Ultratrace determination of inorganic selenium without signal calibration.
To more readily evaluate the complex biogeochemistry of selenium, a flow-through electrochemical method was developed that can accurately determine Se(IV) concentrations in aqueous samples to part-per-trillion levels without signal calibration. Stripping methods were used in conjunction with a high-efficiency, flow-through cell. The cell was designed with a novel gold working electrode that was separated from a porous counter electrode by a Nafion membrane. Because this design permitted exhaustive deposition of selenium from the sample stream as well as efficient coulometric stripping, determinations obeyed Faraday's law over a reasonably wide range of operating conditions. The method had a minimum quantitation limit of approximately 8 ng and a maximum limit of 800 ng for Se(IV). It was reliable for sample volumes as small as 0.5 mL and as high as 20 mL, thereby allowing determinations from part-per-million to just below part-per-billion levels. Interferences from Cu(II) and arsenate were evident, but only when these species were present at concentrations exceeding 10 mg.L-1. Overall, the method had a performance comparable to hydride-generation atomic absorption spectrometry but with less cumbersome equipment and freedom from calibration.
Hazelton
Sandra G
SG
Department of Chemistry, University of North Dakota, Grand Forks, North Dakota 58202-9024, USA.
Pierce
David T
DT
D000818:Animals; D001149:Arsenates / Q000737:chemistry; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002138:Calibration; D002412:Cations; D003300:Copper / Q000737:chemistry; D004563:Electrochemistry; D006801:Humans; D011199:Potentiometry / Q000295:instrumentation / Q000379:methods; D012016:Reference Values; D015203:Reproducibility of Results; D012643:Selenium / Q000032:analysis*; D012680:Sensitivity and Specificity
D001149:Arsenates; D002412:Cations; D003300:Copper; D012643:Selenium; C025657:arsenic acid