Alexandra Hengerics Szabó

Direct silylation of Trypanosoma brucei metabolites in aqueous samples and their GC-MS/MS analysis.

A simple two-step method for the derivatization of polar compounds (lactate, alanine, glycerol, succinate and glucose) using hexamethyldisilazane (HMDS) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) was developed. This method allows direct derivatization of aqueous samples wihout sample pretreatment. The method was used for the analysis of the metabolites of the unicellular organism Trypanosoma brucei. The limits of detection by GC-MS/MS analysis were in the range of 0.02 mg L(-1) for glucose to 0.85 mg L(-1) for lactate.

Gas chromatography with mass spectrometry analysis of phosphoserine, phosphoethanolamine, phosphoglycerol, and phosphate

A new, rapid, sensitive, robust, and reliable method has been developed for the qualitative analysis of phosphoserine, phosphoethanolamine, phosphoglycerol, and phosphate using gas chromatography with mass spectrometry and two-step trimethylsilylation. The method employs hexamethyldisilazane for silylation of the phosphate and hydroxyl groups in the first phase and bis(trimethylsilyl)trifluoroacetamide for silylation of the less-reactive amino groups in the second phase. This order is of key importance for the method because of the different reactivities of the two reagents and the mechanism of derivatization of the active groups of the analytes. Trimethylsilylated derivatives of the analytes were identified on the basis of their retention times and mass spectra. The probable structures of the major fragments were identified in the spectra of the trimethylsilylated derivatives and characteristic m/z fragments were selected for each analyte. Fragments with m/z 73 and 299 occurred in the spectra of all the analytes. The characteristic retention data were employed to calculate the retention indices of the individual silylated phosphorylated substances in the hydrocarbon range C12-C19 for the DB-5ms column. The method was employed to measure the polar fraction of the hydrolysate of the cytoplasmic membrane of Bacillus subtilis. The detection limits vary between 5 μg/mL (trimethylsilylated phosphate) and 72 μg/mL (trimethylsilylated phosphoethanolamine).

The analysis of linear and monomethylalkanes in exhaled breath samples by GC × GC-FID and GC–MS/MS

A new arrangement of the INCAT (inside needle capillary adsorption trap) device with Carbopack X and Carboxen 1000 as sorbent materials was applied for sampling, preconcentration and injection of C6C19n-alkanes and their monomethyl analogs in exhaled breath samples. For the analysis both GC-MS/MS and GC×GC-FID techniques were used. Identification of the analytes was based on standards, measured retention indices and selective SRM transitions of the individual isomers. The GC-MS/MS detection limits were in the range from 2.1 pg for n-tetradecane to 86 pg for 5-methyloctadecane. The GC×GC-FID detection limits ranged from 19 pg for n-dodecane to 110 pg for 3-methyloctane.

Time-dependent changes in milk fatty acid composition of ewes fed a winter ration supplemented with linseed or sunflower oils.

The effects of adding sunflower and linseed oils to a standard winter ration with a lower concentrate content on the milk fatty acid composition in lactating ewes were investigated. Eighteen dairy ewes randomly chosen from the ewe flock were divided into three groups: the first group was fed a winter ration, the second one a winter ration supplemented with sunflower oil, and the third a winter ration supplemented with linseed oil for a period of 12 days. In the treatment groups, the concentrate was partially replaced by 3.0 g/100 g sunflower or linseed oils. Milk samples were taken daily from morning milking for the analysis of fatty acid composition to determine their temporal daily variations. The responses to sunflower oil compared with linseed oil addition after the end of experi - ment were slightly higher for conjugated linoleic acid (CLA) ( P < 0.05), linoleic acid ( P < 0.001), trans-10 18:1 (P < 0.001), 6:0 to 16:0 ( P ≈ 0.05 - P < 0.001), whereas a higher content of α-linolenic acid (ALA) (3-fold) ( P < 0.001), oleic acid ( < 0.001), and 18:0 (P < 0.001) was found in milk after linseed oil addition. The responses to both oil additions were relatively sustainable with regard to CLA, trans-11 18:1 (vaccenic acid, VA), and ALA content after the last 6 days of supplementation. The winter ration supplementation with sunflower or linseed oil led to a 3-fold increase in CLA milk fat content (0.6-2.0 or 1.8 g/100 g fatty acid methyl esters (FAME), P < 0.001) and a 3-fold increase in VA milk fat content (1.2-3.8 or 4.1 g/100 g FAME, P < 0.001), however the content of trans-10 18:1 was 5-6-fold higher, compared with unsupplemented winter ration. Plant oil supplementation enhanced the total content of CLA, VA, ALA by 5.0 and 3.9 g/100 g FAME ( P < 0.001) for linseed and sunflower oil supplementation, and decreased the total content of 12:0, 14:0, and 16:0 by 9.3 and 5.8 g/100 g FAME ( P < 0.001) compared to winter diet, respectively.

Simultaneous analysis of fructose and creatinine in urine samples using GC–MS/MS and enzymatic methods

This work focuses on the simultaneous analysis of creatinine and fructose with the gas chromatographic tandem mass spectrometric (GC–MS/MS) method after silylation with hexamethyldisilazane and N,O-bis(trimethylsilyl)trifluoroacetamide and the comparison of GC–MS/MS and enzyme-catalyzed photometric analysis of creatinine. The GC–MS/MS method allows the direct silylation of urine samples without sample pretreatment before derivatization. Due to this option, the analysis and diagnostics of inborn metabolic diseases are faster than in the case of a separate determination of both analytes.Graphical abstract

GC–MS/MS method for age determination of fingerprints

This work focuses on the monitoring of changes in the time and incident light dependent ratio of endogenous analytes, squalene, and pentadecanoic acid, in fingerprint samples by gas chromatography with tandem mass spectrometry. The method can be used for fingerprint age determination of two age different samples on a glass surface from the same donor or allows identity determination from fingerprints of different persons imprinted at the same time, even in case of their blurring on a glass surface.Graphical abstract

The analysis of polar compounds in cigarette ashes by GC–MS/MS

The newly developed gas chromatography–tandem mass spectrometry method allows the analysis of non-volatile, polar substances in cigarette ash. Only a few mg of ash, derivatized by two-step silanization with hexamethyldisilazane and N,O-bis(trimethylsilyl)trifluoroacetamide, are necessary for the analysis. Samples are directly analyzed after derivatization, without the need of extraction as a next purification step. Differences in chromatographic profiles reflect the composition uniqueness of each matrix and can be used for product authentication by chromatographic fingerprint method. The method was used to differentiate between cigarette ash samples of three cigarette brands (Marlboro, Davidoff, and West) and can be useful for forensic purposes.Graphical abstract