A novel accurate LC-MS/MS method for quantitative determination of Z-lumirubin.

Although phototherapy (PT) is a standard treatment for neonatal jaundice, no validated clinical methods for determination of bilirubin phototherapy products are available. Thus, the aim of our study was to establish a such method for clinical use. To achieve this aim, a LC-MS/MS assay for simultaneous determination of Z-lumirubin (LR) and unconjugated bilirubin (UCB) was conducted. LR was purified after irradiation of UCB at 460 nm. The assay was tested on human sera from PT-treated neonates. Samples were separated on a HPLC system with a triple quadrupole mass spectrometer detector. The instrument response was linear up to 5.8 and 23.4 mg/dL for LR and UCB, respectively, with submicromolar limits of detection and validity parameters relevant for use in clinical medicine. Exposure of newborns to PT raised serum LR concentrations three-fold (p < 0.01), but the absolute concentrations were low (0.37 ± 0.16 mg/dL), despite a dramatic decrease of serum UCB concentrations (13.6 ± 2.2 vs. 10.3 ± 3.3 mg/dL, p < 0.01). A LC-MS/MS method for the simultaneous determination of LR and UCB in human serum was established and validated for clinical use. This method should help to monitor neonates on PT, as well as to improve our understanding of both the kinetics and biology of bilirubin phototherapy products.

Allium Discoloration: Color Compounds Formed during Pinking of Onion and Leek.

Structures and formation pathways of compounds responsible for pink discoloration of onion and leek were studied. A procedure was developed for the isolation and purification of the color compounds from various model systems and their identification by HPLC-DAD-MS/MS. In total, structures of 15 major color compounds were tentatively determined. It was found that the pigment is a complex mixture of highly conjugated species composed of two N-substituted 3,4-dimethylpyrrole-derived rings linked by either a methine or a propenylidine bridge. These two-ring units are further modified by various C1- and C3-side chains. Experiments with isotope-labeled thiosulfinates revealed that the methine bridge and C1-side chains originate from the methyl group of methiin, whereas the C3 units are derived from the propenyl group of isoalliin.

Critical assessment of extraction methods for the simultaneous determination of pesticide residues and mycotoxins in fruits, cereals, spices and oil seeds employing ultra-high performance liquid chromatography-tandem mass spectrometry.

This study addresses a current trend in chemical food safety control represented by an effort to integrate analyses of various groups of food contaminants/toxicants into a single, high-throughput method. The choice of optimal sample preparation step is one of the key conditions to achieve good performance characteristics. In this context, we investigated the possibility to expand the scope of the three multi-analyte extraction procedures employed earlier in other studies for rapid isolation of either pesticides or mycotoxins from plant matrices. Following procedures were tested: A - aqueous acetonitrile extraction followed by partition (QuEChERS-like method), B - aqueous acetonitrile extraction, and C - pure acetonitrile extraction. On the list of target analytes, we had 288 pesticides (including 'troublesome' acidic, basic and base-sensitive compounds) together with 38 mycotoxins (including all EU regulated ones and many 'emerging' toxins on the European Food Safety Authority (EFSA) list). The matrices selected for the experiments, apple baby food, wheat flour, spices and sunflower seeds, represented various composition categories in terms of moisture, fat and extractable compounds (e.g. pigments and essential oils) content. In preliminary experiments, acceptable recoveries (70-120%) for most of analytes were obtained by the analysis of spiked matrices, regardless which extraction procedure was used. However, when analysing dry samples with incurred pesticide residues/mycotoxins, the method C did not enable efficient extraction of some common contaminants. Procedure A, thanks to a higher matrix equivalent compared to the method B and relatively less pronounced matrix effects, enabled lower quantification limits for all analyte/matrix combinations, with the exception of polar mycotoxins and/or pesticides. Higher recoveries for the latter group of analytes could be achieved by the method B; on the other hand, extraction efficiency of non-polar pesticides from fatty matrix was rather poor by this method.

Novel approaches to analysis of 3-chloropropane-1,2-diol esters in vegetable oils.

A sensitive and accurate method utilizing ultrahigh performance liquid chromatography (U-HPLC) coupled to high resolution mass spectrometry based on orbitrap technology (orbitrapMS) for the analysis of nine 3-chloropropane-1,2-diol (3-MCPD) diesters in vegetable oils was developed. To remove the interfering triacylglycerols that induce strong matrix effects, a clean-up step on silica gel column was used. The quantitative analysis was performed with the use of deuterium-labeled internal standards. The lowest calibration levels estimated for the respective analytes ranged from 2 to 5 µg kg(-1). Good recovery values (89-120%) and repeatability (RSD 5-9%) was obtained at spiking levels of 2 and 10 mg kg(-1). As an alternative, a novel ambient desorption ionization technique, direct analysis in real time (DART), hyphenated with orbitrapMS, was employed for no separation, high-throughput, semi-quantitative screening of 3-MCPD diesters in samples obtained by chromatographic fractionation. Additionally, the levels of 3-MCPD diesters measured in reallife vegetable oil samples (palm oil, sunflower oil, rapeseed oil) using both methods are reported. Relatively good agreement of the data generated by U-HPLC-orbitrapMS and DART-orbitrapMS were observed. With regard to a low ionization yield achieved for 3-MCPD monoesters, the methods presented in this paper were not yet applicable for the analysis of these contaminants at the naturally occurring levels.