LED-based tetracycline analyzer for field analysis

Abstract

Tetracycline (TC) is a significant class of antibiotic drugs in human and veterinary medicine. Its extensive use may lead to pollution in the marine environment and residues in foods of animal origin. To perform TC analysis in the field, a portable TC-specific analyzer was developed based on europium-sensitized luminescence. A 385 nm light emitting diode (LED) is used in pulsed mode as the light source to selectively excite TC. In comparison to a conventional xenon flashlamp, its narrower emission band and cleaner post-pulse extinction lead to reduced background and improved sensitivity. The time-resolved luminescence (TRL) signal is detected by a photomultiplier tube (PMT) that is gated to minimize its response to the LED pulse. The energy of individual LED pulses is monitored by a photodiode (PD) for signal normalization. Both instrument operation and data processing are controlled by a laptop computer running a custom LabVIEW program. The PD and the PMT signals are acquired at 4-μs time resolution and 12-bit amplitude resolution. The instrument performance is evaluated using oxytetracycline, a significant member of the TC antibiotics, as a target analyte. The analyzer achieves a 0-3 ppm linear dynamic range (r² = 0.9988) and a 0.021-ppb limit of detection with a typical 5% relative standard deviation.