Reduction in liquid secondary ion mass spectrometry. Comparison of the fission fragment and liquid secondary ion mass spectra of organic dyestuffs.

Mass spectral characterlzatlon of the Intact chromophore of organic dyestuffs, frequently prepared as salts, Is relatlvely faclle wlth desorptlon lonlratlon. The mass spectra obtalned, however, may show the presence of chemlcally altered forms of the chromophore. Comparlson of the flsslon fragment (FF) and llquld secondary Ion mass spectra (Ilquld SIMS) of a serles of dyes reveals enhanced (C + 1)' and (C -I2)' lntensltles In the llquld SIMS spectra of some of the materlals examlned. Thls enhancement appears to be related to reductlon reactlons occurring In the llquld matrlx of the SIMS experlments which result in dye specles welghlng 1 and 2 amu more than the orlglnal chromophore. The absence of the llquld matrlx In the FF experlments precludes such reactlons, and hence the (C + 1)' and (C + 2)' lntensltles observed in the FF spectra are those calculated from the natural abundances of the 13C and "N Isotopes Incorporated In the dye molecules. While the mechanlsm(s) by which reductlon takes place have not been establlshed, the role of the matrlx may be in provldlng radical specles that facllitate reductlon.