REDUCTIVE PYROLYSIS FOR THE DETERMINATION OF AQUEOUS SULFUR-COMPOUNDSWITH A HELIUM MICROWAVE-INDUCED PLASMA

A method for the determination of aqueous sulfur is presented. Sulfur- containing compounds were converted to H2S by a noncatalytic reductive pyrolysis at 1050-degrees-C in the presence of hydrogen gas. The resu ltant H2S was trapped by condensation in a liquid nitrogen trap. Follo wing preconcentration, flash vaporization into a flowing helium stream routed the H2S to a 1.6-kW helium microwave-induced plasma for atomic emission detection. Analytical effects of pyrolysis temperature, hydr ogen flow rate, and sample introduction rate were studied for aqueous solutions of cysteine, methionine, dimethyl sulfoxide, and ammonium su lfate. Results showed linear responses and detection limits of 30 part s per billion when the 921.3-nm nonresonant sulfur atom emission line was monitored and 400 parts per trillion when the resonant sulfur line at 180.73 nm was observed.