DETERMINATION OF ARSENIC IN NATURAL AND T AP WATERS BY ICP-MS

Arsenic determinations in river and tap water samples were done using inductively coupled plasma mass spectrometry (ICP-MS). Two methods wer e considered to overcome the problem of the (ArCl+)-Ar-40-Cl-35 interf erence on As-75(+), these were, 1) the masses of the two ion species w ere separated by high resolution ICP-MS, and 2) a numerical correction of (ArCl+)-Ar-.40-Cl-35 on As-75(+) was done after the measurement by a quadrupole mass filter-based ICP-MS. The results of both methods on the standard reference material of river water SLRS-2 agreed well wit h each other and agreed with the certified value. Determinations of ar senic were performed for river water samples from the Tsukuba area and tap water samples from the Tokyo metropolitian area by the latter met hod. Concentration ranges of 0.43 to 3.42 ng/g for the river water and less than 1.6 ng/g for the tap water were found.