FAQ Frequently asked questions

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Is the fact that the Additive Load has an upward trend normal when it is replaced?

Yes, the addition can contribute to the variation of the lubricant’s additive load.

Based on the result of fluid analysis, is it possible to extend the lubricant change period?

Yes, through the analysis it is possible to check if the lubricant needs to be changed or if it still has a valid useful life.

Can I estimate the percentage of the lubricant’s life through fluid analysis?

With basic fluid analysis tests it is not possible to estimate the service life of the lubricant.

What problems can be associated with high PQI test values?

The PQI is a relative measure of concentration. It detects ferrous particles in condition monitoring programs. The PQI generates relative values, with its own units and not directly convertible for results of other methods.

Low iron levels via spectrometry together with high PQI values ​​indicate the predominance of large ferrous particles. On the other hand, high iron results with low PQI levels suggest that most of the particles are small (less than 10 μm).

What can be the cause of low viscosity detected in used oils of V40 and V100 with the analysis carried out in the first thousand kilometers?

Factors that contribute to changes in viscosity are contamination by another fluid and fuel, which generate excessive fluid burning. It is necessary to check the values ​​of the PQI test. If there are significant variations there may be an indication of wear not related to the contamination suggested above.

Can any untrained operator perform the fluid crackling water test and get a reliable result?

The operator must be trained in accordance with applicable instructions and work standards; being accompanied by a more experienced technician; having hearing and visual sensitivity, and performing the test in a suitable environment with low noise and temperature control.

What does *J mean? 

This flag is a type of data added by the laboratory next to an analytical result and indicates that although the substance has been identified in the sample, its concentration is estimated and not quantified because it is above the limit of detection (LD) but below the limit of quantification (LQ). 

This type of result should be flagged to highlight potential data quality limitations and is added during the validation of the results, which is part of the quality assurance of an analytical laboratory.  

Why do we have to analyze COD when I only need BOD? 

The importance of analyzing COD is for predicting sample dilutions in BOD analysis. As the COD value is superior and the result can be obtained on the same day of the collection, this variable can be used to mark the dilutions. However, it should be observed that the COD/BOD5,20 ratio is different for the several effluents and that, for the same effluent, the relationship changes through treatment, especially the biological one. 

Thus, a gross effluent that presents a COD/BOD5,20 ratio equal to 3/1 may, for example, present a ratio of the order of 10/1 after biological treatment, which acts to a greater extent on the BOD5,20. 

What is COD and BOD?

Both BOD and COD are used as an indirect measure of the amount of organic matter present in a sample. This measurement is important for environmental monitoring, since part of the organic carbon present in fresh waters comes from effluents and residues and its presence in high content can induce the depletion of oxygen present in water and, consequently, cause the disappearance of aquatic organisms. Therefore, the content of organic matter, and indirectly the amount of oxygen required to oxidize it, is an important indicator in determining the degree of pollution of a water body.   

BOD is the amount of oxygen required to oxidize biodegradable organic compounds present in a given sample for stable inorganic forms – such as water, carbon dioxide, sulphates, ammonia, nitrates – through aerobic microbial action. Generally, an incubation period of 5 days at a temperature of 20ºC is used in a test referred to as BOD5,20.  

COD, on the other hand, is the amount of oxygen required to oxidize the organic matter present in a sample through chemical substances, for example, potassium dichromate. An advantage of this test in relation to BOD is that it is performed in a shorter period of time. Another difference is that COD generally results in higher values than those found in the BOD test, because the latter only oxidizes the biodegradable fraction of organic carbon, while the chemical substances used in the COD test can oxidize both the biodegradable and the non-biodegradable portion. This implies that the more the value determined by the test approaches that found by BOD, the more biodegradable the organic matter present in the effluent will be. In addition, COD is used to anticipate the dilution that will be required in the BOD test, since its result is produced in a shorter time. 

What are ecotoxicity tests? 

They are tests that allow us to evaluate the damage that has occurred in the various ecosystems after contamination, and also to predict future impacts on the environment resulting from some human activity.  

These tests use various organisms of different ecosystems, under controlled laboratory conditions, in order to establish the cause/effect relationship of the various sources of pollution on biological communities.  

The results of these tests are applied in order to reduce or eliminate the negative effects of the substances on the environment, particularly waterways. 

Ecotoxicity tests can be classified in two ways:

  1. Acute tests: they detect immediate effects, usually irreparable, by assessing the lethality or immobility of organisms. These are effects that occur after a short period of exposure. 
  2. Chronic tests: they are carried out with the purpose of studying the effect mainly on the survival, growth and reproduction of organisms. They are effects that manifest themselves after days, months or years, depending on the life cycle of the species studied. This effect generally occurs after a prolonged period of exposure. 

What are semivolatile organic compounds (SVOCs)? 

By the definition of method 8270, semi-volatile organic compounds are mostly neutral, acidic and basic organic compounds that are soluble in dichloromethane and able to elute, without derivatization, as peaks in a fused silica capillary column.   

The list of compounds includes polynuclear aromatic hydrocarbons, chlorinated organic hydrocarbons and pesticides, phthalate esters, organophosphate esters, nitrosamines, anilines, pyridines, nitroaromatic compounds and phenols.

What are volatile organic compounds (VOCs or VOCs)? 

Volatile organic compounds (VOCs) are defined by the EPA as substances that at room temperature quickly pass into the vapor state.  

There is also another more widespread definition that classifies VOCs as organic substances that can volatilize under normal indoor conditions of temperature and pressure, due to the low boiling point (less than 200ºC) and high vapor pressure, which in turn are consequences of their low molecular weight and weak intermolecular interactions.   

VOCs are contaminants released, for example, during the production of adhesives, paints, petroleum products and pharmaceuticals.  

What is TPH fingerprint?

TPH fingerprint can identify and quantify products such as turpentine, gasoline, OC PREMIUM oil, BPF oil, hydraulic jack oil, mineral oil, motor oil, kerosene, thinner, and can be used to track a specific customer product. 

 TPH fingerprint analyzes hydrocarbons ranging from 8 to 40 carbons (C8 to C40) and uses the chromatographic profile of the sample to compare with the chromatograms of pure products. 

ALS is certified to perform water and effluent analysis for the determination of Total Petroleum Hydrocarbons (TPH) by Gas Chromatography with Flame Ionization Detector (GC FID), based on the analytical method USEPA 8015 D of the Environmental Protection Agency (EPA). 

What is fractional TPH? 

Fractional TPH is used in the determination of aromatic and aliphatic hydrocarbons separately and generally reports the results by dividing them into bands, which consist of a mixture of hydrocarbons whose carbon bands vary as shown in the table below: 

Oil Bands  Carbon bands 
GRO    6a8carbons (C6 to C10) 
GRO    8 to 10 carbons (C8 to C10) 
RBCA  10 to 12 carbons (C10 to C12) 
RBCA  13 to 16 carbons (C 13 to C 16) 
RBCA  17 to 21 carbons (C17 to C21) 
RBCA  22 to 34 carbons (C22 to C34) 

This type of quantification in ranges is carried out because oil is made up of a complex mixture of chemical substances, and the identification and measurement of each of these species separately would not be practical for the purpose of some types of environmental monitoring.

What are Surrogates ?  

Surrogates are brominated or deuterated compounds added to samples at a known concentration that are used to monitor the performance of organic analyses such as HPLC, GC and GC/MS. 

The recovery rate, that is, how much has been quantified in relation to the known added concentration, is used to evaluate matrix interference effects and method performance. 

These substances used as surrogates are chemically similar to the analyte studied and, therefore, behave similarly during the sample preparation and instrumental analysis stages, but are compounds that are not naturally present in the sample. Because of this, they do not cause interferences or errors in the analysis.

What are the precautions I should take when sending samples by carrier?  

The samples should be sent to the laboratory in the shortest time possible after their collection, preferably, on the same day of collection. The bottles should be stored in suitable boxes/containers to protect them against shocks that may cause breakage, contamination and sample loss. If there is a specification in relation to temperature, one should use proper equipment such as freezers/refrigerators or make use of thermal boxes with ice or previously cooled thermal gel bags. In addition, each bottle should be properly identified with a unique name/code, date and place of collection and it is essential that the customer also sends the correctly filled chain of custody.

Does the ALS report the parameters outside the specification?  

In the report is indicated the parameters that are outside the specification range, as long as the client requests the comparative legislation. 

What is MS and MSD? 

  • MS: Matrix spike.
  • MSD: Matrix Spike Duplicate.   

This second technique is actually an extension of MS, because instead of using only one aliquot of the sample with the addition of the tested analyte, two replicates are prepared. The MSD is used to estimate the analytical accuracy of the recovery, as well as the method in relation to a given matrix.

For metal analysis, for example, if the recovery index is not adequate, the analyte tested on the original sample is added and then passed through a digestion step.

What is Matrix Spikes? 

Matrix Spikes (MS) are aliquots of environmental samples to which known concentrations of the analyte studied have been added prior to preparation, cleaning and analysis. The recovery content of this control – that is, how much was quantified in relation to what was added – is used to verify whether materials present in the sample itself are interfering with the analysis, which in analytics is called matrix effect, and thus to evaluate the performance of the methodology for a particular analyte and matrix, as well as to assess the accuracy of the analysis.  

The difference between the LCS and the spike matrix is that the former is used to demonstrate that the laboratory is capable of performing an analytical procedure – precisely, accurately and within the detection limits of the method – in a non-interfering matrix, while the second one evaluates whether the chosen method is appropriate for the sample matrix, which may contain unknown substances that interact with the analyte and thus interfere with the result of the analysis.  

What is LCS?

It is the English acronym for Laboratory Control Sample, which is used to evaluate the laboratory’s performance in performing analyses of a particular analyte in an interference-free matrix.  

The LCS is somewhat similar to the method’s blank – that it is a similar matrix to the sample, free of the analyte analyzed and other contamination, which goes through all the analytical stages of the method – but a known amount of the analyte studied is added to it. It is prepared and analyzed together with the samples, also using the same methodology.

The recovery rate of the analyte present in the LCS is used, together with other quality control information, to evaluate the acceptability of the data generated for a set of samples analyzed. On the other hand, the recovery rate of the LCS must be within an acceptable range. 

What is QA / QC?

QA stands for quality assurance and QC for quality control.

QA/QC in environmental analysis is a set of actions undertaken with the aim of promoting the accuracy and precision of analytical data and thus increasing its reliability. While quality assurance is characterized as a broader plan to maintain the quality of the program as a whole, used to identify and correct problems associated with the generation of analytical data, quality control is specific to each activity and consists of the steps that will promote the validity of sampling and technical procedures of analysis. 

Quality assurance is implemented through practices such as documenting all technical procedures, conducting training, and documented validation of analytical data.   

Data validation includes the review of sampling documents, verification of analytical data, as well as their evaluation by the project scientists and the resolution of problems present in these data. This set of activities aims to correct suspicious or erroneous electronic data and flag those analytical information with potential limitations.  

The verification of the quality control of the sampling and the laboratory is carried out through the sampling whites (field, equipment, travel), calibration standards, reference materials (standards), surrogates, LCS, analytical method detection limit studies, etc. In addition, there is also the quality control of the externally evaluated laboratory, such as the interlaboratory analyses. 

What is the difference between total and dissolved metals?  

From an operational point of view, a dissolved metal is any kind of metal that passes through a 0.45 µm filter, while the retained fraction is classified as particulate or suspended metal. The sum of the dissolved and particulate/suspended metals gives us the quantification of the total metals. 

What are undeformed samples? Which analyses in the undeformed?

The undeformed sample is collected in such a way that the characteristics that occur in situ are preserved. It is extracted with as little disturbance as possible to try to maintain the original soil structure and the level of moisture and compaction. To collect this type of sample, special samplers are used in boreholes or it is obtained by extraction in investigation wells.    

It is important to emphasize that soils under natural conditions are rarely equal from one point to another.  

This type of sample is used, for example, to determine the total porosity (macro + micropores), natural density, soil density, hydraulic conductivity, void indices and volumetric humidity. 

What are deformed samples? What analyzes in the deformed?  

The concept of deformed or undeformed sample applies only for analysis ofgeotechnical, that is, for the study of soil behavior and / orrocks 

Deformed sample is one that does not maintain all the characteristics observed   in situ.It is extracted by scraping or excavation, which results in the destruction of the original structure of the soil and loss of its characteristics of compactness.

This sample is used in the analysis of natural moisture, real density, organic matter, organic carbon, electrical conductivity, grain size, clay dispersed in water, aluminum, potential acidity, liquidity limit, plasticity limit, plasticity index and fertility.

What does “foam presence” mean in lubricating oil sample analysis?

First, we need to understand how the essay works and what it is for: This foam test consists of stimulating foam formation and checking how it dissipates. When there is no quick disappearance of this foam, this may indicate problems.

Within the system, the coolant is in constant motion, that is, it is always subject to creating this foam. If it does not “break” quickly, it will make heat exchange within the cooling system difficult. The air (which is inside this foam) is a bad conductor and will not let the cooling do its job of keeping the engine at optimum temperature. There are still other issues caused by this scenario, including accelerating system wear.

The most common cause for the presence of foam is air intake, but other causes can result in this persistent foam, so check equipment and investigate the cause.

White Travel

This white consists of bottles filled with distilled water (for metal analysis) or mineral water (for organic analysis). That travel closed together with the empty bottles that will be used to collect the sample and return closed to the laboratory with the collected samples. Contamination in this blank indicates that contamination may have also occurred in the sample, from sources that were not present at the time of collection, and the analytical results of the sample are not accurate.

White from   field

These are bottles filled in the field with distilled water (for metal analysis) or mineral water (for organic analysis) which are exposed to the sampling environment for the same period as the sample.  

The field blank is analyzed with the same methodology used for the sample, and if any contamination is found, then probably the same occurred with the sample during collection or processing in the laboratory.   

White of the method

This white is constituted by a matrix free of interferences, similar to the sample matrix – water, sand or a salt (sodium sulfate) are used, depending on the case-, in which all the reagents used in the sample are added during the stages of the analytical procedure, which include preparation, cleaning and analysis. This blank is used to indicate if there have been any contamination problems during the laboratory steps leading to an increase in analyte concentration or a false positive. The blank result should be less than the method’s LQ. 

White of the equipment

This white consists of the last volume of water used to rinse the equipment that collects the sample and is used to demonstrate that the equipment was not previously contaminated. 

What are quality controls (QC)?  

Quality control (QC) is a set of technical activities – including sampling, calibration and analytical procedures – which are adopted to evidence and promote the production of data with accuracy and precision.  

For the sampling of water, effluents, soils, solid waste and sediments, one of these quality controls is the white one, used to signal if there was contamination of the sample with any foreign material from the collection stage, through transportation, to the analysis. 

What is DL?  

The Detection Limit method’s is the lowest concentration of the analyte that can be detected, but not necessarily quantified under the conditions employed during the analysis. A concentration below DL may not be detected by the method.  

What is LOQ?  

Limit of Quantification is the lowest concentration of an analyte that can be determined with acceptable accuracy and precision under the conditions used during the analysis. 

What is Rush Time? 

Rush Time is any time of analysis inferior to the ALS standard. 

Does ALS reuse their bottles?


Do I have to pay for the bottles?


Can I use the same type of bottle for all analyses?  

No, since each matrix requires a specific type of bottle.

What is Holding Time? 

Holding time is the maximum period indicated between the collection of the sample – maintained under specific conditions – and its analysis, without significant degradation of analytes or their properties. This period depends on the characteristics of the analyte, the type of matrix and the specific constituents of the sample.  

The holding time is established due to the possibility of certain sample constituents suffering degradation or volatilization over time, which would result in an inaccurate measurement of these compounds.   

In order to avoid the degradation of analytes, some samples require preservation by chemical and/or physical means, such as pH adjustment and temperature control, respectively. Thus, it is more likely that the results obtained through the analyses will express the real state of the object studied, whether it is an effluent, water, soil, sediment, industrial waste, gas, indoor air, outdoor air, etc. 

What is environmental analysis and why should I do it? 

Environmental analysis is the characterization and evaluation of the quality of the environment used to determine the degree of impact of any human activity on the level of quality of soil, water and air, as well as the verification of the effectiveness of effluent treatments and the classification of waste. 

Can I keep my oil sample?

The oil sample it is not recommended to stock. So after the collection should be sent immediately.

How should I collect the oil?

After the kits have arrived, follow the step-by-step instructions for collecting all the maintenance plan compartments. For a perfect oil collection, the equipment must be moved and all of its implements must be activated so that the oil circulates through the parts, keeping the particles in suspension.

It is important to remember that if the equipment has been out of operation for more than 30 minutes, it should be moved again. Follow step-by-step to collect all maintenance plan compartments.

For collection, simply cut the hose approximately one hand wider than the dipstick. In the case of the filling nozzle, the size must be sufficient to reach a maximum of 5 cm from the level of the reservoir oil.

The next step is to attach the hose to the pump, so that the tip does not enter the collection bottle. Tighten the nut to secure the hose and uncap the collection bottle, storing the cap in the bag and securing the bottle to the pump. To ensure that the pump is not in contact with the oil, always keep it in an upright position.

Insert the hose into the bottom of the filler neck or dipstick tube and pump. If the oil is not filtered, lower the hose a little more into the tank. As soon as the vial is full, loosen the pump nut to let air in and the oil stop being pulled. Carefully pull the hose from the reservoir, then carefully remove the bottle from the pump and immediately plug it.

With the pump upright, push the hose down and wipe it clean. Turn pump with hose tip up and clean again. Then just pull the hose down. It is important to note that the hose must not be reused and should be discarded in an appropriate place. Watch the step by step here.

Do I need any tools to perform fluid collection?

Yes, at the time of collection it is necessary to have a pump or a collection valve that will aid the flow of the fluid and prevent external contamination.

Should I do oil analysis on stationary machines?

Stationary machines are also subject to possible contamination as a result of problems of different origins. They may arise from inconsistency in the lubricating oil itself, in the equipment or by external factors. Oil analysis on stationary machines enables equipment to be always available if your company needs to use them.

Why should I opt for PQI analysis?

The PQI enables the anticipation of severe wear problems that may not be detected early by traditional atomic emission spectrometry techniques.

How often should I perform fluid collection on my equipment?

Although the original equipment manufacturer’s recommendations provide a good starting point for the development of preventive maintenance practices, sampling intervals can vary easily. The importance of a piece of equipment for production is an essential consideration in determining collection frequency, as well as environmental factors such as hot and dirty operating conditions, short trips with heavy loads and excessive idle times.

What is oil analysis and why should I do it?

Oil analysis is a diagnostic, predictive maintenance tool that has the primary purpose of monitoring and evaluating lubricant and equipment conditions. It enables you to maximize asset performance and reliability by identifying small issues before they become major failures. You can safely extend oil drain intervals and, ultimately, the life of your equipment – saving time and money.

Why the results for a given sample vary among the various sampling and analytical approaches?

The challenge presented when comparing methods containing so many variables involved has led this issue to be an oft-debated question at both technical conferences and in literature. Some variables in question may include:

  • Sampling media: tubes, bags, canisters, oil and solutions are all currently used by the various methods.
  • Analytical instrumentation: GC/MS, GC/ICP and GC/AED.
  • Calibration standards: some methods use liquid standards, while others use vapor-phase standards.
  • Target analyte list: Varies from 5 to 22 siloxane compounds.
  • Reporting limits: vary greatly.
  • Results calculations and reporting formats: some methods report total siloxanes but do not speciate them, others speciate them in various units: mg/m3, mg Si/m3, ppmV, ppmV as Si or µg Si/m3 CH4.

Given these factors, it is not unexpected that there could be variability observed in the results obtained by the various methods.

Can the results be reported in units of “ppmV as Si” or “µg Si/m3 CH4”?

Yes, the laboratory can report results in µg/m3, ppmV as Si or µg Si/m3 CH4. The default report unit is µg/m3, and the standard report also includes a “total Si” value listed at the bottom of each report. Other units/report formats should be requested prior to sample submission. To report µg Si/m3 CH4, the methane concentration needs to be determined by EPA method 3C, which requires the submission of a separate Tedlar bag or summa canister. Please note that methane cannot be collected with the siloxane sorbent tube.

Are the samples considered “dangerous goods”?

Siloxane tubes are neither flammable or toxic, so they can be shipped via standard shipping methods (UPS/FedEx). If samples are collected with Tedlar bags, however, and the sample contains flammable concentrations of methane, then the bag may be characterized as dangerous goods or hazardous goods. It is the shipper’s responsibility to adequately characterize their sample and ship them in compliance with DOT regulations.

Can volatile organic compounds be determined from the siloxane sampling tube?

While this sampling and analytical approach is suitable for a limited list of VOCs, most of the VOCs typically reported by EPA TO-15 or TO-17 are not available with this analysis.

What is the sample Hold Time?

Sorbent tubes are stable for up to fourteen days after sampling and may be stored at room temperature prior to analysis. Tedlar bags may be stored for 72 hours prior to analysis.

Are there advantages in one collection method over the other?

Since both methods yield comparable data, the selection of sampling can be a function of parameters such as sampling preference/familiarity, field time, reporting limits, shipping requirements, and hold time.

What about inclement weather?

In cases of extreme cold, lower recoveries have been observed due to siloxane adherence to the sample tubing. Recommendations to improve recoveries in cold weather include making the sample train as short as possible to minimize losses, using insulated tubing, or sampling with a Tedlar bag.

Will high humidity affect the sample results?

Since some of the siloxane compounds are soluble in water (most notably Trimethylsilanol and D3), high humidity (>90%) may hinder the overall siloxane recovery. Appreciable water build up inside the tubes may also reduce the performance of the sorbent, so in cases where there are visible water droplets it is recommended that a Tedlar Bag be used for collection.

Can the samples be collected and submitted in a Tedlar bag instead of sampling with a tube?

Yes, a Tedlar bag may be used to collect the samples for this analysis. Note, the standard hold time for a Tedlar bag sample is 72 hours from sample collection to analysis. Reporting limits for samples collected with a Tedlar bag will be higher than those for samples collected on a sorbent tube, due to a smaller sample size.

What quality control criteria is followed once a sample is received?

The laboratory follows QA/QC criteria established by the National Environmental Laboratory Accreditation Program(NELAP), which includes, but is not limited to: instrument tuning, internal calibration (ICAL), second source standards verification, continuing calibration verification (CCV), laboratory control standards and duplicates (LCS and LCSD) and method blanks.

How did the lab arrive at a nine-compound target siloxane list?

The analytes are those most frequently referenced in literature as the primary constituents in landfill gas and biogas.

What are the most common siloxanes found in LFG/biogas?

Our field research has consistently detected trimethylsilanol, octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5) in landfill gas. Similarly, D4 and D5 have been observed in biogas, while trimethylsilanol is not typically a significant factor.

How did you validate your in-house developed method?

The laboratory adhered to OSHA’s Organic Chemicals Air Sampling and Analysis Guideline for validating sorbent-based methods. This guideline was followed to validate method parameters such as sampling rate, sample volume, breakthrough studies, sample recoveries, sample hold time, relative humidity, gas-phase standards, field samples and field sample “over-spikes.”

Are there any established standards for siloxane monitoring?

There are currently no state or federal promulgated methods for the sampling and analysis of siloxanes, because currently siloxanes are not subject to regulation under current air quality standards. Rather, monitoring of siloxanes is typically performed to characterize gas streams used in combustion applications (waste to energy applications), or for performance criteria for turbines. There are numerous commercially available siloxanes sampling and analytical methods.

Why couldn’t a uniformly mixed bed of multiple sorbents be used for passive sampling? Wouldn’t you be able to capture more compounds?

If a passive sampler were comprised of a mixed bed of different sorbents, contaminants would preferentially adsorb to the strongest sorbent in the mix. Unlike active sampling, where contaminants travel through each bed in increasing sorbent strength (and only the most volatile compounds are trapped on the strongest sorbent bed), it is likely that many or all compounds would adsorb irreversibly on the strongest sorbent in the mixture.

For example, if a client was sampling a mixture of PCE and breakdown products to vinyl chloride, during active sampling (passing a sample stream through a bed of increasing strength) the PCE and TCE would likely be trapped by the first (weaker) sorbent, mid- range compounds would be trapped by both the weakest and the middle sorbent, and the vinyl chloride would travel through all sorbents until it reached the strongest sorbent in the back of the tube. If everything adsorbed onto the strongest sorbent (as in the case of the mixed-sorbent bed), only the very volatile compounds would be recovered off of the tube.

If multi-sorbent tubes can be used for active sampling to get a longer compound list, why aren’t they used for passive sampling?

Most multi-sorbent tubes are packed such that there are a few centimeters of each material bed packed in the tube sequentially, from weakest to strongest. When thermal desorption tubes are used in a passive mode (called “axial diffusive samplers”), one end of the tube is capped off (the outlet) and a diffusion cap is placed on the other end of the tube (the inlet). With this configuration, air enters the tube through the diffusive end only, and interacts with approximately just the first one to two centimeters of the first sorbent bed.

Over time, it is possible that once the tube is capped contaminants, may come to equilibrium (meaning some compounds will be released from that “weaker” first bed of sorbent and then will preferentially migrate to the other “stronger” beds); generally speaking, however, passive sampling will only yield interaction with the first few centimeters of sorbent, rendering the unexposed sorbent beds virtually useless in passive applications.

What if I want to analyze a compound on the sampler that does not have an established uptake rate?

In many cases this can be done; however, only the mass of the target analyte can be determined and reported. The uptake rate is required, along with the laboratory-quantified mass value (μg/sample), to calculate the average concentration (μg/m3 or ppbV) over the sampling interval.

Are all passive samplers ready to go off-the-shelf or should the laboratory QC them prior to field use?

Laboratory QC of the samplers depends on vendor specifications. Some recommend cleaning and QC prior to deployment, others do not. Consult with the laboratory for vendor recommendations for the sampler selected for your project.

What are the types of passive samplers? For what families of compounds do you have samplers?

There are many types of commercially available samplers for many different families of compounds. ALS routinely offers analysis using the samplers listed below in Table 1 (Reverse side).

Are all samplers the same?

Although all passive samplers operate on the same principle, the housing materials, shapes and sorbent options differ and therefore lend variability. Each sampler has been optimized for an ideal sampling time, relative humidity level, target analyte list, and reporting limits, which also varies among sampler types.

Why do I need to record and provide sampling duration to the laboratory?

The laboratory can merely determine the mass collected on the sorbent for a given analyte unless the sampling duration is provided and an uptake rate is available. In order to convert mass/sampler to mass/volume (µg/m3 or ppbV), the sampling duration must be provided.

Why do you ask that I record the average ambient temperature on the chain of custody? Do humidity or wind speed affect the sampling rate?

Since the uptake rates are established at ambient temperature (298K, or 25°C), a correction factor can be applied for samples collected under non-ambient conditions. In order to apply this correction factor, field conditions should be noted on the chain of custody, otherwise the ambient uptake rates will be used.

How long do I deploy a passive sampler for?

Deployment time depends on the both the type of sampler used and the required reporting limits. Typical sampling rates vary anywhere from eight hours to four weeks. The laboratory can provide you with the vendor-recommended sampling intervals for your project-specific target analyte list.

How do passive samplers for air applications work?

Unlike active sorbent sampling, which requires a sampling pump and has a definitive sample volume, passive sampling involves the collection of organic vapors by way of diffusion. Samplers are deployed near a point of interest (ex. clipped on a garment in the breathing zone, hung in a room, etc.) and left for a specified period of time. Compounds adsorb to the sorbent material by means of diffusion. The respective masses of the target analytes are then converted to time-weighted average concentrations (in units such as µg/m3 or ppbV) using an experimentally derived variable called an “uptake rate.” Uptake rates are a function of both the sorbent material being used and the geometry of the particular sampling device. Each target analyte requires its own established uptake rate, and the variable is expressed as milliliter of compound adsorbed by the sampler sorbent per minute (mL/min). Not every compound has an established uptake rate for a given sampling device. Consult with the laboratory for the most current list of uptake rates for the available sampling devices.