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: Importance of Proper Sample Handling

WETLAB is a certified environmental testing 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 or exceed 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.

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

Sample integrity begins with sample collection.  Start with a sampling plan: know the test parameters required from your permit to ensure you have the correct sample bottle(s). Follow the regulatory requirements to know where you will be collecting samples, how you will collect them (grab or composite), and how and when samples will be stored and transported to the lab.

Sample labels are extremely important for traceability.  Completely fill out the date and time of sample collection, site of collection, initials of sampler, if sample is filtered, 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. Consider sealing the samples in a plastic bag or bucket with an airtight lid.  Begin the chilling process immediately by placing samples on ice, blue-ice, or ice packs and place samples in a dark location, preferably a cooler, to minimize exposure to light. 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 the duration of transit.

Provide a completed Chain of Custody (COC) document 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.  WETLAB’s digital COC can be found online at https://www.wetlaboratory.com/forms/

Sample bottles are provided by the laboratory at no charge, making it easy for you to ensure you are 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 the testing requirements outlined in your permit. The correct bottles will contain the correct preservative and allow for the proper sample volume. The containers are made of a material that is chemically resistant to pollutants, 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 glass or plastic, clear or opaque, 500ml bottles to 1-liter cubitainer.  When collecting the sample, place the lid with the top side down, as not to contaminate the side that may be in contact with the sample.  Do not rinse out the bottle because there may be a preservative in it. Fill the bottle with the amount indicated on the instructions provided with the bottle kit. Do not overfill the bottles to avoid removal of 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 material 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 maintain it as representative of the material 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 a 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 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 in a bottle kit order.  The one factor of sample preservation that is specifically the client’s responsibility is cooling the samples. Temperature guidelines are consistent for all sample matrices.  Samples should be received on ice, and if samples are received more than one day after sampling, they should be received at less than 6 degrees Celsius (42 degrees Fahrenheit). Failure to meet these guidelines may result in samples marked as “non-compliant.”

The hold time for a test begins at the time of collection. Therefore, it is important to know how long it will take for a sample to be received by the laboratory once collected since tests have varying 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. It limits potential 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.


If you have any questions regarding sample integrity and proper sample handling, please contact us today, https://www.wetlaboratory.com/contact/.