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Importance of Drying Flower Samples Prior to Potency Testing

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 are dried to ensure fast and accurate results for compliance testing.

The moisture content of the hemp sample 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. These composite samples are typically obtained by a sample handler, and they should be dry & slightly brittle before being tested by a High-performance Liquid Chromatography (HPLC) instrument. Instructions on how a sample handler conducts official Hemp Sampling & Collection Procedures are listed with the Texas Department of Agriculture (TDA) [1] and USDA [2].

The USDA-AMS created an easy-to-understand sampling procedure for hemp crop compliance sampling and testing [2]. This method recommends states to use licensed sampling agents, also known as ‘Sample Handlers’, to collect representative samples that reflect the potency of the crop. The Sampler Handlers must collect raw hemp that is actively being cultivated, and those plant samples are very wet when collected.

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 approximately 12% moisture content for HPLC analysis of hemp 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 of how to find the dry weight can be found below:

Fortunately, moisture content tests are complimentary with our potency testing services, and can lend farmers peace of mind; yet many skip this step— which ultimately runs the risk of losing their crop due to ignorance of the crops cannabinoid & moisture profile.

Our goal at Ionization Labs is to make compliance testing easy for cultivators, and sample handlers alike. If you would like to submit your information to receive a sampling kit from Ionization Labs, please complete the form below to have us ship you one of our official sampling kits.

References:

  1. Texas Department of Agriculture, Hemp Sampling and Collection Procedure, Accessed Online September 20, 2021
  2. United States Department of Agriculture, AMS, Laboratory Testing Guidelines U.S. Domestic Hemp Production Program, Hemp Testing Guidelines Issued January 15, 2021, Accessed Online September 20, 2021