The Experts below are selected from a list of 27582 Experts worldwide ranked by ideXlab platform
Zhenxiao Cai - One of the best experts on this subject based on the ideXlab platform.
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characterization of dissolved organic matter using high performance liquid chromatography hplc size exclusion chromatography sec with a multiple Wavelength absorbance detector
Chemosphere, 2012Co-Authors: Mingquan Yan, Gregory V Korshin, Dongsheng Wang, Zhenxiao CaiAbstract:High-performance liquid chromatography-size exclusion chromatography (HPLC-SEC) coupled with a multiple Wavelength absorbance detector (200-445 nm) was used in this study to investigate the apparent molecular weight (AMW) distributions of dissolved organic matter (DOM). Standard DOM, namely humic acid, fulvic acid and hydrophilic acid, from the Suwannee River were tested to ascertain the performance and sensitivity of the method. In addition to four compounds groups: humic substances (Peak 1, AMW 16 kD), fulvic acids (Peak 2, AMW 11 kD), low AMW acids (Peak 3, AMW 5 kD), and low AMW neutral and amphiphilic molecules, proteins and their amino acid building blocks (Peak 4, AMW 3 kD), an new group that appears to include low AMW, 6-10 kD, humic substances was found based on investigating the spectra at various elution times. The spectroscopic parameter S(>365) (slope at Wavelengths >365 nm) was determined to be a good predictor of the AMW of the DOM. The detector Wavelength played an important role in evaluating the AMW distribution. For some fractions, such as the humic and low AMW non-aromatic substances, the error in measurement was ± 30% as determined by two-dimensional chromatograms detected at an artificially Selected Wavelength. HPLC-SEC with multiple Wavelength absorbance detection was found to be a useful technique for DOM characterization. It characterized the AMW distributions of DOM more accurately and provided additional, potentially important information concerning the properties of DOM with varying AMWs.
Bahram Hemmateenejad - One of the best experts on this subject based on the ideXlab platform.
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a comparative study between pcr and pls in simultaneous spectrophotometric determination of diphenylamine aniline and phenol effect of Wavelength selection
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007Co-Authors: Bahram Hemmateenejad, Morteza Akhond, Fayezeh SamariAbstract:Abstract Partial least squares (PLS) and principal component regression (PCR) have received considerable attention in the chemometrics for multicomponent analysis where superiority of one over another is a challenging problem yet. Considering the effect of Wavelength selection, a comparison was made between PCR and PLS methods by application those to simultaneous spectrophotometric determination of diphenylamine (DPA), a compound from the third European Union list of priority pollutants, and its environmentally related products aniline and phenol. The UV absorbance spectra of the methanolic solutions of the analytes were measured in the concentration ranges of 1.0–10.0 μg mL −1 and then subjected to PCR and PLS. The models refinement procedure and validation was performed by cross-validation. A modified changeable size moving windows strategy, where optimized the intervals between the sensors in a Selected windows, was also proposed to select the more informative spectral regions for each of the analytes. It was found that Wavelength selection improved the quality of predictions for both regression methods whereas more reliable results were obtained by removing of the highly collinear neighboring Wavelengths. The resultant data explained that PLS produced more or less better results when whole spectral data were used but in the case of Selected Wavelength regions both methods produced similar results and no comments could be given about the superiority of one against another. The major difference was obtaining the higher number of factors for PCR, which is not a significant problem.
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net analyte signal based simultaneous determination of antazoline and naphazoline using Wavelength region selection by experimental design neural networks
Talanta, 2006Co-Authors: Bahram Hemmateenejad, Raoof Ghavami, Ramin Miri, Majtaba ShamsipurAbstract:Net analyte signal (NAS)-based multivariate calibration methods were employed for simultaneous determination of anthazoline and naphazoline. The NAS vectors calculated from the absorbance data of the drugs mixture were used as input for classical least squares (CLS), principal component and partial least squares regression PCR and PLS methods. A Wavelength selection strategy was used to find the best Wavelength region for each drug separately. As a new procedure, we proposed an experimental design-neural network strategy for Wavelength region optimization. By use of a full factorial design method, some different Wavelength regions were Selected by taking into account different spectral parameters including the starting Wavelength, the ending Wavelength and the Wavelength interval. The performance of all the multivariate calibration methods, in all Selected Wavelength regions for both drugs, was evaluated by calculating a fitness function based on the root mean square error of calibration and validation. A three-layered feed-forward artificial neural network (ANN) model with back-propagation learning algorithm was employed to model the nonlinear relationship between the spectral parameters and fitness of each regression method. From the resulted ANN models, the spectral regions in which lowest fitness could be obtained were chosen. Comparison of the results revealed that the net NAS-PLS resulted in lower prediction error than the other models. The proposed NAS-based calibration method was successfully applied to the simultaneous analyses of anthazoline and naphazoline in a commercial eye drop sample.
Mingquan Yan - One of the best experts on this subject based on the ideXlab platform.
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characterization of dissolved organic matter using high performance liquid chromatography hplc size exclusion chromatography sec with a multiple Wavelength absorbance detector
Chemosphere, 2012Co-Authors: Mingquan Yan, Gregory V Korshin, Dongsheng Wang, Zhenxiao CaiAbstract:High-performance liquid chromatography-size exclusion chromatography (HPLC-SEC) coupled with a multiple Wavelength absorbance detector (200-445 nm) was used in this study to investigate the apparent molecular weight (AMW) distributions of dissolved organic matter (DOM). Standard DOM, namely humic acid, fulvic acid and hydrophilic acid, from the Suwannee River were tested to ascertain the performance and sensitivity of the method. In addition to four compounds groups: humic substances (Peak 1, AMW 16 kD), fulvic acids (Peak 2, AMW 11 kD), low AMW acids (Peak 3, AMW 5 kD), and low AMW neutral and amphiphilic molecules, proteins and their amino acid building blocks (Peak 4, AMW 3 kD), an new group that appears to include low AMW, 6-10 kD, humic substances was found based on investigating the spectra at various elution times. The spectroscopic parameter S(>365) (slope at Wavelengths >365 nm) was determined to be a good predictor of the AMW of the DOM. The detector Wavelength played an important role in evaluating the AMW distribution. For some fractions, such as the humic and low AMW non-aromatic substances, the error in measurement was ± 30% as determined by two-dimensional chromatograms detected at an artificially Selected Wavelength. HPLC-SEC with multiple Wavelength absorbance detection was found to be a useful technique for DOM characterization. It characterized the AMW distributions of DOM more accurately and provided additional, potentially important information concerning the properties of DOM with varying AMWs.
Fayezeh Samari - One of the best experts on this subject based on the ideXlab platform.
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a comparative study between pcr and pls in simultaneous spectrophotometric determination of diphenylamine aniline and phenol effect of Wavelength selection
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007Co-Authors: Bahram Hemmateenejad, Morteza Akhond, Fayezeh SamariAbstract:Abstract Partial least squares (PLS) and principal component regression (PCR) have received considerable attention in the chemometrics for multicomponent analysis where superiority of one over another is a challenging problem yet. Considering the effect of Wavelength selection, a comparison was made between PCR and PLS methods by application those to simultaneous spectrophotometric determination of diphenylamine (DPA), a compound from the third European Union list of priority pollutants, and its environmentally related products aniline and phenol. The UV absorbance spectra of the methanolic solutions of the analytes were measured in the concentration ranges of 1.0–10.0 μg mL −1 and then subjected to PCR and PLS. The models refinement procedure and validation was performed by cross-validation. A modified changeable size moving windows strategy, where optimized the intervals between the sensors in a Selected windows, was also proposed to select the more informative spectral regions for each of the analytes. It was found that Wavelength selection improved the quality of predictions for both regression methods whereas more reliable results were obtained by removing of the highly collinear neighboring Wavelengths. The resultant data explained that PLS produced more or less better results when whole spectral data were used but in the case of Selected Wavelength regions both methods produced similar results and no comments could be given about the superiority of one against another. The major difference was obtaining the higher number of factors for PCR, which is not a significant problem.
S G Wadodka - One of the best experts on this subject based on the ideXlab platform.
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uv spectrophotometric determination of hydrochlorothiazide and olmesartan medoxomil in pharmaceutical formulation
E-journal of Chemistry, 2010Co-Authors: A T Hemke, M V Hure, K S Chouha, K R Gupta, S G WadodkaAbstract:A simple, specific, accurate, precise and reproducible method has been developed and validated for the simultaneous estimation of hydrochlorothiazide and Olmesartan medoxomil in combined dosage form by UV spectrophotometric method. UV spectrophotometric method includes Simultaneous equation method (Method I) 271.5 nm and 257.0 nm λmax of both the drugs were Selected, absorbance Ratio method (Method II) 261.5 nm an isoabsorptive Wavelength and 257.0 nm were Selected for estimation of hydrochlorothiazide and Olmesartan medoxomil respectively and Three-Wavelength method (Method III), two Wavelengths were Selected such that hydrochlorothiazide give same absorbances (263.8 and 278.4 nm) at two Selected Wavelength while third Wavelength (316.5 nm) was such that olmesartan gives nearly zero absorbance. The two drugs follow Beer’s law over the concentration range of 5-25 μg/mL. The % recoveries of the both the drugs were found to be nearly 100 % representing the accuracy of the proposed methods. Validation of the proposed methods was carried out for its accuracy, precision, specificity and ruggedness according to ICH guidelines. The proposed methods can be successfully applied in routine work for the determination of hydrochlorothiazide and olmesartan medoximil in combined dosage form.