Determination of amino acid enantiomers in soils |
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| Affiliation: | 1. Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2, 842 15 Bratislava, Slovakia;2. SynthCluster, s.r.o., Komenského 1439, 900 01 Modra, Slovakia;3. Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Prague 2, Czech Republic;4. Institute of Forensic Medicine and Toxicology, General University Hospital in Prague, U Nemocnice 2, 128 08 Prague 2, Czech Republic;5. Univ.-Clinic of Anesthesia and Intensive Care, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria;6. Breath Research Institute of the University of Innsbruck, Rathausplatz 4, A-6850 Dornbirn, Austria;1. University of Tübingen, Environmental Analytical Chemistry, Hölderlinstraße 12, 72074 Tübingen, Germany;2. University of Tübingen, Hydrogeochemistry/Applied Geology, Hölderlinstraße 12, 72074 Tübingen, Germany;1. FAU Erlangen-Nürnberg, Institute of Geography, Wetterkreuz 15, 91054 Erlangen, Germany;2. Leiden University, Faculty of Archaeology, Einsteinweg 2, 2333 CC Leiden, Netherlands;3. University of Vienna, Institute of Classical Archaeology, Franz-Klein Gasse 1, 1190 Vienna, Austria;1. Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China;2. University of Chinese Academy of Sciences, Beijing, 100049, China |
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| Abstract: | Determination of amino acid enantiomers in environmental samples is difficult, because metals and organic impurities interfere with the analyses. We developed a new gas chromatographic method to assess amino acid enantiomer concentrations in complex soil matrices following hot HCl hydrolysis (6 M, 12 h, 105°C). The crucial focus was the establishment of a simple, reliable sample clean-up procedure. The presented method involved the adsorption of the enantiomers on a Dowex 50 W X8 cation exchange resin and the removal of interfering compounds with 0.1 M oxalic acid prior to amino acid elution with 2.5 M NH4OH. After conversion to N-pentafluoropropionyl-amino acid iso-propyl esters, the diastereomers were separated by a Chirasil l-Val capillary column and quantified by a flame ionization or mass selective detector. The lower limit of quantification tested here was ≤1 pg injection amount. The recovery of amino acid enantiomers averaged 99±11% for pure standards and 97±11% for spiked soil hydrolysates. The general applicability of the method was demonstrated by determination of amino acid enantiomers in taxonomically different soils from different geographic regions. The coefficients of variation presented by d/l ratios were 12% for alanine and <10% for the other amino acids. |
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