Rapid detection of Rhodamine B in raw paprika and other food based on SERS technique

Objective: Rhodamine B is one kind of synthetic alkaline triphenylmethane dye, which have been used as a food additive.But now it is proved to be a toxic and cancer-causing substance, and is forbidden to artificially add into food in China and EU. At present, the government has not enacted relevant testing standards, and no on-site test methods was put forward.Therefore it is imminent to establish an on-site rapid detection method.Method: Based on surface enhanced Raman spectroscopy ( SERS) technique, this experiment achieved the rapid detection of rhodamine B in chilli products, such as bacon, fruit juice, wine and other foods, used gold nanoparticle sol as Raman signal enhancement module, a home-made laser Raman spectra pretreatment apparatus and a portable Raman spectrum detector.Result: Compared with the conventional methods, the difference of SERS spectra was not obvious, and the results also were not affected by the sample composition, though the experimental time was shorten from 40⁵0 min to about 10 min, and the minimum detection concentration for RB was 0.5 mg/kg. By using the intensity of 1355 cm^-1 peak as a normalization standard, the recoveries for chili spikes ( 100, 200, 300 μg/L) in chilli powder ranged from 81.1% ~ 87.0% and the relative standard deviations ( RSD) from 2.1% to 3.0%. Conclusion: The actual samples purchased from the supermarket were tested by the quick method mentioned in this study. The results told us that this method was reliable compared with proven technique of LC, and the device used in this experiment is portable and easy to be operated, and the results also showed us that this method can be applied for site inspection and preliminary inspection in laboratory.