Determination of inorganic selenium speciation in waters by ion chromatography-inductively coupled plasma-mass spectrometry using eluant elimination with a membrane suppressor
D. Wallschlager et R. Roehl, Determination of inorganic selenium speciation in waters by ion chromatography-inductively coupled plasma-mass spectrometry using eluant elimination with a membrane suppressor, J ANAL ATOM, 16(9), 2001, pp. 922-925
Selenium speciation in waters is performed by ion chromatography coupled to
inductively Coupled plasma mass spectrometry (IC-ICP-MS). Selenite, selena
te and selenocyanate [Se(IV). Se(VI) and SeCN] are separated with a step gr
adient elution using dilute NaOH as the eluant. After the separation, the e
luant is converted to water on-line by a membrane self-regenerating suppres
sor, and then introduced into the nebulizer. It is shown that the eliminati
on of the NaOH matrix improves analytical performance and instrument Stabil
ity. From 1 mL sample, detection limits (as 3 sigma of the baseline noise)
of 2.5, 1.6 and 2.6 ng L-1 are achieved for Se(IV), Se(VI) and SeCN, respec
tively, if 2% methanol is added to the eluant. Reproducibility of the metho
d was 7.6 10.5% for the three species at the 50 ng L-1 level and 0.4-7.4% a
t the 500 ng L-1 level. The method was validated with SRM 1643d (NIST). The
analytical performance for the three isotopes Se-77, Se-78 and Se-82 is co
mpared under various plasma conditions, and Se-82 is identified as the Most
Suitable isotope yielding the lowest detection limits under any conditions
. As a demonstration of the method's detection power. it is Successfully ap
plied to determine Se speciation in an estuarine water.