Quantitative Analysis of Cannabis and Hemp with HR ICP-OES Application Note · PlasmaQuant 9100 Elite

Introduction

Cannabis and hemp are amongst the oldest crop plants with a history reaching back several millennia. Its first and main use was as textile fiber, which is still its main usage in textiles, ropes, insulation and waterproofing. A second use of cannabis and hemp is the field of food and drug for its nutritional value as well as its medical and recreational effects. Since the beginning of its legalization in 2014 for medical and recreational use, the investigation of toxic trace elements gained more interest to ensure the safety of cannabis products similar to other food and drug products. Since a global guideline for the analysis of hemp and cannabis products, dedicated for the consumption by humans is not yet existent, individual recommendations were created within the regions that legalized the use of these products. For instance, the California Bureau of Cannabis Control states, that laboratories shall investigate residual solvents and processing chemicals; pesticides; microbiological impurities; mycotoxins; water activity and moisture content; filth and foreign material and heavy metals in cannabis and its related products. Often local authorities define elements to be tested according to regulations of the FDA and the US EPA. In USP Chapter <232>, the elements As, Pb, Hg and Cd are classified to be the most toxic in pharmaceutical products. Hence, these “toxic four” are routinely analyzed in cannabis samples as well.

The determination of trace metals in plant materials is routinely done with optical emission spectroscopy with inductively coupled plasma (ICP-OES). However, the typically low trace levels of As, Pb, Hg and Cd require a high sensitivity of the analyzer. In this regard, common ICP-OES instrumentation often lacks thedetection power to securely analyze trace levels in the sub mg/kg range. Therefore, routine labs are often forced to employ the more sensitive ICP-MS technology or to use sensitivity enhancing accessories like an ultrasonic nebulizer (USN) in combination with ICP-OES.

In contrast to the above-mentioned solutions, the method described herein employs a high-resolution ARRAY ICP-OES, the PlasmaQuant 9100 Elite, which is able to achieve limits of detection in the sub μg/L range in a typical measurement solution of plant materials. Due to the long analytical zone of its plasma in combination with a counter gas technology and minimal loss of light throughout the optical path, the PlasmaQuant 9100 Elite offers a sensitivity which makes the use of complex and expensive sample feed accessories (such as USN) obsolete.