Assay of vitamin B in urine by capillary electrochromatography with methacrylate-based monolithic column

Comparison of 1D a 2D ITP-MS performance parameters and application possibilities: Ultratrace determination of B vitamins in human urine

The possibility to investigate analytes at ultra-low concentration levels still remains a hot topic in bioanalysis. In this area, various preconcentration techniques are an integral part of analytical procedures. When applying electromigration separation techniques, an isotachophoresis has been advantageously employed many times for this purpose. To solve current biomedical tasks effectively, an advanced two-dimensional isotachophoretic instrument (in a hydrodynamically closed separation system with an enhanced sample load capacity) hyphenated with mass spectrometry (ITP-ITP-MS) has been proposed by Foret and coworkers. As a continuation, this work represents the first study dealing with a full validation of an ITP-ITP-MS method. In order to see the benefits of an online ITP sample pretreatment (preconcentration and clean-up) on the performance parameters, the developed 2D ITP-MS method was compared with a corresponding 1D ITP-MS method. Application potentialities of the compared methods were demonstrated via a determination of two B vitamins, namely thiamine and pyridoxine, in human urine samples. The developed 2D ITP-MS method showed its enhanced effectivity and usefulness for a routine biomedical use (here, a reliable screening of trace B vitamins in human urine without an offline sample preparation).

Development of a LC-MS/MS method using stable isotope dilution for the quantification of individual B6 vitamers in fruits, vegetables, and cereals

Vitamin B₆ comprises an important set of molecules tightly interwoven with the human amino acid, fatty acid, and carbohydrate metabolism. Analytical methods striving for the quantification of individual B₆ vitamers so far mostly rely on methods based on HPLC in combination with fluorescence detection, but their application encounters multiple difficulties due to the chemical divergence of the single vitamers. The present study describes the development of a method based on LC-MS/MS and stable isotope dilution assay (SIDA) for the simultaneous quantification of five vitamers (PN, PL, PM, PMP, and PNG) of the B₆ group in food samples. [¹³C₃]-PN, [¹³C₃]-PL, and [¹³C₆]-PNG were applied as internal standards for the analysis of PN, PL, and PNG. PM and PMP were quantified via matrix-matched calibration referring to [¹³C₃]-PN. The developed method was validated using starch matrix. The limits of detection and quantification ranged from 0.0028 to 0.02 mg/kg and from 0.0085 to 0.059 mg/kg, respectively, for all analytes. Calculated recoveries varied from 92 to 111%. Intra-injection precisions ranged from 0 to 9%, inter-day precisions from 4 to 10%, and intra-day precisions from 4 to 10%. A total of 14 plant-based food samples including fruits, vegetables, and cereals were examined for their content of vitamin B₆ using the validated method. Furthermore, the first quantitation of PNG without enzymatic steps or divergent internal standards was undertaken utilizing LC-MS/MS and SIDA.