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A direct competitive fluorescence immunoassay (dc-FIA) and a direct competitive enzyme-linked immunosorbent assay (dc-ELISA) for the screening of dimethyl phthalate (DMP) in water samples were developed. The immunoassays utilise polyclonal antibodies against DMP raised in rabbits. The anti-DMP antibodies were linked to horseradish peroxidase (HRP) and fluorescein isothiocyanate (FITC). Under the optimal experimental conditions, the dc-ELISA has a linear working range of 0.1–2000 ng/ml (R 2=0.993) with a limit of detection of 0.09 ng/ml. In the dc-FIA, the linear working range was 0.05–30 ng/ml (R 2=0.996), and the limit of detection was 0.02 ng/ml, which is approximately four-fold more sensitive than the dc-ELISA using the same antibody and coating antigen. The results show low cross-reactivity with other structurally related compounds. The proposed methods are successfully applied to determine the DMP contaminants with a simple extraction procedure, and good recoveries were obtained. [ABSTRACT FROM AUTHOR]

A highly sensitive and specific direct competitive enzyme-linked immunosorbent assay has been developed for the detection of dipropyl phthalate (DPrP) based on antibody-coating format. The specific polyclonal antibodies against DPrP raised in rabbits. The conjugates of the antigen with horseradish peroxidase (HRP) were used as the detectable probe. Under the optimal conditions, the limit of detection of the method was 0.01 ng/mL, and a good quantitative working range of 0.01–16 ng/mL (R2=0.995) was obtained. The cross-reactivities of four structurally related phthalate esters were below 12% and did not interfere significantly the analysis of DPrP. The accuracy of the immunoassay has been evaluated and validated by analyzing real and spiked leachate from plastic food contact materials. The recoveries of DPrP ranged from 85.9% to 109.4%. This developed dc-ELISA was reliable, accurate and highly sensitive. [ABSTRACT FROM PUBLISHER]