Untersuchungen zur chemischen Bestimmung von Threonin und Serin

Zusammenfassung Die Threonin- bzw. die Threonin und Serinbestimmung auf chemischem Wege werden hinsichtlich der beiden wichtigsten Verfahren, nämlich der Oxydation mit Bleitetraacetat und mit Perjodsäure, vergleichend überprüft. Beide Methoden arbeiten, insbesondere nach Einführung einer für die Serinoxydation vorgeschlagenen Abänderung, recht genau. Für die Untersuchung von Aminosäuregemischen oder Eiweißhydrolysaten ist aus erörterten und überprüften Gründen die Perjodat-Oxydation vorzuziehen.     

Method development for the determination of selected pesticides on tobacco by high-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry

A method was developed for the quantitative determination of alachlor, benalaxyl, clomazone, diflubenzuron, dimethomorph, diphenamid, ethofumesate, metalaxyl, methoprene, metobromuron and piperonyl butoxide on tobacco. The pesticides were extracted with water and methanol from five different types of tobacco. The extracts were purified by partition on an extraction cartridge containing diatomaceous earth. The purified extracts were analysed by reversed-phase high-performance liquid chromatography connected to an atmospheric pressure ionisation–electrospray-triple quadrupole mass spectrometer operating in the positive ion mode. Two different transitions and their relative intensities were monitored for unambiguous identification. All pesticides presented overall recovery rates between 35% and 110%. The trueness is near 100% and the interday precision is below 15%. The limits of quantifications are equal or below the guidance residue levels proposed by the Agrochemical Advisory Committee of CORESTA, an association of organisations having scientific research relative to tobacco.     

Development of a capillary electrophoretic method for the analysis of low-molecular-weight amines from metal working fluid aerosols and ambient air

A method for the determination of low-molecular-weight amines from indoor and ambient air was developed using a concentration device followed by CE coupled with indirect spectrophotometric and mass spectrometric detection that enables a reliable, rapid-response and easy-to-operate method. In indirect detection method, the selected amines were separated from interfering metal ions and amino alcohols present in the samples with an imidazole-based buffer with ethanol and EDTA as modifier. By replacing imidazole with ammonium, the final buffer was applicable for MS detection for the analytes with m/z higher than 50. A novel monolithic polymer material based on poly(methacrylate-acrylate) copolymer was developed for sampling short-chain amines from the gaseous phase. The selected analysis conditions were applied to quantify the selected short-chain amines with detection limits for the whole procedure determined between 1 and 2 microg/filter when 40 L air was sampled with 1 L/min velocity. Improved linearity and precision were obtained when the raw, time-scaled electropherogram data were transformed into mobility-scale applied for the determination of the performance characteristics of the methods. The applicability of the process of data transformation into the mobility scale was demonstrated by studying the matrix effect of water-miscible metal working fluid (stable water-oil emulsion) and of ambient air as real samples. CE-indirect UV and CE-MS, combined with the possibility of rapid air sampling, can be useful for the estimation of short-term exposure of the selected biogenic amines.