Fluoroimmunoassay based on suppression of fluorescence self-quenching for ultra-sensitive detection of herbicide...

A highly sensitive heterogeneous fluoroimmunoassay has been developed for monitoring phenylurea herbicide diuron on the basis of suppression of fluorescence self-quenching. Specific antibody against diuron was produced and labeled with rhodamine isothiocyanate at different molar ratios and used as tracer in the developed immunoassay. The analytical sensitivity of immunoassay was enhanced by changing the microenvironment of fluorescence label with glycerin solution after the completion of immunoassay. Enhancer treatment on developed immunoassay showed improvement of fluorescence signal intensity by approximately 4-folds with higher stability compared with the signal determined without enhancer treatment of the wells. The immunoassay has a detection limit of 0.1 ng mL(-1) with good signal precision (approximately 2%) in the optimum working concentration range between 0.01 and 100 ng mL(-1) of diuron. In addition, the use of enhancer improved the stability of fluorescence signal by suppression of self-quenching of fluorescence signal. The proposed method has been applied satisfactorily for the ultra-sensitive detection of herbicide diuron in samples.