Negative ion electrospray high‐resolution tandem mass spectrometry of polyphenols

Representative compounds with a 1,3‐dihydroxybenzene substructure belonging to different important polyphenol classes (stilbenes, flavones, isoflavones, flavonols, flavanones, flavanols, phloroglucinols, anthraquinones and bisanthraquinones) were investigated based on detailed high‐resolution tandem mass spectrometry measurements with an Orbitrap system under negative ion electrospray conditions. The mass spectral behaviour of these compound classes was compared among each other not only with respect to previously described losses of CO, CH₂CO and C₃O₂ but also concerning the loss of CO₂ and successive specific fragmentations. Furthermore, some unusual fragmentations such as the loss of a methyl radical during mass spectral decomposition are discussed. The obtained results demonstrate both similarities and differences in their mass spectral fragmentation under MSⁿ conditions, allowing a characterization of the corresponding compound type. Copyright © 2015 John Wiley & Sons, Ltd.     

Recent applications of gas chromatography with high‐resolution mass spectrometry

Gas chromatography coupled to high‐resolution mass spectrometry is a powerful analytical method that combines excellent separation power of gas chromatography with improved identification based on an accurate mass measurement. These features designate gas chromatography with high‐resolution mass spectrometry as the first choice for identification and structure elucidation of unknown volatile and semi‐volatile organic compounds. Gas chromatography with high‐resolution mass spectrometry quantitative analyses was previously focused on the determination of dioxins and related compounds using magnetic sector type analyzers, a standing requirement of many international standards. The introduction of a quadrupole high‐resolution time‐of‐flight mass analyzer broadened interest in this method and novel applications were developed, especially for multi‐target screening purposes. This review is focused on the development and the most interesting applications of gas chromatography coupled to high‐resolution mass spectrometry towards analysis of environmental matrices, biological fluids, and food safety since 2010. The main attention is paid to various approaches and applications of gas chromatography coupled to high‐resolution mass spectrometry for non‐target screening to identify contaminants and to characterize the chemical composition of environmental, food, and biological samples. The most interesting quantitative applications, where a significant contribution of gas chromatography with high‐resolution mass spectrometry over the currently used methods is expected, will be discussed as well.     

Assessment of tandem mass spectrometry and high‐resolution mass spectrometry for the analysis of bupivacaine in plasma

Triple quadrupole mass spectrometers coupled with high performance liquid chromatography are workhorses in quantitative bioanalyses. They provide substantial benefits including reproducibility, sensitivity and selectivity for trace analysis. Selected reaction monitoring allows targeted assay development but datasets generated contain very limited information. Data mining and analysis of nontargeted high‐resolution mass spectrometry profiles of biological samples offer the opportunity to perform more exhaustive assessments, including quantitative and qualitative analysis. The objectives of this study were to test method precision and accuracy, to statistically compare bupivacaine drug concentration in real study samples and to verify if high‐resolution and accurate mass data collected in scan mode can actually permit retrospective data analysis, more specifically, extract metabolite related information. The precision and accuracy data presented using both instruments provided equivalent results. Overall, the accuracy ranged from 106.2 to 113.2% and the precision observed was from 1.0 to 3.7%. Statistical comparisons using a linear regression between both methods revealed a coefficient of determination (R²) of 0.9996 and a slope of 1.02, demonstrating a very strong correlation between the two methods. Individual sample comparison showed differences from ?4.5 to 1.6%, well within the accepted analytical error. Moreover, post‐acquisition extracted ion chromatograms at m/z 233.1648 ± 5 ppm (M ? 56) and m/z 305.2224 ± 5 ppm (M + 16) revealed the presence of desbutyl‐bupivacaine and three distinct hydroxylated bupivacaine metabolites. Post‐acquisition analysis allowed us to produce semi‐quantitative evaluations of the concentration–time profiles for bupicavaine metabolites. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural characterization of intact antibodies by high‐resolution LTQ Orbitrap mass spectrometry

Recombinant monoclonal antibodies (MAbs) can be heterogeneous due to modifications that can occur during expression, purification or during storage. These large multichain proteins (～150 kDa) are structurally challenging for detailed characterization to identify the sites of modifications. We report the use of LTQ Orbitrap mass spectrometry to accurately measure the average masses of individual glycoforms by direct infusion of an intact antibody. To identify the site‐specific modification of methionines in the antibody caused by forced oxidation, we used a ‘middle‐down’ approach. The antibody was subjected to limited digestion using the endoproteinase Lys‐C and reduced to generate Fab heavy chain, single chain Fc and light chain fragments (～25 kDa each). These species were subjected to on‐line liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) analysis using an LTQ Orbitrap, where these large precursors were dissociated by higher‐energy collisions in the C‐trap. High resolution and accuracy achieved for resulting fragments allowed us to show in a site‐specific manner that only the methionines in the Fc heavy chain were oxidized under the studied conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

Fast and sensitive analysis of beta blockers by ultra‐high‐performance liquid chromatography coupled with ultra‐high‐resolution TOF mass spectrometry

This paper presents a method for the determination of acebutolol, betaxolol, bisoprolol, metoprolol, nebivolol and sotalol in human serum by liquid–liquid extraction and ultra‐high‐performance liquid chromatography coupled with ultra‐high‐resolution TOF mass spectrometry. After liquid–liquid extraction, beta blockers were separated on a reverse‐phase analytical column (Acclaim RS 120; 100 × 2.1 mm, 2.2 μm). The total run time was 6 min for each sample. Linearity, limit of detection, limit of quantification, matrix effects, specificity, precision, accuracy, recovery and sample stability were evaluated. The method was successfully applied to the therapeutic drug monitoring of 108 patients with hypertension. This method was also used for determination of beta blockers in 33 intoxicated patients.