Mechanisms in hydride generation AAS

Determination of Selenium by Atomic Absorption Spectrometry With Simultaneous Retention of Selenium(IV) and Tetrahydroborate(III) on an Anion-exchange Resin Followed by Flow Injection Hydride Generation From the Solid Phase

“…In the load position, Fig. 1(a), the sample of selenite (SeO 3 22 ) and the borohydride were mixed and pumped through the column for a period of 1, 2 or 3 min, resulting in the simultaneous retention of both anions (SeO 3 22 , or possibly Se 22 , and BH 4 2 ). At the same time, the loop of valve 1 was filled with acid, while the de-ionized water carrier was pumped constantly through the system.…”

“…Borohydride bound to a stationary phase in a column has been used for hydride generation of arsenic 5,6 and selenium. 7,8 However, the only advantage reported over the use of an aqueous solution of BH 4 2 was the suppression of some matrix interferences.…”

“…A variety of reactions have been used to convert the analyte in solution into the hydride. [1][2][3][4][5][6][7][8] There are also several reports of electrochemical hydride generation [9][10][11] and of thermochemical gas-phase hydride generation. 12 In the case of solution reactions, a metalacid combination, or more commonly reaction with borohydride is employed for hydride generation.…”

“…13 Although some precursors are hydrated cations in the appropriate oxidation state, as for example with Pb IV ; for most analytes the precursor may well exist as an oxo-anion which is reduced prior to the final hydride transfer reaction, as would be the case with Se IV . Initial applications used NaBH 4 pellets, but an aqueous solution stabilized by potassium or sodium hydroxide 4 may be conveniently used and is currently the most popular reagent. Other forms of borohydride have been used.…”

“…In early applications of the technique, the March reaction, based on a metal-acid system such as Zn-HCl producing nascent hydrogen which reacted with the analyte to form the hydride, was used. 3 The more commonly used reaction for hydride formation is the BH 4 2 -acid reaction. 13 Although some precursors are hydrated cations in the appropriate oxidation state, as for example with Pb IV ; for most analytes the precursor may well exist as an oxo-anion which is reduced prior to the final hydride transfer reaction, as would be the case with Se IV .…”