A priori method of evaluating uncertainties in qualitative chromatographic analysis: probabilistic approach

Probabilistic algorithms to evaluate result reliability in qualitative chromatographic analysis are discussed in the paper. The elementary uncertainty (P₀), concerned with a single test (comparison of sample and reference peak positions), is treated as the sum of misidentification and omission probabilities. Both constituents are calculated separately using the simplified model and Laplace functions. In the model, the main reasons for elementary uncertainties are random normally distributed deviations during retention characteristic measurement. Algorithms to calculate both constituents of P₀ have to take into account real measurement precision, supposed composition of the sample, content of the database, chosen coincidence criterion and other factors. At a high selectivity of retention, the 3 value is recommended as the most convenient coincidence criterion. It leads to more reliable and unambiguous attribution of peaks in the chromatogram. For cases that are more complicated, the probabilistic algorithms based upon Bernoulli theorem are proposed to calculate the summary uncertainty of identification, concerned with the multiple test. They take into account P₀ value, the number of repeated single tests (n) in the similar or different conditions, and chosen identification criterion K (minimal number of coincidences). The above-mentioned algorithms lead to a priori optimisation of the mode of operation of any identification software system associated with the chromatograph. They can be useful during a metrological validation of corresponding qualitative analysis methods.Presented at the Second International Conference on Metrology—Trends and Applications in Calibration and Testing Laboratories, November 4–6, 2003, Eilat, Israel.The opinions reflected in this paper are those of the author only. AQUAL does not necessarily endorse them.     

淫羊藿药材一些混淆物种的FTIR鉴别研究

淫羊藿是一味药用历史悠久的传统中药, 具有补肾壮阳之功效。《中国药典》规定使用五种来源的淫羊藿——淫羊藿Epimedium brevicornu Maxim.、箭叶淫羊藿E.sagittatum(Sieb. et Zucc.) Maxim.、柔毛淫羊藿E.pubescens Maxim.、朝鲜淫羊藿E.koreanum Nakai和巫山淫羊藿E.wushanense T.S.Ying,但这几种药材的鉴别特征描述比较简单,传统鉴定技术很难实现这些种类和常见混淆物种的鉴别。文章采用傅里叶变换红外光谱(FTIR)及其二阶导数谱对常见淫羊藿易混淆药材——淫羊藿与朝鲜淫羊藿,柔毛淫羊藿与保靖淫羊藿E.baojingense Q.L.Chen & B.M.Yang、星花淫羊藿E.stellulatum Stearn、竹山淫羊藿E.zhushanense K.F.Wu&S.X.Qian,柔毛淫羊藿与部分天平山淫羊藿E.myrianthum Stearn,箭叶淫羊藿与粗毛淫羊藿E.acuminutum Franch.共4对易混淆药材进行鉴别研究。根据不同物种淫羊藿药材红外光谱特征的不同,基本上实现常见易混淆物种的快速鉴别。该方法有助于解决淫羊藿药材物种混乱问题。     

拉曼光谱技术在宝石学研究中的应用

拉曼光谱技术已被成功地应用于宝石学研究和宝石鉴定领域。拉曼光谱技术可以准确地鉴定宝石内部的包裹体,提供宝石的成因及产地信息,并且可以有效、快速、无损和准确地鉴定宝石的类别——天然宝石、人工合成宝石和优化处理宝石。但是,该技术也存在着一定的局限性。     

鹅膏菌的傅里叶变换红外光谱研究

利用傅里叶变换红外光谱对云南野生鹅膏科蘑菇子实体及孢子进行了研究,二者的光谱差异显著。子实体光谱的最强峰出现在蛋白质酰胺Ⅰ的特征峰1 655 cm-1附近,在碳水化合物的C—O特征振动峰1 077, 1 042 cm-1附近也有强吸收,表明鹅膏科蘑菇子实体的主要成分是蛋白质和碳水化合物;孢子的三个强峰在2 926,2 855,1 747 cm-1,归属为脂类物质的吸收。在1 800～750 cm-1,不同属、不同种的鹅膏科蘑菇光谱有区别,以此可以区分不同种类的蘑菇。此外,隐花青鹅膏菌不同部位的光谱也有差异,表明蘑菇的化学组分在子实体的不同部位有不同分布。利用傅里叶变换红外光谱可以区分不同种类的蘑菇。     

白僵蚕的红外指纹图谱鉴别研究

采用红外光谱技术研究了健康蚕,不同季节和品种的白僵蚕醇溶部位的红外指纹图谱,采用共有峰率和变异峰率双指标序列法对其图谱的结构特征进行了分析鉴别。结果表明：白僵蚕醇溶部位具有稳定而独特的红外指纹图谱。健康蚕的红外指纹图谱与白僵蚕的红外指纹图谱明显不同,两图谱共有峰率仅为63.0%,变异峰率较大,健康蚕相对于白僵蚕变异峰率达41.2%;不同品种、不同季节的白僵蚕的红外指纹图谱相似,但也存在一定差异,其中不同品种的白僵蚕的红外指纹图谱最低共有峰率为76.0%,最高为92.0%,春季与秋季白僵蚕醇溶部位的红外指纹图谱共有峰率为73.1%。白僵蚕醇溶部位的红外指纹图谱可以用作鉴定白僵蚕,区别不同品种和季节的白僵蚕的一种手段。     

Identification and quantitation of phenolics from green beans by high-performance liquid chromatography

Summary High-performance liquid chromatography with diode-array detection has been used for the separation and quantitation of phenolics from fresh and processed green beans. Whole beans, pods and seeds of green beans were studied separately. Chromatographic profiles from pods were more complex than those found in seeds. Flavonol glycosides were confined to quercetin and kaempferol classes and they were typical of external parts of the fruit. Flavan-3-ols monomers ((+) catechin and (−) epicatechin) as well as procyanidins structures were identified in pods and seeds. Chromatographic profiles from processed beans revealed a polyphenolic composition similar to those found in pod fresh green beans. The chromatographic method was carefully validated in regard to precision and accuracy. High reproducibility of peak area (RSD<3%) and calibration slopes (RSD<4%) was obtained. Recoveries between 94–104% revealed good accuracy for the overall method. Application to quantitative determination in a representative number of samples allowed good knowledge of the phenolic composition of green beans (Phaseolus vulgaris v.vulgaris).     

Acknowledgement to our referees

Abstract

In the hydrosphere sulfates of the following origin may exist: (1) evaporitic; they come from the leaching of sulfate rocks, (2) biological, formed by sulfur-oxidizing bacteria and (3) anthropogenic, which get into water with wastes, fertilizers or acid rains. Chemical analyses may reveal sulfates in water, but their origin cannot be assessed by means of chemical analysis. The sulfates of various origin may differ in their isotopic compositions. However, sometimes we can observe the similarity of δ³⁴S of sulfates whose origin was entirely different. This similarity may be so suggestive that it could be misleading.

This paper presents patterns of completely different sulfates whose δ³⁴S are similar, though they have nothing in common. Other tables present patterns of sulfates whose origin is similar or even the same but their δ³⁴S are characterized by great variety. All of the isotopic data presented in the tables were specially chosen from some of the results of the studies of the sulfates in waters in Poland.

Isotopes techniques are becoming more popular and are useful for studies in many fields. These patterns may be a warning against drawing hasty conclusions from the results of δ-measuring.     

基于等质量肽段末端标记策略的质谱鉴定新算法

等质量肽段末端标记(Isobaric peptide termini labeling,IPTL)是一种使用轻、重同位素分别对肽段的C端和N端进行等重标记的技术.在对使用这种标记技术得到的数据进行一级谱分析时,由于肽段的质量相同,不会增加样本的复杂性,而在处理二级谱的数据时,可利用成对的b、y离子进行分析.本研究利用IPTL方法得到的实验数据设计了一种新的打分算法:全部离子打分算法(All ions scoring algorithm,AISA).AISA在对数据进行处理时,可以同时得到定性和定量信息.在Q-Exactive HeLa和Human-HCC-HL数据集上的蛋白定量覆盖率分别达到99%和100%.在Q-Exactive HeLa 2D RPLC数据集上,AISA算法鉴定到的PSM、唯一肽段和蛋白质分别比Morpheus高15%、26%和22%.在Human-HCC-HL数据集上,AISA算法鉴定到的PSM、唯一肽段和蛋白质分别比Morpheus高24%、39%和27%.在Q-Exactive HeLa和Human-HCC-HL数据集上蛋白质定量比值的平均值非常接近1,分别为1.18和0.90;在0.5~2.0区间内的定量比值分别为91%和94%.     

An iterative rational fraction polynomial technique for modal identification

The rational fraction polynomial (RFP) modal identification procedure is a well known frequency domain fitting technique. To deal with a linear problem, the RFP procedure does not directly minimize the fitting error, i.e. the difference between the experimental and the analytical frequency response function, but a frequency weighted function of it: this causes bias in the modal parameter estimates. In this paper an iteration procedure is proposed which uses the output of the RFP technique as a starting estimate, and minimizes the true fitting error, expressed as a first order Taylor expansion of the identified parameters. Results are quite satisfactory: the fitting error is notably reduced after few iterations. Moreover, less computational modes with respect to the original RFP method are needed to obtain a good fit in a given frequency band.A first version of this paper was presented at 17th Int. Seminar on Modal Analysis, Leuven (Belgium), 23–25 September 1992, and preprinted in the Proceedings.     

Identification of Mechanical Properties by Displacement Field Measurement: A Variational Approach

We study a parameter identification problem associated with a two-dimensional mechanical problem. In the first part, the experimental technique of determining the displacement field is briefly presented. The variational method proposed herein is based on the minimization of either a separately convex functional or a convex functional that leads to the reconstruction of the elastic tensor and the stress field. These two reconstructed fields are continuous and piecewise linear on a triangulation of the two-dimensional domain. Some numerical and experimental examples are presented to test the performance of the algorithms.