Quantitative Analysis of Residual Solvents in Hemp Oil by Full Evaporation Headspace Gas Chromatography/ Mass Spectrometry

Importance of the Topic

Recent changes in legislation and increased consumer use of hemp oil products have highlighted the need to monitor residual solvents from extraction processes. These solvents, if present above allowable limits, pose health risks and undermine product quality. A robust analytical method ensures compliance with state regulations and protects consumer safety.

Objectives and Study Overview

This study evaluates a full evaporation headspace gas chromatography mass spectrometry technique using automated sample introduction to quantify residual solvents in hemp oil. The method aims to meet or exceed the allowable concentration limits defined by the State of California across five solvent categories.

Methodology

Samples of cold pressed hemp oil were weighed directly into 10 mL headspace vials and spiked with known standards to generate five point calibration curves in triplicate. Two calibration ranges were established: low level from 0.005 to 1 ppm for category I and II solvents and a higher range from 1 to 1000 ppm for category III, IV and V solvents. Incubation was performed at 100 degrees Celsius for 15 minutes with orbital agitation. Headspace was sampled and injected in split mode (3 to 1 for low level and 10 to 1 for higher level standards). SIM detection was used for low level analytes and full scan for higher concentrations.

Instrumentation

• Gas Chromatograph Agilent 7890 coupled to 5977B mass selective detector
• GERSTEL MultiPurpose Sampler with headspace option and cooled injection system CIS 4
• Capillary column CP Select 624 CB, 30 m x 0.25 mm id, 1.4 µm film thickness
• Carrier gas helium at 1 mL per minute constant flow
• Oven program: hold at 30 degrees Celsius for 3 minutes then ramp at 15 degrees per minute to 260 degrees Celsius and hold for 5 minutes
• Software control GERSTEL Maestro

Main Results and Discussion

Linearity across all analytes was excellent with an average correlation coefficient of 0.995. Method precision was demonstrated with an average relative standard deviation of 2.56 percent. For category I and II solvents, method reporting limits down to 0.005 ppm were achieved, three orders of magnitude below the action levels, using SIM mode. Category III through V solvents showed reporting limits of 1 to 50 ppm, with satisfactory chromatographic separation and quantitation in full scan mode.

Benefits and Practical Applications

• Minimal sample preparation enhances throughput
• Automated headspace sampling reduces operator error
• Sufficient sensitivity to verify compliance with stringent state limits
• Applicable to quality control of consumer and medicinal cannabis products

Future Trends and Opportunities

Further improvements may include wider use of SIM detection for higher concentration solvents to lower reporting limits and integration with laboratory data systems for high throughput testing. Expanding the method to other cannabis matrices such as extracts, edibles and topicals can broaden its application. Advances in automation and analytics software will continue to enhance accuracy and efficiency.

Conclusion

The full evaporation headspace GC/MS method with GERSTEL automation provides a fast, precise and reliable approach to quantify residual solvents in hemp oil. Its excellent sensitivity, minimal preparation and strong regulatory compliance make it a valuable tool for cannabis product testing laboratories.

References

• [1] Markelov M and Guzowski JP Analytical Chimica Acta 276 1993 235
• [2] California Bureau of Cannabis Control Proposed Text of Regulations July 2018