Simultaneous Determination of 49 Antibiotics Residues in Pork by a Modified QuEChERS Method Based on Silanized Melamine Sponge Coupled with Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry

Two new types of elastic porous silanized melamine sponges (MeS) were prepared by silylation reaction using octadecyltrichlorosilane (OTS) and N-[3-(trimethoxysilyl)propyl]ethylenediamine (ATS), which were respectively designated as OTS@MeS and ATS@MeS. The silanized sponges were used to develop a modified quick, easy, check, effective, rugged, and safe (QuEChERS) method that can quickly and efficiently separate interfering matrices from the extract through spontaneous solution infiltration and physical extrusion. In this study, an analytical method using the modified QuEChERS procedure combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for the simultaneous determination of 49 antibiotic residues in pork. Samples were extracted with 10 mL of acetonitrile containing 0.1% acetic acid, and then salted out with 2.0 g of Na2SO4 and 0.5 g of NaCl. After centrifugation, a 1 mL aliquot of the supernatant was cleaned up with a mixture of OTS@MeS and ATS@MeS. The chromatographic separation was conducted on an Agilent ZORBAX Eclipse Plus C18 column with gradient elution using a mobile phase comprised of methanol and aqueous solution (methanol/water, 5:95, V/V) containing 0.1% formic acid and 5 mmol/L ammonium acetate. The qualitative and quantitative detection were performed by multiple-reaction monitoring (MRM) using an electrospray ionization source in the positive ion mode. The results showed that the correlation coefficients for all analytes were greater than 0.999. The matrix effects (ME) were in the range of −13.5%−10.9%. The limits of detection (LOQ) and quantitation (LOQ) were 0.1–10.0 and 0.3–33.3 μg/kg, respectively. The recoveries at three spiked levels ranged from 65.0% to 112.7%, with intra- and interday relative standard deviations (RSDs) of 0.3%–11.8% and 2.4%–18.4%, respectively. The developed method was simple, rapid, highly sensitive and accurate, and could be used for the efficient and rapid determination of the 49 antibiotics residues in pork

Polymorphisms of XRCC4 are involved in reduced colorectal cancer risk in Chinese schizophrenia patients

<p>Abstract</p> <p>Background</p> <p>Genetic factors related to the regulation of apoptosis in schizophrenia patients may be involved in a reduced vulnerability to cancer. XRCC4 is one of the potential candidate genes associated with schizophrenia which might induce colorectal cancer resistance.</p> <p>Methods</p> <p>To examine the genetic association between colorectal cancer and schizophrenia, we analyzed five SNPs (rs6452526, rs2662238, rs963248, rs35268, rs2386275) covering ~205.7 kb in the region of XRCC4.</p> <p>Results</p> <p>We observed that two of the five genetic polymorphisms showed statistically significant differences between 312 colorectal cancer subjects without schizophrenia and 270 schizophrenia subjects (rs6452536, p = 0.004, OR 0.61, 95% CI 0.44-0.86; rs35268, p = 0.028, OR 1.54, 95% CI 1.05-2.26). Moreover, the haplotype which combined all five markers was the most significant, giving a global <it>p </it>= 0.0005.</p> <p>Conclusions</p> <p>Our data firstly indicate that XRCC4 may be a potential protective gene towards schizophrenia, conferring reduced susceptibility to colorectal cancer in the Han Chinese population.</p

Investigation on the Energy-Absorbing Properties of Bionic Spider Web Structure

In recent years, spider webs have received significant attention due to their exceptional mechanical properties, including strength, toughness, elasticity, and robustness. Among these spider webs, the orb web is a prevalent type. An orb web’s main framework consists of radial and spiral threads, with elastic and sticky threads used to capture prey. This paper proposes a bionic orb web model to investigate the energy-absorbing properties of a bionic spider web structure. The model considers structural parameters such as radial line length, radial line cross-sectional diameter, number of spiral lines, spiral spacing, and spiral cross-sectional diameter. These parameters are evaluated to assess the energy absorption capability of the bionic spider web structure. Simulation results reveal that the impact of the radial line length and spiral cross-sectional diameter on the energy absorption of the spider web is more significant compared to the radial line cross-sectional diameter, the number of spiral lines, and spiral spacing. Specifically, within a radial line length range of 60–80 mm, the total absorbed energy of a spider web is inversely proportional to the radial line length of the web. Moreover, the number of spiral lines and spiral spacing of the spider web, when within the range of 6–10 turns and 4–5.5 mm, respectively, are proportional to the total energy absorbed. A regression equation is derived to predict the optimal combination of structural parameters for maximum energy absorption. The optimal parameters are determined as follows: radial line length of 63.48 mm, radial line cross-sectional diameter of 0.46 mm, ten spiral lines, spiral spacing of 5.39 mm, and spiral cross-sectional diameter of 0.48 mm

Analysis of Compounds Dissolved in Nonpolar Solvents by Electrospray Ionization on Conductive Nanomaterials

Electrospray ionization mass spectrometry (ESI-MS) technique has limitations in analysis of compounds that are dissolved in nonpolar solvents. In this study, ambient ionization of compounds in solvents that are not "friendly" to electrospray ionization, such as n-hexane, is achieved by conductive nanomaterials spray ionization (CNMSI) on nanomaterial emitters, including carbon nanotubes paper and mesodendritic silver covered metal, which applies high voltages to emitters made of these materials without the assistance of polar solvents. Although the time intensity curves (TIC) commonly vary from 4.5% to 23.7% over analyses, protonated molecular ions were found to be the most abundant species, demonstrating good reproducibility of the technique in terms of ionized species. Higher mass spectrometric responses are observed in analyzing nonpolar systems than polar systems. 2-Methoxyacetophenone, 4-methylacetophenone, benzothiazole, quinolone, and cycloheptanone as low as 2 pg in n-hexane can be directly detected using the developed method. The developed technique expands the analysis capability of ESI-MS for direct, online analysis of nonpolar systems, such as low polarity extracts, normal phase liquid chromatography eluates, and synthetic mixtures

Grazing exclusion reduced soil respiration but increased its temperature sensitivity in a Meadow Grassland on the Tibetan Plateau

Understanding anthropogenic influences on soil respiration (R-s) is critical for accurate predictions of soil carbon fluxes, but it is not known how R-s responds to grazing exclusion (GE). Here, we conducted a manipulative experiment in a meadow grassland on the Tibetan Plateau to investigate the effects of GE on R-s. The exclusion of livestock significantly increased soil moisture and above-ground biomass, but it decreased soil temperature, microbial biomass carbon (MBC), and R-s. Regression analysis indicated that the effects of GE on R-s were mainly due to changes in soil temperature, soil moisture, and MBC. Compared with the grazed blocks, GE significantly decreased soil carbon release by 23.6% over the growing season and 21.4% annually, but it increased the temperature sensitivity (Q(10)) of R-s by 6.5% and 14.2% for the growing season and annually respectively. Therefore, GE may reduce the release of soil carbon from the Tibetan Plateau, but under future climate warming scenarios, the increases in Q(10) induced by GE could lead to increased carbon emissions

Determination of Sulfonamides in Chicken Muscle by Pulsed Direct Current Electrospray Ionization Tandem Mass Spectrometry

A simple and rapid approach for the simultaneous detection of trace amounts of six sulfonamides in chicken muscle was developed using pulsed direct current electrospray ionization tandem mass spectrometry (pulsed-dc ESI-MS/MS). The pretreatment of chicken muscle samples consisted of two steps: acetonitrile extraction and <i>n</i>-hexane delipidation. Sulfonamides do not need to be derivatized or chromatographed prior to pulsed-dc ESI-MS/MS. The factors affecting the performance of pulsed-dc ESI-MS/MS were studied. Under optimum conditions, the quantitative performance of pulsed-dc ESI-MS/MS was validated according to European Union Decision 2002/657/EC, and the sensitivity of pulsed-dc ESI-MS/MS was 3 times higher than that of ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The limits of detection obtained by pulsed-dc ESI-MS/MS were in the range of 0.07–0.11 μg/kg. The proposed method was simple, rapid, and sensitive, and was successfully used for quantitation and rapid screening of sulfonamides in real chicken muscle samples