Efficient Photochemical Vapor Generation of Bismuth and Selenium in Low Concentration of Isopropyl Alcohol and Organic Acid Medium

A highly efficient photochemical vapor generation (PVG) method for bismuth (Bi) and selenium (Se) using low-concentration isopropyl alcohol (IPA) and low molecular weight organic acid (LMWOA) is proposed. Under optimal conditions (200 mM IPA, 1 mM oxalic acid (OA), and 10 mg L−1 Co(II)), a PVG efficiency of 93 ± 1% was achieved for Bi within 70 s of UV irradiation, which is the highest efficiency reported for Bi PVG systems to date. Coupled with ICP-MS, the method provides a limit of detection (LOD; 3σ) of 0.2 ng L−1, offering an 8-fold sensitivity enhancement over conventional pneumatic nebulization (PN). Under selected conditions (400 mM IPA, 5 mM formic acid (FA), and 2 mg L−1 Mo(VI)), a PVG efficiency of 60 ± 1% and an LOD of 4.0 ng L−1 were achieved for Se within 100 s of UV irradiation, and no significant difference in analytical sensitivity was observed between Se(IV) and Se(VI). Therefore, rapid and direct determination of total inorganic Se in water samples can be achieved. This system reduced the consumption of organic reagents by approximately 10-fold compared to conventional PVG systems. Mechanistic studies revealed that the volatile products were Bi(CH3)3 and Se(CH3)2, and that Co/Mo nanoparticles were generated in situ. The synergistic photolysis of OA/FA and IPA continuously provides reductive radicals while efficiently quenching •OH, whereas the Co/Mo nanoparticles served as reactive interfacial sites to accelerate PVG kinetics. The proposed methodology was successfully validated using natural water, soil, sediment and biological samples, and its applicability was further extended to other metalloids (As, Sb, Te) and transition metals (Co, Ni), highlighting its potential as a green and sensitive analytical strategy.