Screening for More than 1,000 Pesticides and Environmental Contaminants in Cannabis by GC/Q-TOF.

A method has been developed to screen cannabis extracts for more than 1,000 pesticides and environmental pollutants using a gas chromatograph coupled to a high-resolution accurate mass quadrupole time-of-flight mass spectrometer (GC/Q-TOF). An extraction procedure was developed using acetonitrile with solid phase extraction cleanup. Before analysis, extracts were diluted 125:1 with solvent. Two data mining approaches were used together with a retention-time-locked Personal Compound Database and Library (PCDL) containing high-resolution accurate mass spectra for pesticides and other environmental pollutants. (1) A Find-by-Fragments (FbF) software tool extracts several characteristic exact mass ions within a small retention time window where the compound elutes. For each compound in the PCDL, the software evaluates the peak shape and retention time of each ion as well as the monoisotopic exact mass, ion ratios, and other factors to decide if the compound is present or not. (2) A separate approach used Unknowns Analysis (UA) software with a peak-finding algorithm called SureMass to deconvolute peaks in the chromatogram. The accurate mass spectra were searched against the PCDL using spectral matching and retention time as filters. A subset PCDL was generated containing only pesticides that are most likely to be found on foods in the US. With about 250 compounds in the smaller PCDL, there were fewer hits for non-pesticides, and data review was much faster. Organically grown cannabis was used for method development. Twenty-one confiscated cannabis samples were analyzed and ten were found to have no detectable pesticides. The remaining 11 samples had at least one pesticide and one sample had seven detectable residues. Quantitative analysis was run on the confiscated samples for a subset of the pesticides found by screening. Two cannabis samples had residues of carbaryl and malathion that were estimated to be about 10 times greater than the highest US Environmental Protection Agency tolerance set for food and about 4,000 times greater than the Canadian maximum residue limits for dried cannabis flower.

High-resolution gas chromatography/mass spectrometry method for characterization and quantitative analysis of ginkgolic acids in Ginkgo biloba plants, extracts, and dietary supplements.

A high-resolution gas chromatography/mass spectrometry (GC/MS) with selected ion monitor method focusing on the characterization and quantitative analysis of ginkgolic acids (GAs) in Ginkgo biloba L. plant materials, extracts, and commercial products was developed and validated. The method involved sample extraction with (1:1) methanol and 10% formic acid, liquid-liquid extraction with n-hexane, and derivatization with trimethylsulfonium hydroxide (TMSH). Separation of two saturated (C13:0 and C15:0) and six unsaturated ginkgolic acid methyl esters with different positional double bonds (C15:1 Δ8 and Δ10, C17:1 Δ8, Δ10, and Δ12, and C17:2) was achieved on a very polar (88% cyanopropyl) aryl-polysiloxane HP-88 capillary GC column. The double bond positions in the GAs were determined by ozonolysis. The developed GC/MS method was validated according to ICH guidelines, and the quantitation results were verified by comparison with a standard high-performance liquid chromatography method. Nineteen G. biloba authenticated and commercial plant samples and 21 dietary supplements purported to contain G. biloba leaf extracts were analyzed. Finally, the presence of the marker compounds, terpene trilactones and flavonol glycosides for Ginkgo biloba in the dietary supplements was determined by UHPLC/MS and used to confirm the presence of G. biloba leaf extracts in all of the botanical dietary supplements.

Evaluation of a new column backflushing set-up in the gas chromatographic-tandem mass spectrometric analysis of pesticide residues in dietary supplements.

This study evaluated the use of a new concurrent backflushing set-up in the multiresidue analysis of pesticides in dietary supplement matrices using gas chromatography-tandem mass spectrometry (GC-MS/MS). The backflushing configuration employed a purged union installed between a short, 5-m long capillary column and a 15-m analytical column of the same column diameter (0.25 mm i.d.), stationary phase type (HP-5MS UI) and film thickness (0.25 µm). This set-up is more time- and cost-effective than the use of post-run or mid-column backflushing configurations because the backflushing starts as soon as the last analyte elutes from the short column, thus preventing the less volatile matrix components from reaching the longer analytical column and MS source. As opposed to the analysis without backflushing, the column does not need to be kept at a higher temperature for an extended period of time, resulting in about 50% increased sample throughput on the instrument (a run time of 20 min). Optimization of the GC-MS/MS method is discussed in detail, especially when it comes to the selection of MS/MS transitions, optimization of injection conditions using a programmable temperature vaporizer (PTV) inlet in solvent vent mode, and optimization of the backflushing parameters. The optimized method showed very good long-term performance, which was evaluated in a 2.5-day uninterrupted sequence (without any system maintenance) of repeated injections of various dietary supplement extracts containing over one hundred pesticides, mainly those with limits set for herbal drugs and preparations by the U.S. and European Pharmacopoeias.

Simultaneous screening and target analytical approach by gas chromatography-quadrupole-mass spectrometry for pesticide residues in fruits and vegetables.

A full-scan GC/quadrupole/MS method has been developed to perform large-scale screenings of pesticides and simultaneous quantification of 95 target compounds in a single run of 21 min. The screening method was performed by using a deconvolution of the spectrum of the full-scan data files acquired under a retention time locked method. The identification performance of the screening method was evaluated in eight different food matrixes at three different concentrations. The system was equipped with a programmable temperature vaporizing inlet, allowing 10 microL injections. The LOQ in the full-scan mode and linearity were studied for four different matrixes. Correlation coefficients > 0.99 were achieved in all cases, and the LOD was < 20 microg/kg for 80% of the studied pesticides. Maintenance of the system was reduced by the use of a QuickSwap device that provided backflush capabilities by reversing column flow immediately after elution of the last compound of interest. The combined screening and target method was used in the analysis of more than 100 food samples, including a carrot sample from the European Proficiency Test FV 10, with good results.