Photochemical vapor generation of platinum in mixed formic acid and acetic acid: enhanced effect from cobalt and molybdate ions

Abstract

Herein, a novel photochemical vapor generation (PVG) of platinum (Pt) is reported in a mixed formic (FA)/acetic acid (AA) medium. The PVG efficiency of Pt was largely enhanced by the addition of Co(II) or Mo(VI). A mixture of low concentrations of FA and AA was found to be markedly superior to either FA or AA alone for efficient PVG of Pt. Mo(VI) was first identified as a sensitizer for Pt. The developed PVG system was coupled to inductively coupled plasma mass spectrometry (ICP-MS), and limits of detection (LODs) as low as 0.04 ng L⁻¹ for the Mo(VI)-assisted system and 0.02 ng L⁻¹ for the Co(II)-assisted system were obtained (3σ, n = 11) under selected conditions. These LODs were 15–30 times lower than the recent reports concerning Co(II)/Cd(II) synergistically assisted PVG for Pt systems in AA medium alone, and no segmentation of the linear dynamic range was observed as well. The method was successfully applied to the determination of Pt in environmental water samples, and spike recoveries between 93% and 108% were obtained. Mechanistic studies were conducted separately for Mo(VI)- and Co(II)-assisted PVG reactions, and the volatile Pt species were inferred to be Pt(CO)_x(CH₃)_y in both systems. Upon UV irradiation, Co–Pt bimetallic nanoparticles were observed in the Co(II) system, whereas only Pt nanoparticles were detected in the Mo(VI) system, indicating that distinct sensitization pathways were followed by Co and Mo. This work provides a robust technical foundation for trace Pt analysis in aquatic environments and offers new scientific insights into the photochemical transformation of Pt in natural waters.