Abstract:Developing portable devices for extraction and detection of oxytetracycline (OTC) in soil, and developing accurate methods for on-site analysis of OTC in soil is of great importance to ensure the safety of agricultural environment and human health. The existing devices for OTC extraction require additional devices to meet the needs for on-site extraction, and the low sensitivity of the on-site detection method limits its application in accurate detection of trace OTC in soil. Integration circuits provide ideas of hardware integration design for soil OTC extraction-detection devices because of the advantages of simple circuitry, low failure rate, low power consumption, and high reliability;the photoelectrochemical (PEC) aptasensor is expected to achieve accurate detection of OTC for its high sensitivity, good selectivity, and easy portability. A portable device was developed for extraction and PEC detection of OTC in soil by designing an integrated hardware circuit. Firstly, a portable device for extraction of OTC in soil was designed and developed with STM32F103ZET6 as the control core. The extraction of OTC from soil was accomplished using the developed portable device and laboratory device, respectively, and the extraction precision was verified by using ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Subsequently, a portable PEC detection device was prepared by using integrated Bi2S3-C3N4 based screen-printed electrodes, low-power LEDs, and a miniaturized electrochemical workstation. The design of hardware circuit and light source darkroom had the function of controlling the timing switching of the LEDs during PEC detection and avoiding the interference of the external light source on the output PEC signal. Lastly, the portable extraction-PEC detection device was used for on-site analysis of OTC in soil. Results showed that the extraction precision of the developed portable device was accordance with that of the laboratory device;and the portable PEC detection device had a linear range of 1×10-8~1×10-6mol/L and a detection limit of 5.33×10-9mol/L was obtained for OTC detection;and the results of the on-site analytical method for OTC were basically agree with the results of the UPLC-MS/MS method. This work would realize the on-site analysis of OTC in soil and provide technological support for soil treatment.
