QuEChERSER sample preparation and analysis of pesticides in hemp products by ITSP+LPGC- and back-flushed UHPLC- comparing MS/MS with Orbitrap detection

LIGHTFIELD, ALAN R.; MICHLIG, NICOLÁS; REPETTI, MARÍA R.; LEHOTAY, STEVEN J.

Granada

Workshop; 13th European Pesticide Residues Workshop; 2020

Universidad de Almería

For legal possession and use throughout the USA, hemp and hemp products must have THC concentration < 0.3%. The agricultural, food, medical, and other communities have started to study and market hemp due to its high content of cannabinoids, protein, fiber and other ingredients. As with other agricultural commodities, pesticides may be used during production and a large suite of residues need to be monitored in hemp. The aim of this work was to evaluate and validate the newly developed QuEChERSER (mega/mini-)method [1] to determine pesticide residues in hemp plants, flowers, powders, oils, edibles, and animal feed pellets using ultrahigh-performance liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS) with column back-flushing and instrument-top sample preparation + low-pressure gas chromatography (ITSP+LPGC-MS/MS). Orbital ion trap (Orbitrap) detection was compared with triple quadrupole MS/MS in both GC- and LC- analyses. QuEChERSER involves extraction of 2 g sample with 10 mL 4/1 (v/v) acetonitrile/water by shaking, followed by centrifugation. For UHPLC, a 200 μL portion is taken and solvent exchanged into initial mobile phase conditions and ultra-centrifuged prior to analysis. For ITSP+LPGC, the remaining extract is partitioned with 4/1 (w/w) anh. MgSO4/NaCl and 1 mL is taken for automatic mini-SPE cleanup and 10 min analyses in parallel with 10 min UHPLC analyses. In the latter case, the column is back-flushed with 1/1 (v/v) methanol/acetonitrile mobile phase for 3 min between each injection to keep the system clean and avoid ghost peaks. In MS/MS, 107 pesticides and metabolites were monitored with choices and levels set in accordance with regulations from California, Nevada, Oregon, and Canada. A multi-level validation approach was conducted in which pesticides were grouped into 3 categories (low, medium and high) with 0.5X, 1X, and 10X spiking levels for each category over multiple days for each matrix type. Preliminary MS/MS results show that despite hemp being a very complex matrix, 70-120% recoveries with RSDs