Determination of malachite green in environmental water using cloud point extraction coupled with surface-enhanced Raman scattering

Abstract

A novel, simple and ultra-sensitive method, for rapid detection of trace malachite green (MG) in environmental water using cloud point extraction (CPE) coupled with surface-enhanced Raman scattering (SERS) is described. The colloidal gold nanoparticles (AuNPs) were synthesized by reduction of chloroauric acid (HAuCl4) with trisodium citrate and were used as SERS substrates. The SERS substrates were found to produce enhancement factors of 1.52 × 106 for MG by employing the SERS peak at 1175 cm−1. After the optimization of SERS conditions including the volumes of ethanol, colloidal AuNPs and HCl, the present method was linear for MG at 1175 cm−1 and 1618 cm−1 over the concentration range of 0.5–35.0 μg L−1 and 2.5–40.0 μg L−1, with the correlation coefficients (r) of 0.9971 and 0.9960. The limits of detection (LODs) were 0.10 μg L−1 and 0.70 μg L−1, and the intra- and inter-day relative standard deviations (RSDs) of detection were in the range of 2.0–2.5% and 1.9–3.2% at 1175 cm−1 and 1618 cm−1, respectively. Recoveries obtained by analyzing 4 spiked environmental water samples at 2 levels were between 93.1 and 106.0%.