Quantitation of cobalt in Chinese tea by surface-enhanced Raman spectroscopy in combination with the spectral shape deformation quantitative theory

A surface-enhanced Raman spectroscopy (SERS) method for the quantification of Co2+ in Chinese tea was developed in this contribution. SERS-enhancing substrates with a high selectivity for Co2+ were prepared by attaching 2-(bis (pyridin-2-ylmethyl)amino)ethane-1-thiol onto the surfaces of Ag nanoparticles. A calibration model based on the spectral shape deformation quantitative theory was derived to address the poor reproducibility problem in SERS assays due to the practical impossibility in controlling the number and distribution of "hot spots" on or close to the surface of enhancing substrates. The proposed SERS platform was applied to the quantification of Co2+ in Chinese tea samples and achieved quite satisfactory quantitative results. The average relative deviation between the quantitative results of the proposed SERS platform and those of inductively coupled plasma mass spectrometry was about 6.0%. It is therefore reasonable to expect that the proposed SERS platform can be a competitive alternative for the quantification of Co2+ in food samples.