RESIDUAL SOLVENTS

INTRODUCTION

An independent blind study was conducted by PhytoVista laboratories for The Centre for Medical Cannabis (CMC) involving 30 major retail CBD oil brands in Europe. One of their tasks was to determine whether residual solvents used in the CBD extraction step were present in end products that are sold to consumers. The results of the study revealed that one product contained residual cyclohexane, seven products dichloromethane and one product ethanol. Even though the levels were not alarmingly high, they still exceeded food limit safety levels.

TASK

Develop a method for the determination of residual solvents with boiling points up to 140 °C.

RESULT

The method was developed by using gas chromatography coupled with a flame ionization detector. Headspace sampling technique was used in order to minimize the matrix effects, since only a volatile phase of the sample is injected onto the chromatographic column. Figure 1 (chromatogram) shows the resolution of 12 selected residual solvents. They were prepared in the following concentrations (expressed as ppm (part per million) with respect to the sample concentration):

  • Methanol 300 ppm
  • Ethanol 500 ppm
  • Diethyl ether 500 ppm
  • Acetone 500 ppm
  • Acetonitrile 41 ppm
  • Dichloromethane 60 ppm
  • n-Hexane 29 ppm
  • Diisopropyl ether 500 ppm
  • Ethyl acetate 500 ppm
  • Tetrahydrofuran 72 ppm
  • Cyclohexane 388 ppm
  • Toluene 89 ppm

 

The limit of quantification of the method varies among solvents, since it depends upon the response factor of the individual solvent. However, in general even few ppms of individual solvent can be quantified.

Figure 1. Separation of twelve selected residual solvents.

GOOD TO KNOW: Since our laboratory is equipped with a mass-selective detector we can also firstly identify all residual solvents that are present in various samples (even traces of solvents can be detected). We can then further accurately quantify them in the second step by using a separate method. Our analysis of residual solvents is not limited just to above presented solvents, but we can also meet needs of each individual client and include other solvents as well. 

CONCLUSION:

Our laboratory can accurately determine the content of residual solvents in various cannabis products. If you are not sure which solvents are present in your sample, we can also reliably identify them by use of mass-selective detector and then perform further quantification.