1. One-step conversion of dipicolinic acid to its dimethyl ester using monomethyl sulfate salts for GC-MS detection of bacterial endospores
- Author
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Trenton C. Pulsipher, Milton L. Lee, Jon A. Kimball, Tai V. Truong, H. Dennis Tolley, Richard A. Robison, Calvin H. Bartholomew, and Aaron N. Nackos
- Subjects
chemistry.chemical_classification ,Detection limit ,Tetramethylammonium hydroxide ,Chemistry ,General Chemical Engineering ,fungi ,Inorganic chemistry ,General Engineering ,Salt (chemistry) ,Alkali metal ,Dipicolinic acid ,Endospore ,Analytical Chemistry ,chemistry.chemical_compound ,Reagent ,Gas chromatography–mass spectrometry ,Nuclear chemistry - Abstract
Methyl sulfate (MeSO4−) salts were explored as thermochemolysis–methylation (TCM) reagents for gas chromatographic (GC) analysis of dipicolinic acid (DPA) as its dimethyl ester (Me2DPA) from bacterial endospores. The reaction was carried out under non-pyrolytic conditions by inserting a small coiled wire filament coated with the sample and reagents directly inside a GC injection port at 290 °C. Above 10 : 1 methyl donor/DPA ratios, alkali metal salts of MeSO4− effected 80–90% conversion of DPA to Me2DPA, which was 10–20 times more active than the same amount of tetramethylammonium hydroxide (TMA-OH) at this temperature. A quaternary salt mixture consisting of 1 : 3 : 1 : 3 TMA+/Na+/OH−/MeSO4− methylated spore DPA with an average conversion of 86% (mean conversion by TMA-OH under the same conditions was 4%). Therefore, the sensitivity for detection of bacterial endospores was increased over 20-fold compared to that observed with the more commonly employed TMA-OH methylating reagent. The limit of detection by this method was 9 × 104 total spores. Mechanisms describing the observed behavior are proposed and discussed. This is the first use of MeSO4− as a TCM reagent for GC.
- Published
- 2011