Portable tetracycline analyzer based on LED-excitation europium-sensitized luminescence

Described in detail here is the design of a portable tetracycline (TC) analyzer based on europium-sensitized luminescence (ESL). The instrument operation and data processing are controlled by a laptop computer running a custom LabVIEW program. A 385-nm light emitting diode (LED) is used in pulse mode as excitation source. Compared to a conventional xenon flashlamp, an LED has a narrow emission bandwidth, weak residual radiation, and orders-of-magnitude-lower cost, weight, and power consumption. The time-resolved luminescence (TRL) signal is detected by a gated photomultiplier tube (PMT), and normalized by monitoring the energy of individual LED pulses with a photodiode (PD). Over three orders of magnitude (0.1–100 ppb TC), the TRL signal maintains linear dependence on TC concentration; beyond 100 ppb filter effects becomes obvious. A 0.060-ppb limit of detection (LOD) is achieved with a typical ∼5% relative standard deviation (R.S.D.). The background noise corresponds to ∼0.05 ppb. At 16 pounds, the analyzer is readily deployable for field analysis.