三维荧光二阶校正法快速测定块茎类蔬菜、土壤和污水中克百威残留量

克百威是一种高效内吸广谱氨基甲酸酯类杀虫剂.本文充分利用荧光光谱仪操作简单、灵敏度高,化学计量学二阶校正算法具有的"二阶优势",将三维荧光(EEM)与化学计量学交替三线性分解(ATLD)算法相结合,实现了红薯、土豆、红萝卜、土壤和污水5种实际复杂体系中克百威残留量的直接快速定量测定.当选取组分数为2时,用ATLD获得的平均回收率分别为(99.0±5.3)%、(97.2±4.2)%、(102.7±5.9)%、(101.1±3.8)%和(91.3±1.9)%.另外,还用椭圆置信区间(EJCR)测试和品质因子,如灵敏度(SEN)、选择性(SEL)、检测下限(LOD)和预测均方根误差(RSMEP)评估了该种算法的准确性.实验结果表明,该方法能以"数学分离"代替繁琐的"化学分离",成功地解决实际复杂体系中内源干扰物质与分析物光谱重叠所引起的难分辨的问题,可用于未知干扰共存下克百威含量的直接快速定量测定.     

Sorting variables by using informative vectors as a strategy for feature selection in multivariate regression

A new procedure with high ability to enhance prediction of multivariate calibration models with a small number of interpretable variables is presented. The core of this methodology is to sort the variables from an informative vector, followed by a systematic investigation of PLS regression models with the aim of finding the most relevant set of variables by comparing the cross‐validation parameters of the models obtained. In this work, seven main informative vectors i.e. regression vector, correlation vector, residual vector, variable influence on projection (VIP), net analyte signal (NAS), covariance procedures vector (CovProc), signal‐to‐noise ratios vector (StN) and their combinations were automated and tested with the main purpose of feature selection. Six data sets from different sources were employed to validate this methodology. They originated from: near‐Infrared (NIR) spectroscopy, Raman spectroscopy, gas chromatography (GC), fluorescence spectroscopy, quantitative structure‐activity relationships (QSAR) and computer simulation. The results indicate that all vectors and their combinations were able to enhance prediction capability with respect to the full data sets. However, regression and NAS informative vectors from partial least squares (PLS) regression, both built using more latent variables than when building the model presented in most of tested data sets, were the best informative vectors for variable selection. In all the applications, the selected variables were quite effective and useful for interpretation. Copyright © 2008 John Wiley & Sons, Ltd.     

Progress in oscillographic chronopotentiometry

The investigation on oscillographic chronopotentiometry after 2000 is reviewed. The development course of oscillographic chronopotentiometry is looked back. Some new instrumentations and new methods about oscillographic chronopotentiometry as well as applications of chemometrics in oscilloanalysis are introduced. The prospects of oscillographic chronopotentiometry development are also discussed in this paper.     

Multicomponent Chemometric Determination of Colorant Mixtures by Voltammetry

Abstract

A quantitative chemometric approach, iterative target transformation factor analysis (ITTFA), was applied to the simultaneous determination of mixtures of four food colorants (Amaranth, Sunset Yellow. Tartrazine and Ponceau 4R) by adsorptive voltammetry. The conventional and first-derivative voltammograms of the quaternary mixtures were used to perform the optimization of the calibration procedure by the ITTFA models. The proposed method was applied satisfactorily to the determination of a set of synthetic quaternary mixtures of colorant in phosphate/citric acid buffers (pH 5.7) and acceptable results were obtained. No significant advantages were found with the application of derivative technique in this voltammetric work.     

Pattern Recognition of Nebbiolo Wine as a Function of the Fungicide Treatment of the Grape

ABSTRACT

Principal component analysis and classification techniques were used to investigate the effect on the properties of wine of different fungicide treatments performed on the grapes. 55 variables were determined, 17 on the grape just-collected and the others on the wines. 27 samples of grape and wine were considered, produced in 1992, 1993" acceptdate="and 1994. The wines were classified as a function of the production year but no important correlation was found between fungicide treatment and the wine features. The classification was performed by a SIMCA method.

Clustering analysis, on the other hand, allowed a separation of the wine samples in three clusters, relative to three main kinds of grape treatments, i.e. based on i) copper sulfate, ii) copper hydroxide and iii) Mancozeb (the only one that does not contain Cu). The treatments based on copper oxychloride and the blank, that are the less active or characterized treatments, gave mixed results within the three clusters.     

化学计量学方法在光谱解析中的应用进展

本文对近20年来化学计量学在光谱分析测试中的应用进行了评述。指出了化学计量学在光谱分析中的重要性和应用前景。引用文献共129篇。     

Development of Advanced Chemometric-Assisted Spectrophotometric Methods for the Determination of Cromolyn Sodium and Its Alkaline Degradation Products

Advanced and sensitive spectrophotometric and chemometric analytical methods were successfully established for the stability-indicating assay of cromolyn sodium (CS) and its alkaline degradation products (Deg1 and Deg2). Spectrophotometric mean centering ratio spectra method (MCR) and chemometric methods, including principal component regression (PCR) and partial least square (PLS-2) methods, were applied. Peak amplitudes after MCR at 367.8 nm, 373.8 nm and 310.6 nm were used within linear concentration ranges of 2–40 µg mL⁻¹, 5–40 µg mL⁻¹ and 10–100 µg mL⁻¹ for CS, Deg1 and Deg2, respectively. For PCR and PLS-2 models, a calibration set of eighteen mixtures and a validation set of seven mixtures were built for the simultaneous determination of CS, Deg1 and Deg2 in the ranges of 5–13 µg mL⁻¹, 8–16 µg mL⁻¹, and 10–30 µg mL⁻¹, respectively. The authors emphasize the importance of a stability-indicating strategy for the investigation of pharmaceutical products.     

Differentiating Westlake Longjing tea from the first‐ and second‐grade producing regions using ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry‐based untargeted metabolomics in combination with chemometrics

There are numerous articles published for geographical discrimination of tea. However, few research works focused on the authentication and traceability of Westlake Longjing green tea from the first‐ and second‐grade producing regions because the tea trees are planted in a limited growing zone with identical cultivate condition. In this work, a comprehensive analytical strategy was proposed by ultrahigh performance liquid chromatography‐quadrupole time‐of‐flight mass spectrometry‐based untargeted metabolomics coupled with chemometrics. The automatic untargeted data analysis strategy was introduced to screen metabolites that expressed significantly among different regions. Chromatographic features of metabolites can be automatically and efficiently extracted and registered. Meanwhile, those that were valuable for geographical origin discrimination were screened based on statistical analysis and contents in samples. Metabolite identification was performed based on high‐resolution mass values and tandem mass spectra of screened peaks. Twenty metabolites were identified, based on which the two‐way encoding partial least squares discrimination analysis was built for geographical origin prediction. Monte Caro simulation results indicated that prediction accuracy was up to 99%. Our strategy can be applicable for practical applications in the quality control of Westlake Longjing green tea.