A simple and effective way to enhanee fast‐atom bombardment mass spectra of sulfonic acids

Abstract

A technique for the simplification of fast-atom bombardment (FAB) spectra of polysulfonic acids, especially azo dyes complicated by sodium, is discussed. The sodium may be present as the sulfonate salt or the salt may be formed during FAB analysis from impurities present in the sample. The incorporated sodium as well as other impurities which may be present in commercial samples are removed by means of a simple cationic-exchangeresin procedure, yielding simplified and unambiguous FAB spectra of the sodium-free material.In the past, sulfonic acids and sulfonic acid salts could not be analyzed directly by mass spectrometry. Derivatization to more volatile compounds was necessary in order to obtain usable spectra. Salts were converted to their corresponding sulfonic acids and then, typically, to trimethylsilyl or methyl esters prior to electron-ionization (EI) mass spectral analysis.' However, difficulties encountered in both the derivatization procedure and the mass spectral analysis often led to questionable results.The direct analysis of sulfonic acids and sulfonic acid salts became feasible with the development of fastatom bombardment (FAB) mass spectrometry. Sulfonic acid compounds when pure can readily be analyzed by this technique. However, the presence of impurities even at low levels will complicate or suppress the spectra, making interpretation difficult. This is particularly true when trying to obtain FAB spectra of compounds containing more than one sulfonic acid or sulfonate moiety. One class of such sulfonic acid compounds is that of the commercial dyestuffs. A quick and effective means of enhancing such FAB spectra is to pretreat the sample by passing an aqueous solution of the dye through an ion-exchange-resin column prior to FAB analysis.

Formation of the bisulfite anion (HSO3–, m/z 81) upon collision‐induced dissociation of anions derived from organic sulfonic acids

“…[20][21][22][23][24][25][26][27][28] Negative-ion mass spectra of alkyl and aryl sulfonates indicate that the major product ion produced by collision-induced fragmentation is the sulfur trioxide radical anion (SO 3 -Á , m/z 80). [20][21][22][23][24][25][26][27][28] On the other hand, some sulfonates are known to give the bisulfite anion (HSO 3 -, m/z 81). [20,28] For example, in the collision-induced dissociation (CID) mass spectra of fluorotelomer sulfonates, the base peak is observed at m/z 81 indicating the formation of the bisulfite anion.…”

Effect of tautomerization on the fast-atom bombardment tandem mass spectra of azo dyes

“…Clearly, more information about the structure of these compounds can be obtained by analyzing the product-ion spectra of both the (M -Na)-and (M -H)-ions. Shimanskas et al[33] have suggested removing the metal ions from dyes prior to analysis to ' ::j a .,---'-------,-------,----------,-(M3~~)-'jj0 'i' '1,------1-----,-'"~L…”