Immunosensors for pollutants working in organic media. Study of performances of different tracers with luminescent detection

A comparative study of enzymatic and non-enzymatic labels combined with luminescence detection, developed for immunosensing of pesticide residues (carbaryl, 1-naphthol, irgarol 1051) in organic media, is presented. Peroxidase and alkaline phosphatase enzymes with fluorogenic (3-p-hydroxyphenylpropanoic acid) and luminogenic (AMPPD derivative) substrates, respectively, were assessed as enzymatic markers. As an alternative, terbium(III) chelate, with time-resolved fluorescence detection, was evaluated as a non-enzymatic label. The best sensitivity was achieved by use of alkaline phosphatase in an immunocomplex capture assay format (I ₅₀ values 0.06, 0.27, and 7.45 μg L⁻¹ in buffer, 1:1 methanol–buffer, and methanol, respectively). Results were also good (I ₅₀ 1.00 and 6.30 μg L⁻¹ for water and aqueous–organic mixture, respectively) for Tb(III) chelate in an immobilized conjugate assay format. Use of alkaline phosphatase label to measure carbaryl (100 ng L⁻¹) in different spiked river water samples, after solid-phase extraction and analyte elution with an ethyl acetate–methanol mixture, resulted in recoveries ranging from 81 to 98%, with acceptable precision (CV 4–14%, n=4).