Quantification of Cadmium in Rice by Surface-enhanced Raman Spectroscopy Based on a Ratiometric Indicator and Conical Holed Enhancing Substrates

Abstract

A surface-enhanced Raman spectroscopy (SERS) based method was developed for the quantification of Cd²⁺ in rice. Gold nano-particles (AuNPs) modified with trimercaptotriazine served as a ratiometric SERS probe for the detection of Cd²⁺. A conical holed substrate was used to further enhance SERS signals, and hence to improve the sensitivity. A calibration model based on the spectral shape deformation quantitative theory was employed to mitigate the influence of variations in the number and distribution of “hot spots”. The proposed SERS method was applied to quantitative analysis of Cd²⁺ in three types of rice, and achieved satisfactory quantitative results with accuracy comparable to that of the reference method—inductively coupled plasma mass spectrometry. The limit of detection of the proposed method was estimated to be 8 μg kg⁻¹. The proposed SERS method has the potential to become a fast screening method for the detection of Cd²⁺ in rice.