Suitable analysis of α-amino acids by a direct combination of thin-layer chromatography and matrix-assisted laser desorption/ionization mass spectrometry in conjunction with post-chromatographic fixed-charge derivatization.

On-spot fixed-charge derivatization has been suggested for the modification of α-amino acids for their analysis by thin layer chromatography/matrix-assisted laser desorption ionization (TLC/MALDI) mass spectrometry. The approach was based on post-chromatographic treatment of separated analytes by tris(2,6-dimethoxyphenyl)methenium salt and triethylamine. The reaction proceeded smoothly in mild conditions and gave rise to pink-red colored derivatives, containing permanent positive charge. Their MALDI mass spectra, recorded directly from TLC plates, revealed intense peaks corresponding to decarboxylated cationic parts. All derivatives are characterized by high ionization efficiency, which indicates the high sensitivity of the developed method for analyzing amino acids. Applicability of the method to analysis of amino acids was demonstrated on artificial mixtures and dietary supplement.

A simple, inexpensive, non-enzymatic microwave-assisted method for determining bisphenol-A in urine in the form of trimethylsilyl derivative by GC/MS with single quadrupole.

Humans are widely exposed to bisphenol-A (BPA) owing to the ubiquitous use of this chemical in consumer products. Increasing attention is paid to the effect of BPA, because it has the hormone-like structure and it can potentially adversely affect. A simple, efficient, cheap analytical procedure for quantitative determining the analyte is reported in this paper. The suggested method includes the sample preparation based on a double liquid-liquid microextraction combined with non-enzymatic acidic hydrolysis under the influence of microwave radiation of the BPA conjugates with glucuronic and phosphorous acids followed by trimethylsilylation and GC/MS detection. The detection and quantification limits of BPA in the human urine sample are 0.3 and 1 ng/mL respectively. The calibration curve for this analyte is linear with a correlation coefficient of > 0.99 in the range of 1-50 ng/ml. Method recoveries were between 86 % and 110 %, while repeatability was below 10 %. The method was satisfactorily applied to the determination of target compounds in human urine samples from 20 randomly selected individuals. The detection frequency in urines was 40 %. The maximum detected concentration of BPA was 479 ng/mL. The proposed non-enzymatic method is simple, fast, inexpensive and suitable for the determination of BPA in urine samples in the framework of biomonitoring studies and bioanalytical analyses.

Post-chromatographic fixed-charge derivatization for the analysis of hydroxyl-containing compounds by a combination of thin-layer chromatography and matrix-assisted laser desorption/ionization mass spectrometry.

A simple and convenient on-spot derivatization has been suggested for the modification of hydroxyl-containing compounds for their analysis by thin layer chromatography/matrix-assisted laser desorption ionization mass spectrometry (TLC/MALDI). The proposed approach was based on post-chromatographic acylation of separated analytes by 3-bromopropionyl chloride with simultaneous quaternization of pyridine. In contrast to the initial alcohols not ionizable in TLC/MALDI conditions, the derivatives, containing permanent positive charge, revealintense peaks of their cationic moieties in MALDI mass spectra recorded directly from TLC plates. The method was tested on a series of mammalian and plant sterols, phenols and terpene alcohols.

Composite glycerol/graphite/aromatic acid matrices for thin-layer chromatography/matrix-assisted laser desorption/ionization mass spectrometry of heterocyclic compounds.

New composite matrices have been suggested for the analysis of mixtures of different synthetic organic compounds (N-containing heterocycles and erectile dysfunction drugs) by thin layer chromatography/matrix-assisted laser desorption ionization time-of-flight mass spectrometry (TLC/MALDI-TOF). Different mixtures of classical MALDI matrices and graphite particles dispersed in glycerol were used for the registration of MALDI mass spectra directly from TLC plates after analytes separation. In most of cases, the mass spectra possessed [M+H]+ ions; however, for some analytes only [M+Na]+ and [M+K]+ ions were observed. These ions have been used to generate visualized TLC chromatograms. The described approach increases the desorption/ionization efficiencies of analytes separated by TLC, prevent spot blurring, simplifies and decrease time for sample preparation.

Preliminary silylation for structure determination of oligomeric silsesquioxanes by matrix- assisted laser desorption/ionisation mass spectrometry.

The potential of preliminary silylation for the determination of numbers of hydroxyl groups in separate molecules of oligomeric silsesquioxanes by matrix-assisted laser desorption/ionisation mass spectrometry has been demonstrated for the first time. Derivatisations allowing the introduction of trimethylsilyl, tert-butyldimethylsilyl and pentafluorophenyldimethylsilyl groups were tested. It was shown that more reliable structure elucidation of individual oligomers can be achieved knowing the number of hydroxyl groups thus determined.