Banghorowitz0939

In this work, a single cross-linking functional monomer, 2,5-divinylterephthalaldehyde, was designed and synthesized to simplify the preparation of molecularly imprinted polymers (MIPs). In the presence of estradiol as a template, MIPs were successfully prepared using 2,5-divinylterephthalaldehyde along with a solvent and initiator. This method reduced most of the complex variables encountered in the traditional synthesis. Characterization of the morphology and structure of the MIPs was performed by scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. Compared with non-imprinted polymers, the MIPs had higher adsorption capacities for five estrogens with imprinting factors above 2.9. The MIPs had high extraction efficiencies, good functional properties, long lifetimes, and good reproducibility, which made them suitable for solid-phase microextraction (SPME). Coupled with ultra-high performance liquid chromatography tandem mass spectrometry, the MIP-based fibers were applied to SPME for the analysis of five estrogens in milk samples. Under the best conditions, the established method had a wide linear range (0.5-10000 ng kg-1), low limits of detection (0.08-0.26 ng kg-1) and quantification (0.26-0.87 ng kg-1), good precision (3.2-8.1%, n = 6), and fiber-to-fiber reproducibility (4.3%-8.8%, n = 3). The MIPs-based fibers can be reused at least 60 times without apparent loss of extraction efficiency. Finally, this method was applied to the determination of target estrogens in milk samples with satisfactory relative recoveries (84.3%-105%, relative standard deviation ≤ 7.8%).Citrinin is a toxic small organic molecule produced as a secondary metabolite by fungi types Penicillium, Monascus and Aspergillus and is known to contaminate various food commodities during postharvest stages of food production. During the last 10 years, most reported methods for citrinin analysis employed enzyme-linked immunosorbent assays or high-performance liquid chromatography. Over this same time period, liquid extraction, solid-phase extraction, dispersive liquid-liquid microextraction and QuEChERS were the most cited sample preparation and clean-up methods. In this review the advantages and disadvantages of the various sample preparation, separation and detection methods for citrinin analysis over the last decade are evaluated. Furthermore, current trends, emerging technologies and the future prospects of these methods are discussed.A new mode of dispersive solid phase extraction based on in situ formation of adsorbent in aqueous phase has been introduced as an efficient method for the extraction of some pesticide residues in fruit juice samples. In this method, polycarbonate which is an inexpensive polymer is used as an adsorbent for the first time. The method is followed by dispersive liquid-liquid microextraction for more enrichment of the analytes. In the present study, a proper amount of the polymer is dissolved in N,N-dimethyl formamide and the obtained solution is injected into an aqueous phase containing the analytes. After injection, polycarbonate particles are formed and adsorbed the analytes. Then, the adsorbent is separated from the aqueous solution and eluted by acetone. The obtained acetone phase is mixed with 1,1,1-trichloroethane and the mixture is dispersed into deionized water and a cloudy solution is formed. Ultimately, after centrifugation, the obtained sedimented phase containing the extracted analytes is injected into gas chromatography-flame ionization detection. In the proposed method, the adsorbent synthesis step, which often is a time-consuming, expensive, and laborious step in most adsorbent-based sample preparation methods, has been removed. Moreover, there is no need for sonication or vortex agitation. Under the optimized experimental conditions, the relative standard deviation was equal or less than 7% for intra- (n = 6) and inter-day (n = 5) precisions at a concentration of 50 µg L-1 of each pesticide. The limits of detection and quantification were in the ranges of 0.34-1.2 and 1.1-4.0 µg L-1, respectively. Pembrolizumab mouse In addition, extraction recoveries and enrichment factors varied in the ranges of 44-89% and 220-443, respectively.A new and sensitive analytical method for the simultaneous determination of secondary lipid peroxidation aldehydes has been successfully developed and validated. Malondialdehyde, acrolein, formaldehyde, acetaldehyde, propanal, and pentanal were extracted and derivatized using 2,4-dinitrophenylhydrazine (DNPH) by gas-diffusion microextraction (GDME) combined with dispersive liquid-liquid microextraction (DLLME) for gas chromatography-mass spectrometry (GC-MS) analysis. The experimental conditions have been optimized by experimental designs. The analytical method validation, in accordance to the Food and Drug Administration (FDA) guidance, provided good results in terms of linearity with r2≥0.9974, in the range from 0.15 or 0.3 µg·g-1 to 3 µg·g-1. Limits of detection and limits of quantification were 0.05 or 0.10 and 0.15 or 0.3 µg·g-1, respectively. Precision was tested as a relative standard deviation (RSD≤ 9.5%) and recoveries were between 95% and 110%. The method was applied in the characterization of aldehydes in forty-eight edible oil samples; with the highest concentration found in pomace olive oil for malondialdehyde at 6.64 µg·g-1.Comprehensive two-dimensional gas chromatography (GC×GC) based on flow-modulation (FM) is gaining increasing attention as an alternative to thermal modulation (TM), the recognized GC×GC benchmark, thanks to its lower operational cost and rugged performance. An accessible, rational procedure to perform method translation between the two platforms would be highly valuable to facilitate compatibility and consequently extend the flexibility and applicability of GC×GC. To enable an effective transfer, the methodology needs to ensure preservation of the elution pattern, separation power, and sensitivity. Here, a loop-type thermal modulation system with dual detection (TM-GC×GC-MS/FID) used for the targeted analysis of allergens in fragrances is selected as reference method. Initially, six different columns configurations are systematically evaluated for the flow-modulated counterpart. The set-up providing the most consistent chromatographic separation (20 m x 0.18 mm dc x 0.18 μm df + 1.8 m x 0.18 mm dc x 0.18 μm df) is further evaluated to assess its overall performance in terms of sensitivity, linearity, accuracy, and pattern reliability.