A simple, rapid and low-cost determination method of benzo(a)pyrene in fried and baked foods was proposed by high performance liquid chromatography combined with vesicular coacervative supramolecular solvent (SUPRAS) extraction. The vesicular coacervate was composed of 1-octanol and tetrabutylammonium bromide. 200 mg of dried samples with 600 lL SUPRAS could be mixed to extract benzo(a)pyrene. Neither evaporation nor further clean-up steps for the extracts were needed. The overall sample treatment took approximately 30 min, and several samples could be simultaneously treated using conventional lab equipment. Then, benzo(a)pyrene was analyzed via liquid chromatography-fluorescence detection. Parameters affecting the extraction efficiency were investigated and optimized. The results showed good linearity of benzo(a)pyrene with the coefficients of determination (R 2) of more than 0.9999 in the range of 0.1-50.0 lg/kg. The limit of detection of the method was 0.11 lg/kg. Recoveries for spiked samples in the range of 1-10 lg/kg were between 89.86 and 100.01%, with relative standard deviations from 1.20 to 3.20%. Benzo(a)pyrene was present in food samples (including instant noodles, biscuits, rice crust and fried bread stick) at concentrations in the range of 0.08-0.39 lg/kg according to the proposed method. The proposed pretreatment method significantly reduces the analysis time. Furthermore, the solventless approach is in accordance with the green chemistry development trend and has significant application prospects.
The optical absorption detector is one of the most commonly used detectors for high performance liquid chromatography (HPLC). As a core part of this kind of detector, the designs of flow cells, where light passes through samples for acquiring samples information, will affect the performance of a detector. In order to enhance the signal to noise ratio of detectors and reduce the bands broadening that come from flow cells, it is necessary to design a flow cell with a longer optical path length and a less cell volume while maintaining the luminous flux. However the limitations of the machining capacity make it difficult to increase the optical path length, reduce the cell volume and keep or increase the luminous flux simultaneously. It is a challenge to optimize the designing and machining of flow cells so as to improve the performance of detectors. This review discusses the development of designing flow cells based on the detection principle in some aspects of increasing the optical path length, reducing the cell volume, taking the advantages of total reflection and so on. At the same time, some of the designs are illustrated in detail. These various ideas and structures are significant references for designing flow cells and developing optical absorption detectors.
The double qualitative principle is a new composite qualitative method based on retention time and the characteristic peaks of the absorption spectra. Using a self-designed and assembled diode array detector (DAD), a high performance liquid chromatography (HPLC) system was constructed. The illegal additive auramine O in six kinds of herbal slices and the active ingredient schisandrin in Jujube kernel Tianma capsules were separated and qualitative analyzed using the HPLC-DAD system. The results showed that there were similar peaks in the chromatograms of pollen typhae and Jujube kernel Tianma capsules when comparing the target analytes. However, the probabilities of the targets were excluded by comparing the absorption spectra. The application results indicated that, based on the double qualitative principle of retention time/absorption spectrum, the interference of impurities in the samples could be well eliminated and the false positives could be avoided. This provides a reference method for the study of traditional Chinese medicine components.
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