Sparks (775) 355-0202 | Elko (775) 777-9933 | Las Vegas (702) 475-8899
Sparks (775) 355-0202
Elko (775) 777-9933
Las Vegas (702) 475-8899
Western Environmental
Testing Laboratory
Lessons from the Lab: Sample Integrity/Temperature Focus

Western Environmental Testing Laboratory (WETLAB) is a certified laboratory, specializing in organic and inorganic testing.  Our goal is to provide high quality, legally defensible data.  As a certified laboratory, we assume the responsibility of providing results that are accurate, reliable, reproducible, and valid for compliance monitoring.  We work to meet our clients’ needs and meet local, state, and federal regulations for environmental testing.  In order to meet our client and regulatory obligations it is important to understand that a test result is only as good as the sampling and handling that was performed before analysis.  Therefore, in this month’s newsletter we would like to highlight the importance of sample integrity and how this will ensure a continued trend of high-quality data that is valid for compliance monitoring.

Sample integrity means a sample was collected and maintained in a state of unimpaired condition, uncompromised, and most accurately representative of the source from which it was sampled.  Sample integrity begins with sampling and is followed through the life of the sample to analysis.  There are 6 specific characteristics that will be described here that when adhered to can ensure the sample data is accurate, reliable, reproducible, and valid for compliance monitoring.

The test containers, preservation, and hold times can be found from the EPA under 40CFR, part 136, Table II – Required containers, Preservation Techniques, and Hold Times.

Sample integrity begins with sampling.  It is best practice to have a sampling plan: know the test parameters required either from a permit or other regulatory requirement to ensure you have the correct sample bottle.  Per the regulatory requirements, know where you will be collecting samples, how you will collect them (grab or composite), how long will it take to get the samples to the lab and how will they be transported (in a cooler on ice).  If the samples will remain in the custody of the client for more than one day is sample storage in a cooled environment (refrigerator) available?

Sample labels are extremely important for traceability.  Completely fill out the date and time of sample collection, site of collection, initials of sampler, if field filtered or total, and any field measurements or observations that are client specific.

Transportation of samples isn’t always recognized as integral to sample integrity, but in fact it is one of the most important steps.  The transfer of samples is an important time where preservation begins, and the utmost care should be taken to prevent contamination and degradation.  Seal samples in a plastic bag or bucket with an airtight lid.  Begin the chilling process immediately by placing samples on wet-ice, blue-ice, or ice packs.  Place samples in a dark location, preferably a cooler to minimize exposure to light.  If necessary, separate wastewater samples from drinking water by placing them in different coolers or individual zip lock bags.  If shipping samples, make sure they are packed with sufficient ice to remain cool during transit.

Provide a completed chain of custody (COC) when relinquishing samples to the laboratory.  The COC is a legally defensible document with information specific to the sampling plan, sample information, and transfer of custody to the laboratory.  Please retrieve our digital COC at https://www.wetlaboratory.com/forms/ .

Sample bottles are provided by the laboratory at no charge.  We would prefer you are able to sample using the correct containers.  To request a bottle kit, submit a request to WETLAB here https://www.wetlaboratory.com/bottle-order-form/ .  The containers will be specific to the sample matrix (water, soil, sludge, or other) and testing requirements.  The correct bottles provided to the client will contain the correct preservative and allow for the proper sample volume.  The containers are made of an inert material to minimize any reaction with pollutants, they have lids that seal to prevent contamination, and are clean and free of contaminants.  Sample containers vary in color, material, and size.  They may be clear or opaque, glass or plastic, 500ml bottles or 1-liter cubitainer.  When sampling, place the lid with the top side down so as not to contaminate the side that may be in contact with the sample.  When filling the sample bottles DO NOT rinse out the bottle because there may be a preservative in it, fill the bottle to the etched line or completely full (based on instruction provided with bottle kit), and don’t overfill the bottles, which again could remove any preservative present in the bottle.

When collecting samples use the appropriate bottles provided by the laboratory to ensure sufficient volume is provided for the parameters of interest, the number of analytes being tested, and the sample matrix.  The sample volume should be easy for transport, large enough to be a representative sample from the source from which it was sampled, and sufficient to provide the laboratory the ability to split the sample, perform repeat analysis, and adequately run quality control samples.

Sample preservation will hold a sample as close to its natural state and representative of the source from which it was sampled.  Sample preservation protects a sample from natural biological or chemical degradation.  If a sample is not preserved properly the natural biological and chemical consistency of the matrix can change the chemistry and compromise the sample.  For example, pH can change in minutes, volatile compounds may be lost, bacteria can decompose constituents, and chemical reactions may change the analytes of interest into different species (for example NO2 can oxidize to NO3).  There are different types of preservation: thermal (cooling to <6 degrees C), chemical preservation (sodium thiosulfate to dechlorinate samples), pH control (adding nitric acid to metals containers to lower pH or NaOH to CN to raise pH), and the bottle type if it is amber or opaque (minimize exposure to light which can degrade certain compounds).

The specific bottle types and chemical preservatives are supplied correctly to the client in a bottle kit order.  The one factor of sample preservation that is specifically the client’s responsibility is cooling the samples.

The following temperature guidelines pertain to ALL SAMPLE MATRICES.

  • If a COC is marked ‘as compliant’ then samples received for VOCs, TCLP-VOCs, SOCs, and SVOCs must be received on ICE.  If they are received more than one day after sampling, they should be received at less than 6 degrees Celsius.


  • If a COC is marked as ‘non-compliant’ then samples received for VOCs, TCLP-VOCs, SOCs, and SVOCs should be received on ICE.  If they are received more than one day after sampling, they should be received at less than 6 degrees Celsius.

The hold time for a test starts when the sample is collected.  Therefore, it is important to know how long it will take for a sample to be received by the laboratory after sampling because some tests have short hold times.  A hold time may be measured in minutes, hours, days, or months depending on the constituent of interest.  A hold time is intended to ensure analysis begins within a certain timeframe that maintains the true representation of the sample and it limits the chemical degradation and biodegradation caused from the natural makeup of the sample.  If analysis is performed past the hold time the analytical data will be flagged with a qualifier to represent the failed quality control for sample integrity.  The best practice is to analyze a sample as soon as possible; the shorter time elapsed between collection and analysis will lead to more reliable results.

Environmental monitoring is important to maintain the health and safety for public use and consumption and to protect natural resources to sustain healthy habitats and ecosystems.  At WETLAB we know our client data is vital to public health, environmental monitoring, and policy.  Therefore, we want to provide critical information to help solve environmental problems.  This is a collaborative effort between the laboratory and our clients, and it begins and ends with sample integrity.  The objective for all stakeholders is to provide data that is accurate, reliable, reproducible, and valid for compliance monitoring.  This comes down to proper sample collection in the correct containers, with sufficient sample volume and preservation, and transported to the laboratory within the analytical hold time.

If sample integrity is compromised between sample collection and analysis there are consequences which can be critical to the client.  Samples received by the laboratory that fail a quality control measure for sample integrity will either be reported with a comment on the analytical report identifying the non-compliance factor or more seriously the samples can be rejected.  The laboratory doesn’t want to process samples that have been damaged or altered in such a way that makes the data not valid for compliance because it can be rejected at the highest level by a regulator.

Our Client Services Department wants successful sampling and data reporting for our clients.  We understand the hard work, time, and resources that go into planning, collecting samples, and transporting them to the lab; therefore, we want to help you before you do this to ensure you have the correct equipment, information, and instructions.  WETLAB is here to serve our clients and adhere to analytical methods and environmental regulations specifically targeting sample integrity.  We extend our expertise out to you to better prepare our clients for high quality, legally defensible data.  Please contact us before any major sampling events or if you have any questions.  We are always happy to help.




Nevada State Public Health Laboratory. Nevada State Public Health Laboratory Chemistry Directory of Services. 16 Feb. 2021, med.unr.edu/nsphl. Accessed 25 Mar. 2021.

U.S. Environmental Protection Agency. (2017).  U.S. EPA Interim Revised NPDES Compliance Inspection Manual, Chapter 5. Office of Enforcement and Compliance Assurance.  EPA Publication Numbr:305-k-17-001. 20 Jan. 2017

“9060 SAMPLES”, Standard Methods For the Examination of Water and Wastewater. DOI: 10.2 105/smww.2882.184