sample

Tap water, groundwater, surface water, seawater, factory effluent and water from treatment ponds have very different matrices. Samples with high salinity or many interfering substances may need extra sample preparation steps, which affects both the equipment required and the time per run.

5. Lowest concentration you need to detect

If the limit you must report is very low, your options narrow immediately, and this may point to a segmented flow analyzer rather than a discrete analyzer. Give the value you actually need to report, not a standard limit that is easy to pass.

What makes prices differ

The same instrument model can be quoted at quite different prices, because a quotation covers more than the instrument itself. The factors with the greatest effect, in order, are:

• Number of parameters analyzed — each parameter needs its own reagent set and settings. The more values you report, the more sets you need to buy.
• Built-in digestion or distillation — work such as total nitrogen, total phosphorus or total cyanide needs a sample preparation step first. Having the instrument do this internally is convenient but costs more. Digesting separately in a block digestion system is more economical, but someone has to carry out that step.
• Number of reagent positions and refrigeration — some reagents must be kept cool to stay stable throughout the run. The number of refrigerated positions therefore determines how many parameters you can keep loaded without frequently swapping reagents.
• Sample tray capacity — a tray that holds more samples means the instrument can run unattended for longer without anyone refilling it, which is of direct value to labs that are short of staff.
• Service contract — whether it covers only annual calibration, or also includes consumable parts and repair visits when the instrument has a problem. This is the part that makes the numbers differ most over the long term, but it is often left out when prices are compared quickly.

A point to note when you compare quotations from several suppliers: compare on “can the same type of instrument do the same work?”, not on the final figure alone. A lower price may not include the digestion unit your work needs, or may provide fewer reagent positions, so that you have to swap reagents every day.

Ongoing costs people often forget

The instrument price is a single, one-time payment, but the cost that stays with the lab throughout the instrument’s working life is the ongoing cost. It should be assessed when you choose the instrument, not discovered once it is in use.

• Reagents — the largest share of ongoing costs, and a clear point of difference between discrete analyzers and segmented flow analyzers, because the volume used per test is not the same. If you run a heavy workload every day, this difference adds up to a significant amount within a single year.
• Pump tubes — a consumable that wears with use. Worn tubes cause errors in the volumes drawn and dispensed, which skews analytical results. Ask at the quotation stage how often they need replacing and where they can be bought.
• Light source lamp — as light intensity drops, the absorbance of both the samples and the calibration curve shifts together, noise increases, and the LOD and LOQ rise as a result. This may mean you can no longer report low values as you could before.
• Daily system running time — a cost that is not in the quotation but is real. An instrument that can start up and shut down automatically gives staff back time in the morning and evening for other work.
• Annual calibration and maintenance — ask from the start whether there is a team in the country that can do this work, and whether spare parts are ready to ship, because these two points determine how long the instrument will be out of service when there is a problem.

Specifications worth comparing

When you compare instruments, only a few figures truly affect day-to-day work. Below are the specifications of the two models Thai Unique supports, compared point by point and taken directly from the manufacturer’s technical documentation.

Parameters we confirm can be run on the SEAL AQ400 in Thailand include alkalinity, ammonia, chloride, hexavalent chromium, color, cyanide, nitrate, nitrite, ortho-phosphate, silica, sulfate and total phosphate, among others.

For the SEAL AA500, the parameters customers in Thailand most often request quotations for are nitrate, nitrite, total cyanide, phenol, ammonia and total nitrogen.

If your work includes total nitrogen or total phosphorus that must be digested first, and you routinely process dozens of samples at a time, consider a block digestion system such as SEAL BD50 and BD28 as well. Calculated per number of samples per run, it is more cost-effective than having the analyzer digest samples internally.

After-sales support in Thailand

Even the analyzer with the best specifications can give wrong results if it is not installed correctly, not calibrated accurately, or operated by users who were never properly trained. This part should therefore be in the quotation from the start, not discussed later.

Just as important as the instrument price is who will calibrate it, and whether that person really knows the analytical methods you use. Automated water analyzers have many variables that must be adjusted for each sample type, so the person who sets them up needs to understand the chemistry of the method, not just the buttons on the screen.

Thai Unique’s team are PhD-level specialists based in Thailand. They support you all the way from helping choose the right analytical method for your sample type, through installation, calibration and training, to ongoing after-sales support, and more than 95% of on-site issues are resolved within the country.

Both families of automated water analyzers discussed in this article are available in Thailand through Thai Unique, with installation, calibration and after-sales support teams based in the country.

If you would like our team to look at your lab’s workflow before you decide, contact us: phone 0-2629-0191-6 or email customer.service@thaiunique.com

Frequently asked questions

How much does the SEAL AQ400 cost?

There is no single price, because each project has different specifications and accessories. The factors with the greatest effect are the parameters you must report, the number of samples per day, the standard methods you must use, and the service contract you choose. The fastest route is to send us your sample type, number of samples per day and the parameters you must report, and we will put together a configuration and a quotation that fit your work.

How do I choose between a discrete analyzer and a segmented flow analyzer?

In principle, a discrete analyzer uses less sample and reagent per test and switches parameters quickly, so it suits work with many different parameters but not many samples per parameter. A segmented flow analyzer lets reagents and samples flow into the instrument continuously so that the reaction goes to completion, so it stands out for low detection limits and accuracy in repetitive work with large numbers of samples, such as seawater or environmental monitoring. As a result, a segmented flow analyzer uses larger volumes of reagents and samples than a discrete analyzer.

Our samples arrive at very different concentrations. Do we have to dilute them ourselves?

You do not need to dilute every sample by hand. An instrument like the AQ400 can be programmed to pre-dilute, and it automatically re-dilutes when a value is out of range, without re-running the whole batch. This reduces both time and manual dilution errors.

How little sample and reagent does each test use?

The AQ400 uses between 3 and 500 microliters of sample and between 10 and 600 microliters of reagent per test, depending on the method. This matters a great deal when sample volume is limited, such as water from sites that are hard to sample, or samples that have already been through several preparation steps.

Are calibration and ongoing support available in Thailand?

Yes. Thai Unique covers everything from installation, calibration and training to ongoing after-sales support, with a team based in Thailand. Contact: phone 0-2629-0191-6 · customer.service@thaiunique.com

How many sample preparation routes are there, and how do you choose?

The question to ask before choosing sample preparation equipment is not “what instruments does our lab have?” but “what are we analyzing, and in what kind of sample?” These two factors, the analyte and the matrix, determine the route you need to follow, not the brand or model of the instrument.

If the analyte is an element, such as heavy metals analyzed by ICP-OES, ICP-MS or AAS, the goal of sample preparation is to release all of the elements of interest from the sample into solution. That is digestion.

But if the analyte is an organic compound, such as pesticides, organic pollutants or PFAS, the goal changes: extract the target compounds without destroying them, and without letting anything from the equipment get into the sample. That is solvent extraction.

These two routes use different types of instruments and are judged by different criteria. Using an instrument from one route for work on the other often gives results that cannot be reproduced, which then shows up at QC with no cause that can be found.

Route 1 — Digestion for elemental analysis: why this step determines result quality

When heavy metal results come out lower than they should, or replicates do not agree, the cause is often not the measuring instrument at the end, but the digestion step, and it is usually one of these three issues.

1. Temperature too low or uneven

A hot plate does not heat evenly across its surface. Vessels at the edge and vessels in the center see different conditions. As a result, some samples digest completely and others do not, and the values scatter.

2. Open systems lose volatile elements

Elements such as mercury or arsenic can be lost during digestion if the vessel is not closed. The reported value will be lower than the true value, with no warning sign at all.

3. Atmospheric pressure caps the temperature

At atmospheric pressure, an acid boils at a certain temperature and cannot get any hotter. Closed-vessel microwave digestion lets the temperature rise above the acid’s boiling point at atmospheric pressure, so samples break down more completely.

CEM MARS 6 is a microwave digestion system designed to address all three of these issues. CEM states that it reduces sample preparation time by more than 70% compared with traditional techniques.

How do you achieve the temperature control that USEPA methods require?

USEPA methods for sample digestion do not only specify which acid to use and for how long. They also specify the temperature profile the sample must go through. The question that follows is: in practice, how do you know that the sample in each vessel really reaches those temperatures?

Typical microwave digestion systems measure the temperature of one control vessel and assume the other vessels are the same. This costs one position in every run, and if the samples in the other vessels have a different composition, the reading is only a proxy, not the actual value for those vessels.

iWave on the MARS 6 uses contactless, in-situ measurement: it measures the temperature of the sample in each vessel directly, without a control vessel or probe. No position is lost to a control vessel, and you know how hot each vessel really is.

The sensor gives temperature readings accurate to ±2 °C and adjusts microwave power within 2 seconds of receiving a reading. This is what makes the temperature profile set by the method actually happen in every vessel, not just in the one being measured.

Microwave digestion or block digestion: which suits which work?

This question cannot be answered with “which one is better”, because the two approaches meet different needs. Microwave wins on digestion quality and speed per run, while block digestion wins on samples per run and cost per sample.

Work where block digestion is still clearly more cost-effective is Total Kjeldahl Nitrogen and total phosphorus, when dozens of samples are run at a time on a routine basis. The SEAL BD50 holds 50 positions for 75 or 100 mL digestion tubes, while the BD28 holds 28 positions for 250 mL digestion tubes.

What is often overlooked when comparing block digestion systems is the quality of the controller and surrounding accessories, not just the number of wells. The BD50 and BD28 controller can program digestions of up to 30 steps, set temperatures from room temperature to 450 °C with a set-point accuracy of ±2 °C, and control the heating rate as finely as 1 °C per minute, which is essential to prevent bumping.

Two other accessories have a direct effect on result consistency. A draft shield stops air currents in the fume hood from blowing across the digestion tubes, so every well stays at the same temperature. Teardrop stoppers trap and condense digestion vapors so they flow back down, reducing acid loss and preventing cross-contamination between digestion tubes.

Choose digestion vessels for the work, not for what you already have

In a microwave digestion system, the vessels determine how many samples one run can take and how difficult a sample they can handle. These two always trade off: the vessels that fit the most samples per run are not the ones that withstand the highest pressure.

• MARSXpress — runs up to 40 vessels per batch, in 20, 55 or 75 mL volumes. It is the option for work that focuses on samples per run, such as service labs that receive samples in large batches.
• EasyPrep Plus — 12 vessels at 100 mL, for work that needs higher temperatures or pressures.
• iPrep — 16 vessels at 110 mL, another option for samples that are hard to digest.

The most reliable way to choose is to start from the most difficult sample in your routine work, not the one you run most often. Vessels that can handle difficult samples can also handle easy ones, but not the other way round.

As for methods, the system comes with more than 100 pre-programmed methods covering common sample types. Select one on the screen and start. You still need to choose a method that suits each lab’s sample matrix and analysis, so it is not entirely hands-off. For specialized samples, our team can help adapt the method.

Route 2 — Solvent extraction for organic compounds

Extracting organic compounds from soil and sediment takes time, solvent and staff supervision. The classic problem is that someone has to stand at the fume hood for the whole run, and each run ends up with different conditions because it depends on who does the work.

CEM EDGE is an automated solvent extraction system that combines pressurized fluid extraction and dispersive SPE in a single step. According to CEM’s documentation, the system meets the requirements of US EPA Method 3545A and is at least 3 times faster than other pressurized fluid extraction systems, with filtration, cooling and system rinsing built into a single run.

What really removes steps is the Q-Cup, a 3-piece assembly, together with the Q-Disc, which filters the sample as part of the process. There is no need to filter again before analysis, a step that takes time and is a point where the sample can pick up extra contamination.

In practice, this gives two results: staff who used to watch over the extraction step can move on to other tasks, and every sample set is kept under the same conditions in every run. The second point is what makes QC results more stable.

PFAS work adds another layer

PFAS has become a topic that exporters and factories are increasingly asked about, and the standard method cited most often is EPA Method 1633A. Thailand does not yet have legal requirements on PFAS, so for now the pressure comes mainly from downstream customers and export markets.

What sets PFAS work apart from general extraction work is not how difficult the extraction is, but contamination from the equipment itself. Parts inside the instrument that contain PFAS create a background that cannot be separated from the sample. This means that however good the measuring instrument at the end is, if the background comes from the sample preparation equipment, the results cannot be trusted.

CEM EDGE PFAS is designed specifically for this work. Every part that contacts the sample has been tested and shown to be PFAS-free, and the system automatically extracts, filters, cools and rinses itself before the next sample. CEM’s documentation states that this instrument extracts 40 PFAS compounds from soil and tissue, following EPA Method 1633A.

If your lab is assessing whether to take on PFAS work, the deciding point is not only the measuring instrument at the end. It is whether your sample preparation step can control background contamination.

Steps after sample preparation that are often skipped

Many labs invest in a digestion or extraction system and stop there, even though three further steps also affect the numbers they report.

• Volume adjustment — if the final volume is not made up consistently for every sample, all the effort to control temperature during digestion is wasted, because the values calculated back to the original concentration will be off as well.
• Filtration — samples that still contain particles interfere with both the sample introduction system and the detector. Some systems, such as EDGE, filter as part of the process with the Q-Disc, but with other methods you need to plan this step yourself.
• Storage before measurement — how long and at what temperature samples are stored while they wait for analysis affects some analyte groups, especially organic compounds. If the instrument queue is long, the storage conditions should be clearly defined in your workflow.

Choosing a sample preparation method that suits the analyte and matrix is not something the instrument specifications alone can answer. You also need to consider the standard methods you must use and the real characteristics of your samples. Thai Unique’s team are PhD-level specialists who work directly with sample preparation in Thailand. If you send us your sample type, the analytes you need to report and the standard methods you reference, we can help assess which approach to use. Contact: phone 0-2629-0191-6 · customer.service@thaiunique.com

For details of the products related to this article, see the pages for CEM MARS 6, CEM EDGE, CEM EDGE PFAS and the SEAL BD50 / BD28 block digestion systems.

The digestion and extraction systems discussed in this article are available in Thailand through Thai Unique, with installation, calibration and after-sales support teams based in the country.

Frequently asked questions

Is the only difference between microwave and hot plate digestion the speed?

No, it is not just speed. Closed-vessel microwave digestion reaches temperatures above the acid’s boiling point at atmospheric pressure, so samples break down more completely. Because it is a closed system, fewer volatile elements are lost. Every vessel also sees similar conditions, so results are more reproducible than on a hot plate, which does not heat evenly across its surface.

How many samples can be digested in one run?

It depends on the vessels you choose. MARSXpress vessels can run up to 40 vessels per batch in 20, 55 or 75 mL volumes. High-pressure vessels for difficult work, such as EasyPrep Plus, give 12 vessels at 100 mL, and iPrep gives 16 vessels at 110 mL. Work that focuses on sample numbers and work that focuses on difficult matrices therefore use different types of vessels.

Do we need to develop our own methods?

In most cases, you do not need to start from scratch. The system comes with more than 100 pre-programmed methods covering common sample types, though you still need to choose a method that suits your lab’s sample matrix and analysis. For specialized samples, our team can help adapt the method.

Can we use our existing digestion system for PFAS work?

We do not recommend it, because the main problem in PFAS work is contamination from the equipment’s own parts. A system designed specifically for this work has been tested to confirm that every point that contacts the sample is PFAS-free, and it includes a system rinse between samples to reduce carryover.

What needs to be prepared before installation?

Requirements for electrical supply, fume hoods and installation space differ by instrument type and model, so there is no single answer that fits every case. The most reliable approach is to tell us the model you are interested in and your site conditions, so we can check them before you decide to buy. We will then send you the installation requirements for that model.

• Repeat measurements give different values

• The same sample, measured on different days, gives different results

• Results take so long that QC decisions come too late

Often, these problems are not caused by the person doing the measurement. They come from “the nature of the sample” and “the analytical method” that was chosen.

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First, understand how many kinds of “water” a sample contains

Water in a sample falls into 2 main forms:

• Free Water — water that is not bound and evaporates easily

• Bound Water — water bonded to large molecules such as carbohydrates and proteins. It is hard to evaporate and needs high energy and a long time to remove.

This difference between the forms of water is where the errors that many people overlook begin.

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And this is the price you pay.

A moisture error of just 1–2% on the production line

can mean lost yield, more rejected product, and a shelf life that does not match what was specified.

Every lot that passes with an error nobody notices — is a cost that quietly adds up.

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Most errors in moisture analysis are not caused by carelessness.

They come from choosing an analysis method and analysis time that do not suit the type and condition of the sample.

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Which problem does your lab run into most often?

If you are looking for a moisture analysis solution that suits your production line, we are ready to advise you specifically on the method. Please feel free to contact us.

There are currently two main approaches: a gas analyzer connected to a chamber for continuous measurement, and a multi-chamber system installed permanently in the field to collect data for a whole season without anyone on site.

Why measurement continuity matters more than you might think

Soil gas flux does not change gradually. It rises and falls very quickly in response to events in the field, especially rain and fertilizer application. If data points are too far apart, the figures you get are an average of the quiet periods, not a true picture of the whole season.

In Picarro test documentation, rainfall was simulated in a closed chamber system. After water was added to the soil, the N₂O emission rate tripled within 2 minutes and kept climbing. CH₄ spiked and then gradually fell, while CO₂ was first suppressed and then recovered.

Note that the three gases responded to the same event in different ways and at different times. This is why measuring one gas and inferring the others does not work, and why measurement frequency becomes a technical requirement, not just a matter of convenience.

In practice, if your project will report figures that must stand up to verification, you first need to show whether your data cover the peak periods, not just how many data points you have.

Which gases need to be measured

The three main gases for agricultural soil flux work are N₂O, CH₄ and CO₂. Each comes from a different process in the soil and responds differently to field management. Choose the full set your project has to report, not whatever the instrument happens to measure.

N₂O needs the highest precision. Its atmospheric concentration is very low, but its global warming potential is high. Capturing its rate of increase in a chamber over a short period therefore requires an instrument that reads at ppb level.

NH₃ and H₂O can also be measured, but they have limitations you should know before planning. Both adsorb onto equipment surfaces, so readings respond more slowly than the real change, and they carry over between measurements. The design of the gas sampling system therefore matters more for these two than for the other gases.

Approach 1 — An analyzer connected to a chamber for continuous measurement

This approach suits work that needs to show real dynamics over short periods, such as research that must explain mechanisms, or projects that must prove a change in field management really reduces emissions.

Picarro G2508 measures five gases at once in a single instrument: N₂O, CH₄, CO₂, NH₃ and H₂O. It uses CRDS and gives a new reading every 8 seconds or less. N₂O precision at 5-minute averaging is about 0.6 ppb, and water vapor effects are corrected automatically, so it can be connected to a soil chamber and log continuously right away.

The point to check during planning is what is feasible on site. The instrument weighs 22.6 kg, runs on 100–240 V mains power and operates at 10–35 °C. It therefore needs a location with reasonable temperature control and a stable power supply. It can be used in the field as long as its temperature is kept within the specified range (10–35 °C).

Approach 2 — A multi-chamber system installed in the field

If the goal is to collect data for a whole season without sending staff to watch over it, this approach is a better fit. It is designed to stay installed in the field and run on its own for months.

LICA SF-9000 connects to anywhere from 1 to 18 chambers. It measures CO₂ over 0–6,000 ppm with accuracy better than 1% of reading, and logs data continuously to an SD card with no staff on site. It operates from -20 to 60 °C, which comfortably covers field conditions in Thailand.

The benefit goes beyond saving labor. Because several chambers can be connected at once, the system covers spatial variability within a plot better than a single measurement point. Data reviewers often ask about this, because soil in the same plot does not emit gas equally at every point.

Approach 3 — A portable instrument for surveying many sites

Some projects are not yet ready for a permanent installation, but need to survey several plots to find where a measurement system should actually go. This work needs an instrument that can be carried anywhere and started up quickly.

LICA PS-9600 is a portable instrument that uses a CRDS laser to measure CH₄, CO₂ and H₂O at the same time. CH₄ precision is no more than 1.2 ppb at 10-second averaging, and 0.6 ppb at 100 seconds. The instrument weighs 8 kg and operates from -20 to 50 °C.

The most cost-effective way to use it is as a survey step first, to decide where to invest in a permanent system, instead of guessing and installing it in the wrong place.

Isotope work — when you need to know where the carbon comes from

Some projects do not only ask how much is emitted. They ask where the detected carbon or water comes from. That is a different question, and it needs a different kind of instrument.

Picarro L2140-i is used for water isotope work and lets you choose a mode to match your workload. Standard mode handles 27 samples per day. Express mode handles up to 50 samples per day for δ18O and δ2H. Survey mode gives rough estimates at up to 900 injections per day, so samples can be grouped first to reduce memory effects in the actual measurement run.

Picarro lists special options, including running Express together with Survey, which cuts the measurement time for 100 samples by up to 68 hours. For work that requires 17O-excess, the instrument reaches a precision of 15 per meg (0.015‰), a level that previously required a specialized IRMS laboratory.

Which approach suits which kind of work

The three approaches above do not compete with each other. Each one answers a different need. The table below shows where to start based on the type of work you do.

If you are still unsure, the quickest way is to start with three questions: which gases do you have to report, how many points will you measure, and how many seasons will the project run? These three answers alone rule out most of the options.

What to plan beyond the instrument

A budget that covers only the analyzer is often not enough. A flux measurement system has other parts that are just as necessary, and they are often thought of too late.

• Number of chambers — this sets both the cost and the credibility of the data, because too few measurement points will not cover the variability within a plot.
• Power supply — for systems installed in the field, plan from the start where the power will come from and what the backup is during outages, because data lost in mid-season often cannot be recovered.
• Data storage and retrieval — systems that log to an SD card need regular visits to collect the data. Decide who does this and how many weeks apart.
• Equipment inspection visits — equipment in the field is exposed to rain, sun, dust and animals. Set a fixed inspection schedule, rather than visiting only after data has been lost.
• Raw data management — a full season of continuous data is a large volume. Agree from the start where it will be stored, who will process it and what format it must be delivered in.

Designing a flux measurement plan that produces usable data is as much a research task as an instrument task. You need to decide how many points to use, how often to measure and how to handle the raw data. Thai Unique’s team are PhD-level specialists based in Thailand, so we can help from the measurement-plan design stage, not only when the instrument is installed.

If you would like our team to help assess which approach suits your project, send us the number of measurement points, the gases you need to report and the project duration. Contact us: Tel. 0-2629-0191-6 · customer.service@thaiunique.com

For the products related to this article, see the Picarro G2508, LICA SF-9000, LICA PS-9600 and Picarro L2140-i pages.

The gas analyzers and chamber systems mentioned in this article are available in Thailand through Thai Unique, with installation, calibration and after-sales support teams based in the country.

Frequently asked questions

Can I collect samples in bottles and send them to a lab instead?

It depends on the purpose of the measurement. Collecting samples in bottles and measuring them later in the laboratory gives the amount at that moment. It can serve as baseline data, but only for a single point in time, so it cannot be used to measure flux. Bottle sampling gives only an amount, whereas flux is the amount per unit area per unit time. Bottle samples therefore lack time information, system parameter information, and information on the pressure and diffusion of the various soil matrices at that location.

How many gases can one instrument measure?

It depends on the model. Picarro G2508 measures five gases at once: N₂O, CH₄, CO₂, NH₃ and H₂O. LICA PS-9600 measures CH₄, CO₂ and H₂O with a CRDS laser, and SF-9000 focuses on CO₂ and H₂O for long-term monitoring. The right choice depends on which gases your project has to report.

Does a system installed in the field need someone on site?

No. Multi-chamber systems are designed to collect data continuously and log it to an SD card on their own. One example is the SF-9000, which connects 1–18 chambers and operates from -20 to 60 °C. What you need to plan is the power supply and the schedule of equipment inspection visits.

What precision is enough for N₂O work?

Atmospheric N₂O concentrations are low, so capturing the rate of increase in a chamber requires ppb-level precision. For example, the G2508 gives an N₂O precision of about 0.6 ppb at 5-minute averaging, which is enough to calculate the rate of increase over a short period.

How much does a complete system cost?

A flux measurement system has several parts: the analyzer, the number of chambers required, the power system and the software. The number of chambers and the gases to be reported affect the price the most. Send us the number of measurement points, the gases you need to report and the project duration, and we will put together a set that fits your work.