原子吸收分光光度计检定最佳测试条件的选择

介绍原子吸收分光光度计检定最佳测试条件的选择技巧。     

Selection of Wavelength Range and Number of Factors to be Used in the PLS Treatment of Spectrophotometric Data

Abstract

A procedure for selection of wavelength range and number of factors to be used in partial least square calibration that involves the calculation of prediction residual sum of squares (PRESS) in different conditions is proposed. The best model takes into account the minimum PRESS value that does not show significant differences with respect to the corresponding model with fewer factors. The ability of the proposed method to minimize errors in partial least squares (PLS) prediction is demonstrated by applying it to the resolution of phenytoine (DPH) and phenobarbital (PB) binary mixtures with errors less than 2.8%; the results are compared with those obtained using another wavelength selection procedure. The ensuing method, which was validated by high performance liquid chromatography (HPLC), also gives good results with real samples (pharmaceutical preparations).     

变量选择中的正交变换法及苯酚和苯胺类衍生物色谱比移值的预测

正交变换法是变量选择的一种可行方法,但该种方法非常依赖于正交变换过程中变量的排序,侧重比较了不同排序方法,其中,后退法可以得到较好的结果。文中采用此种方法对由苯酚及苯胺类化合物所衍生的变量进行了正交变换,并对上述化合物的色谱比移值进行了预测。同时,与前进选择法、后退剔除法和逐步回归法几种传统方法进行了比较,得到了有启示性的结果。     

The electrodeless discharge lamp: a prospective tool for photochemistry: Part 3. The microwave photochemistry reactor

A simple and original microwave photochemical reactor is described in detail. It consists of an electrodeless discharge lamp placed into the reaction vessel in a modified domestic microwave oven. The microwave field generates ultraviolet radiation by the lamp at the same time when it interacts with the reaction mixture. The construction, experimental set-ups, applications, and safety precautions are discussed.     

3种现场快速水质检测仪的性价对比

选择了市场上口碑好、占有率高的3款便携式水质现场应急检测设备,通过准确度、精密度、检测时长及价格等指标,以权重积分法对3款仪器进行了比选,结果表明德国MN公司的PF-12型便携式多参数分光光度计的综合性能最优.     

中英化学教材“化学反应速率”内容比较研究

“化学反应速率”综合体现了微粒观、实验观及科学本质观等化学基本观念,是提高学生科学素养的重要载体。从内容选取、内容编排与内容呈现3个方面对英国索尔特高级化学课程教材与国内化学教材中“化学反应速率”相关内容的编写进行比较,并简要阐述几点对化学教材编写和化学教学的启示。     

基于准等重二甲基化标记的高通量蛋白质组选择性交叉标记装置

面对生物学及精准医学等领域多变量、大样本量的蛋白质组定量分析的需求,高通量的定量标记及分析已经成为近年来蛋白质组学方法发展的趋势。发展了一种基于准等重二甲基化标记策略的高通量肽段末端选择性交叉标记装置（pIDL-StageTip）,借助简单的装置及离心力,有效地增加了定量标记的通量,并保证了肽段末端两步标记反应时间的可控性及操作的简便性。通过优化酸性条件下NaBD₃CN与NaBH₃CN体系的标记条件,得到了标准蛋白质酶解产物100%的标记效率、95%以上的标记选择性;在人源蛋白质组复杂体系下,标记效率大于99%,标记选择性为100%。基于该装置的定量方法具有很高的定量准确度及精密度。该装置为实现高可操作性、高准确度、高通量的蛋白质组定量标记提供了一个可靠的解决方案。     

Packings and stationary phases for biopolymer separations by HPLC

Summary Packings and stationary phases applied to high resolution separations of proteins, enzymes, and nucleic acids must satisfy a series of distinct criteria that are different from those usually required by HPLC of low molecular weight non-biologically active analytes. These requirements have been met through substantial improvements in classical gel media together with novel developments in silica supports, and have led to a family of products with tailor-made and reproducible properties. Supports consisting of cross-linked organic gels, and inorganic materials (mostly silicas) are now available with graduated particle sizes, pore sizes, porosities and surface areas as well as non-porous beads. A whole range of stationary phases, such as reversed phase, hydrophobic interaction, ion exchanger and affinity packings, were designed for application as chemical sensors for biopolymer recognition in adsorptive chromatography. The phase systems are operated in the gradient mode, giving high resolution and high peak capacities. In addition, aqueous liquid-liquid partitioning systems have been developed for the fractionation of proteins and nucleic acids. Size exclusion media complete the set of HPLC variants enabling a discrimination of proteins according to their size and shape in an isocratic elution mode. Basically, protein purification and isolation is a multistage process where-by the HPLC variants are combined in a logistic sequence, utilizing the different selectivities of the phase systems and thus maximising resolution, speed and throughput.     

Vinegar classification based on feature extraction and selection from headspace solid-phase microextraction/gas chromatography volatile analyses: a feasibility study

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC) and multivariate data analysis were applied to classify different vinegar types (white and red, balsamic, sherry and cider vinegars) on the basis of their volatile composition. The collected chromatographic signals were analysed using the stepwise linear discriminant analysis (SLDA) method, thus simultaneously performing feature selection and classification. Several options, more or less restrictive according to the final number of considered categories, were explored in order to identify the one that afforded highest discrimination ability. The simplicity and effectiveness of the classification methodology proposed in the present study (all the samples were correctly classified and predicted by cross-validation) are promising and encourage the feasibility of using a similar strategy to evaluate the quality and origin of vinegar samples in a reliable, fast, reproducible and cost-efficient way in routine applications. The high quality results obtained were even more remarkable considering the reduced number of discriminant variables finally selected by the stepwise procedure. The use of only 14 peaks enabled differentiation between cider, balsamic, sherry and wine vinegars, whereas only 3 variables were selected to discriminate between red (RW) and white wine (WW) vinegars. The subsequent identification by gas chromatography-mass spectrometry (GC-MS) of the volatile compounds associated with the discriminant peaks selected in the classification process served to interpret their chemical significance.     

Matrix-assisted laser desorption/ionization-mass spectrometry of cuticular lipid profiles can differentiate sex, age, and mating status of Anopheles gambiae mosquitoes

Malaria is a devastating mosquito-borne disease, which affects hundreds of millions of people each year. It is transmitted predominantly by Anopheles gambiae, whose females must be >10 days old to become infective. In this study, cuticular lipids from a laboratory strain of this mosquito species were analyzed using a mass spectrometry method to evaluate their utility for age, sex and mating status differentiation. Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS), in conjunction with an acenaphthene/silver nitrate matrix preparation, was shown to be 100% effective in classifying A. gambiae females into 1, 7–10, and 14 days of age. MALDI-MS analysis, supported by multivariate statistical methods, was also effective in detecting cuticular lipid differences between the sexes and between virgin and mated females. The technique requires further testing, but the obtained results suggest that MALDI-MS cuticular lipid spectra could be used for age grading of A. gambiae females with precision greater than with other available methods.