Numerous studies have shown that pesticide residues in tea exceeding the maximum residue limits (MRL) can cause harmful effects on the human body. There are many limitations in the existing analytical methods for pesticide residues in tea, so new analytical methods need to be developed. We developed a limit test method that combines thin-layer chromatography with Raman imaging microscopy (TLC-RIM). Seven residual pesticide components in tea (Avermectin, Methomyl, Carbendazim, Imidacloprid, Chlorothalonil, Azoxystrobin, and Acetamiprid) could be preliminarily separated by TLC and then irradiated by a 532 nm laser. Raman spectra of seven pesticides obtained by Raman imaging microscopy could be used to test whether the pesticide residues in tea exceed the MRL. The limits of detection of the seven pesticides were 0.04, 0.10, 0.24, 0.20, 0.12, 0.12, and 1.0 mg/mL, respectively. The simulated positive test showed that the matrix in tea did not interfere with the test of the seven pesticides. When the pesticides were tested within 8 h, the RSD of the peak heights of the seven pesticides were 1.2%~9.6%; the test results of three batches of tea showed that the imidacloprid in one batch of tea exceeded its MRL, and the results were consistent with that by UPLC-MS/MS. The TLC-RIM is fast, sensitive, stable, specific, and reliable.

Residual quinolones in food that exceed their maximum residue limit (MRL) are harmful to human health. However, the existing methods used for testing these residues have limitations; so, we developed a new limit test method called TLC-SERS to rapidly determine the levels of residues of the following: enrofloxacin (A), ciprofloxacin (B), ofloxacin (C), fleroxacin (D), sparfloxacin (E), enoxacin (F), gatifloxacin (G), and nadifloxacin (H). The residues ware preliminarily separated via TLC. The tested compounds’ position on a thin-layer plate were labeled using their relative R_f under 254 nm ultraviolet light, and an appropriate amount of nanometer silver solution was added to the position. The silver on the plate was irradiated with a 532 nm laser to obtain the SERSs of the compounds. The results show significant differences in the SERS of the eight quinolones: the LODs of H, A, D, E, C, G, F, and B were 9.0, 12.6, 8.9, 19.0, 8.0, 8.7, 19.0, and 12.6 ng/mL, respectively; and the RSD was ≤4.9% for the SERS of each quinolone. The limit test results of 20 samples are consistent with those obtained via UPLC–MS/MS. The results indicate that TLC-SERS is a specific, sensitive, stable, and accurate method, providing a new reference for the rapid limit test of harmful residues in foods.

Sulfonamides are not only widely applied in clinics but also highly valued in animal husbandry. Recently, it has become common for sulfonamide residues to exceed the standard limits in food, which can affect human health. Current regulations limit these residues. Therefore, we constructed a new limit test method to rapidly determine the levels of sulfonamide residues. Six sulfonamides were detected using the latest method called TLC-SERS, namely, sulfamethasone (A), sulfamethazine (B), sulfadoxine (C), sulfamethoxydiazine (D), sulfamethoxazole (E), and sulfathiazole (F). The optimal conditions for SERS detection were investigated for these six drugs, and the separation effects of different TLC spreaders on them were compared. Then, we successfully established a separation system using dichloromethane–methanol–ammonia in a ratio of 5:1:0.25 (v/v/v), which provided good separation effects on the six drugs. The residues were preliminarily separated via TLC. A silver sol solution was added to the spot on the silica gel G plate at the corresponding specific shift values, and SERS detection was performed. The sample solution was placed on the spot under a 532 nm laser, and the SERS spectrum was collected and analyzed for the six sulfonamides. The results showed obvious variations in the SERS spectrum among the six sulfonamides, with the LODs being 12.5, 6.4, 6.3, 7.1, 18.8, and 6.2 ng/mL from A to F, respectively, and an RSD of <3.0%. Within 48 h, the SERS signal for each sulfonamide drug was kept stable, with an RSD of <3.0%. The detection results of 20 samples using the TLC-SERS method were consistent with those obtained by UPLC-MS/MS. The established TLC-SERS method is simple and fast, providing a useful reference for the rapid detection of residue limits in food.

The aim of this study was to establish a new method for the determination of homoisoflavanones (Ⅲ, Ⅳ, V) in polygonatum odoratum(POD) by combination of thin layer chromatography (TLC) and chemical derivative resonance Raman spectroscopy (RRS). The twice chromatography method of TLC was used to improve the specificity of the component to be tested; the method of the relative Rf was used to reduce the use of the reference substance of the component to be tested; the chemical derivatization method was used to improve the signal intensity of Raman spectrum for the component to be tested in POD, so as to obtain a trace amount fingerprint structure information of the measured component. The method exhibits robust specificity, high sensitivity, and reliable stability, there by offering a novel reference approach for the identification and evaluation of homoisoflavanones (Ⅲ, Ⅳ, V) in POD.

The objective of this study was to establish a novel method for the detection of lean meat powder (salbutamol sulfate and terbutaline sulfate) residues in commercially available pig liver based on diazo coupling reaction by combining thin layer chromatography (TLC) with surface-enhanced resonance Raman scattering (SERRS). TLC was used to separate samples; after determining the spots of each component, diazo coupling reaction was carried out on the spots in situ to generate azo compounds, and then the spots of azo compounds mixed with silver sol on the TLC plate were qualitatively detected by SERRS. The limit of detection (LOD) of salbutamol sulfate was as low as 0.14 μg kg⁻¹, and that of terbutaline sulfate was as low as 0.04 μg kg⁻¹. The influence of the sample matrix in TLC-SERRS detection of salbutamol sulfate and terbutaline sulfate was investigated by experiment on a simulated positive sample, and salbutamol sulfate and terbutaline sulfate in commercially available pig liver were detected. Compared with the reported method (HPLC-MS/MS), this method has the advantages of strong specificity, high sensitivity, rapidity and low cost. It provides a new reference method for establishing and perfecting the safety system of veterinary drug residues.

Numerous studies have shown that quinolones residues in the foods exceeding the MRL is harmful to the human health. There are some limitations in the existing methods for the residues, so we developed a new limit test method (TLC-SERS) to rapidly determine following residues: enrofloxacin(A), ciprofloxacin (B), ofloxacin(C), fleroxacin(D), sparfloxacin(E), enoxacin(F), gatifloxacin(G) and nadifloxacin(H). The residues can be preliminarily separated by TLC. Labeling the tested compounds’ position on the thin layer plate by their relative Rf under 254nm ultraviolet, and an appropriate amount of nanometer silver solution should be added to the position. The silver on the plate should be irradiated with 532nm laser to obtain SERS of the compounds. The results showed a significant differences of the 8 quinolones’ SERS; the LOD of the H, A, D, E, C, G, F and B were orderly 9.0, 12.6, 8.0, 19.0, 8.0, 8.4, 9.0 and 12.6 ng/mL, and the RSD≤4.9% for SERS of each quinolones.The limit test results of the 20 samples was consistent with that determined by the UPLC–MS/MS. The above results indicate that the TLC-SERS is specific, sensitive, stable, and accurate, providing a new reference for the rapid limit test of harmful residues in foods.