In-situ visual and ultrasensitive detection of phosmet using a fluorescent immunoassay probe

It is necessary to develop new detection methods of pesticide residues because pesticide residues endanger human health. In this study, a fluorescent immunoassay probe (PDs-Ab) was designed in order to establish an in-situ visual and ultrasensitive detection method of phosmet. PDs-Ab probe which could recognize phosmet was synthesized by coupling phosmet antibody with polymer dots (PDs) based on poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-(1-cyanovinylene-1, 4-phenylene)]. The experiment results showed PDs-Ab probe was used not only for fluorescent imaging but also for ultrasensitive detection of phosmet. The fluorescent imaging realized in-situ visual and semi quantitative detection of phosmet residues on apple surfaces. The ultrasensitive detection of phosmet utilized a poly (dimethylsiloxane) (PDMS) sheet. Phosmet and PDs-Ab probe were orderly loaded on PDMS sheet, and eluted by absolute ethanol. The fluorescence intensity of absolute ethanol eluant increased in proportion to the concentration of phosmet. The limit of detection for phosmet was 0.4 ng/L with a correlation coefficient of 0.9968. The PDMS sheet was served to concentrate trace phosmet and eliminate the fluorescence interference from excess PDs-Ab. Also, this method was used to monitor phosmet residues in real samples, such as lake water, orange peels and Chinese cabbage leaves, with acceptable recovery range from 97.15% to 102.1%.