Determination of sulfate and nitrate anions in rainwater by mass spectrometry

In recent years mass spectrometry has emerged as one of the most powerful trace analysis techniques. Mass spectrometry is characterized by exceptional sensitivity (10/sup -12/ g) combined with the ability to distinguish elemental and isotopic compositions. The advantages of this technique have been, however, largely limited to organic analysis and to elemental analysis. Attempts to analyze complex anions such as the sulfate and nitrate involved in acid precipitation processes have invariably produced results which were unsatisfactory for routine analytical use. Small inorganic anions can be analyzed from glycerol solution with very high sensitivity if a cationic surfactant is added to the solution prior to analysis. The surfactant covers the surface of the analyte droplet and behaves much like an anion exchange resin in that it can bind certain anions selectively to the surface. Quantities of nitrate as small as 10/sup -5/ M in the analyte solution are readily detected. In this paper the application of this methodology to the analysis of natural precipitation is reported. 15 references, 1 figure, 1 table.