PLS and PARAFAC applied to determination of noscapine in biological fluids by excitation-emission matrix fluorescence

A method for the direct determination of noscapine, an opium alkaloid, in biological fluids such as urine and human plasma has been developed using excitation-emission matrix fluorescence measurements and chemometrics techniques based on partial least squares (PLS) and parallel factor (PARAFAC) analysis. A two-factor PARAFAC trilinear model without restrictions was used in the data analysis. The excitation wavelength range was from 285 to 315 nm and the emission was recorded from 325 to 500 nm. The calibration graph was constructed using sixteen standard solutions in the concentration range from 0.50 to 21.00 smg/ml for noscapine. The capabilities of the method for the analysis were evaluated by determining noscapine in synthetic and real samples with satisfactory results. In addition, a PLS model was built at one excitation wavelength and used to determine noscapine in a series of synthetic and real samples. The accuracy of the proposed methods, evaluated through the root mean square error of prediction (RMSEP) for noscapine by PARAFAC and PLS models was 0.2375 and 0.4901, respectively. The best model was obtained using PARAFAC analysis. This result shows that molecular fluorescence spectroscopy can be used for the development of robust analytical methods for the direct determination of noscapine on a complex background such as urine and human plasma. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 3, pp. 49–54, March, 2007.     

磷脂膜色谱用于评价药物与有序磷脂膜的相互作用磷脂膜色谱用于评价药物与有序磷脂膜的相互作用

目的使用磷脂膜色谱考察药物与有序磷脂膜的相互作用。方法使用磷脂膜色谱测定药物与有序磷脂膜的相互作用强度，表示为药物的膜亲和性参数(lg K_IAM)。使用正辛醇/水系统测定药物的疏水性参数(lg DO/W,7.4)。结果在有机调节剂百分比(φ) 0～30%范围内，容量因子对数值(lg K′_IAM)与φ呈现良好线性关系；对于3种有机调节剂(甲醇、乙醇和乙腈)，lg K′_IAM与φ间曲线截距相同，但斜率有显著差别。从对羟基苯甲酸甲酯到丁酯，每增加一个CH₂对测定的亲脂性参数差值(Δlg K_IAM和Δlg DO/W,7.4)具有相似的影响，但是从对羟基苯甲酸到甲酯的差值却明显偏离这个规律。结论磷脂膜色谱是一个简便、有效和快速的用于评价药物与有序磷脂膜相互作用的工具。     

Relationships between the lipophilicity of some 1,4-piperazine derivatives of aryloxyaminopropanols and their beta-andrenolytic activity

Nineteen 1,4-piperazine derivatives of aryloxyaminopropanol were evaluated with respect to beta-adrenolytic activity. The retention factors obtained from HPLC, RM values obtained from partition TLC and the lipophilic Hansch's (4) constants pi were determined and the compounds were studied with respect to their lipophilicity based on chromatographic properties. The study of the influence of different substituents introduced at the para position on the phenyl ring on the retention factor indicated the log k vs. the number of carbon atoms in R1 substituent to be a linear relationship. Attempts have been made to relate the beta-adrenolytic activity to the lipohydrophilic parameters by deriving a quantitative relationship between them. Significant parabolic correlation was observed between the beta-adrenolytic activity and the logarithm of the retention factor, log k. An analogous relationship was obtained between the beta-adrenolytic activity of the compounds and the RM values obtained from partition TLC as well as Hansch's lipophilic constants pi.     

Near-Infrared Imaging for Studying Homogeneity of Protein-Sugar Mixtures

Purpose To investigate the applicability of near-infrared (NIR) imaging for assessing the homogeneity of dried protein-sugar formulations.Methods Physical mixtures of lysozyme and trehalose in different ratios were prepared and analyzed by near-infrared (NIR) imaging with a spatial resolution of 10 or 40 μm. To define and select the best imaging strategy, besides visual inspection of the images, several approaches for data processing were tested: single wavelength intensity, peak/height ratio of two specific wavelengths, correlation coefficient with a reference spectrum and principal component analysis (PCA). In order to relate the contrast directly to concentration differences of lysozyme and trehalose, quantitative models were created based on correlation coefficient and partial least squares (PLS) regression. The selected imaging method was applied to compare the homogeneity of a supercritical fluid (SCF) dried and a freeze-dried lysozyme-trehalose mixture.Results All tested methods confirmed each other and showed spatial heterogeneity in the lysozyme and trehalose contents of the physical mixtures. However, multivariate data processing methods (correlation coefficient and PCA/PLS) resulted in more distinct contrasts than univariate approaches (single wavelength analysis) and allowed a quantitative estimation of the homogeneity. As shown by NIR imaging in combination with the correlation coefficient or the PLS method, the SCF dried lysozyme-trehalose formulation was at least as homogeneous as its lyophilized counterpart, at 10 μm pixel size resolution.Conclusions NIR imaging is a useful tool for studying the homogeneity of dried protein-sugar formulations.     

Influence of physico-chemical parameters of some barbituric acid derivatives on their retention on an amide embedded RP silica column

Retention parameters of 45 different barbituric acid derivatives were determined on an amide embedded RP silica column (Discovery RP-AmideC16) using non-buffered water–acetonitrile eluent systems. Linear correlation were calculated between the logarithm of the capacity factor and the acetonitrile concentration in the eluent. To determine the retention behavior of barbituric acid derivatives, stepwise regression analysis (SRA) and principal component analysis (PCA) followed by two-dimensional nonlinear and modified nonlinear mapping was used. It can be concluded, the retention of barbituric acid derivatives are governed mainly by the steric parameters of the substituents. Principal component analysis indicated that the barbituric acid derivatives have mixed retention on this amide embedded RP silica column in water–acetonitrile eluent.     

Development of a Preformulation Lipophilicity Screen Utilizing a C-18-Derivatized Polystyrene-Divinylbenzene High-Performance Liquid Chromatographic (HPLC) Column

Alkane/water partition coefficients have been predicted from the retention times of solutes using a C-18-derivatized polystyrene-divinylbenzene HPLC column (Act-I). Several classes of compounds, with molecular weights from 78 to 379 and partition coefficients ranging over several orders of magnitude, were included in the present study. A high correlation coefficient (0.953) was obtained from log-log plots of alkane/water partition coefficient versus capacity factor. A poor correlation was observed for octanol/water partition coefficients, presumably due to the hydrogen-bonding capability of octanol. The alkane/water correlation suggests that the system is devoid of significant specific solute-stationary phase interactions which are known to impart anomalous retention behavior to traditional reverse phase columns. Deviations of calculated alkane/water partition coefficients (and Hansch II_alkane coefficients) from observed values could not be explained in terms of solute (or substituent) polarizability, dipole moment, -para, or pK _HB values, further suggesting that specific interactions between the stationary phase and the solute are not significant. A molecular weight dependence that was independent of lipophilicity was observed. Thermodynamic and extrathermodynamic parameters of retention were obtained in order to investigate retention mechanisms for the Act-I column. The molecular weight dependence does not appear to be due to size exclusion or entropic expulsion of the solute from the stationary phase. Hansch II substituent coefficients calculated from retention times were found to be similar for benzene and steroid derivatives. Thus, the Act-I column may be utilized as a rapid lipophilicity screen for drug candidates of similar molecular weight.     

Near-infrared chemical imaging (NIR-CI) on pharmaceutical solid dosage forms-comparing common calibration approaches

Near-infrared chemical imaging (NIR-CI) is the fusion of near-infrared spectroscopy and image analysis. It can be used to visualize the spatial distribution of the chemical compounds in a sample (providing a chemical image). Each sample measurement generates a hyperspectral data cube containing thousands of spectra. An important part of a NIR-CI analysis is the data processing of the hyperspectral data cube. The aim of this study was to compare the ability of different commonly used calibration methods to generate accurate chemical images. Three common calibration approaches were compared: (1) using single wavenumber, (2) using classical least squares regression (CLS) and (3) using partial least squares regression (PLS1). Each method was evaluated using two different preprocessing methods. A calibration data set of tablets with five constituents was used for analysis. Chemical images of the active pharmaceutical ingredient (API) and the two major excipients cellulose and lactose in the formulation were made. The accuracy of the generated chemical images was evaluated by the concentration prediction ability. The most accurate predictions for all three compounds were generated by PLS1. The drawback of PLS1 is that it requires a calibration data set and CLS, which does not require a calibration data set, therefore proved to be an excellent alternative. CLS also generated accurate predictions and only requires the pure compound spectrum of each constituent in the sample. All three calibration approaches were found applicable for hyperspectral image analysis but their relevance of use depends on the purpose of analysis and type of data set. As expected, the single wavenumber method was primarily found useful for compounds with a distinct spectral band that was not overlapped by bands of other constituents. This paper also provides guidance for hyperspectral image (or NIR-CI) analysis describing each of the typical steps involved.     

Dependence of the retention of some barbituric acid derivatives on a porous graphitized carbon column on their physicochemical parameters

The retentions of 45 barbituric acid derivatives were determined on a porous graphitized carbon column (PGC) in unbuffered methanol-water eluent mixtures at various organic phase concentrations and the retention data were correlated with the various hydrophobic and electronic parameters of barbituric acid derivatives. Each derivative showed symmetric peaks in each eluent proving the good separation characteristics of the PGC column without buffering the eluent. Significant linear correlations were found between the logk' value and the concentration of the organic mobile phase in the eluent. Stepwise regression analysis indicated that the retention of barbituric acid derivatives is mainly governed by the electronic parameters, and the lipophilicity of various substituents did not affect significantly the retention, although the eluents were typical reversed-phase eluents.     

偏最小二乘回归及其在消尔疴口服液紫外分光光度分析中的应用

偏最小二乘法在对因变量矩阵分解的同时,也依据主成分分析法将自变量矩阵分解,充分利用了两者的信息及内在联系,所得回归模型稳定性好,预示能力强。应用于消尔疴口服液的紫外分光光度分析中,同时测定了两主要成分磺胺噻唑和磺胺二甲嘧啶的含量,平均回收率分别为99.8%和100.4%,变异系数0.52%和0,60%,结果满意。     

Simultaneous spectrophotometric determination of chlordiazepoxide and clidinium using multivariate calibration techniques

Three multivariate modelling approaches including partial least squares regression (PLS), genetic algorithm‐partial least squares regression (GA‐PLS), and principal components‐artificial neural network (PC‐ANN) analysis were investigated for their application to the simultaneous determination of chlordiazepoxide and clidinium levels in pharmaceuticals. A set of synthetic mixtures of drugs in ethanol and 0.1 M HCL was made, and the prediction abilities of the aforementioned methods were examined using RSE% (relative standard error of the prediction). The PLS and PC‐ANN methods were found to be comparable, and GA‐PLS produced slightly better results. The predictive models that we built were successfully applied to simultaneously determine the levels of chlordiazepoxide and clidinium in coated tablets. Copyright © 2010 John Wiley & Sons, Ltd.     

TLC separation of carbohydrates on silica gel modified with copper (II) salts

Impregnation of silica gel was conducted by immersion method with the help of copper (II) sulfate and ammonia complex: Cu(NH3)4(2+). The adsorbents thus obtained were used for the analysis of carbohydrates of mono-di-oligosaccharides. The influence of the pH of the impregnating solution (pH = 5 and pH = 8) on the retention of the analysed compounds was examined. The results were interpreted in view of the process of metal ions complexation by sugar molecules in water. The effects of organic modifiers: propanol-2, methyl-ethyl ketone, acetonitrile, acetone added to the water phase on the retention and selectivity of the sugars determination on the modified stationary phase were studied.     

Selection of mobile phase in high-performance liquid chromatographic determination for medicines

A convenient method was developed to select mobile phase to separate drugs commonly used in clinical therapy, using high-performance liquid chromatography (HPLC). The separation conditions determined by this method were similar for each compound. Two kinds of mobile phase, a mixture of acetonitrile-phosphate buffers, pH 4.2 and 2.5, was used and the composition of mobile phase used for a drug in HPLC analysis was systematically determined as follows: (1) the retention time of a drug was measured under the gradient condition, (2) this retention time value was applied to the regression equation which was determined from the retention time values of p-hydroxybenzoate derivatives under the gradient condition and the concentration of acetonitrile in mobile phase, giving about 5 min of retention time, (3) percentage of acetonitrile in the isocratic condition was calculated from this regression equation and a target drug was eluted with the mobile phase consisting of the calculated concentration of acetonitrile. According to the proposed method, the composition of mobile phase, with which retention time value was between 4 to 8 min in the isocratic condition, was examined for 75 drugs clinically used. Seventy-two of the 75 drugs were analyzed well in the mobile phase, their composition was calculated by the regression equation, and the peak shape of each compound was observed to be sharp. Using this method, the time required for not only the setting of HPLC conditions but also the analysis will be shortened.     

Potential of immobilized artificial membrane chromatography for lipophilicity determination of arylpropionic acid non-steroidal anti-inflammatory drugs

Molecular lipophilicity can be expressed by logP or more conveniently by logk, i.e. determined by the traditional shake-flask technique or by liquid chromatography. The logk of 11 arylpropionic non-steroidal anti-inflammatory drugs (NSAIDs) was determined at pH 7.4 of the eluent using two stationary phases i.e. octadecylsilane phase and an immobilized artificial membrane (IAM.PC.MG) packing. The chromatographic retention factors extrapolated to 100% aqueous phase (logk(wODS) and logk(wIAM)) were correlated with n-octanol/water lipophilicity parameters (logP) and with n-octanol/water partition coefficients corrected for ionization at pH 7.4 (logD7.4). In this series of compounds, significant linear correlations (r>0.94) between the chromatographic parameters (logk(wIAM)) and the reference lipophilicity data (logP and logD7.4) were described. Moreover, regression analysis between the lipophilicity parameters and some pharmacokinetic data for the drugs under study were performed. The logk(wIAM) parameter over n-octanol/water partition data seems to provide a good model to obtain lipophilicity parameters of arylpropionic acid NSAIDs for quantitative structure-activity relationships studies.     

人工北虫草指纹图谱研究

目的:建立人工北虫草TLC和HPLC法指纹图谱。方法:TLC法以三氯甲烷-乙酸乙酯-异丙醇-水(5∶2∶6∶0.6)为展开剂,磷酸氢二钠制备的GF_(254)板展开;HPLC法以乙腈-水梯度洗脱,检测波长260nm。结果:HPLC法精密度、重复性、稳定性试验中共有峰面积、保留时间的RSD均小于3.0%;不同产地的人工北虫草相似度大于0.9。结论:该方法简便可靠,可作为控制人工北虫草质量的依据。