Dynamics of gel isoelectric focusing with ampholytic dyes monitored by camera in real-time

The dynamics of gel isoelectric focusing were studied by using amphoteric low-molecular-mass colored substances (isoelectric point markers). The polyacrylamide gel in slab format was in direct contact with the electrodes. In addition to isoelectric focusing with a pH gradient composed of synthetic carrier ampholytes, pH gradients created by simple buffers of acetic acid, 2-(N-morpholino)ethanesulfonic acid, histidine and N,N,N',N'-tetramethylethylenediamine were applied. The progress of the electrofocusing process was monitored by a charge-coupled device camera and video recording. The gradient profile and dynamics were approximated from the positions of isoelectric point markers, which were focused both on boundaries between individual zones of simple buffers and within the zones themselves. The obtained animated records enabled the observation of the entire real focusing run within fractions of a minute, which is useful both for the understanding and optimization of the focusing.     

Determination of heterocyclic aromatic amines (HAA) in commercially available meat products and fish by high performance liquid chromatography—Electrospray tandem mass spectrometry (HPLC-ESI-MS-MS)

Summary Ten heterocyclic aromatic amines (HAA) (1)–(10) were analyzed in commercially available meat products and fish. After sample preparation by Extrelut treatment and subsequent solid phase extraction applying propylsulphonic and C₁₈ silica cartridges, HPLC-ESI-MS-MS using selected reaction monitoring (SRM) and d₃-PhIP and d₃-MeIQx as internal and external standards, respectively, revealed the widely distributed presence of PhIP (8) and MeIQx (4), ranging from 0.1 to 5.3 ng g⁻¹ and 0.1 to 5.2 ng g⁻¹, respectively. Lower amounts were found for 4,8-DiMeIQx (5) and 7,8-DiMeIQx (6), ranging from 0.2 to 2.0 ng g⁻¹ and 0.1 to 0.2 ng g⁻¹, respectively. The other HAA under study, i.e. IQ, MeIQ, 4,7,8-TriMeIQx, Glu-P-1, and Glu-P-2 were not determinable under the experimental conditions used (determination limit 0.1 ng g⁻¹).     

含一般模糊弹性约束的广义模糊变量线性规划

建立并讨论了一类含有一般模糊弹性约束的广义模糊变量线性规划问题.首先,简单介绍了结构元方法并对结构元加权排序中权函数表征决策者风险态度进行了深入分析.然后选取风险中性的决策者来定义序关系,应用Verdegay模糊线性规划方法将含一般模糊弹性约束的广义模糊变量线性规划转化经典的线性规划问题,简化了原问题的求解.最后通过数值算例进一步说明了该方法的有效性.     

Comparison of the effectiveness of epoxy cure accelerators using a fluorescent molecular probe

A simple optical method for quantitative comparison of the effectiveness of epoxy cure accelerators, used for speeding up the crosslinking process of epoxy resins with cyclic anhydrides, is described. Fluorescent molecular probes and a miniature fiber optic spectrometer have been applied for measurement of the cure kinetics of a model epoxy resin/anhydride composition in the presence of various cure accelerators. A quantitative index of accelerator performance has been determined for several of the most common accelerators.     

Adoption of Common Schemes for Single and Sequential Extractions of Trace Metal in Soils and Sediments

Abstract

The various methods for determining the mode of occurrence of trace metals in sediments and soils have a long history which dates back to the determinations of the availability of metals for plant nutrition performed earlier. Various methods have been developed in the 70′s and 80′s dealing with both single and sequential extraction schemes. Although some schemes received wide acceptance, none of them developed into a commonly accepted procedure. As a result, the information obtained was site-specific and the interpretation of the results scientist-specific. The workshop on single and sequential extraction in sediments and soils held at Sitges     

Monitoring of Airborne Organic Vapors Using Ion Mobility Spectrometry

Abstract

Automated, continuous monitoring of organic vapors in air under three field designs for plume drift was demonstrated using a hand-held ion mobility spectrometer (IMS) in characterizing IMS behavior as a point sensor. In one field study, the IMS was placed 50cm from a 9m² grass plot contaminated with methylsalicylate and response to airborne vapors was recorded during a 13hr period of atmospheric turbulence to illustrate susceptibility of point sensors to wind direction. A similar study under near-quiescent atmospheric conditions was made using dimethylsulfoxide. In a third study, the plume from a point source of dipropyleneglycolmonomethylether was interrogated over a 25m × 12m grid downwind with windspeeds of 6–18km h^?. Laboratory studies were used to measure instrumental response times and influences from potentially interfering atmospheric organic pollutants.     

Determination of trans,trans‐muconic acid in workers' urine through ultra‐performance liquid chromatography coupled to tandem mass spectrometry

A novel method for the biological monitoring of benzene‐exposed workers has been developed through ultra‐performance liquid chromatography coupled to tandem mass spectrometry. The method uses trans,trans‐muconic acid in urine as the benzene‐exposure biomarker. The method was developed using a triple quadrupole mass spectrometer with enough sensitivity to facilitate diluting and injecting the urine samples directly, rather than performing a solid‐phase extraction procedure as is common in the available protocols. Moreover, compared with a conventional high‐pressure liquid chromatography system, the separation power provided by the ultra‐performance liquid chromatography system allows a 10‐fold reduction in run time. The method was adjusted to a dynamic range of between 198.9 and 4916.7 µg/L to cover the biological exposure index of trans,trans‐muconic acid in urine. Also, the method demonstrated intra‐day and inter‐day precision at 98%, and accuracy within an acceptable range of 101 ± 8%. The method has been used to quantify various types of urine samples, such as workers' urine and inter‐laboratory proficiency tests. Depending on the sample, the quantified levels ranged from less than the limit of quantitation to 3836.7 µg/L. No levels exceeding the calibration range were detected in the urine of workers, and the reported concentrations in urine for the proficiency tests were, as expected, based on known values. Moreover, the new method using sample dilution and faster chromatographic run was more effective, facilitating fast communication of results, as needed, to decision‐makers. Copyright © 2012 John Wiley & Sons, Ltd.     

Fast analysis of triterpenoids in Ganoderma lucidum spores by ultra‐performance liquid chromatography coupled with triple quadrupole mass spectrometry

A rapid and reliable method was established for simultaneous determination of main triterpenoids in Ganoderma lucidum spores using ultra‐high‐performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC‐TQ‐MS). The established method was validated in terms of linearity, sensitivity, precision, accuracy and stability, and was successfully applied to determine the contents of 10 main triterpenoids in different batches of G. lucidum spores. The analysis results showed that moderate levels of triterpenoids were found in G. lucidum spores. In addition, a MS full scan with a daughter ion scan experiment was performed to identify the potential derivatives of triterpenoids present in G. lucidum spores. As a result, a total of 22 triterpenoids from different G. lucidum spores were unequivocally or tentatively identified via comparisons with authentic standards and literatures. This method provides both qualitative and quantitative results without the need for repetitive UPLC‐MS analyses, thereby increasing efficiency and productivity, making it suitable for high‐throughput applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Identification and quantification of the antipsychotics risperidone,aripiprazole, pipamperone and their major metabolites in plasma using ultra‐high performance liquid chromatography–mass spectrometry

The antipsychotics risperidone, aripiprazole and pipamperone are frequently prescribed for the treatment in children with autism. The aim of this study was to validate an ultra‐high performance liquid chromatography–mass spectrometry method for the quantification of these antipsychotics in plasma. An ultra‐high performance liquid chromatography–mass spectrometry assay was developed for the determination of the drugs and metabolites. Gradient elution was performed on a reversed‐phase column with a mobile phase consisting of ammonium acetate, formic acid in methanol or in Milli‐Q ultrapure water at a flow rate of 0.5 mL/min. The method was validated according to the US Food and Drug Administration guidelines. The analytes were found to be stable enough after reconstitution and injection of only 5 μL improved the accuracy and precision in combination with the internal standard. Calibration curves of all five analytes were linear. All analytes were stable for at least 72 h in the autosampler and the high quality control of 9‐OH‐risperidone was stable for 48 h. The method allows quantification of all analytes. The advantage of this method is the combination of a minimal injection volume, a short run‐time, an easy sample preparation method and the ability to quantify all analytes in one run. Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental study and numerical modeling of brittle fracture of carbonate rock under uniaxial compression

The brittle carbonate rock taken from the Tarim Oilfield is tested in laboratory under uniaxial compression. The acoustic emission (AE) is used to monitor the microcracking activity in rock during the experiment. Moreover, the 3D tomograms of carbonate rock after uniaxial compression are obtained by using CT imaging technology, which indicates that microcracks mutually interconnect and eventually form macroscopic fractures after failure. The PFC2D is used to model the behavior of brittle rock including microcracks propagation. The stress–strain curve and cracks distribution in rock model are obtained from the PFC simulation. The numerical results agree with the experimental test well.