Highly sensitive and selective method for detection of trace amounts of nitrite in aquaculture water by SERRS coupled with diazo reaction

Based on modified diazo reaction, a novel surface-enhanced resonance Raman scattering (SERRS) method employed for ultrasensitive, highly selective, and ultra-trace determination of nitrite in aquaculture water was demonstrated. The azo dyes, which are formed by 4-aminothiophenol, nitrite, and N-(1-naphthyl) ethylenediamine dihydrochloride in acid conditions, can exhibit high SERS signal on Ag nanoparticles. Subsequently, the concentration of nitrite can be determined from the intensity of SERRS of derivative. Under optimal conditions, a linear relationship between Raman intensity and the nitrite concentration was found in the range of 0.1–15.0 μmol L −1 with a good correlation coefficient (R 2  = 0.9921) at 1380 cm −1 , and the limit of detection can reach as low as 16.4, 24.0, 9.0, and 24.6 nmol L −1 at 1138, 1332, 1380 and 1418 cm −1 , respectively. Additionally, the results indicate that the present method can be applied to detect nitrite in real aquaculture water samples without influence of interfering ions. This study provides a feasible method for accurate, trace, and fast field detection of nitrite in aquaculture water with strong potential to be used for on-line and on-site optical sensors of nitrites.