THE USE OF NAFION DRYER TUBES FOR MOISTURE REMOVAL IN FLOW-INJECTION CHEMICAL-VAPOR GENERATION ATOMIC-ABSORPTION SPECTROMETRY

A significant problem with flow injection chemical vapor generation at omic absorption spectrometry is a loss of sensitivity and blockage of transfer lines due to excessive moisture transported to the atom cell or lodged in the transfer line. A Nafion dryer tube was used to remove moisture from the wet carrier gas stream. The hygroscopic Nafion memb rane removed water at 1.7 mg/min at an efficiency of 95 +/- 4% when Sn Cl2 was used as the reductant. When 0.4% (m/v) borohydride was used as the reductant, 2.3 mg/min of water was removed at an efficiency of 91 +/- 3%. No measurable change in precision was observed and a 5% reduc tion in peak height sensitivity (vs. PTFE) was seen for mercury when u sing the Nafion transfer line. At 60 degrees C the Nafion dryer remove d 4.9 mg/min of water vapor at an efficiency of 93 +/- 3%. The loss of mercury vapor through the Nafion membrane was no more than 0.04%. Onl y a 3% reduction in peak height sensitivity was observed for the deter mination of arsenic and selenium. Detection limits for mercury, calcul ated from calibration data, were 77 ppt, 20 ppt and 150 ppt for the PT FE tube, the model MD-250 dryer and the model MD-125 dryer, respective ly.