Dennisrobertson0103

PSA tape samples from several manufacturers of duct, masking, and electrical tape were analyzed from the adhesive and backing side. Direct desorption FAPA provides top-surface selectivity and the tape mass spectra are dominated by more peaks at lower m/z, many of which correspond to polymer additives. LAS gives access to sampling from all of the tape layers and the FAPA mass spectra is extended to higher m/z, while polymer fragmentation patterns are evident. Principal components analysis (PCA) was implemented to assess the ability of each technique to distinguish and categorize identified tape classes within the sampled population. The complementary nature of the resulting mass spectra from direct desorption vs LAS FAPA was evident from the PCA as different tape brands sub-sets were discriminated by each technique. The differentiation obtained by combining both methods is already competitive, or better, than conventional techniques, with the additional benefits of AMS.The use of porous carrier and coating sorbents in stir bar sorptive extraction (SBSE) contributes to the improvement of extraction efficiency and dynamics. Herein, porous nickel foam (NF) with large surface area and magnetic property was used as the carrier of stir bar. NF was added into the mixture of graphene oxide (GO) and reducing agent, and reduced graphene oxide (RGO) coating was obtained on the surface of NF substrate by in situ hydrothermal reduction. The characterization results of Fourier transform infrared spectroscopy, X-ray power-diffraction and scanning electron microscope showed that GO was partially reduced into RGO, and the RGO coating was uniformly loaded on the NF surface. The obtained RGO-NF composite was used as the stir bar coating for the analysis of six benzotriazole (BZTs) UV absorbents. The extraction efficiency was between 48 and 64% for six BZTs. RGO-NF stir bar exhibited faster adsorption/desorption kinetics than commercial polydimethylsiloxane coated stir bar (50 min vs 120/360 min) due to its porous structure and large specific surface area. On this basis, a method of RGO-NF coated stir bar sorptive extraction combined with high performance liquid chromatography (HPLC)-DAD was established for the determination of six BZTs. Under the optimized conditions, the limits of detection were 0.33-0.50 μg/L for six target BZTs, and the linear range was 1-100 μg/L. The proposed method merits good ability to resist matrix and was used to analyze six BZTs in environmental water samples. The recoveries of target BZTs were obtained within 83.0-112% in the spiked East Lake water and 97.0-111% in the spiked Yangtze River water, respectively.Cysteine (Cys) is a biological thiol. Aberrant changes in thiol levels are associated with the development and pathogenesis of various diseases, including liver damage, Alzheimer's disease, weakness, and cardiovascular diseases. Therefore, thiol detection in biological samples has great importance in health monitoring and disease prediction. In this study, we developed a ratiometric fluorescence nanosensor combined with carbon dots (CDs)-doped mesoporous silica and fluorescein-based fluorescent probes loaded in pores for Cys detection. The nanosensor emitted fluorescence at 450 nm upon excitation at 370 nm. In the presence of Cys, the fluorescence emission from the probe could be selectively enhanced, whereas that from CDs could be changed. Thus, a ratiometric fluorescent sensor was developed. This sensor can eliminate the potential influence of background fluorescence and other analyte-independent external environmental factors. The nanosensor was utilized to monitor Cys levels in human serum, and satisfactory results were obtained. Results indicated that the nanosensor can be utilized as an excellent fluorescent nanocomposite material in practical biological applications.Probe electrospray ionization (PESI) is an ambient ionization mass spectrometry technique (AIMS) that is primarily used in qualitative studies, though researchers have recently combined it with sample preparation for the quantitative analysis of various analytes in biological matrices. This study presents a method that integrates solid-phase microextraction with PESI for direct coupling to a triple quadrupole mass spectrometer, and examines its ability to quantitate drugs of abuse. Intra- and inter-probe reproducibility experiments were conducted to assess the stability and reproducibility of the extraction-phase-coated PESI probes (coating length 2 mm; coating thickness 6.5 μm). This research is the first documented instance wherein highly sensitive determinations were successfully attained using these microextraction and micro-desorption techniques in conjunction with small volumes of sample and extraction phase. A mixture consisting of IPA/H2O (1/1 v/v) + 0.1% FA was determined to be the optimal desorption solvent for SPME-PESI-MS/MS, as it facilitated high analyte enrichment in a picolitre of the solvent, which acted at the same time as efficient electrospray media. Furthermore, a method of quantifying drugs of abuse in 30 μL of plasma without matrix modification was also developed. This method had an intra-day accuracy within the 80-120% range for all eight drugs of abuse at concentrations of 3, 30, and 90 pg μL-1; the exception to this result was lorazepam at 30 pg μL-1, which had an intra-day accuracy of 122%. The lower limit of quantification (LLOQ) for fentanyl and nordiazepam was pg μL-1; the LLOQ for buprenorphine, codeine, diazepam, lorazepam, and propranolol was 5 pg μL-1; and the LLOQ of oxazepam was 10 pg μL-1.Peroxynitrite (ONOO-) is a series of basic biological oxidants involved in physiological and pathological processes. selleck The detection of ONOO- in biological systems has been challenging due to its extremely short half-life and low steady-state concentration. In this work, a ratiometric fluorescent nanoprobe for ONOO- was constructed by coupling covalently of graphene quantum dots (GQDs) with cyanine 5.5 (Cy5.5). This nanoprobe (GQD-Cy5.5) could selectively accumulate in mitochondrial, appears two strong fluorescence emission peaks at 520 and 694 nm. In the presence of ONOO-, the intensity of fluorescence emission peak at 520 nm increased and the intensity of fluorescence emission peak at 694 nm decreased. The ratio (F520 nm/F694 nm) of fluorescence intensity at two emission peaks had a good linear relationship with the concentration of ONOO- in the range of 0-6.0 μM, and the detection limit was 0.03 μM. The excellent properties of the nanoprobe enable its applications in the ratiometric fluorescence imaging of endogenous ONOO- in cell mitochondria.