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In this paper, Zinc oxide (ZnO) hybridized with graphite-like C 3 N 4 (ZnO/g-C 3 N 4 ) nanoflowers based solid phase microextraction (SPME) coating was prepared on fiber using in situ hydrothermal growth method for gas chromatographic -mass spectrum (GC- MS) separation and analysis target analytes in complex matrixes for the first time. The proposed hybrid ZnO/g-C 3 N 4 fiber exhibited wide linearity for the pesticide residues in range of 0.003–5.0 ng mL −1 . The limits of detection (LOD) were 0.001–0.0025 ng mL −1 . The relative standard deviation (RSD) for three replicate extractions using one fiber was ranged from 2.3% to 7.6%. The fiber to fiber RSD was 5.3–11.3% (n = 3). This method was successfully used for simultaneous determination of nine pesticide residues in cucumber, pear, Green tea and Minjiang water with satisfactory recoveries of 79.1–103.5%. These results indicated that the ZnO/g-C 3 N 4 composite provided a promising alternative in sample pretreatment and analysis. [ABSTRACT FROM AUTHOR]

The main quest for the implementation of direct SPME to complex matrices has been the development of matrix compatible coatings that provide sufficient sensitivity towards the target analytes. In this context, we present here a thorough evaluation of PDMS-overcoated fibers suitable for simultaneous extraction of different polarities analytes, while maintaining adequate matrix compatibility. For this, eleven analytes were selected, from various application classes (pesticides, industrial chemicals and pharmaceuticals) and with a wide range of log P values (ranging from 1.43 to 6). The model matrix chosen was commercial Concord grape juice, which is rich in pigments such as anthocyanins, and contains approximately 20% of sugar (w/w). Two types of PDMS, as well as other intrinsic factors associated with the PDMS-overcoated fiber fabrication are studied. The evaluation showed that the PDMS-overcoated fibers considerably slowed down the coating fouling process during direct immersion in complex matrices of high sugar content. Longevity differences could be seen between the two types of PDMS tested, with a proprietary Sylgard ® giving superior performance because of lesser amount of reactive groups and enhanced hydrophobicity. Conversely, the thickness of the outer layer did not seem to have a significant effect on the fiber lifetime. We also demonstrate that the uniformity of the overcoated PDMS layer is paramount to the achievement of reliable data and extended fiber lifetime. Employing the optimum overcoated fiber, limits of detection (LOD) in the range of 0.2–1.3 ng/g could be achieved. Additional improvement is attainable by introducing washing of the coatings after desorption, so that any carbon build-up (fouling) left on the coating surface after thermal desorption can be removed. [ABSTRACT FROM AUTHOR]

In this work, a correlation study of monoclonal antibody-based enzyme-linked immunosorbent assays (ELISAs) and a liquid chromatography–electrospray mass spectrometric (HPLC/ESI/MS/MS) method for the determination of N-methylcarbamate insecticides carbofuran, carbaryl and methiocarb in fruit baby food is presented. The comparison of performance characteristics of the two methods was carried out by simultaneous analysis of apple–strawberry baby food (GPC purified) extracts spiked with N-methylcarbamates at six different concentration levels. Results obtained by ELISA correlated well with those obtained by LC/MS/MS, both in terms of trueness and precision. Recoveries, i.e. the ratio of the determined concentration to the known spiked concentration, were in the 60–100% range for ELISA and in the 73–104% range by LC/MS/MS with the RSDs from seven replicate analyses 3.6–23.3 and 1.7–8.2%, respectively. The influence of sample pre-treatment on the analytical performance of immunoassay method was also assessed. Using ELISA recoveries close to 90% were obtained even in crude non-purified baby food extracts. The limits of detection (LODs) by ELISA were 0.3, 0.04 and 0.02 μg/kg−1 for carbofuran, carbaryl and methiocarb, respectively, whereas using LC/MS/MS 1 μg/kg was the detection limit for all three insecticides. The results clearly indicate that the developed ELISA is suitable for the fast, quantitative and reliable determination of carbaryl, carbofuran and methiocarb in baby food even for the analysis of crude non-purified extracts. [Copyright &y& Elsevier]