Drewchan2351

6 μmol/L (S/N=3). Moreover, the internal standard method was further applied to the quantitative determination of tranexamic acid content in three kinds of toothpaste and two kinds of nutrient solutions in facial masks. The results showed that the average tranexamic acid content in three toothpaste samples was 4.05, 0.24, and 6.06 mg/g, while that in two facial masks was 51.3 and 7.98 mg/mL. The recoveries for the above-mentioned samples were within the range 92.5% to 104.0%, implying satisfactory results.Long-term exposure to pyrethroid insecticides is detrimental to the nervous system, reproductive system, and immune system in humans. Therefore, enrichment detection of pyrethroid pesticides is imperative. In this study, a novel carbonyl-iron powder composite silica monolithic column was first prepared for the enrichment of pyrethroid pesticide residues in tea samples. Then, the target analytes were thermally desorbed and online-injected into a gas chromatography-tandem mass spectrometry (GC-MS/MS) system. In the present method, hydroxy-terminated polydimethylsiloxane (PDMS) was covalently bonded to the surface of the SiO2 network and subsequently bonded with the carbonyl-iron powder. After the target analytes were adsorbed and concentrated in the PDMS spots, high-frequency induction heating was used for GC-MS/MS sampling. Under the optimal conditions, the detection limits of the pyrethroid pesticide residues were 3.8 to 7.5 μg/kg, and the relative standard deviation was 3.2% to 6.8% (n=6). The extraction recgh degree of automation, and good universality. This method has high significance for sample preparation and for the extraction of pesticide residues in complex matrices.At present, the kinds and the hazards of phenolic compounds in water were unclear. Research aimed at methods for the simultaneous detection of multiple phenolic compounds is still in its nascent stages. It is necessary to establish a method for the simultaneous determination of phenolic compounds in water. An analytical method was developed for the simultaneous determination of the 18 phenolic compounds in water by gas chromatography-tandem mass spectrometry (GC-MS/MS) coupled with solid phase extraction (SPE). The phenolic compounds in water were enriched and separated on an SPE column. The optimal pretreatment method was established by optimizing the chromatographic and mass spectrometric conditions. The effects of the initial pH of the water sample, type of eluting solvent, and dosage of the washing solution were investigated. Then, the 18 phenolic compounds in the water samples were determined. The optimal pretreatment extraction conditions were determined to be as followsfinal pH of water sample, 3.0; el.4 μg/L. The contents and kinds of phenolic compounds in the rivers and lakes were highest. However, the contents of phenolic compounds in the domestic water were adverse compared with the rivers and lakes, in accord with National Standard GB 8537-2008. As opposed to traditional analytical methods, the present method is characterized by simple operation without derivative or the need for anhydrous sodium sulfate for water removal, as well as high sensitivity, good stability, and reliability. The establishment of this method has important theoretical and practical significance for the development of standards and for the control of residue phenolic residue levels in water.A method combining accelerated solvent extraction (ASE) with magnetic solid-phase extraction (MSPE) and gas chromatography-mass spectrometry (GC-MS) was developed for the simultaneous detection of polycyclic aromatic hydrocarbon (PAH) and organochlorinepesticide (OCP) residues in soil samples. The analytes in the soil samples were extracted using an acetone/n-hexane (11, v/v) mixture for 5 min at 100℃. Then, the extraction pool was heated for 5 min under an extractive pressure of 11.032 MPa for three cycles. The extraction pool was washed with an acetone/n-hexane (11, v/v) mixture accounting for 60% of the pool volume, followed by nitrogen purging for 100 s. The extract was purified by MSPE using self-made magnetic ZIF-8/nZVI materials at room temperature. 20-Hydroxyecdysone The analytes were detected by GC-MS/MS. Under the optimized conditions, good linearities were obtained for the 16 PAHs and the 23 OCPs in the range of 5-200 μg/kg, with correlation coefficients (r2) above 0.99. The limits of detection (LODs) were 0.04-1.21 μg/kg. At three spiked levels in the soil samples, the recoveries of the 39 analytes were between 63.9% and 112.1%, with relative standard deviations (RSDs) between 0.4% and 26.2%. The method was demonstrated to be successful for the determination of 16 PAH and 23 OCP residues in soil samples, with good recoveries.Silica monolith particles with sizes of 2-5 μm and pore sizes of 20-60 nm were obtained by grinding, flotation, pseudomorphic transformation, and hydrothermal treatment of the silica monolith prepared by the sol-gel method. The pseudomorphic transformation was performed with a dual micellar templating system consisting of Capstone FS-66, a partially fluorinated anion surfactant, and cetyltrimethylammonium bromide (CTAB), a commonly used cation surfactant. Hydrothermal treatment with a sodium carbonate solution was adopted to further expand the pore size. Scanning electron microscopy (SEM) images and N2 adsorption-desorption isotherm measurement results of the silica monolith particles before and after the treatments clearly demonstrated the changes in morphology caused by these treatments. Afterward, a long-chain polyethylene glycol (PEG) containing silane was bonded on the surface of the as-prepared particles, and the resulting products were characterized by elemental analysis and FT-IR spectroscopy analysis, and evaluated by high performance liquid chromatography (HPLC). Elemental analysis and thermogravimetric analysis (TGA) of the bonded stationary phase revealed that the bonding amount of PEG on the silica surface is about 8%. It has been shown that silica monolith particles can be treated and modified for the separation of proteins in size exclusion chromatography mode. It is also demonstrated that the bonded stationary phase can be used for the separation of ribonuclease A and lysozyme in hydrophobic interaction chromatography mode, and for the separation of highly polar compounds (picolinic acid, levodopa, melamine, and catechol) in hydrophilic interaction chromatography mode. The results indicate the versatility of the PEG-bonded stationary phase and its promising application to multi-modal separation in HPLC.