Hemp is a crop with various therapeutic benefits, helping people curb illnesses and diseases for thousands of years.
It has the potential to be used as a renewable and sustainable resource for a variety of applications as diverse as building materials, clothing, and plastics. But, until December of 2018, hemp production was illegal in the United States.
The 2018 Farm Bill legalized the cultivation of hemp in the US, allowing states to implement their own additional varying degrees of restrictions and testing guidelines.
Under FDA regulations, the most important and known provision is that the plant material must contain a Total THC of less than 0.3%.
Unlike the marijuana plant, which often contains high THC levels, hemp flower should have a total THC concentration of below 0.3% to be legally processed and sold in the United States. That is why the USDA requires a credible and accurate analysis of THC concentrations through strict testing requirements.
There may be some obstacles along the way, but testing helps hemp growers stay in compliance. By utilizing hemp testing, cultivators can better understand the growth patterns of different strains to harvest peak cannabidiol (CBD) levels, and other valuable compounds, before tipping the scales with too much THC.
Below are the various testing methods and equipment used by laboratories for compliance testing:
Hemp plants naturally produce cannabinoids that determine the overall effect and strength of the plant material. Hemp and cannabis products are widely used to treat diseases or alleviate symptoms, so understanding the potency of a hemp batch is fundamental.
Cannabinoid testing looks at the total amount of cannabinoid content of all cannabinoids present in the sample. This includes tetrahydrocannabinol (THC), cannabidiol (CBD), cannabigerol (CBG), tetrahydrocannabivarin (THCV), and many more.
This test is typically performed by liquid chromatography with UV detectors to determine the amounts of major cannabinoids. Most accredited hemp testing laboratories use high-performance liquid chromatography (HPLC), the standard for analyzing cannabinoid profiles.
Analysis of minor or trace cannabinoids is becoming more common with mass spectrometry, while FTIR spectroscopy is often used to test the potency of oils, crude extracts, and distillates in production and manufacturing environments.
Terpenes exist in both hemp and marijuana plants, and the potency of every hemp batch differs depending on soil type, climate, time of harvest, and age of the crop.
Terpenes work together with cannabinoids, which leads to the entire therapeutic profile of the plant. This theory is known as the “entourage effect,” which means that cannabinoids and terpenes interact to intensify each other’s benefits and counteract potential side effects. Together, two compounds may also produce an effect not seen from either, when taken individually.
The equipment needed for analyzing terpene profiles is a GC instrument with a headspace autosampler and an appropriate spectral library. Every instrument for residual solvent testing, which is a test required by most states, can also be used for a terpene profile analysis.
Most states do not require this test, but it is highly recommended.
Hemp extraction to produce materials for oils, edibles, and other products often utilize solvents including propane, butane, propane, acetone, and isopropanol. These solvents may be harmful, so they must fall below a specific and safe threshold in the final product.
The hemp industry aims to completely avoid these toxic solvents and, instead, employ supercritical carbon dioxide, ethanol, or water in extraction procedures.
Residual solvent testing requires gas chromatography (GC). A small amount of extract is placed into a vial and heated to mimic the natural evaporation process. The evaporation of the solvents from the sample is often referred to as the “headspace.”
The headspace is extracted with a syringe and placed in the injection port of the GC. This method is known as the full-evaporated technique (FET).
The best choice for this test is a GCMS instrument with a headspace autosampler, which can also be used for pesticide and terpene profile analysis.
Pesticides help hemp growers avoid the infestation of their crops by pests and disease-ridden insects. However, studies have shown that pesticide residues on hemp can pose significant risks upon consumption. It is essential for hemp growers to manage their pest infestations while being mindful of pesticide use.
Unregulated pesticides sprayed on hemp plants can transfer to the human body during inhalation or ingestion, posing severe health risks including liver damage, weakened muscle function, and cancer.
Click here to view the EPA-approved list of pesticides that can be used on hemp.
Pesticide testing is one of the more complex analyses, using two different instruments depending on the state’s requirements. For most pesticides, liquid chromatography-mass spectrometry (LCMS) is most suitable and operates similarly with HPLC. However, LCMS requires a different detector and sample preparation.
Some pesticides do not ionize well with an LCMS. In this case, use a gas chromatography-mass spectrometry (GCMS) instrument. The same principles of HPLC apply: injecting a sample, separating it on a column, and detecting it with a detector.
The optimal choice for this test is an LC-MS/MS system or HPLC system with a triple quadrupole mass spectrometer, which provides low detection limits and high sensitivity levels.
Some states require moisture content and water activity testing. Moisture content data allows product manufacturers and extractors to know how much of the hemp biomass is usable compounds.
Dry hemp flowers typically have a moisture content of 5% to 12%. Moisture content above 12% has the potential to start growing mold. If it has less than a 5% moisture content, the plant material will adopt a dust-like texture.
Read more on how to properly store and package a dry hemp flower to avoid contamination.
The best way to test the moisture content of a hemp product is using the thermogravimetric method with a moisture balance instrument.
The process involves placing the sample of hemp into the sample chamber for an initial reading. The moisture balance instrument will start to heat up until the moisture is evaporated out of the sample, which leads to the final reading.
A final reading is conducted to determine the percent weight of moisture in the original sample.
Growers can prevent mold in dry flowers by monitoring water activity (aW). While the moisture content is the total amount of water in the sample, water activity is the residue water that may produce mold.
Some states recommend checking moisture content, while other states recommend monitoring water activity.
Heavy metals are considered to be toxic and can enter hemp plants from contaminated soil. Heavy metals are a group of hazardous metals consisting of cadmium, lead, mercury, and arsenic. Farmers are required to ensure that their samples meet the allowable concentration levels for the four hazardous metals.
Heavy metal testing requires inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS analyzes different masses of each element to determine which metals are present in a sample and at what concentrations.
Hemp plants can be contaminated with microorganisms such as bacteria, mold, yeast, and mildew.
Bacteria such as Escherichia coli and Salmonella and fungal toxins, such as mycotoxins and aflatoxins can cause severe illnesses and allergic reactions when ingested. Most states require hemp testing labs to analyze samples for any microbial or fungal growth.
Microbial testing needs an LCMS to identify strains of mycotoxins. However, determining the amount of microorganisms can be challenging.
This testing can be done through enzyme-linked immunosorbent assay (ELISA), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), or quantitative polymerase chain reaction (qPCR).
For mycotoxin analysis, a high-sensitivity LC-MS/MS instrument is needed. In addition to the standard LC, using an MS/MS selective detector allows for detection levels up to 1000 times higher than a conventional LC-UV instrument.
Hemp testing ensures quality assurance and quality control. Hemp growers benefit from testing, whether for meeting state compliance or certifying a product. Lab testing services can eliminate various risks and ensure the delivery of a final quality product free from contaminants.
Are you seeking accuracy and validation in your test results? Rely on us at Zera Hemp Labs and we’ll take care of it. Send us your hemp samples!