New Guide for Analysis of Residual Solvents in Liquid Samples Containing Terpenes by a Heat Sensitive Method Using Head-Space Gas Chromatography (HS-GC)
1. Scope
This guide is for the testing of residual solvents in liquid samples that contain terpenes. The guide utilizes low heat parameters for headspace-gas chromatography (HS-GC).
This guide can be used when analyzing various liquid samples for residual solvents. Liquid samples could include in-process terpene blends, isolated liquid terpenes, finished product essential oils, liquid ingredients containing terpenes and other chemical classes such as terpenoids, esters, and aldehydes, among others.
Note: For ease of comprehension, this guide will use the term “terpenes” as an umbrella word to encompass all chemical compounds that are volatile liquids that impart an aroma or taste. These can include terpenes, terpenoids, esters, aldehydes, thiols, and more.
This guide can be used when analyzing liquid samples containing either naturally extracted or synthetically created terpenes for residual solvents. This guide can be used regardless of whether the product or material analyzed contains cannabinoids.
Residual solvents can also be a contaminant in cannabinoid material, regardless of the presence of terpenes. It is suggested that the user of this guide tests all of the individual components of a product containing cannabinoids for residual solvents to understand the source of the residual solvents.
This guide may be used in conjunction with mass spectrometry (MS), flame ionization (FID), or other detector types as implemented and validated by the user of this standard.
This guide does not cover the prevention of interferences between terpenes and residual solvent peaks, which can occur depending on the detector type and method parameters the user of this standard employs.
This guide is applicable to volatile analytes regulated as residual solvents. It is the responsibility of the user of this standard to understand what analytes are regulated under the appropriate AHJ.
Note: All analytes tested by this guide must be demonstrated and appropriately validated by the user of this document to be performed on the user’s specific instrument.
This guide can be used as the primary analysis for residual solvents or as a secondary analysis to verify a residual solvent result above the AHJ set action limit. It is the responsibility of the user of this standard to know the action limits associated with each analyte set by the appropriate AHJ.
This guide does not discuss the procedure to calibrate the instrument for residual solvent quantitation.
This guide discusses the sample preparations for liquid samples that are prepared volumetrically.
This guide is not the only method that can be employed to reduce false positive residual solvent results. Interaction with oxygen has also been demonstrated to cause terpenes to undergo chemical reactions that produce residual solvents. Reducing or eliminating the oxygen in the sample may be another method a user can employ. This guide will only discuss the method of reducing heat exposure during the analysis of the sample.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
This guide is for the testing of residual solvents in liquid samples containing terpenes using headspace-gas chromatography (HS-GC) with either a mass spectrometer or flame ionization detectors (MS or FID). Both MS and FID are being used with HS-GC in cannabis and hemp testing labs, and this standard was developed to be applicable to HS-GC independent of (and adaptable to) the type of detector used. While HS-GC is already commonly used to analyze volatile materials for residual solvents, the temperature settings of standard methods have been shown to artificially increase the levels of the residual solvents. Heat exposure can cause volatile compounds, such as terpenes and terpenoids, to undergo chemical degradation and produce residual solvents. Subsequently, the levels of residual solvents detected by the instrument are not indicative of the levels in the starting material. This guide outlines the settings laboratories can program into the HS-GC parameters to reduce the time the liquid sample is exposed to elevated temperatures, reducing false positives. This guide may be used to analyze a variety of residual solvents and can be used as a primary analysis method or a secondary method to verify results.
This guide does not go into how to calibrate the instrument or which residual solvents to analyze. As such, this guide is intended to be used in conjunction with Work Item WK87437 Standard Test Method for Analysis of Residual Solvents in Cannabis Extracts using Head-Space Gas Chromatography (HS-GC). When the work item is published, this guide will replace DXXXX with the applicable document number.
This guide does not propose solutions for other factors of false positive results, such as overlapping peaks or oxidation, although these methods may produce similar results as this guide. Terpene peaks may overlap with residual solvent peaks. Additionally, oxidation reactions with terpenes and terpenoids have also been shown to create residual solvents. This guide will not cover methods to reduce oxidation of the liquid sample.
This guide only covers the preparation of liquid samples, which can be measured volumetrically. This guide is not solely applicable to terpenes and can cover other molecular compounds such as esters, alcohols, ketones, thiols, and more. For ease of reading, “terpenes” will be used as an umbrella term throughout the guide. This guide can be utilized with samples with or without cannabinoids as long as the liquid is fluid enough to be measured volumetrically.
WK89949 - New Guide for Analysis of Residual Solvents in Liquid Samples Containing Terpenes by a Heat Sensitive Method Using Head-Space Gas Chromatography (HS-GC) | ASTM
