A modulation approach with 4-hydroxybenzhydrazide as the modulating agent was designed for constructing 2,4,6-triphenoxy-1,3,5-benzene-based covalent organic frameworks (COFs). The COFs materials were employed as solid phase microextraction (SPME) coatings for the extraction of phthalate esters (PAEs). Various experimental conditions including extraction temperature, extraction time, salt concentration, and desorption time were investigated and optimized. The introduction of modulating agent into the synthesis of fibers significantly enhanced the extraction efficiency towards PAEs. The linear range was 1–100 μg L ‒1 and the detection limits in the range of 0.032–0.451 μg L ‒1 were achieved with good linearity ranged from 0.9904 to 0.9970. Inter-batch and intra-batch relative standard deviations were in the ranges of 0.83–4.67% and 3.08–9.73%, respectively. Moreover, the developed coating fibers were used for the extraction of PAEs in water samples and satisfactory recoveries were achieved.
Derivatization is usually employed in immunoassay for detection of metabolites of nitrofurans and avoiding derivatization could be preferable to achieve an efficient screening. In the study, we designed four haptens of 4-hydroxybenhydrazide (HBH), the nifuroxazide metabolite. The effect of hapten structures on antibody affinity were evaluated and one monoclonal antibody was produced by using the Hapten C with a linear alkalane spacer arm. After optimization, an enzyme linked-immunosorbent assay (ELISA) was established with an 50% inhibition concentration of 0.25 ng mL −1 for HBH, which could ensure the direct detection of HBH without derivatization. The limit of detection of the ELISA for HBH was 0.12 µg kg −1 with the recoveries of 90.1–96.2% and coefficient of variation (CV) values lower than 9.1%. In conclusion, we produced several high affinity antibodies to HBH with new designed hapten and developed an icELISA for the direct detection of HBH without derivatization in chicken.
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