A microfluidic sample preparation and droplet SERS detection all-in-one device for online analysis of deltamethrin in meat products

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool to acquire the fingerprint information of molecules rapidly, sensitively, and noninvasively. Its application in sample analysis, however, suffers from low repeatability due to the interference of the sample matrix. To address this issue, a microfluidic device was developed to realize all-in-one sample preparation and SERS detection for the online analysis of deltamethrin in meat products. This device was constructed using a microfluidic sample preparation unit and a droplet SERS detection unit. Through flow rate control, analytes at appropriate concentrations can be continuously encapsulated into online-generated microdroplets with SERS substrate Ag nanoparticle-coated Au nanoparticles. Stronger intensities with smaller relative standard deviations were observed by accumulating the Raman signals of microdroplets. Using the microfluidic SERS device, the enhancement factors of rhodamine 6G and deltamethrin were 2.7 × 10⁷ and 3.8 × 10⁵, respectively, with RSDs less than 4.0% (<i>n</i> = 19). Moreover, this device can be reused more than 7 times through simple cleaning procedures. The established microfluidic SERS analytical method has a linear range of 30.0-500 μg L^-1 with a correlation coefficient of 0.9953, and the limit of detection was 11.6 μg L^-1 (S/N = 3). The established microfluidic SERS method was applied to deltamethrin analysis in chicken skin, chicken and grass carp; 32.8 μg kg^-1 of deltamethrin was found in the chicken skin sample. The accuracy and precision of the method were confirmed by high-performance liquid chromatography and recovery test results, indicating its potential for application in food safety.