Simultaneous hydrothermal decomposition and methylation: High resolution gas chromatography-mass spectrometry for polymer characterization

One-step conversion of to its using salts for GC-MSdetection of bacterial endospores

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.

Introduction to pyrolysis-capillary gas chromatography

By breaking large molecules into characteristic smaller fragments, analytical pyrolysis extends the use of gas chromatography to the analysis of polymeric materials, including natural polymers such as cellulose as well as synthetics. An understanding of the chemistry involved permits interpretation of the information present in these molecular fragments, with application to polymer and copolymer microstructure in addition to routine identification and quality control. Whether microfurnace, Curie-point or resistively heated filament, the pyrolysis device must be interfaced efficiently to the gas chromatography to make use of the resolving power afforded by capillary columns.