EFFECTS OF A MEMBRANE DESOLVATOR ON THE ANALYTICAL PERFORMANCE OF A 120 W HELIUM MICROWAVE-INDUCED PLASMA - AQUEOUS DESOLVATION

The effect of a flat-sheet membrane desolvator (FSMD) on the analytica l performance of a low-power (120 W) He-MIP (helium microwave-induced plasma) is examined. Ultrasonic nebulization with conventional desolva tion of an aqueous solution resulted in a dull, red, unstable plasma t hat was extinguished if the carrier gas how rate was greater than 1.2 L/min. Using the FSMD with this system resulted in an enhancement of t he plasma stability and a significant reduction of the reddish emissio n from hydrogen atoms. Also, without the FSMD, only weak chlorine emis sion signals were observed when 1000 ppm aqueous Cl solution was nebul ized, but with the FSMD intense chlorine signals were observed with a detection limit of 1.0 mu g/mL. Sensitivity improvement factors for Cu , B, P, Cd, and Ph ranged from 1.5 to 20. Greater improvements were se en for ''harder to excite'' elements.