With official hemp sampling going into high gear during this peak harvest season, freshly trimmed hemp samples are being submitted to potency testing labs at an increased rate. Compliance testing is at the top of every hemp cultivator's mind during harvest season. Therefore, it is vital that flower or biomass samples moisture content is tracked to ensure accurate results for compliance testing.
The moisture content in hemp samples impacts the cannabinoid concentration present in the plant. Testing must be done on plants that display 5-12% moisture content to ensure accurate analysis. With the proper moisture content, hemp testing labs are able to perform full cannabinoid analyses on a dry weight basis, meaning the percentage of cannabinoids after excluding moisture in the sample.
Moisture content is typically expressed as the ratio of the amount of water in a given sample to the amount of dry solid plant material. Composite samples that include buds, leaves, and biomass are the most common official samples provided to laboratories. These composite samples, obtained by a sample handler, should be dry and slightly brittle before being tested by a high performance liquid chromatography (HPLC) instrument. Instructions on how a sample handler should conduct official Hemp Sampling & Collection Procedures are listed with the Texas Department of Agriculture (TDA) [1] and USDA [2].
The USDA’s Agricultural Marketing Service (AMS) created an easy-to-understand sampling procedure for hemp crop compliance sampling and testing [3]. This method requires states to use licensed sampling agents, also known as sample handlers, to collect representative samples that reflect the potency of the crop. The sampling agents must collect raw hemp that is actively being cultivated.
Sampling is done to hemp prior to harvest, and cultivating licensees are instructed to send the samples directly to the laboratory for testing. Freshly trimmed raw hemp maintains a moisture content between 60-75% water by weight. Excess moisture content greater than 15% can skew testing results, and overly dry samples can alter the chemical makeup of the plant leading to an inaccurate potency result.
For this reason, the USDA has recommended hemp samples to contain approximately 12% moisture content for HPLC analysis of cannabinoid potency. In addition, sample results must be presented on a dry weight basis, meaning that the moisture content at the time of testing must be subtracted from the weight of sample prior to calculating the cannabinoid content in the biomass. The equation to determine dry weight can be found below:
Moisture content is determined through drying balances called moisture analyzers. During the process, a wet sample is placed into a pan on the balance. A drying program is then initiated which activates a heating source and begins the drying procedure. During the process, the instrument tracks the weight loss of the sample as the moisture evaporates. Once complete, the moisture analyzer provides moisture content as a percentage using the equation above.
Figure 1. Example of a Moisture Analyzer (Retrieved from: Sartorius)
Fortunately, moisture content tests are conducted with every official hemp flower potency test at Ionization Labs. This allows the lab to provide cannabinoid concentration on a dry weight basis for flower samples.
Our goal at Ionization Labs is to make compliance testing easy for cultivators and sample handlers alike. If you would like to receive a sampling kit from Ionization Labs, please email labservices@ionizationlabs.com or call 737-231-0772 to have us ship you one of our official sampling kits.
References:
- Texas Department of Agriculture, Hemp Sampling and Collection Procedure, Accessed Online September 20, 2021
- United States Department of Agriculture, AMS, Sampling Guidelines for Hemp U.S. Domestic Hemp Production Program, Issued January 15, 2021, Accessed Online September 20, 2021 https://www.ams.usda.gov/sites/default/files/media/SamplingGuidelinesforHemp.pdf
- United States Department of Agriculture, AMS, Laboratory Testing Guidelines U.S. Domestic Hemp Production Program, Issued January 15, 2021, Accessed Online September 20, 2021 https://www.ams.usda.gov/sites/default/files/media/TestingGuidelinesforHemp.pdf
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