Introduction

Cannabis and hemp products are becoming much more available for medicinal and recreational use making routine testing for toxic heavy metals much more important.  Advion Interchim Scientific introduces the SOLATION^® ICP-MS for the analysis of heavy metals in cannabis plant and cannabis product samples.  While there are no federal guidelines for heavy metals in cannabis, states where cannabis use and production are legal have adopted exposure limits and QC criteria for Arsenic, Cadmium, Mercury, and Lead based on USP<233>.  Here, we report the results of our sample analysis using these guidelines. 

Methods

Cannabis flower was purchased locally and finely ground for analysis.  Samples are prepared using a microwave digestion system (CEM Mars 6, Matthews, NC).   Method validation for USP<233> is based on accuracy, using spike recoveries, repeatability based on the %RSD of six independently digested replicate, and ruggedness, where those 6 replicates are run a second time by another analyst, another instrument, or on another day.  The spike levels are based on the “action level” defined by the California maximum permitted daily exposure (PDE) limits as a guide:  Lead 0.5 µg/g, Arsenic and Cadmium 0.2 µg/g, and Mercury 0.1 µg/g are used to define the 100% spike level.  Samples are also spiked at 50% and 150% of the action level. 

Preliminary Data

For digestion, 0.5 g (+/- 0.002g) of sample is treated with 9mL conc. HNO3 and 1mL conc. HCl in a microwave vessel and allowed to react for 15 minutes prior to being capped.  The vessels are loaded onto the carousel in the microwave and the “one touch” cannabis method, supplied by CEM, is used.  Samples are brought to 200°C in 30 minutes, held there for 10 minutes, and allowed to cool.  The result is a clear, particle free solution. The SOLATION^® ICP-MS was used to analyze the samples for As, Cd, Hg, and Pb after digestion and dilution.  The results show that the SOLATION^® ICP-MS was able to produce accurate values as measured by the spike recoveries which were well within the 70-150% range.  The results from the 6 independent digests were within the defined limit of 20% RSD.  Repeat analysis of the 6 digests on a separate day showed good agreement with the initial results and were within the 25% RSD spec. defined by USP<233>.  Overall results show that the SOLATION^® ICP-MS is an effective instrument for the analysis of cannabis and hemp samples.

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