Application and evaluation of Standard-Addition Isotope-Dilution Mass Spectrometry (SA-IDMS) and online solid phase extraction (SPE) to pesticide analysis in cannabis products

Abstract

The aim of this master thesis was the establishment of an Isotopic Dilution Mass Spectrometry (IDMS) standard addition (SA) method and its evaluation in combination with matrix effects, especially cannabis. With the growing number of states that legalize the usage of cannabis, the need for analysis and quality control arose as well. The SA-IDMS works basically like a classic standard addition in the terms of sample preparation with the exception that isotope standard material is additionally added in equivalent amounts to the rising amounts of the added reference material. In this work the SA-IDMS method was adapted and tested for the analysis of pesticides within cannabis. Furthermore, it was investigated whether the analysis benefits from online or offline SPE as an additional sample preparation. The SA-IDMS method was first tested with the pure mixtures of pesticides, melamine and cyanuric acid. Melamine and cyanuric acid were mixed with infant formula powder (matrix) and extracted. This showed quantitative data in the correct magnitude (ng/g sample), but it was not reproducible at first, as the matrix appeared to be quite disruptive. The addition of SPE to the analysis of a fresh sample showed better results, as did the pure solutions without matrix. Pesticide samples were then prepared by adding reference material to cannabis tea and subsequent extraction with organic solvents for measurement by SA-IDMS. Here the method yielded accurate results even without online and offline SPE implementation, with the only caveat that the isotopic material should match the analyte exactly. The results suggest that the use of SA-IDMS is possible and could help to deal with matrix effects, with the only downside of quite an intensive sample preparation for large quantities. However, for small and problematic sample numbers this method may be the preferred solution. SPE can help further to reduce the contamination of the instrument by the matrix and further improve accuracy without additional analysis time when SPE is performed online.