Development of a portable device for the detection of tetracycline contents in the aquatic products

Development of efficient and reliable detection methods for sensitive detection of tetracycline residues is of great significance to ensure the foods quality and human health. Due to the lack of accuracy and convenience of the existing methods in detection of tetracycline residue, a portable photoelectrochemical (PEC) device for detection of tetracycline was designed and developed in this work, and the feasibility of the developed device to detect tetracycline residues in fish was further explored. For the development of the portable device, light emitting diode (LED) and STC89C52 microcontroller were employed as excitation light source and control core, respectively. In order to avoid the interference of external light on the detection results of the LED activated PEC sensor, a darkroom of light source was designed for the detection device, which was obtained by using 3D printing method. Then the output signal of the light source and the accuracy for the current signal collection of the developed device was studied. The results showed that the output signal of LED excitation light source was stable, and by comparison, the signal collected by the developed portable device was basically consistent with the commercial CHI660E electrochemical workstation used in the laboratory, which proved that the developed detection device has good accuracy for the collection of current signal and can be further used. For the construction of the PEC sensor, an integrated screen printing electrode was used to replace the traditional three-electrode system to further simplify the detection device, Bi2S3/g-C3N4 was used as photoactive material for the construction of the sensing interface and aptamer was used as the specific recognition element for selective recognition of target tetracycline. By the combination of the developed portable device and the proposed PEC sensor, a simple method for sensitive and on-site detection of tetracycline was finally fabricated. The current of the PEC sensor increased gradually with the increase of the tetracycline concentration, and the logarithm of the current signal of the sensor and the tetracycline concentration showed a good linear relationship within the range of 1×10-11 - 1×10-8 mol/L. The detection limit was 3×10-12 mol/L. Compared with the methods reported in the literatures, the proposed method had a lower detection limit, and the detection cost of the portable device-based detection method was relatively much lower. By virtue of the high specificity of aptamer, the constructed sensor could be used for selective detection of tetracycline in the present of four other kinds of antibiotics (oxytetracycline, ofloxacin, aureomycin and roxithromycin). Fish was selected as a model and a standard addition method was used for real sample analysis, the recovery rate of tetracycline residue in actual fish samples was 92% - 94%, the relative error was no higher than 8.0%, and the relative standard deviation was 1.7% - 3.5%. In order to verify the accuracy of the portable method, the results were also compared with the ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the results of the two methods were basically consistent, which showed that the detection method based on portable PEC detection device has good accuracy and reliability for the detection of tetracycline residues in fish. In addition, by the computer software programming and the analysis of the liner relationship between the current signal and the tetracycline concentration, the developed portable device could obtain the target tetracycline concentration results directly by using the organic light emitting diode (OLED) displayer. This work provides a new way for accurate and on-site analysis of tetracycline in aquatic products and other samples.