A colorimetric assay for the determination of trace arsenic based on in-situ formation of AuNPs with synergistic effect of arsine and iodide.

In this work, we propose a colorimetric assay for the determination of trace arsenic based on in-situ formation of AuNPs with the synergistic effect of arsine (AsH3) and iodide. AsH3, generated by hydride generation of AsIII in the sample or standard solution, enters into the HAuCl4 solution containing polyvinyl alcohol (PVA) and KI, and then reacts rapidly to form AuNPs, resulting in the solution color changing from light yellow to pink. Hydride generation applied here not only produces a strong reducing agent AsH3, but also effectively reduces matrix interference. The introduction of I- promotes the reaction by reducing the Au precursor from trivalent state to monovalent state, thus accelerating the formation of AuNPs with AsH3 and improving the sensitivity for the detection of arsenic. Trace AsIII as low as 10 μg L-1 in 3 mL sample solution can produce the change in color visible to the naked eye. Moreover, the use of the stabilizer PVA and the gaseous strong-reducing agent AsH3 evenly dispersed in the reaction solution lead to the formation of well-distributed and fine AuNPs of size changing little with the dosage of AsH3. The whole analysis process only takes 30 min under ambient condition without complicated synthesis and pretreatment. The proposed assay is simple, stable, sensitive and selective, providing a convenient and cost-effective choice for on-site trace arsenic detection in real samples.