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Selenite and Selenate Quantification by Hydride Generation‐Atomic Absorption Spectrometry, Ion Chromatography, and Colorimetry
Author(s) -
Blaylock Michael J.,
James Bruce R.
Publication year - 1993
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1993.00472425002200040031x
Subject(s) - chemistry , detection limit , atomic absorption spectroscopy , colorimetry , absorbance , selenate , hydride , distilled water , chromatography , colorimetric analysis , selenium , reproducibility , analytical chemistry (journal) , mass spectrometry , metal , quantum mechanics , physics , organic chemistry
The need for a routine, inexpensive method with nanomolar detection limits for soluble SeO 2− 3 and SeO 2− 4 is increasing as Se research on soil‐plant‐water systems intensifies and speciation of Se valence states is required. This study was undertaken to compare hydride generation‐atomic absorption spectrometry (HGAAS), colorimetry using 2,3‐diaminonaphthalene (DAN), and ion chromatography (IC) as suitable methods for analysis of SeO 2− 3 and SeO 2− 4 in soil extracts and water samples. Selenium standards in solutions of either 1.0 m M KH 2 PO 4 , CaSO 4 , and KNO 3 , or in distilled water were analyzed to determine detection limits (DL), limits of quantitation (LOQ), and practicality for routine use of the above methods. A 0.1 mM K 2 HPO 4 /KH 2 PO 4 soil extract spiked with 2.0 or 20 µM SeO 2− 3 and SeO 2− 4 was also used to compare the precision of the three methods. The HGAAS method was the most sensitive (0.212 absorbance units/ µM ) and had the lowest DL for SeO 2 3 (0.03 µ mol Se/L) of the three methods employed. Detection limits for the DAN and IC methods were significantly higher (18 and 0.24 µ mol Se/L, respectively). Poor reproducibility between methods was obtained for SeO 2− 4 content of the soil extract containing 20 µM SeO 2− 4 , with concentrations ranging from 9.1 ± 1.2 µ mol/L determined by HGAAS to 24.6 ± 0.05 µ mol/L by IC. The variability and poor recovery of SeO 2− 4 was due to variabilty in efficiency of the HCl reduction required to reduce SeO 2− 4 to SeO 2− 3 before analysis in the HGAAS and DAN procedures. Selenium determinations in samples where low detection limits (<0.1 µM ) are required are most effectively accomplished with HGAAS. Colorimetry requires greater effort and time from the analyst to obtain the low detection limits of HGAAS, but is useful in that only a visible light spectrometer is required. Ion chromatography is capable of automated determinations of Se 2− 3 and SeO 2− 4 directly in combination with other ions of interest and may be appropriate for soil solution Se analysis where Se speciation is required.