Multi-criteria decision making in micellar liquid chromatographic separation of chlorophenols

Separation optimization of quercetin, hesperetin and chrysin in honey by micellar liquid chromatography and experimental design

The chemometrics approach was applied for the separation optimization of flavonoid markers (quercetin, hesperetin and chrysin) in honey using micellar liquid chromatography (MLC). The investigated method combines SPE of flavonoids from honey using C(18) cartridge and their separation and quantification by micellar liquid chromatography. A two level full factorial design was carried out to evaluate the effect of four experimental factors including concentration of SDS, alkyl chain length of the alcohol used as the organic modifier (N), volume percentage of the organic modifier (V(m)) and volume percentage of acetic acid (AcOH) in mobile phase on analytes retention times. Experiments for analytes retention times modeling and optimization of separation were performed according to central composite design. Multiple linear regression method was used for the construction of the best model based on experimental retention times. Pareto optimal method was used to find suitable compatibility between resolution and analysis time of analytes in honey. The optimum mobile phase composition for separation and determination of analytes in honey were [SDS]=0.124  mol/L; 7.8% v/v ethanol and 5.0% v/v AcOH. Limits of detection and linear range of flavonoid markers were 0.0079-0.0126, 0.05-50.0  mg/L, respectively.

Multi-criteria decision making approach and experimental design as chemometric tools to optimize HPLC separation of domperidone and pantoprazole

This paper deals with multiple response simultaneous optimization using the Derringer's desirability function for the development of a reversed-phase HPLC method for the simultaneous determination of domperidone and pantoprazole in commercial pharmaceutical preparations. Twenty experiments, taking the retention factor of the first peak, the two resolutions, and three retention times as the responses with three important factors, mobile phase composition, buffer molarity and flow rate, were used to design mathematical models. The experimental responses were fitted into a second order polynomial and the six responses simultaneously optimized to predict the optimum conditions for the effective separation of the studied compounds. The optimum assay conditions were: methanol-acetonitrile-dipotassium hydrogen phosphate (pH 7.0; 15.3 mM) (20:33:47, v/v/v) as the mobile phase and at a flow rate of 1.19 ml/min. While using this optimum condition, baseline separation with a minimum resolution of 2.0 and a run time of less than 6 min were achieved. The method showed good agreement between the experimental data and predictive value throughout the studied parameter space. The optimized assay condition was validated according to ICH guidelines to confirm specificity, linearity, accuracy and precision.

Statistical designs and response surface techniques for the optimization of chromatographic systems

This paper describes fundamentals and applications of multivariate statistical techniques for the optimization of chromatographic systems. The surface response methodologies: central composite design, Doehlert matrix and Box-Behnken design are discussed and applications of these techniques for optimization of sample preparation steps (extractions) and determination of experimental conditions for chromatographic separations are presented. The use of mixture design for optimization of mobile phases is also related. An optimization example involving a real separation process is exhaustively described. A discussion about model validation is presented. Some applications of other multivariate techniques for optimization of chromatographic methods are also summarized.

Recent advances in capillary electrophoresis and capillary electrochromatography of pollutants

Recent advances in the CE and CEC separation, detection, and sample preparation methodologies applied to the determination of a variety of compounds having current or potential environmental relevance have been overviewed. The reviewed literature has illustrated the wide range of CE applications, indicating the continuing interest in CE and CEC in the environmental field.

Simultaneous optimization of resolution and analysis time in mixed micellar liquid chromatography of coumarins by use of a utility function

A chemometrics approach has been used to optimize the separation of eight coumarin compounds by mixed micellar liquid chromatography. A utility function, a multi-criterion decision-making (MCDM) method, was tested for evaluation of two different measures of chromatographic performance (resolution and analysis time). The effect of six experimental parameters on a chromatographic response function (CRF) was investigated. The factors studied were the concentrations of SDS and Brij-35, alkyl-chain length of the alcohol used as organic modifier, organic modifier concentration, mobile phase pH, and temperature. The experiments were performed according to a face-centered cube response-surface experimental design. For evaluation of the chromatograms a simple linear response function was used which expressed as a summation of two optimization criteria, resolution and analysis time. Then calculated CRF values were fitted to a polynomial model to correlate the CRF values with the variables and their interactions. The regression model obtained was characterized by both its descriptive and predictive ability (R=0.963 and R2cv=0.861) and used, by means of a grid-search algorithm, to optimize the chromatographic conditions. Experiments performed under the optimum conditions predicted by the model produced a chromatogram of high quality. The model was also verified by the good agreement observed between predicted and experimental values of the chromatographic response function under the optimum conditions.

Kinetics of T lymphocyte responses to persistent antigens

Long term sequential study of immune responses in the same individuals is difficult from the time commitment required and the problem of maintaining enough subjects to provide for comparative analysis. We closely studied one hundred women with silicone mammary devices through cross sectional analysis up to 26 years post implantation and a similar sample of women to 6 years post explantation. The T cell index, calculated from tritiated thymidine incorporation during lymphoblast transformation, rose to a post implant peak at 10.5-12.0 years, falling progressively over the next 14.0-15.5 years to values indicative of probable immune quiescence. Post explantation, the index rose over the first 3 years and then sharply declined to within the range for unexposed controls. The shape of these time curves contains considerable information referent cell dynamics for both stimulatory and inhibitory factors and for demonstrating net group effects, appropriate to analysis in the cross sectional perspective. When a subset of four women was studied frequently and sequentially up to 8 years, an internal oscillatory pattern emerged, focusing attention on both the stimulatory and the inhibitory aspects of long term clonal expansion. IL-2 has stimulatory and inhibitory properties at different levels of production and is considered a prime candidate as the essential cytokine. The equations have details, however, which require exploration beyond any such provisional conclusion. The analytic process was aided by normalization of oscillatory data to eliminate subject variability and by Pareto optimization to assess the trend shown by normalization. Pareto analysis revealed two minimally coordinated oscillations, one over time and the other along net clonal expansion or decline of the siloxane specific T lymphocyte clone. The segments of the time related oscillation greatly exceeded the reaction times of cytokines currently known to be active in T cell regulation. Although the ultimate controlling factor(s) may be cytokine or chemokine combinations, the data are compatible with some more basic regulatory factor(s) of cell integrity, including limits on the number of cell divisions which can be sustained in long term immunopathic lesions, among other processes.

Simultaneous optimization of the resolution and analysis time in micellar liquid chromatography of phenyl thiohydantoin amino acids using Derringer's desirability function

The chemometrics approach was applied for simultaneous optimization of resolution and analysis time of nine phenyl thiohydantoin amino acids in micellar liquid chromatography. Derringer's desirability function, a multi-criteria decision making method, was tested for the evaluation of the two different chromatographic performance goals. The effect of five experimental parameters on a chromatographic response function formed using two sigmoidal desirability functions was investigated. The sigmoidal functions were used to transform the optimization criteria, resolution and analysis time, into the desirability values. The factors studied were the concentration of sodium dodecyl sulfate, alkyl chain length of the alcohol used as the organic modifier, organic modifier content, mobile phase pH and temperature. The experiments were performed according to a face-centred cube response surface experimental design to map the chromatographic response surface. Then, calculated chromatographic response functions were fitted to a polynomial model. The obtained regression model was characterized by both descriptive and predictive ability (R2 = 0.988 and R(2)cv = 0.973). The model was verified, as good agreement was observed between the predicted and experimental values of the chromatographic response function in the optimal condition. Based on the results of the study, combination of response surface mapping with Derringer's desirability function allows to predict the best operating condition in micellar liquid chromatography of phenyl thiohydantoin amino acids with respect to resolution and analysis time.