Determination of selenium using different techniques

Abstract

Background: Voltametric methods represent a cost-effective and efficient alternative to conventional spectroscopic techniques for determining selenium species, particularly within the 0–10 ppm concentration range. While atomic absorption spectroscopy, due to the atomisation step, allows only for total Se determination, voltammetry typically provides a signal only for Se(IV). Therefore, a combination of atomic spectroscopy and voltammetry is supposed to be an approach for the determination of individual Se species (Se(IV), Se(VI)) in model solutions as well as in real samples. Therefore, this study compared the performance of Flame Atomic Absorption Spectroscopy (FAAS) and Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) with anodic stripping square wave voltammetry (ASSWV) using an unmodified glassy carbon electrode (GCE) and a pencil graphite electrode. Results: Selenium quantification was conducted using stock solutions of Se(IV), Se(VI), and Se(0), with measurements validated by model samples. It was shown that the form of selenium does not significantly affect the AAS analytical performance. Conversely, while FAAS showed a detection limit of 0.896 mg/L, it was 0.57 mg/L Se(IV) for ASSWV and only 5.2 μg/L for GFAAS. Anodic square wave voltammetry using GCE provided linear calibration in a 1.2–9.7 mg/L range, while FAAS technique was linear up to 50 mg/L. FAAS appeared more reliable for total Se determination in real samples, revealing 33 ± 5 mg/L and 37 ± 1 mg/L of Se in deionized water and acetic acid leachates of hazardous waste. Voltammetry using GCE electrodes revealed 4.9 ± 0.8 and 6 ± 2 mg/L of Se(IV) in respective leachates with Se(IV) portion calculated as 14.9 and 17 % in respective leachates. Significance and novelty: These findings highlight voltammetry as a viable and selective approach for selenium speciation in complex matrices, complementary to spectroscopic methods. Furthermore, graphite-based electrodes provide higher sensitivity than GCE, but their geometric stability must be secured.