One-step conversion of dipicolinic acid to its dimethyl ester using monomethyl sulfate salts for GC-MS detection of bacterial endospores

摘要

Methylsulfate(MeSO4?)saltswereexploredasthermochemolysis–methylation(TCM)reagentsforgaschromatographic(GC)analysisofdipicolinicacid(DPA)asitsdimethylester(Me2DPA)frombacterialendospores.Thereactionwascarriedoutundernon-pyrolyticconditionsbyinsertingasmallcoiledwirefilamentcoatedwiththesampleandreagentsdirectlyinsideaGCinjectionportat290°C.Above10?:?1methyldonor/DPAratios,alkalimetalsaltsofMeSO4?effected80–90%conversionofDPAtoMe2DPA,whichwas10–20timesmoreactivethanthesameamountoftetramethylammoniumhydroxide(TMA-OH)atthistemperature.Aquaternarysaltmixtureconsistingof1?:?3?:?1?:?3TMA+/Na+/OH?/MeSO4?methylatedsporeDPAwithanaverageconversionof86%(meanconversionbyTMA-OHunderthesameconditionswas4%).Therefore,thesensitivityfordetectionofbacterialendosporeswasincreasedover20-foldcomparedtothatobservedwiththemorecommonlyemployedTMA-OHmethylatingreagent.Thelimitofdetectionbythismethodwas9×104totalspores.Mechanismsdescribingtheobservedbehaviorareproposedanddiscussed.ThisisthefirstuseofMeSO4?asaTCMreagentforGC...