Multiparametric curve fitting XV. statistical analysis and goodness-of-fit test by the least-squares algorithm MINOPT

Estimation of nonlinear regression quality leads to examination of quality of parameter estimates, a degree of fit, a prediction ability of model proposed and quality of experimental data. Statistical analysis serves for computation of confidence intervals of parameters and confidence bands, the bias of parameters and bias of residuals. Goodness-of-fit test examines classical residuals using various diagnostics and identifies influential points. Mentioned topics of nonlinear model building and testing contained in MINOPT program from CHEMSTAT package are illustrated

FPGA Based Robotic Motion Control System

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Physico-chemical characterization of some beta blockers and anti-diabetic drugs - potentiometric and spectrophotometric pKa determination in different co-solvents

In the present study we have determined the fundamental physico-chemical properties such as, ionization constant (pKa) and lipophilicity (log P) of some b-blockers and anti-diabetic drugs. The apparent ionization constant (psKa) of selected drugs were determined using potentiometric titration in various co solvent-water mixtures (methanol, ethanol, acetonitrile and dioxane) at different temperatures (25 to 45 °C) and ionic strengths (0.15 to 0.5 M). Effect of temperature, ionic strength and dielectric constant on dissociation constant has been compared. The aqueous pKa values were then obtained by Yasuda-Shedlovsky extrapolation. In the case of water-soluble drugs (Amiloride hydrochloride, metoprolol tartrate and propranolol hydrochloride), the extrapolated results were in good agreement with that of pKa values measured in aqueous solutions under the same experimental conditions, while for the water insoluble drugs (atenolol, amlodipine besylate, gliclazide, glipizide, glibenclamide and pioglitazone), the extrapolated results were in good agreement with the literature values. For few of the selected drugs, the psKa was determined spectrophotometrically and the results were compared with that of potentiometry in various co solvent mixtures. The measured log P values of selected drugs showed acceptable range to that of literature values

Multiparametric curve fitting XIV. Modus operandi of the least-squares algorithm MINOPT

Hybrid least-squares algorithm MINOPT for a nonlinear regression is introduced. MINOPT from CHEMSTAT package combines fast convergence of the Gauss-Newton method in a vicinity of minimum with good convergence of gradient methods for location far from a minimum. Quality of minimization and an accuracy of parameter estimates for six selected models are examined and compared with different derivative least-squares methods of five commercial regression packages