On-line determination of 3,5,6-trichloro-2-pyridinol in human urine samples by surface plasmon resonance immunosensing

An immunochemical method for the analysis of 3,5,6-trichloro-2-pyridinol (TCP), a major urinary metabolite of chlorpyrifos, is developed using a surface plasmon resonance (SPR)-based biosensor. The stability of the assay was assessed by covalently linking the analyte derivative to a thin, gold-modified sensor surface. For optimization of analyte derivative immobilization, sensor chips were activated via alkanethiol monolayers with terminal amine or carboxyl groups. Binding inhibition tests were performed in untreated urine samples and compared to those obtained in distilled water and PBS was used as control. In all cases, similar detection limits, at the micrograms per litre level (0.1–0.24 μg L⁻¹), were attained for TCP assays independently of the dilution buffer. Reproducibility of measurements was studied throughout more than 130 regeneration cycles, which allowed the repeated use of the same immunosensor surface without significant variation of the SPR signal. All measurements were developed in real-time in only 10 min, using a SPR portable system. The device could be applied as a valuable analytical method to both environmental screening and clinic diagnostics.