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.

Application of GC/Q-ToF Combined with Advanced Data Mining and Chemometric Tools in the Characterization and Quality Control of Bay Leaves.

Correct identification of the true bay leaf (Laurus nobilis) and its substitutes is important not only for the quality control of the products, but also for the safety of the consumers. L. nobilis is often substituted or confused with other species, such as Cinnamomum tamala, Pimenta racemosa, Syzygium polyanthum, and Umbellularia californica. In the present study, the potential of gas chromatography combined with quadrupole time-of-flight mass spectrometry for the profiling of various bay leaf products was evaluated for the first time. Thirty-nine authenticated samples representing the true bay leaf and the four commonly substituted species were analyzed. An automatic feature extraction algorithm was applied for data mining and pretreatment in order to identify the most characteristic compounds representing different bay leaf groups. This set of data was employed to construct a sample class prediction model based on stepwise reduction of data dimensionality followed by principal component analysis and partial least squares discriminant analysis. The statistical model, with demonstrated excellent accuracies in recognition and prediction abilities, enabled the correct classification of commercial samples including complex mixtures and essential oils. In addition, in-house developed personal compound database and library with retention time locking offered the advantage of combining retention time matching with accurate mass matching, resulting in high confidence of compound identification for each bay leaf subgroup. At least three marker compounds were identified for each bay leaf species that could be used to discriminate among them.

A comparison of sorptive extraction techniques coupled to a new quantitative, sensitive, high throughput GC-MS/MS method for methoxypyrazine analysis in wine.

Methoxypyrazines are volatile compounds found in plants, microbes, and insects that have potent vegetal and earthy aromas. With sensory detection thresholds in the low ng L(-1) range, modest concentrations of these compounds can profoundly impact the aroma quality of foods and beverages, and high levels can lead to consumer rejection. The wine industry routinely analyzes the most prevalent methoxypyrazine, 2-isobutyl-3-methoxypyrazine (IBMP), to aid in harvest decisions, since concentrations decrease during berry ripening. In addition to IBMP, three other methoxypyrazines IPMP (2-isopropyl-3-methoxypyrazine), SBMP (2-sec-butyl-3-methoxypyrazine), and EMP (2-ethyl-3-methoxypyrazine) have been identified in grapes and/or wine and can impact aroma quality. Despite their routine analysis in the wine industry (mostly IBMP), accurate methoxypyrazine quantitation is hindered by two major challenges: sensitivity and resolution. With extremely low sensory detection thresholds (~8-15 ng L(-1) in wine for IBMP), highly sensitive analytical methods to quantify methoxypyrazines at trace levels are necessary. Here we were able to achieve resolution of IBMP as well as IPMP, EMP, and SBMP from co-eluting compounds using one-dimensional chromatography coupled to positive chemical ionization tandem mass spectrometry. Three extraction techniques HS-SPME (headspace-solid phase microextraction), SBSE (stirbar sorptive extraction), and HSSE (headspace sorptive extraction) were validated and compared. A 30 min extraction time was used for HS-SPME and SBSE extraction techniques, while 120 min was necessary to achieve sufficient sensitivity for HSSE extractions. All extraction methods have limits of quantitation (LOQ) at or below 1 ng L(-1) for all four methoxypyrazines analyzed, i.e., LOQ's at or below reported sensory detection limits in wine. The method is high throughput, with resolution of all compounds possible with a relatively rapid 27 min GC oven program.

Evaluation of GC-ICP-MS/MS as a New Strategy for Specific Heteroatom Detection of Phosphorus, Sulfur, and Chlorine Determination in Foods.

For the first time in the literature, application of a GC-ICP-MS/MS method for the selective and sensitive detection of specific heteroatoms of phosphorus, sulfur, and chlorine has been accomplished. As a proof of concept, organophosphorus, organosulfur, and organochlorine pesticides in various food matrices have been studied. For the detection of organophosphorus and organosulfur pesticides, oxygen was used in the collision reaction cell (CRC) to convert P (m/z 31) to PO(+) (m/z 47) and S (m/z 32) to SO(+) (m/z 48). Similarly, ClH2(+) (m/z 37) was monitored after the reaction of Cl (m/z 35) with hydrogen in the CRC for the determination of organochlorine pesticides. Real food samples (baby food purees, fresh vegetables, loose tea) were screened for their pesticide content, following preparation of triplicate extracts using QuEChERS (quick, easy, cheap, effective, rugged, and safe). Excellent linearity with correlation coefficients R ≥ 0.997 was achieved, and the lowest detection limits obtained for the organophosphorus, organosulfur, and organochlorine pesticides were 0.0005, 0.675, and 0.144 µg/kg, respectively.

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.

An integrated approach utilising chemometrics and GC/MS for classification of chamomile flowers, essential oils and commercial products.

As part of an ongoing research program on authentication, safety and biological evaluation of phytochemicals and dietary supplements, an in-depth chemical investigation of different types of chamomile was performed. A collection of chamomile samples including authenticated plants, commercial products and essential oils was analysed by GC/MS. Twenty-seven authenticated plant samples representing three types of chamomile, viz. German chamomile, Roman chamomile and Juhua were analysed. This set of data was employed to construct a sample class prediction (SCP) model based on stepwise reduction of data dimensionality followed by principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). The model was cross-validated with samples including authenticated plants and commercial products. The model demonstrated 100.0% accuracy for both recognition and prediction abilities. In addition, 35 commercial products and 11 essential oils purported to contain chamomile were subsequently predicted by the validated PLS-DA model. Furthermore, tentative identification of the marker compounds correlated with different types of chamomile was explored.

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.