Simultaneous Determination of Phenolics and Polymethoxylated Flavones in Citrus Fruits by Ultra-High Performance Liquid Chromatography Coupled with Triple-Quadrupole Mass Spectrometry (UHPLC-QqQ-MS)

Phenolic and polymethoxylated flavones are important bioactive components in citrus fruit. Here, a rapid and sensitive method based on ultra-high performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-QqQ-MS) was developed for the simultaneous determination of phenolic and polymethoxylated flavones in the peels and pulp of mandarins, tangelos, and oranges. Three phenolic acids and eight flavonoids, including polymethoxylated flavones, were separated and determined using positive and negative ion modes in a single chromatographic run of only 11?min using the multiple reaction monitoring detection mode. The method was validated with high recoveries from 96.1% to 103.5%, good precision with interday relative standard deviations less than or equal to 7.3%, intraday relative standard deviations ≤2.64%, low limits of detection from 1.0 to 18?µg L^–1, and low limits of quantitation in the range from 3.0 to 61?µg L^–1. The application of this UHPLC-QqQ-MS/MS method to the citrus extracts of three cultivars showed that mandarin fruits contained the highest total amounts of the 11 analytes, followed by tangelos and oranges. This study provides a reliable and quantitative method that can be used for the development of functional products and quality evaluation of citrus fruits.     

Real-time monitoring traces of SF6 in near-source ambient air by ion mobility spectrometry

The leakage of sulphur hexafluoride (SF₆) gas threats the global climate changes and personnel safety. Monitoring the concentration of SF₆ in its application places is an industry regulation. In this study, ion mobility spectrometry (IMS) was developed for fast monitoring traces of SF₆ in near-source ambient air. Due to the water is an important part of the natural air and affects most atmospheric measurements, the operating parameters of IMS monitoring SF₆ were optimised for quantitative analysis of SF₆ at different relative humidity (RH). It is discovered two main product ions SF₆^? and SOF₄^? by IMS at different RH. The calibration curves of SF₆ were investigated by its relationship with the peak intensity of SOF₄^– for real application. The time resolution of the measurement was obtained less than 1 s and the limit of detection (LOD) achieved 0.16–0.68 ppm with a data averaging of 30 times. At last, the simulated application of monitoring SF₆ leakage was tested in the fume hood of our lab. The results showed a great potential application prospect of IMS in monitoring SF₆ in the ambient air of its application places.     

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

Voltammetric procedures for trace metals analysis in polluted natural waters using homemade bare gold-disk microelectrodes of 25- and 125-μm diameters have been determined. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25 Hz is applied for analysis, whereas in unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. The peak potentials of the determined trace metals are shifted to more positive values compared to mercury drop or mercury-coated electrodes, with Zn always displaying 2 peaks, and Pb and Cd inversing their positions. For a deposition step of 120 s at ?1.1 V, without stirring, the 25-μm gold-disk microelectrode has a linear response for Cd, Cu, Mn, Pb and Zn from 0.2 μg L^?1 (1 μg L^?1 for Mn) to 20 μg L^?1 (30 μg L^?1 for Zn, Pb and 80 μg L^?1 for Mn). Under the same analytical conditions, the 125-μm gold-disk microelectrode shows linear behaviour for Cd, Cu, Pb and Zn from 1 μg L^?1 (5 μg L^?1 for Cd) to 100 μg L^?1 (200 μg L^?1 for Pb). The sensitivity of the 25-μm electrode varied for different analytes from 0.23 (±0.5%, Mn) to 4.83 (±0.9%, Pb) nA L μmol^?1, and sensitivity of the 125-μm electrode varied from 1.48 (±0.7%, Zn) to 58.53 (±1.1%, Pb  nA L μmol^?1. These microelectrodes have been validated for natural sample analysis by use in an on-site system to monitor Cu, Pb and Zn labile concentrations in the Deûle River (France), polluted by industrial activities. First results obtained on sediment core issued from the same location have shown the ability of this type of microelectrode for in situ measurements of Pb and Mn concentrations in anoxic sediments.      

The activity of Au supported on various types of carbon in the ring transformation reactions of methyloxirane

Summary  Vezetéknév     

Trace analysis and occurrence of anhydroerythromycin and tylosin in influent and effluent wastewater by liquid chromatography combined with electrospray tandem mass spectrometry

Two wastewater treatment plants (WWTPs) of northern Colorado were monitored for anhydroerythromycin and tylosin. An analytical method has been developed and validated for the trace determination and confirmation of these compounds in the raw influent and final effluent water matrices. This method was used to evaluate the occurrence and fate of these compounds in WWTPs. The method uses solid-phase extraction and liquid chromatography–tandem mass spectrometry with positive electrospray ionization. Detection and quantification was performed using selected reaction monitoring, and a method detection limit of between 0.01 and 0.06 μg/L was obtained. Unequivocal confirmation analysis of analyte identity according to the criteria (based on the use of identification points) of the 2002/657/EC European Commission Decision was possible with satisfactory results. Average recoveries for the two compounds ranged from 89.2±9.7% for raw influent to 93.7±6.9% for effluent wastewaters. The within-run precision of the assay was found to be always less than 14.1% for the two analytes. The overall precision was always less than 13.7%. The relative uncertainty of the present assay was also evaluated and the combined relative uncertainty ranged from 6.4 to 15.5% over three days of the validation study. These compounds were partially removed in the WWTPs with a removal efficiency of >50%. The measured concentrations in raw influents and effluents ranged from 0.09–0.35 and 0.04–0.12 μg/L for anhydroerythromycin to 0.06–0.18 and ND–0.06 μg/L for tylosin, respectively. The results indicate that WWTP effluents are relevant point sources for residues of these compounds in the aquatic environment. These occurrence results were compared with those in WWTP wastewaters of other countries.     

液液萃取-高分辨气相色谱-高分辨双聚焦磁质谱法测定尿中羟基多环芳烃代谢物

建立了灵敏、准确的液液萃取-高分辨气相色谱-高分辨双聚焦磁质谱(LLC-HRGC-HRMS)同时测定人体尿样中8种多环芳烃(PAHs)代谢物的方法。将2 mL尿液与氘或¹³C标记的同位素内标物进行混合,在抗坏血酸的存在下酶解偶联目标物,再将游离化合物用甲苯-戊烷(1∶4, v/v)萃取后浓缩至近干,再用甲苯复溶,衍生后经HRGC-HRMS分离和测定。1-羟基萘在0.14～41.6μg/L、1-羟基菲在0.05～8.33μg/L、2-羟基菲在0.04～8.33μg/L、其他5种代谢产物在0.02～8.33μg/L范围内线性关系良好,相关系数>0.99,方法的检出限为0.006～0.042μg/L,平均回收率为81.4%～127.0%,日内和日间精密度分别为2.7%～6.9%和5.1%～10.9%(n=6)。应用该方法测定330份人群尿液样本,3-羟基■和6-羟基■未检出,其他6种PAHs代谢物检出率为100%。该方法灵敏、准确、稳定,适用于人尿中8种PAHs代谢物的定量分析。     

NIR-plasmon-enhanced Systems for Energy Conversion and Environmental Remediation

The introduction of plasmons is an important method to solve the insufficient utilization of the full spectrum of solar energy by semiconductor catalysts. However, semiconductor catalysts combined with traditional noble metal plasmons(Au, Ag) can only extend the absorption spectrum to partially visible light. In order to further improve the photoenergy absorption efficiency of catalysts, they need to be able to effectively utilize near-infrared light, which has become a new research direction. Recent studies have shown that traditional noble metal plasmons can absorb a part of NIR through special morphology, size control and material composite. At the same time, gratifying achievements have been made in the application of plasmonic semiconductors with broad spectrum absorption in catalysis. This article reviews the principles of generating and regulating plasmonic effects in different catalytic systems. The applications of plasmon absorption of near-infrared light in energy conversion and environmental remediation have also been presented.     

Continuous-flow photochemistry: An expanding horizon of sustainable technology

Understanding the unique characteristics of continuous-flow photochemistry will lead to a paradigm shift in the way we enhance sustainability and wellbeing. In this mini-review, we first provide a succinct overview of working principles of this technique and discuss several recent synthetic protocols. Then, emphasis is given to those representative examples which address environmental issues such as indoor air pollutants and water contamination. Finally, recent progress made using this technique to deal with rising CO₂ emission, solar energy utilization and biomedical equipment is described. It is believed that this mini-review could inspire more chemists to utilize this technique in their research, either in the academic or industrial field.     

Atmospheric pressure chemical ionization in gas chromatography-mass spectrometry for the analysis of persistent organic pollutants

Atmospheric pressure chemical ionization (APCI) was primarily applied as the ion source for liquid chromatography-mass spectrometry (LC–MS). While APCI started to be used in gas chromatography-mass spectrometry (GC–MS) in 1970s, GC-APCI-MS was not widely used until recently. As a soft ionization technique, APCI provides highly diagnostic molecular ions, which is favored for the wide-scope screening. With the capability of tandem mass spectrometry (MS/MS), GC-APCI-MS methods with high sensitivity and selectivity have been developed and applied in the analysis of persistent organic pollutants (POPs) in environment and biological samples at trace levels. The present review introduces the history of the APCI source, with emphasis on mechanisms of ionization processes under the positive and negative ionization modes. Comparison between GC-APCI-MS and GC–MS with traditional electron ionization (EI) and chemical ionization (CI) are provided and discussed for selectivity, sensitivity and stability for the analyses of POPs. Previous studies found that the GC-APCI-MS methods provided limits of detection (LODs) around 10–100 times lower than other methods. An overview of GC-APCI-MS applications is given with the discussions on the advantages and drawbacks of various analytical methods applied for the analyses of POPs.     

Membrane Introduction Mass Spectrometry (MIMS): A Versatile Tool for Direct,Real‐Time Chemical Measurements

Membrane introduction mass spectrometry (MIMS) is a direct, continuous, on‐line measurement technique. It utilizes a membrane to semi‐selectively transfer analyte mixtures from a sample to a mass spectrometer, rejecting the bulk of the sample matrix, which can be a gas, liquid or solid/slurry. Analyte selectivity and sensitivity are affected by optimizations at the membrane, ionization and the mass spectrometer levels. MIMS can be roughly classified by the acceptor phase that entrains analyte(s) to the mass spectrometer after membrane transport, either a gaseous acceptor phase (GP‐MIMS) or condensed acceptor phase (CP‐MIMS). The aim of this article is to provide an introduction to MIMS as a technique and to explore current variants, recent developments and modern applications, emphasizing examples from our group, the Applied Environmental Research Laboratories as well as selected work from others in this emerging area. Also provided is a synopsis of current and future directions for this versatile analytical technique. Copyright © 2014 John Wiley & Sons, Ltd.