Densitometric Kinetic Stability Studies of Some Plant Extracts Using Different Regression Methods

JPC – Journal of Planar Chromatography – Modern TLC -     

Polarographic chemometric determination of zinc and nickel in aqueous samples

Polarographic chemometric methods were applied to the determination of zinc and nickel in aqueous solutions previously acidified with 0.1 M acetate buffer (pH 4.2). The studied methods are multivariate methods including classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS); derivative ratio methods (first, ¹D and second, ²D derivative ratio). A comparative study was considered. The studied chemometric methods do not need the presence of any reduction potential shift reagent in spite of the great overlap between the two metals polarograms. A training set consisting of 10 binary mixture solutions in the possible combinations containing 0.13–9.30 μg/ml Zn(II) and 0.20–12.25 μg/ml Ni(II) was used to develop the chemometric calibrations (CLS, PCR and PLS). A validation set containing the synthetic mixtures in the range of 0.29–9.00 μg/ml for Zn(II) and 0.30–11.60 μg/ml for Ni(II) was used to validate the multivariate calibrations. Same mixtures were used to develop the derivative ratio methods. The polarograms were recorded and their current values were measured within the potential range −920 to −1052 mV at 2 mV intervals. The mean percentage recoveries obtained using CLS, PCR and PLS were found to be 99.5 ± 1.5%, 100.0 ± 1.1% and 100.0 ± 1.0% for Zn(II) and 99.4 ± 1.3%, 99.7 ± 1.2% and 99.9 ± 1.0% for Ni(II), respectively. The mean percentage recoveries obtained using ¹D at −950 mV, ¹D at −1010 mV, ¹D at −950 mV–¹D at −1010 mV and ²D at −986 mV for Zn(II) were found to be 99.7 ± 1.2%, 99.2 ± 1.6%, 99.4 ± 1.4% and 99.4 ± 1.4%; and using ¹D at −1030 mV and ²D at −1010 mV for Ni(II) were found to be 100.5 ± 1.3% and 100.4 ± 1.3%, respectively. Interferences due to the presence of Cd, Co, Pb, Fe, Mn, Ca, Mg, Cu and Al were studied. The applicability of the proposed methods was assessed through the determination of both metals in tap drinking-water. Samples were subjected if required up to a 20-fold preconcentration step by microwaving in pyrex vessels. The results were compared with those obtained using the zincon and the heptoxime colorimetric reference methods for the determination of zinc and nickel, respectively.     

Application of multivariate methods to the simultaneous Fourier Transform Infrared (FT-IR) spectrometric determination of stereo-isomers; quinine and quinidine

The two stereo-isomers; quinine and quinidine have been determined in their mixtures in the IR region using chemometric multivariate methods, principal component regression (PCR) and partial least squares (PLS). A training set of thirty synthetic binary mixture solutions in the possible combinations containing 0.0 - 4.0 and 4.0 - 0.0% w/v quinine and quinidine, respectively in chloroform was used to develop the multivariate calibrations. A validation set containing thirty synthetic binary mixtures of variable ratios in the range of 0.2 - 4.0 and 4.0 - 0.2% w/v for quinine and quinidine, respectively in chloroform was used to validate the developed calibrations. The results of analysis of the validation synthetic mixtures were found to be 100.5+/-0.44% (R.S.D.%=0.44) and 100.5+/-0.38% (R.S.D.%=0.38) for quinine and 100.1+/-0.67% (R.S.D.%=0.67) and 100.1+/-0.68% (R.S.D.%=0.68) for quinidine using PCR and PLS models, respectively.     

Economic Electrochemical Sensors for the Determination of Eszopiclone in Pharmaceutical Formulation with Greenness Profile Assessment

Electrochemical-ion-selective-sensors offer green, rapid, economic and simple analytical-tool in pharmaceutical industry, control processes, physiological measurements and environmental monitoring. In this study, two sensors were introduced for eszopiclone (EZP) determination in pure-form and in pharmaceutical-dosage-forms using drug-ion-exchanger association complex fabrication technique. Two different ion-exchangers were used and compared, tetrakis (4-chlorophenyl) borate in sensor1 and tetraphenyl borate in sensor 2. Such sensors showed superior performance at pH 3.5 over a wide-range of EZP concentration. The proposed method was also assessed using GAPI and analytical Eco-scale. Low cost, short analysis-time, simplicity and greenness of the proposed sensors allow their use for high-through-put analysis in quality-control laboratories.