Ion Trap Tandem Mass Spectrometer Research Articles

Liquid chromatography/microspray mass spectrometry for bacterial investigations.

Cellular proteins (biomarkers) specific to any individual microorganism, determined by the direct mass spectral analysis of the corresponding intact cellular suspension, can be applied for the rapid and specific identification of the organisms present in unknown samples. The components of the bacterial suspensions, after a rapid separation over a C18 reversed-phase microcapillary column, were directly subjected to on-line electrospray ionization followed by analysis using an ion trap tandem mass spectrometer. This approach is equally effective for gram-positive as well as gram-negative bacteria but has a distinct advantage over our earlier reported method involving matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). During electrospray ionitation mass spectrometry (ESI-MS), liquid samples can be directly analyzed and there is the potential for developing tandem mass spectral methods for more specific identification of the individual organisms present in crude bacterial mixtures. The total analysis time leading to unambiguous bacterial identification in samples was less than 10 minutes and the results were quite reproducible. Miniaturization of the instrumentation along with total automation of this simple process could have immense impact on field operations. Routine, rapid, cost-effective field monitoring of environmental samples, agricultural products, samples from food processing, industrial sites and health institutions for suspected bacterial contamination could be a reality in the near future. Potential utility in biological, medical, bioprocessing, pharmaceutical, and other industrial research is also enormous.

Monitoring muramic acid in air (after alditol acetate derivatization) using a gas chromatograph-ion trap tandem mass spectrometer

Muramic acid is a chemical marker for bacterial peptidoglycan. Air monitoring was performed in a stable and a dairy. Airborne dust was collected for 68–95 h on Teflon filters for muramic acid analysis. Filters were cut in two and the replicates analyzed separately. The filters and associated dust were heated in sulfuric acid to release muramic acid. Muramic acid was converted to muramicitol pentaacetate lactam and analyzed by gas chromatography-tandem mass spectrometry using a non-polar GC column (DB-5MS). An ion trap tandem mass spectrometer was used for detection. The precursor mass spectrum of muramic acid was dominated by one major high mass ion m z 403 (loss of ketene, m z 42, from the molecule, MW 445) and m z 198 was the most abundant ion in daughter spectra. Both ions retained the unique lactam ring structure. Using multiple reaction monitoring (MRM), the transition m z 403 to m z 198 was used in quantitation. 13C-labeled muramic acid was used as an internal standard (monitoring the corresponding ion transition m z 412 to m z 205). MRM chromatograms were free of extraneous background peaks. Excellent sensitivity was also observed with daughter spectra for m z 403 allowing absolute identification of muramic acid in airborne dust.