Effects of aggregating agents on the analysis of histamine in squid muscle via surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) signals of histamine collected via Au–Ag core–shell nanoparticles (Au@Ag NPs; diameter: entire particle, 43 ± 4 – 96 ± 8 nm; Au seed, 20 ± 2 nm) as affected by aggregating agents (AAs; 1 – 106 μmol/L) including NaCl, MgCl2, NaClO4, and Mg(ClO4)2 were investigated in an attempt to develop a simple and sensitive SERS analytical approach for histamine in squid muscle. Results showed that the effects of AAs on SERS intensities of histamine depended on their types and concentrations, and the addition of an AA at its optimal concentration could result in as much as 139% – 375% increase in the SERS signal of histamine. The incorporation of NaClO4 (1 × 104 μmol/L) based upon Au@Ag NPs (diameter, 59 ± 6 nm) led to the best SERS amplification effect. As low as 5 mg/kg of histamine in squid muscle could be detected, and the histamine levels in squid muscle (0 – 400 mg/kg, n = 27) predicted by partial least square regression model were highly correlated with their actual levels in squid samples (R2 = 0.987). This study showed the possibility of greatly amplifying SERS signals of an analyte via selecting the appropriate type and concentration of an AA.