Philip L. Wylie

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.

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.

High-Throughput, Sub ng/L Analysis of Haloanisoles in Wines Using HS-SPME with GC-Triple Quadrupole MS

Haloanisole contamination causes development of “cork taint,” a musty off-aroma in affected wines. Cork taint results in significant economic loss for the wine and allied industries every year, therefore extensive quality-control procedures have been established at wineries and cork production facilities to monitor levels of haloanisoles in cork products. Because of the extremely low human sensory thresholds for these compounds (~1 to 4 ng/L for 2,4,6-trichloroanisole in wine), highly sensitive analytical methods are needed to detect the haloanisoles at threshold concentrations or lower. We present a method for the simultaneous analysis of four haloanisoles in wine—2,4,6-trichloroanisole (TCA); 2,3,4,6-tetrachloroanisole (TeCA); 2,3,4,5,6-pentachloroanisole (PCA); and 2,4,6-tribromoanisole (TBA)—that have been frequently associated with cork taint aromas in wines. Headspace solid-phase microextraction (HS-SPME) coupled to a GC-triple quadrupole MS was used to obtain limits of quantification that were ≤1.0 ng/L and below sensory threshold levels. The method is fully automated, requires no sample preparation other than the addition of internal standards, and is high throughput, with a 10-min extraction time and a 5-min incubation prior to extraction. This method can be readily adapted to screen for haloanisoles in cork extracts.

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., LOQs 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.

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.

Analysis Of Pinot Noir Wines By HS-SPME GC/Q-TOF: Correlating Geographical Origin With Volatile Aroma Profiles

HS-SPME GC/MS has proved to be very sensitive for the analysis of wine volatiles. As shown in Figure 5, HS-SPME GC/Q-TOF was able to detect 2,4,6trichloroanisole (responsible for a musty or “cork taint” aroma in wine) at 0.1/L (parts per quadrillion). From each of the 45 wine samples (15 vineyards, 3 replicate fermentations), 10 mL of wine and 3 g NaCl were added to each of three headspace vials and data were acquired: HS-SPME Conditions: