PYROLYSIS-GAS CHROMATOGRAPHY MASS-SPECTROMETRY OF ARSENIC INORGANIC-COMPOUNDS

Pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) of As4S6 (orpiment), As4S4 (realgar), As4O6 (arsenolite), NaH2AsO4 (sodium di-H-orthoarsenate) was performed using a platinum-filament pyrolyzer heated at 700-degrees-C for 10 s and coupled to a capillary gas chromatograph/ion trap mass spectrometer. As4 was observed as a pryolysis fragment in the programs of all compounds. Pyrolysis of NaH2AsO4 equivalent to 100 ng of As, produced a strong As4 chromatographic peak. As4S3 and As4S4 were detected as pyrolysis products of As4S6 (orpiment). As4S4 (realgar) and As4O6 (arsenolite) were detected as intact molecules after pyrolysis. By contrast, intact As4S6 was not detected after pyrolyses in the range 400-700-degrees-C. As4 was detected as an impurity in the painting layer of an Egyptian mummy. The mass spectra of such arsenic compounds, none of which is included in the NIST library of spectra, are reported. Advantages and limitations of PY/GC/MS as a technique for the qualitative detection of arsenic inorganic compounds are discussed.