Liquid chromatography tandem mass spectrometry analysis of photodegradation of a diazo compound: a mechanistic study.

The photolytic degradation of the diazo dye, Amido Black, using UV/H(2)O(2) has been carried out experimentally and parameters for most efficient dye degradation have been determined. The degradation of the dye was followed by UV-Vis spectroscopy, HPLC, and LC-MS and is proposed to be initiated by ()OH radicals formed by the photolysis of H(2)O(2). A detailed study was also carried out using LC-MS and LC-MS/MS to determine the degradation pathway of the dye as well as to identify some of the intermediate products formed. Our results suggest that Amido Black degradation occurs preferentially by ()OH radical attack at the more electron rich diazo functionality of the molecule. Furthermore, evidence is presented that subsequent steps in this diazo dye degradation pathway include radical denitration, radical desulfonation and radical diazotization. This report is one of the very few studies that have proposed possible mechanistic pathways for the degradation pathways of a diazo compound.

On-probe sample pretreatment for the detection of proteins above 15 KDa from whole cell bacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

A rapid methodology is described for the enhancement of the signal-to-base-line (S/B) ratio of high molecular weight protein signals from whole cell bacteria analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The procedure involves depositing growing bacteria colonies from culture dishes directly onto the MALDI probe followed by treatment of the sample spot with a 2 microL aliquot of 40% ethanol prior to the addition of a ferulic acid matrix solution (12.5 mg dissolved in 17% formic acid/33% acetonitrile/50% H(2)O). Protein signals of more than 20 kDa were routinely produced from both Gram positive and Gram negative bacteria prepared in this manner. Moreover, a substantial number of intense protein signals were also produced in the more 'conventional' fingerprint region extending from 4 to 20 kDa. This approach is rapid, easy to implement into existing methodologies, and does not require any special hardware.