Influence of experimental conditions on the liquid secondary ion mass spectra of sulfonated azo dyes

✍ Scribed by Susan D. Richardson; Alfred D. Thruston Jr; John M. McGuire; George L. Baughman

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 409 KB
• Volume: 26
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210261004

✦ Synopsis

Two monosulfonated and eight disulfonated azo dyes of varying relative molecular mass were examined by liquid secondary ion mass spectrometry (LSIMS). The effects of matrix, concentration, primary beam energy, and mode of operation were addressed in order to optimize sample ionization, whilst minimizing interference from matrix ions. Seven matrices were investigated: glycerol, thioglycerol, 3-nitrobeazyl alcohol, diethanolamine, 2hydroxyethyl disullide, a 1 : 1 (v/v) mixture of 2-hydroxyethyl disullide and thioglycerol, and a 1 : 3 (v/v) mixture of dithioerythritol and dithiothreitol. Of these matrices, 3-nitrobenzyl alcohol produced LSIMS spectra that exhibited the most intense sample ions and the least interference from matrix ions. Minimum concentratiorrs of 0.4 pg/pl and 4 pg/pl (dye in matrix) were necessary to produce useful full-scan spectra for monosulfonated azo dyes and disulfonated azo dyes, respectively; maximum sample ion intensities were obtained with concentrations ranging from 20 pg/pl to 60 pg/pl. A primary ion beam (cesium) of 10 to 15 kV produced the greatest secondary ionization efficiency, and a negativeion analysis mode produced more useful spectra than those obtained in the positive-ion mode.