Isolation and Determination of Sterols in Rapeseed Oil by HPLC-MS

This article has been retracted     

Solid-phase extraction using a molecularly imprinted polymer for the selective purification and preconcentration of norfloxacin from seawater

Abstract

A highly selective and effective method for the purification and preconcentration of norfloxacin (NFX) in seawater samples was developed based on molecularly imprinted solid-phase extraction (MISPE). The molecularly imprinted polymer was synthesized by precipitation polymerization. Methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were used as the functional monomer and crosslinker, respectively. The resulting molecularly imprinted polymer (MIP) showed high adsorption for NFX and was selective for its solid-phase extraction. An offline MISPE method followed by high performance liquid chromatography with diode array detection was established for the determination of NFX in seawater. The recoveries of spiked seawater samples using the MISPE columns were satisfactorily higher than 77.6%. The relative standard deviation was less than 5.60%, and the limit of detection was 0.027?μg L^?1. Four seawater samples obtained from the Bohai Sea were analyzed, and NFX was found only at one location at a concentration of 0.280?μg L^?1.     

Separation and Identification of Oligomeric-Hindered Amine Light Stabilizer Uvasorb HA 88 by High-performance Liquid Chromatography (HPLC) Coupled With Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALSI-TOF-MS)

Abstract

Uvasorb HA 88 is widely used as a light stabilizer to prevent plastic polymer degradation. Its high molecular weight and oligomeric characters provide challenge for quality control. In this study, high-performance liquid chromatography (HPLC) coupled with electrospray ionization time of flight mass spectrometry (ESI-TOF MS) was applied for separation and detection of Uvasorb HA 88. The synthesis scheme was deduced and confirmed by the characterization of Uvasorb HA 88 products from different batches. Direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was employed for the detailed characterization of chemical composition of Uvasorb HA 88. Furthermore, a reliable reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with MALDI-TOF MS method was established and the weight-average and number-average molecular masses were calculated. The results revealed that six oligomers with repeat unit numbers from 1 to 4 were present in Uvasorb HA 88. A molecular weight of up to 6808?g mol^?1 was detected and two new series of oligomers were reported for the first time. Different series of oligomers and positional isomers were observed in Uvasorb HA 88. This work provides a suitable method to evaluate the technical grade of Uvasorb HA 88 as well as comprehensive characterization of complex oligomeric hindered amine light stabilizers.     

Characterization of River Natural Organic Matter by High-Performance Size Exclusion Chromatography

The molecular weight of natural organic matter from the Yeongsan and Seomjin Rivers and the discharge from the wastewater treatment plants were analyzed for seasonal characteristics by high-performance size exclusion chromatography. The distribution of molecular weights demonstrated relationships with microbial activity and seasonal variations with temperature. Dissolved organic carbon and total organic carbon for the Seomjin River were from 1.6 to 3.1 mg L^?1; for the Yeongsan River system, these parameters were between 2.0 and 8.0 mg L^?1. There were no significant differences between upstream and downstream organic matter. The biochemical oxygen demand (0.8–2.5 mg L^?1) for the Seomjin River was less than the chemical oxygen demand (2.9–5.0 mg L^?1). Similarly, the biochemical oxygen demand (0.9–4.6 mg L^?1) for the Yeongsan River was lower than the chemical oxygen demand (3.8–10.6 mg L^?1). The molecular weight of aromatic compounds increased as the water temperature decreased in October, whereas the molecular weights of proteins decreased as the water temperature increased. These results suggest that as microbial activity increased, natural organic matter with a smaller molecular weight may be employed as an energy source by microorganisms. As a result, seasonal variation of the water temperature may influence the distribution of organic matter in the rivers based on molecular weight and microbial activity such that the smaller natural organic matter was more readily degraded by microorganisms.     

Simultaneous Determination of Phenylpropanolamine Hydrochloride and Isopropamide in Capsule∗ by High Performance Liquid Chromatography Using CROWNPAK Column

Abstract

A procedure is described for the assay of phenylpropanolamine hydrochloride & isopropamide by HPLC using CROWNPAK column and detection at 200 nm. The system was aqueous perchloric acid as mobile phase containing 5 % methanol. Linearity studies were carried out using peak height measurements. There was > 99 % recovery and coefficient of variation was < 2% for formulation. The procedure was rapid, accurate, precise and specific for the assay of phenylpropanolamine HCl in presence of isopropamide.     

Ionic/electronic conductivity regulation of n-type polyoxadiazole lithium sulfonate conductive polymer binders for high-performance silicon microparticle anodes

Low-cost silicon microparticles(SiMP),as a substitute for nanostructured silicon,easily suffer from cracks and fractured during the electrochemical cycle.A novel n-type conductive polymer binder with excellent electronic and ionic conductivities as well as good adhesion,has been successfully designed and applied for high-performance SiMP anodes in lithium-ion batteries to address this problem.Its unique features are attributed to the stro ng electron-withdrawing oxadiazole ring structure with sulfonate polar groups.The combination of rigid and flexible components in the polymer ensures its good mechanical strength and ductility,which is beneficial to suppress the expansion and contraction of SiMP s during the charge/discharge process.By fine-tuning the monomer ratio,the conjugation and sulfonation degrees of the polymer can be precisely controlled to regulate its ionic and electronic conductivities,which has been systematically analyzed with the help of an electrochemical test method,filling in the gap on the conductivity measurement of the polymer in the doping state.The experimental results indicate that the cell with the developed n-type polymer binder and SiMP(~0.5 μm) anodes achieves much better cycling performance than traditional non-conductive binders.It has been considered that the initial capacity of the SiMP anode is controlled by the synergetic effect of ionic and electronic conductivity of the binder,and the capacity retention mainly depends on its electronic conductivity when the ionic conductivity is sufficient.It is worth noting that the fundamental research of this wo rk is also applicable to other battery systems using conductive polymers in order to achieve high energy density,broadening their practical applications.     

Parallelizing simulated annealing algorithms based on high-performance computer

We implemented five conversions of simulated annealing (SA) algorithm from sequential-to-parallel forms on high-performance computers and applied them to a set of standard function optimization problems in order to test their performances. According to the experimental results, we eventually found that the traditional approach to parallelizing simulated annealing, namely, parallelizing moves in sequential SA, difficultly handled very difficult problem instances. Divide-and-conquer decomposition strategy used in a search space sometimes might find the global optimum function value, but it frequently resulted in great time cost if the random search space was considerably expanded. The most effective way we found in identifying the global optimum solution is to introduce genetic algorithm (GA) and build a highly hybrid GA+SA algorithm. In this approach, GA has been applied to each cooling temperature stage. Additionally, the performance analyses of the best algorithm among the five implemented algorithms have been done on the IBM Beowulf PCs Cluster and some comparisons have been made with some recent global optimization algorithms in terms of the number of functional evaluations needed to obtain a global minimum, success rate and solution quality.     

高效液相色谱中同系物保留值收敛现象的研究

在讨论影响溶质保留行为因素的基础上，建立了描述同系物保留值收敛现象的一般模型，对12种同系物（共38组数据）在6种不同组成的二元流动相和8种固定相中的保留值进行了回归分析，相关系数r≥0．974，标准偏差SD≤0．05．绘制了这些同系物的三维保留图形及投影图，并据此对同系物收敛现象及其物理意义进行了讨论，建立了计算收敛点坐标的简便方法．     

用2-(5-硝基-2-吡啶偶氮)-5-二乙氨基苯酚反相高效液相色谱测定痕量铁、钴、镍

本文采用新试剂2-(5-硝基-2-吡啶偶氮)-5-二乙氨基苯酚(5-NO_2-PADAP)为柱前衍生试剂,不需对离子试剂,用含40mmol/L 的 pH6.0的乙酸-乙酸钠缓冲溶液和10~(-4)mol/LEDTANa_2的甲醇-水溶液(67.5:32.5)为流动相,在 ODS 柱上,20min 内 HPLC 测定了 Fe(Ⅲ)、CO(Ⅱ)和 Ni(Ⅱ)的5-NO_2-PADAP 的络合物,这是同类衍生试剂中最简单流动相体系。当信噪比 SNR=2时,检出限分别为0.17、0.17和0.09ng/ml。是同类体系中灵敏度最高的。方法用于同时测定硝酸试剂和茶叶中的铁、钴和镍,结果良好。     

Hydrocarbon group-type analysis of coal liquids by high-performance liquid chromatography

Summary A rapid method is described for the determination of hydrocarbon groups in coal liquids. Analysis is carried out by high-performance liquid chromatography on a LiChrosorb NH₂ column with n-hexane as the mobile phase. The separation is controlled only by the number of double bonds in a given hydrocarbon molecule. It is essentially independent of the molecular mass for a large variety of compounds investigated. Example of the separation of hydrogenated derivatives of anthracene and of a coal liquid fraction are presented.