**4. Conclusions**

In this study, the as-prepared Ag nanowire SERS substrate was tested as a potential tool to determine tartrazine in large yellow croaker for the first time. Highly uniform and high-quality

Ag nanowires were synthesized in a time-efficient and cost-effective manner, which displayed the substantially enhanced effect on standard tartrazine solution detection. The results showed that the lowest detectable concentration was 10 ng/mL. The PLS model demonstrated good predictability. In terms of recovery rate, time, cost and SERS signal, the optimal sample preparation method (i.e., W+M+C) was selected and could be detected at concentration levels as low as 25.48 ng/cm2, which fully satisfies the actual detection requirements. Hence, the established SERS approach showed remarkable performance in determining tartrazine residue in large yellow croaker.

**Author Contributions:** J.S. performed the experiments and wrote the original manuscript. Y.Z. gave theoretical and practical guidance. Y.H. provided worthy advice on work design and modified the manuscript. Y.F. helped design figures and analyzed experimental data. K.L. contributed to the research design, data analysis and manuscript preparation. All authors commented on the manuscript.

**Funding:** This research was funded by the National Key Research and Development Program of China, gran<sup>t</sup> number 2017YFC1600706.

**Conflicts of Interest:** The authors declare no conflicts of interest.
