Determination of selenite, selenate and selenocyanate in waters by ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS)

Abstract

Dissolved inorganic selenium (Se) speciation in environmental and industrial waters is determined by ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS). The three species selenite (Se(IV)), selenate (Se(VI)) and selenocyanate (SeCN) are separated by anion-exchange chromatography on a Dionex AS-16 column using gradient elution with NaOH (17.5-100 mmol L 21 ). Prior to HG-AFS detection, selenate is pre-reduced on-line to selenite by reaction with 5.8 mol L 21 HBr at 100 uC. From a 1 mL sample, detection limits of 26, 33 and 34 ng L 21 were achieved for Se(IV), Se(VI) and SeCN, respectively. The reproducibility of standard solutions, as well as of native and spiked real-world samples, was on the order of 5-10%. Spike recoveries for a wide variety of real-world samples are quantitative for all three species. The method was validated by good agreement between the measured speciation patterns for SRM 1643d and two real-world samples with the certified or measured total Se concentrations, respectively. The method was applied to determine Se speciation in a petroleum refinery waste water, where SeCN was the only detected species, and in a gold mine waste water, where smaller fractions of Se(IV) and Se(VI) were encountered besides the major species SeCN.

Determination of Inorganic Selenium Species in Dietary Supplements by Hyphenated Analytical System HPLC-HG-AAS

“…In the hyphenated systems, detection has been performed mainly by the spectrometric methods from among which the ICPMS systems were most often used (Hill et al 2003;Pedersen and Larsen 1997;Łobiński and Szpunar 1999). Determination of inorganic selenium species can be also performed with detection performed by AFS or AAS systems in combination with hydride generation after preliminary on-line reduction of the Se(VI) species (Wallschlaeger and Bloom 2001;Bermejo et al 2001). Moreover, on-line mineralisation of organoselenium compounds permits determination of organic species of selenium also in HGAAS systems (Marchante-Gayón et al 1996).…”

On-line pre-reduction of Se(VI) by thiourea for selenium speciation by hydride generation

“…Among the pre-reduction methods, 6 mol L − 1 HCl [16], K 2 S 2 O 8 -NaOH/HCl [17,18] and HBr/KBrO 3 [19][20][21][22] are the pre-conversion media frequently used before HG by borohydride. On the other hand, K 2 S 2 O 8 -NaOH/HCl can be used to convert all Se species into selenate, followed by reduction to selenite by HCl; bromine involved in HBr/KBrO 3 medium was proved to play a key role in the conversion of Se (VI) to Se(IV), but it has also been known to be a potential interference to HG [23]. Recently, ultraviolet (UV) radiation has been used in Se speciation analysis [24].…”

A novel indicator system for catalytic spectrophotometric determination and speciation of inorganic selenium species (Se(IV), Se(VI)) at trace levels in natural lake and river water samples

“…Among the pre-reduction methods, 6 M HCl [16], K 2 S 2 O 8 -NaOH/HCl [17][18], and HBr/KBrO 3 [19][20][21][22] are the pre-conversion media frequently used before HG by borohydride. On the other hand, K 2 S 2 O 8 -NaOH/HCl can be used to convert all Se species into selenate, followed by reduction to selenite by HCl; bromine involved in the HBr/KBrO 3 medium was proved to play a key role in the conversion of Se(VI) to Se(IV), but it has also been known to be a potential interference to HG [23]. Recently, ultraviolet (UV) radiation has been used in Se speciation analysis [24].…”