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%.