Homogeneous immunoassay of atrazine in water by terbium-entrapping liposomes as fluorescent markers.

Atrazine (Atr) was conjugated to mastoparan (Mast) cytolytic peptide; Mast-Atr derivative was used as cytolytic agent on liposomes trapping Tb/citrate complex. This was applied in a time-resolved fluoroimmunoassay for detection of Atr in water. The cytolytic activity was read by means of time-resolved fluorescence after adding an excess of dipicolinic acid (DPA). Tb/citrate-entrapping liposomes are easy to prepare, and the assay is carried out in a short incubation time and in a range between 10 pg and 100 ng. The procedure was applied to analyse samples taken from Adda River and from irrigation ditches in an agricultural area around the town of Lodi. Recovery in samples spiked with two different Atr concentrations was between 95 and 105%.