Ternary Mobile Phase Composition Research Articles

Dual Organic Modifier, Solid Core Technology and Quality by Design Based Tripartite Synergistic Model for Development and Validation of Stability Indicating Method by Reverse Phase-High Performance Liquid Chromatography for Assay and Impurities of Etoricoxib Tablets

Tripartite synergistic model of solid core technology, dual organic modifiers and combined mixture design was implemented to achieve combined assay and related substances method by reverse phasehigh performance liquid chromatography with short run time, enhanced sensitivity and improved resolution between multiple impurity peaks. pH of mobile phase, ternary mobile phase composition and high performance liquid chromatography column temperature are experimented as variable parameters. Acetonitrile and isopropyl alcohol mixture was experimented as dual organic modifier. Special focus was given to detailed methodology of dealing with elution order changes by assigning negative sign for resolution. Separation of etoricoxib and related impurities was evaluated as a case study to prove this concept. The method was developed with Ascentis® Express C18, 150×4.6 mm, 2.7 μ column. Mobile phase comprised of buffer (0.1 % v/v ortho phosphoric acid, pH 3.6), acetonitrile and isopropyl alcohol (65.3:29:5.7 v/v) with a flow rate of 1.0 ml/min and ultraviolet detection at 285 nm. Forced degradation studies revealed that the method was stability indicating, suitable for both assay and impurities of drug product. The recoveries for impurities and assay were found to be in the range of 94.0 %-111.0 % and 97.9 %-101.8 %, respectively. Linearity was established for impurities and assay in the range of 0.25-2.0 μg/ml and 125-750 μg/ml, respectively. The method was validated as per international conference on harmonisation guidelines. The method can be successfully employed for determination of assay and impurities of etoricoxib in bulk drugs and formulations.

Simultaneous Determination of Paracetamol, Propyphenazone and Caffeine in Presence of Paracetamol Impurities Using Dual-Mode Gradient HPLC and TLC Densitometry Methods.

Two chromatographic methods were validated for the determination of the widely prescribed analgesic and antipyretic drug combination of paracetamol (PC) (recently integrated into the supportive treatment of COVID-19), propyphenazone (PZ) and caffeine (CF) in the presence of two PC impurities, namely 4-aminophenol and 4-nitrophenol. A “dual-mode” gradient high-performance liquid chromatography method was developed, where the separation was achieved via “dual-mode” gradient by changing both the ternary mobile phase composition (acetonitrile: methanol: water) and the flow rate. This enables a good resolution within a relatively shorter analysis time. The analysis was realized using Zorbax Eclipse XDB column C18, 5 μm (250 × 4.6 mm) and the UV detector was set at 220 nm. The other method is a thin-layer chromatography densitometry method, where the separation was achieved using a mobile phase composed of chloroform: toluene: ethyl acetate: methanol: acetic acid (6: 6: 1: 2: 0.1, by volume). Densitometric detection was performed at 220 nm on silica gel 60 F254 plates. The developed methods were fully validated as per the ICH guidelines and proved to be accurate, robust, specific and suitable for application as purity indicating methods for routine analysis of PC in pure form or in pharmaceuticals with PZ and CF in quality control laboratories.

Ternary isocratic mobile phase optimization utilizing resolution Design Space based on retention time and peak width modeling

An optimization procedure of ternary isocratic mobile phase composition in the HPLC method using a statistical prediction model and visualization technique is described. In this report, two prediction models were first evaluated to obtain reliable prediction results. The retention time prediction model was constructed by modification from past respectable knowledge of retention modeling against ternary solvent strength changes. An excellent correlation between observed and predicted retention time was given in various kinds of pharmaceutical compounds by the multiple regression modeling of solvent strength parameters. The peak width of half height prediction model employed polynomial fitting of the retention time, because a linear relationship between the peak width of half height and the retention time was not obtained even after taking into account the contribution of the extra-column effect based on a moment method. Accurate prediction results were able to be obtained by such model, showing mostly over 0.99 value of correlation coefficient between observed and predicted peak width of half height. Then, a procedure to visualize a resolution Design Space was tried as the secondary challenge. An artificial neural network method was performed to link directly between ternary solvent strength parameters and predicted resolution, which were determined by accurate prediction results of retention time and a peak width of half height, and to visualize appropriate ternary mobile phase compositions as a range of resolution over 1.5 on the contour profile. By using mixtures of similar pharmaceutical compounds in case studies, we verified a possibility of prediction to find the optimal range of condition. Observed chromatographic results on the optimal condition mostly matched with the prediction and the average of difference between observed and predicted resolution were approximately 0.3. This means that enough accuracy for prediction could be achieved by the proposed procedure. Consequently, the procedure to search the optimal range of ternary solvent strength achieving an appropriate separation is provided by using the resolution Design Space based on accurate prediction.

Combined Effect of Temperature and Ternary Mobile Phase Composition on the Retention in Ternary Isocratic and Gradient Elution RP-LC under Isothermal Conditions. Application to the Retention Prediction of Four Macrolide Antibiotics

Retention models considering simultaneously ternary mobile phase organic contents and column temperature (T) were developed by a direct combination of equations expressing separately the dependence of the retention upon each of these factors. Thus, a combination of a linear dependence of the logarithm of the solute retention factor, ln k (T), against 1/T, i.e. ln k (T) = a + b/T, and of either a linear or a quadratic dependence of ln k upon the compositions of a binary mobile phase, gave two different expressions for the logarithm of the solute retention factor in terms of both temperature and organic contents in the ternary mobile phase. The effectiveness of the above models was tested in the prediction of isothermal retention of a mixture of four macrolide antibiotics under ternary isocratic and gradient elution conditions using mobile phases modified by methanol and acetonitrile. The limiting case of using ternary eluents with constant ratio of the concentrations of the two organic modifiers was also tested.

Separation of theophylline, caffeine and related drugs by normal-phase capillary electrochromatography.

A capillary electrochromatography (CEC) method has been developed for the separation of theophylline, caffeine and five related drugs on a normal-phase column with UV or photodiode array detection. Several binary, ternary and quaternary mobile phase compositions are evaluated for optimal resolution and elution of these drug analytes. The importance of selecting suitable organic solvents, buffer electrolyte, pH and applied voltage is demonstrated by a systematic study. Excellent separation is achieved for the eight drugs using a ternary mobile phase composition of isopropanol/hexane/1 mM Tris (52:40:8, pH 8), with an efficiency of 63000 theoretical plates per meter at room temperature. Detection limits are typically at the low microg/mL level. The developed method is simple to use and it gives acceptable day-to-day reproducibility.

Preparative high-performance liquid chromatography of echinocandins

The isolation of fermentation derived small bioactive molecules remains extremely challenging due to the presence of many analogues with similar physicochemical behavior. Removal of analogue impurities typically involves crystallization and/or preparative HPLC. The normal-phase preparative HPLC for the purification of fermentation derived echinocandins is described. Resolution of key impurities from the product of interest, pneumocandin B o, is accomplished using a ternary ethyl acetate–methanol–water mobile phase with silica gel as the sorbent. Plate counts, measured with small molecules, show that the column efficiency is excellent under the operating conditions despite the use of an irregular silica and unusually high levels (greater than 6%) of water in the mobile phase. The results of optimization studies indicate the product solubility, retention and resolution of key analogue impurities are strong functions of the ternary mobile phase composition. The normal-phase HPLC process was optimized by carrying out eluent flow-rate (linear velocity) and column loading studies. The results of these experimental studies indicate that both yield and productivity are a function of linear velocity and product loading and that a tradeoff exists between these two parameters.

Structure-driven retention model for optimization of ternary solvent systems in reversed-phase liquid chromatography

A new approach is presented fro the prediction of retention in reversed-phase liquid chromatography using ternary mobile phase compositions. The solvation parameter model is used to create the system constants that characterize the properties of the mobile and stationary phases in terms of the relative ease of cavity formation, and differences in dispersion, lone pair electron, dipole-type, and hydrogen-bond association interactions for all solvent compasitions employed. A statistical mixture-design approach provides system surfaces and models for the variation of individual system constants as a function of ternary solvent composition. The models for the system surfaces allow the retention factor to be predicted as a function of mobile phase composition for any compound whose descriptor values are known, or can be obtained from estimation rules or determined by experiment. The method is validated using a large literature data base for the retention factor of up to 46 varied aromatic solutes in 72 methonolacetonitrile-water and methonol-tetrahydrofuran-water mobile phase compositions.

Mixture-design approach to retention prediction using the solvation parameter model and ternary solvent systems in reversed-phase liquid chromatography

A new approach for the prediction of retention in reversed-phase liquid chromatography using ternary mobile phase compositions is presented. The solvation parameter model is used to generate system constants characteristic of the capability of the chromatographic system for defined solvent–solvent and solute–solvent interactions. A mixture-design approach is then used to construct system surfaces for each system constant over all mobile phase compositions. These surfaces are smooth and devoid of irregular features. Models derived from these surfaces allowed us to predict the retention of a varied group of 36 solutes on a porous polymer sorbent, PLRP-S 300, at a methanol–acetonitrile–water composition not included in the data used to construct the system surfaces. The accuracy of the predicted retention factors was similar to that obtained by fitting the solvation parameter model to the same experimental data.

Determination of amiodarone and desethylamiodarone in plasma with a standardised extraction and chromatographic optimisation procedure

A previously described optimisation procedure was tested by developing suitable HPLC systems for the determination of amiodarone and desethylamiodarone in plasma. Chromatography is performed on a cyano-column (CN-column) in the reversed-phase mode. The optimisation strategy consists of carrying out a gradient elution from which an appropriate solvent strength for isocratic elution is determined. Binary and ternary mobile phase compositions with the same solvent strength but with different solvent selectivity are then used to evaluate selectivity. The anti-arrhythmic drugs are extracted from plasma using an ion-pair extraction procedure with sodium-n-octylsulphate as ion-pairing agent.

Use of Three-Dimensional Minimum -Plots for Optimization of Mobile Phase Composition for RP-HPLC Separation of Sulfonamides

The use of mixture designs for the mathematical modeling of the dependence of the capacity factor (k) on ternary mobile phase composition in RP-HPLC was investigated. Regression models for 11 sulfonamides in three ternary mobile phase systems [water:methanol:acetonitrile, water:methanol:tetrahydrofuran (THF), and water:THF:acetonitrile] were calculated. Evidence was found that it is possible to transfer the regression models between columns using the same packing materials. The calculated models were used for the optimization of the separation of three mixtures in these mobile phase systems. The optimization method employed was an extension of the window diagram method of Laub and Purnell to three interdependent variables and non-linear models. It appears that the method is well suited for the optimization of routine analyses because of the large amount of information it provides.

Automated multiparameter optimisation of high-performance liquid chromatographic separations using the sequential simplex procedure

The use of the sequential simplex procedure for the automated optimisation of mobile phase composition, temperature and flow-rate is described. The simplex procedure has been incorporated into a BASIC program for a microcomputer-controlled chormatograph and has been used in the development of reversed-phase ion-pair separations where pH, ion-pair concentration, ternary mobile phase composition, eluent flow-rate and temperature have all been simultaneously and automatically optimised.