Rapid and reliable detection and quantification of organophosphorus pesticides using SERS combined with dispersive liquid–liquid microextraction

Rapid and reliable detection and quantification of pesticide residues in complex matrices by surface enhanced Raman spectroscopy (SERS) remain challenging due to the low level of target molecules and the interference of nontarget components. In this study, SERS was combined with dispersive liquid–liquid microextraction (DLLME) to develop a rapid and reliable method for the detection of organophosphorus pesticides (OPPs). In this method, DLLME was used to extract and enrich two representative OPPs (triazophos and parathion-methyl) from a liquid sample, and a portable Raman spectrometer was used to analyze the separated sediment using homemade gold nanoparticles colloids as enhancing substrates. The results showed that the developed method displayed good sensitivity and stability for the detection and quantification of triazophos and parathion-methyl with R2 ≥ 0.98. The calculated limits of detection (LODs) in the simultaneous detection of triazophos and parathion-methyl were 2.17 × 10−9 M (0.679 ppb) and 2.28 × 10−8 M (5.998 ppb), and the calculated limits of quantification (LOQs) were 7.23 × 10−9 M (2.26 ppb) and 7.62 × 10−8 M (19.098 ppb), respectively. Furthermore, the developed SERS method was successfully applied to the detection of triazophos and parathion-methyl in apple juice with recoveries between 78.07% and 110.87% and relative standard deviations (RSDs) ≤ 2.06%. Therefore, the developed DLLME facilitated liquid SERS method exhibited good sensitivity and stability for the rapid detection and quantification of OPPs and had the potential to be applied to the rapid detection of OPPs in complex matrices.