Multicomponent flow injection based analysis with diode array detection and partial least squares multivariate calibration evaluation. Rapid determination of Ca(II) and Mg(II) in waters and dialysis liquids

Flow injection analysis (FIA) with multiwavelength scanning of the FIA peaks using a diode array detector (DAD) has been combined with a multivariate calibration approach applying the partial least squares (PLS) method for the data evaluation. In this way, various side effects like dilution of the reagent, high blank, absorbance changes due to the pH gradient throughout the peak and/or the other interferences can be accounted for. Thus, even with a simple FIA manifold instrumentation the satisfactory results of multicomponent analysis are obtained. The method described has been checked on analysis of binary (Ca and Mg) and ternary (Ca, Mg and Cu) mixtures with pyridylazo resorcinol (PAR) as reagent and applied for rapid determination of calcium and magnesium in dialysis liquids and waters.     

Simultaneous spectrophotometric determination of ethinylestradiol and levonorgestrel by partial least squares and principal component regression multivariate calibration

Two spectrophotometric methods for the determination of Ethinylestradiol (ETE) and Levonorgestrel (LEV) by using the multivariate calibration technique of partial least square (PLS) and principal component regression (PCR) are presented. In this study the PLS and PCR are successfully applied to quantify both hormones using the information contained in the absorption spectra of appropriate solutions. In order to do this, a calibration set of standard samples composed of different mixtures of both compounds has been designed. The results found by application of the PLS and PCR methods to the simultaneous determination of mixtures, containing 4–11 μg ml⁻¹ of ETE and 2–23 μg ml⁻¹ of LEV, are reported. Five different oral contraceptives were analyzed and the results were very similar to that obtained by a reference liquid Chromatographic method.     

偏最小二乘紫外分光光度法同时测定甲基苯甲醛三种同分异构体

将偏最小二乘法(PLS)用于紫外分光光度数据的解析,建立了同时测定甲基苯甲醛3种同分异构体的模型。在230～304 nm范围内,将测得的48个样品的吸光度值作为校正集,另18个样品的吸光度值作为预测集用于建模。所建立的邻、间、对甲基苯甲醛模型的平均回收率分别为101.2%、100.2%和98.9%;均方根误差(RMSE)分别为0.2667、0.3853和0.2118;预测浓度范围分别为4.6～16.2μg/mL、5.8～17.4μg/mL和6.5～20.6μg/mL。讨论了混合物中3种同分异构体浓度比例对测定结果的影响,并确定了最佳的浓度比例范围。对模拟样品进行加标回收率试验。并通过与顺、反丁烯二酸两种同分异构体测定结果的比较,得出了有意义的结论。     

Simultaneous quantitative analysis of overlapping spectrophotometric signals using wavelet multiresolution analysis and partial least squares

The mathematical bases and program algorithms of discrete wavelet transform (DWT), multiresolution and Mallat’s pyramid algorithm were described. The multiresolution analysis (MRA) based on Daubechies orthogonal wavelet basis was studied as a tool for removing noise and irrelevant information from spectrophotometric spectra. After wavelet MRA pre-treatment, eight error functions were calculated for deducing the number of factors. A partial least squares based on wavelet MRA (WPLS) method was developed to perform simultaneous spectrophotometric determination of Fe(II) and Fe(III) with overlapping peaks. Data reduction was performed using wavelet MRA and principal component analysis (PCA) algorithm. Two programs, SPWMRA and SPWPLS, were designed to perform wavelet MRA and simultaneous multicomponent determination. Experimental results showed the WPLS method to be successful even where there was severe overlap of spectra.     

测定锗的二极管阵列检测-流动注射分光光度法

研究了在溴化十六烷基三甲铵（ＣＴＭＡＢ）存在下，锗与２，３，７－三羟基－９－小杨基荧光酮－６（ＳＡＦ）的显色反应，采用二极管阵列检测器，建立了检测微量锗的流动注射分光光度法。将该法应用于食品和中草药中锗的测定，取得了满意的结果。锗在０～３．０ｍｇ／Ｌ范围内线性良好，检出限为０．０１２ｍｇ／Ｌ，样品加标回收率为８１．０％～９８．５％，相对标准偏差小于８．４％。实验表明，该法灵敏、快速，准确度高、精密     

偏最小二乘-同步荧光光谱法同时测定两种蒽环类抗生素

将偏最小二乘法(PLS)用于同步荧光光谱严重重叠的多柔比星(doxorubicin, DOX)和柔红霉素(daunorubicin, DNR)两组分混合体系进行波谱解析, 建立了该混合体系含量同时测定的新方法. 在pH 3.45 B-R缓冲溶液中, 波长差Δλ=55 nm时, 用测得的25个混合标样的同步荧光原始光谱、一阶导数光谱值建立模型. DOX和DNR在质量浓度为0.05～3.0 μg/mL范围内呈现良好的线性关系, 所建立的测定二者模型的相关系数分别为0.9897和0.9909; 平均回收率分别为101.0%和101.4%; 预测均方根误差(RMSEP)分别为0.1400和0.1395; 预测相对标准误差(SEP)分别为0.1541和0.1525. 该方法可应用于尿液样品的分析测定.     

Simultaneous determination of potassium guaiacolsulfonate, guaifenesin, diphenhydramine HCl and carbetapentane citrate in syrups by using HPLC-DAD coupled with partial least squares multivariate calibration

A simple and rapid analytical procedure was proposed for the determination of chromatographic peaks by means of partial least squares multivariate calibration (PLS) of high-performance liquid chromatography with diode array detection (HPLC-DAD). The method is exemplified with analysis of quaternary mixtures of potassium guaiacolsulfonate (PG), guaifenesin (GU), diphenhydramine HCI (DP) and carbetapentane citrate (CP) in syrup preparations. In this method, the area does not need to be directly measured and predictions are more accurate. Though the chromatographic and spectral peaks of the analytes were heavily overlapped and interferents coeluted with the compounds studied, good recoveries of analytes could be obtained with HPLC-DAD coupled with PLS calibration. This method was tested by analyzing the synthetic mixture of PG, GU, DP and CP. As a comparison method, a classsical HPLC method was used. The proposed methods were applied to syrups samples containing four drugs and the obtained results were statistically compared with each other. Finally, the main advantage of HPLC-PLS method over the classical HPLC method tried to emphasized as the using of simple mobile phase, shorter analysis time and no use of internal standard and gradient elution.     

Simultaneous determination of Sb(III) and Sb(V) by partial least squares regression

A method for simultaneous spectrophotometric determination of Sb(III) and Sb(V) using multivariate calibration method is proposed. This method is based on the development of the reaction between the analytes and pyrogallol red at pH 2.00. The selection of variables was studied. A series of synthetic solutions containing different concentrations of Sb(III) and Sb(V) were used to check the prediction ability of the partial least squares model. The calibration curves were linear over the range of 0.3-3.4 and 0.3-3.0 μg ml⁻¹ for Sb(III) and Sb(V), respectively. The detection limits were 0.177 and 0.200 μg ml⁻¹ for Sb(III) and Sb(V), respectively.     

Simultaneous determination of copper, nickel, cobalt and zinc using zincon as a metallochromic indicator with partial least squares

The partial least squares (PLS) applied to the simultaneous determination of the divalent ions of copper, nickel, cobalt and zinc based on the formation of their complexes with 2-carboxy-2′-hydroxy-5′-sulfoformazyl benzene (zincon). The absorption spectra were recorded from 515 through 750 nm. The effect of pH on sensitivity and the selectivity was studied in the range 3.0-10.0 and the pH 8.0 was choused according to net analyte signal (NAS) as a function of pH. The concentration range for Cu²⁺, Ni²⁺, Co²⁺and Zn²⁺ in solution calibration sets were 0-2.6, 0-4.6, 0-3.0 and 0-4.92 ppm, respectively. The root mean squares differences (RMSD) for copper, nickel, cobalt and zinc were 0.0181, 0.0488, 0.0309 and 0.0463, respectively.     

Simultaneous kinetic spectrophotometric determination of cyanide and thiocyanate using the partial least squares (PLS) regression

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN⁻ and SCN⁻ ions is described. The method is based on the difference in the rate of the reaction between CN⁻ and SCN⁻ ions with chloramine-T in a pH 4.0 buffer solution and at 30 °C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578 nm in the time range 20-180 s after initiation of the reaction with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0 ng mL⁻¹ for CN⁻ and SCN⁻ ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples.     

偏最小二乘分光光度法同时测定痕量铁、锰、铜、锌、钴和镍

痕量Fe^3 ,Mn^2 ,Cu^2 ,Zn^2 ,Co^2 ,Ni^2 与2－（5－溴－2－吡啶偶氮）－5－二乙氨基苯酚（5－Br-PADAP)和溴化十六烷基三甲基铵（CTMAB）在PH8．3时发生高灵敏显色反应，所形成的三元胶束络合的吸收光谱严重重叠，采用偏最小二乘法（PLS）辅助分光光度法测定了合成试样及饲料中上述6种痕量组分，结果表明，PLS法是化学计量学中一种可适用于基体较复杂的实际试样中痕量组分分光度同时测定的多元计算方法。     

偏最小二乘-分光光度法同时测定福美锌和代森锰农药残留量

利用紫外可见分光光度法研究了农药福美锌和代森锰与苯基荧光酮的相互作用,发现反应后的产物分别在波长为551和554 nm处最大有吸收,但光谱严重重叠.实验采集了450～700 nm波长范围吸光度数据,并对该数据进行一阶求导后用偏最小二乘法处理,据此建立了偏最小二乘-分光光度法同时测定福美锌和代森锰两种农药的新方法.福美锌和代森锰的线性范围分别为0.3～6.0和0.2～3.5 μg/mL;检出限分别为0.22和0.13 μg/mL.混合样品分析无需分离,方法简单、快速.用于水果、大米和自来水等实际样品测定.     

Maintenance of a calibration model for near infrared spectrometry by a combined principal component analysis-partial least squares approach

A novel strategy for building and maintaining calibration models has been developed for use when the future boundaries of the sample set are unknown or likely to change. Such a strategy could have an impact on the economics and time required to obtain and maintain a calibration model for routine analysis. The strategy is based on both principal component analysis (PCA) and partial least squares (PLS) multivariate techniques. The principal action of the strategy is to define how “similar” a new sample is to the samples currently defining the calibration dataset. This step is performed by residuals analysis, following PCA. If the new sample is considered to have a spectrum “similar” to previously available spectra, then the model is assumed able to predict the analyte concentration. Conversely, if the new sample is considered “dissimilar”, then there is new information in this sample, which is unknown to the calibration model and the new sample is added automatically to the calibration set in order to improve the model. The strategy has been applied to a real industrial dataset provided by BP Amoco Chemicals. The data consists of spectra of 102 sequential samples of a raw material. The strategy produced an accurate calibration model for both target components starting with only the first four samples, and required a further 17 reference measurements to maintain the model for the whole sampling sequence, which was over a 1-year period.     

Simultaneous spectrophotometric determination of iron and vanadium by H-point standard addition method and partial least squares regression in micellar medium

Simultaneous determination of total iron and vanadium by H-point standard addition method (HPSAM) and partial least squares (PLS) is described. Gallic acid (GA) in a cationic micellar solution of CTAB was used for determination of iron and vanadium in different oxidation states at pH 5. The presence of a micellar system enables total iron and vanadium to be determined with improved sensitivities. The total relative standard error for applying the PLS method to 15 synthetic samples in the ranges 0.20–15.00 μg ml⁻¹ iron and 0.20–8.00 μg ml⁻¹ vanadium was 2.2%. The results of applying the H-point standard addition method showed that iron and vanadium can be determined simultaneously with the concentration ratios of iron to vanadium from 10:1 to 1:20 in the mixed sample. Both HPSAM and PLS methods showed suitable abilities to resolve accurately overlapped absorption spectra of the compounds. Both proposed methods were successfully applied to the determination of Fe and V in several synthetic alloy solutions.     

Multivariate analysis of remote laser-induced breakdown spectroscopy spectra using partial least squares,principal component analysis,and related techniques

Quantitative analysis with laser-induced breakdown spectroscopy traditionally employs calibration curves that are complicated by chemical matrix effects. These chemical matrix effects influence the laser-induced breakdown spectroscopy plasma and the ratio of elemental composition to elemental emission line intensity. Consequently, laser-induced breakdown spectroscopy calibration typically requires a priori knowledge of the unknown, in order for a series of calibration standards similar to the unknown to be employed. In this paper, three new Multivariate Analysis techniques are employed to analyze the laser-induced breakdown spectroscopy spectra of 18 disparate igneous and highly-metamorphosed rock samples. Partial Least Squares analysis is used to generate a calibration model from which unknown samples can be analyzed. Principal Components Analysis and Soft Independent Modeling of Class Analogy are employed to generate a model and predict the rock type of the samples. These Multivariate Analysis techniques appear to exploit the matrix effects associated with the chemistries of these 18 samples.     

Multivariate calibration by partial least squares for the quantitative phase analysis using Rietveld method

The present work used multivariate calibration by Partial Least Squares (PLS) to produce a Net Analyte Signal as a way of establishing the independent influence of each phase in the Quantitative Phase Analysis with the Rietveld method for three sources of potential error: preferred orientation, linear absorption and counting statistics. Ternary mixtures of Al₂O₃, MgO and NiO were employed and organized in three groups with different degrees of variation in the weight fractions of the three constituents. An analysis of variance indicated that the partial selectivity of the least variation group differed significantly from the other groups. As for the phases, MgO partial selectivity was significantly different. This is due to a strong correlation between the linear absorption and counting statistics in the region of the (2 0 0) reflection of the MgO phase that is strongly affected by preferred orientation and also corresponds to the strongest reflection for MgO as well as for NiO. On the whole, by using matrices of similarity, a great similarity was observed between the nominal weight fractions of the phases and the weight fractions observed by means of the Rietveld method. However, such similarity diminishes as the weight fractions of the phases of the mixture become closer to each other and, in the group of mixtures with least variation of weight fractions, the method is unable to quantify the small differences between the phases, even if these errors may be considered small relative to the weight fractions themselves. Copyright © 2008 John Wiley & Sons, Ltd.     

Near-infrared spectra combined with partial least squares for pH determination of toothpaste of different brands

Near-infrared spectroscopy(NIR),which is generally used for online monitoring of the food analysis and production process, was applied to determine the internal quality of toothpaste samples.It is acknowledged that the spectra can be significantly influenced by non-linearities introduced by light scatter,therefore,four data preprocessing methods,including off-set correction, 1st-derivative,standard normal variate(SNV) and multiplicative scatter correction(MSC),were employed before the date analysis. The multivariate calibration model of partial least squares(PLS) was established and then was used to predict the pH values of the toothpaste samples of different brand.The results showed that the spectral date processed by MSC was the best one for predicting the pH value of the toothpaste samples.     

Rapid simultaneous determination of protoporphyrin IX, uroporphyrin III and coproporphyrin III in human whole blood by non-linear variable-angle synchronous fluorescence technique coupled with partial least squares

Fluorescence spectroscopy provides high sensitivity in quantitative analysis. However, due to spectral interference, it is difficult to determine the individual components of fluorescent multi-component mixtures in such complicated and important body matrices as blood, urine and feces without any pre-separation. In this study, a simple and rapid approach based on non-linear variable-angle synchronous fluorescence spectrometry coupled with partial least squares analysis (NLVASF/PLS) was developed for the simultaneous determination of protoporphyrin IX (PP), uroporphyrin III (UP) and coproporphyrin III (CP). The detection limits were 0.18, 0.29 and 0.24 nmol L⁻¹ for protoporphyrin IX (PP), uroporphyrin III (UP) and coproporphyrin III (CP), respectively. The individual components of blood porphyrins were quantified, by this method, simultaneously in one scan with only about 30 s. The recoveries of this method were above 80% in human whole blood samples. This method provided a potential tool for the determination of porphyrins in whole blood and the differential diagnosis of porphyria, especially for rapid routine screening of large number of samples.