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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]

Carbon dots as new nanomaterials, have been widely used in rapid detection because of their nondestructive, real-time detection characteristics. Improving the sensitivity and selectivity of the method in complex real samples is new challenge and requirement for sensing technology. Here, we report an ultrasensitive fluorescence immunoassay (FIA) for trace diethyl phthalate (DEP) using red carbon dots@SiO2 (R-CDs@SiO2) as tags. SiO2 as a nanocarrier can effectively improve the bio-functionalization and utilization rate of carbon dots. Moreover, several R-CDs embedded in SiO2 nanospheres can magnify the fluorescence signal and improve sensitivity. R-CDs@SiO2 conjugate anti-DEP antibody (Ab) as fluorescent immunosensor, which can specifically recognize DEP. Under optimization conditions, the detection limit (LOD) of this FIA was calculated as 0.0011 ng/mL. In addition, the recoveries of this established FIA ranged from 96.8 to 108.5%, showing satisfactory accuracy. Compared with GC-MS/MS (LOD µg/mL), the sensitivity of the FIA was significantly improved. As a result, the FIA developed using R-CDs@SiO2 as tags has a high potential for determining trace DEP. [ABSTRACT FROM AUTHOR]

"Turn on" fluorescence immunoassay of endocrine diethyl phthalate. [Display omitted] • Fluorescence turn-on immunoassay of endocrine diethyl phthalate. • Red carbon dots can reduce interference of autofluorescence. • Red carbon dots as tags can improve the sensitivity of immunoassay. • "Turn-on" probe can reduce the interference of actual sample medium. Diethyl phthalate (DEP), as the environmental endocrine, would interfere with people's endocrine system and has greatly harm in health. Here a sensitivity, eco-friendly fluorescence immunoassay technique was established based on "turn-on" red carbon dots (R-CDs) conjugated anti-DEP antibody (Ab) as the immunoprobe for the detection of DEP in daily supplies. The R-CDs will "turn-on" fluorescence when it in formamide solution, due to the change of the electron distribution on the surface and electronic charge transfer of the red carbon dots. The use of "turn-on" R-CDs as immunoprobe effectively increased the sensitivity of the immunoassay. Moreover, the R-CDs conjugated anti-DEP Ab without any additional embellishment. Under the optimal conditions, a good linear was established with the DEP concentration range of 5 × 10−2 ng/mL–10 ng/mL, the low limit of detection (LOD) of the proposed method was 0.0056 ng/mL. This project has satisfactory accuracy with recoveries ranging from 96.0% to 115.1%. Our research provides an accurately, simply and sensitivity strategy to detect the content of environmental endocrine DEP in daily supplies. [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]