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Making a Proficiency-based Remote Laparoscopic Skills Program for the COVID-19 Age.
Gas chromatography (GC)-high-resolution mass spectrometry (HRMS) with accelerated solvent extraction (ASE)-purification simultaneously coupled to the isotope internal standard method is proposed for the determination of 32 polychlorinated biphenyls (PCBs) in aquatic products. Synchronous purification was achieved by adding 2 g of anhydrous sodium sulfate, 1 g of Cleanert Florisil, and 50 g of neutral alumina as the adsorbent to the ASE system. The PCBs were extracted from aquatic product samples using a dichloromethane-n-hexane (11, v/v) mixture at 100 ℃ with two extraction cycles. The extracting solution was purified twice with 0.5 mL concentrated sulfuric acid. After concentration to a constant volume, the target compounds were detected by GC-HRMS and quantified by the isotope internal standard method. Under the optimized conditions, the relative standard deviations (RSDs) of the mean relative response factor (RRF) for the 32 PCBs in the range of 0.1-20 μg/L were less than 15%. The limits of quantification were 0.3-1.9 ng/kg. At three spiked levels (5, 20, and 50 ng/kg) in grass carp and sea bass, the recoveries of the 32 PCBs were between 71.9% and 119.0%, with the RSDs varying from 3.5% to 19.6%. This method effectively reduces the matrix interference and shows high sensitivity, good reproducibility, and stable recovery, thus proving useful for the detection of PCBs in aquatic products.A method for the determination of vitamin K1 and vitamin K2 in modulation milk powder was developed by high performance liquid chromatography (HPLC) coupled with post-column reduction. The samples were dissolved in water, lipase hydrolyzed, saponified with 2.5 mol/L sodium hydroxide solution and ethanol solution, extracted with n-hexane, and dissolved in methanol after concentration. The vitamin K were first separated on an Xbridge C18 column and then on a zinc powder reduction column, and detected using a fluorescence detector. The excitation and emission wavelengths were 326 nm and 432 nm, respectively. An external standard method was used for quantification. The results showed that the linearities of vitamin K1 and vitamin K2 was in the ranges of 0.0025-2.0 μg/mL and 0.01-2.0 μg/mL, respectively, with correlation coefficients both greater than 0.999. The spiked recoveries were 80.39%-94.39% and the precisions were 0.85%-3.98%. The limits of detection of vitamin K1 and vitamin K2 were 0.07 μg/100 g and 0.2 μg/100 g, respectively. The limits of quantification of vitamin K1 and vitamin K2 were 0.2 μg/100 g and 0.8 μg/100 g, respectively. The method has high sensitivity and good repeatability, and gives accurate results. It is suitable for the analysis and determination of the vitamin K1 and vitamin K2 in formula milk powder.A method was developed for the determination of nine antioxidants in vegetable oils by high performance liquid chromatography (HPLC). The samples were extracted with methanol, and the fat in the samples was degreased by freezing. Separation of the targeted compounds was performed on an XBridge C18 column in gradient elution mode using methanol-0.1% (v/v) formic acid aqueous solution as the mobile phase. The analytes were detected using a diode-array detector by the external standard method. The stability and storage conditions for the nine antioxidants were systematically investigated. Ascorbyl palmitate (AP) was introduced into the preparation and pre-treatment of the targets. The concentration of AP was optimized to improve the stability and recovery of the targets. The effects of different extraction solvents and purification methods on the extraction efficiencies were discussed. The results showed that the nine antioxidants could be separated well under the optimized conditions. Good linear relationships in the linear range were obtained, and the correlation coefficients (R2) were greater than 0.999. The average recoveries of the nine antioxidants ranged from 85.3% to 104.1%, with RSDs of the method ≤5.0%. The limits of quantitation (LOQs) for the nine synthetic antioxidants were in the range of 0.6-3.0 mg/kg. The method is simple, rapid, sensitive, and it shows good recovery and reproducibility.A method for the preparation and certification of the reference material of tenuazonic acid (TeA) and tentoxin (TEN) in wheat flour was developed. This method provided methodological references to develop of standard material for analyzing alternaria toxins in grains. The wheat flour reference materials were based on wheat grains which were naturally contaminated with alternaria toxins. The certified values for TeA and TEN were determined by isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) and cooperated certification of multiple laboratories. The wheat flour reference materials were stored at room temperature, protected from light and characterized by low uncertainty. The wheat flour reference materials are currently the only wheat flour reference materials that naturally contaminate TeA and TEN, and it can be used in the evaluating related analytical methods involved in food safety risk monitoring, product quality testing and quality control measurements.A method was developed for the simultaneous determination of 18 pesticide residues in environmental water by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS). The samples were purified and enriched by a large-volume SPE apparatus through a Cleanrt®-PEP SPE column at a rate of 2 mL/min. After being concentrated 50-fold, the samples were detected by UPLC-MS/MS and quantified by the external standard method. The target compounds showed good linearity in the range of 0.5-50 μg/L, with linear correlation coefficients (R2) ≥0.995. At spiked levels of 10, 100 and 1000 ng/L, the average recoveries of the 18 pesticides in the three different environmental water samples were 71.3%-105.9%, and the relative standard deviations (RSDs, n=5) were 1.3%-9.9%. LOQs of the 18 pesticides were 10 ng/L. The method was applied to the detection of the water environment around Tai'an City, and no pesticide residues were detected at any of the collection sites. The method has the advantages of good purification effect, high versatility, sensitivity, and accuracy, and operational simplicity. The method is suitable for the determination of the 18 pesticides in environmental water.A rapid method based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of 37 mycotoxins having various physicochemical properties in grain and animal feed samples. The 37 analytes were extracted from ground samples with acetonitrile-water-formic acid (8415.90.1, v/v/v) by 20 min vibration, and purified using a commercial MLJ-1 pass-through solid-phase extraction (SPE) clean-up cartridge. The analytes were then separated on a reversed-phase BEH RP18 column by a gradient elution program with 0.1 mmol/L ammonium acetate (containing 0.1% (v/v) formic acid) aqueous solution and 0.1% (v/v) formic acid methanol solution as mobile phases. selleck chemicals The separated analytes were detected by MS/MS in the multiple reaction monitoring (MRM) mode via ESI+/- ionization. The results showed that the purification was completed in 1 min and that the 37 analytes could be separated on the chromatographic column in 15 min. The 37 mycotoxins showed a linear relationship within their respective linear ranges, and the correlation coefficients of the matrix-matched calibration curves were greater than 0.98. The average recoveries at four spiked levels (limit of quantification (LOQ), LOQ×5, LOQ×10, LOQ×25) for all the targets except fumonisins ranged from 80% to 120%, with the relative standard deviations (RSDs) lower than 20% (n=6). The limits of quantification (LOQs) for all the analytes were between 2 and 40 μg/kg. The proposed method is simple, fast, and accurate, thus being suitable for detecting multiple mycotoxins in grain and animal feed samples.In order to cope with the differences in international trade regulations, it is necessary to establish a rapid non-targeted screening method for triazole fungicides in food. Therefore, a non-targeted method based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was established for the rapid screening of triazole fungicides in tomatoes. Tomato samples were extracted with acetonitrile and then purified by QuEChERS. The purified solution was separated on a BEH C18 column (100 mm×2.1 mm, 1.7 μm) using a gradient mobile phase consisting of acetonitrile and water (both containing 0.1% formic acid). Full information tandem mass spectrometry (MSE) acquisition using electrospray ion source under positive ion mode was performed. The 19 triazole fungicides were divided into eight groups based on their structural differences. The secondary mass fragments of eight typical standards in the eight groups of triazole fungicides were analyzed, and then, the regularities of the characteristic fragment ions and neutral loss fragments produced by collision-induced dissociation of the triazole fungicides were summarized. The fragmentation regularity was further verified by the other 11 triazole fungicides. A total of 16 tomato samples collected from local supermarkets in Beijing were screened using this non-targeted method. Diniconazole was identified and confirmed in one sample, which demonstrated that the method could achieve rapid and accurate non-targeted screening of triazole fungicides in tomatoes. The proposed method is highly efficient, sensitive, and accurate, thus providing a reference for screening triazole fungicide residues in food.A method for the determination of 10 pyrethroid pesticide residues in tea was established by multi-plug filtration cleanup (m-PFC) method combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). Different extraction solvents (acetonitrile, acetone and ethyl acetate) and extraction methods (immersion without water and immersion with water) were compared. The effect of two kinds of QuEChERS pipes and m-PFC column on the purification of tea extracts and the pesticide recoveries were compared. The results showed that the tea samples could be extracted most efficiently when using acetonitrile without immersion in water. The m-PFC column had a good purification effect on the tea extract and could guarantee a high recovery rate. Good linear relationships were observed for the 10 pyrethroid pesticides, and the correlation coefficients (R2) were greater than0.9980. The average recoveries for the 10 pyrethroid pesticides were in the range of 87.5%-111.3% at four spiked levels, and the RSDs were in the range of 2.1%-8.9%. The LODs and LOQs were 0.001-0.015 mg/kg and 0.003-0.05 mg/kg, respectively. The method was applied to the determination of the 10 pyrethroid pesticides in 50 tea samples. The detection rate of the pyrethroid pesticides was 48%, but all the pesticide residues were below the national standard limits. Compared with the traditional QuEChERS and solid phase extraction methods, this method has the advantages of operational simplicity as well as high accuracy and good precision. The establishment of this method provides a new strategy for the rapid detection of pyrethroid pesticide residues in tea.
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