Purification of RhIFN- in Bacteria Bodies with Acetic Acid-Water as Mobile Phase in RPLC

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RP‐HPLC enantioseparation of β‐adrenolytics using micellar mobile phase without organic solvents

Enantioseparation of a few commonly administered racemic β‐adrenolytics (namely, carvedilol, betaxolol, salbutamol and bisoprolol) has been achieved using a water micellar mobile phase containing surfactants (sodium dodecyl sulphate and Brij‐35) without organic solvents as a new approach in RP‐HPLC. Two chiral derivatizing reagents based on enantiomerically pure (S )‐(−)‐levofloxacin were synthesized using N ‐hydroxysuccinimide and N ‐hydroxybenzotriazole as the activation auxiliaries. Diastereomeric derivatives of the chosen β‐adrenolytics were synthesized under microwave irradiation in a very short reaction time. The (S )‐(−)‐levofloxacin moiety enhanced molar absorbance of the diastereomeric derivatives resulting in very low limit of detection (1.618 and 4.902 ng/mL, respectively, for diastereomeric derivatives of (RS )‐betaxolol and better resolution with lower retention times (for all the analytes), in comparison to literature reports. There was 15–20 times less consumption of mobile phase because of lower retention time.     

Optimized separation of pesticide enantiomers by chiral high-performance liquid chromatography

Summary A computer-assisted method is described for optimization of multi-component, mobile phase selection for separating enantiomers of four pesticides in normal-phase HPLC. The method is based on the triangle, solvent-selection concept using a statistical scanning method. The optimization of the separation over the experimental region is based on a special polynomial estimation from seven experimental runs, and resolution (R_s) is used as the selection criterion. Excellent agreement was obtained between predicted and experimental data.     

Chiral Ligand-Exchange Chromatography for Separation of Three Stereoisomers of Octahydroindole-2-carboxylic Acid

A novel HPLC method is described for separation of the three stereoisomers of octahydroindole-2-carboxylic acid (Oic), an intermediate in the synthesis of perindopril. The chiral mobile phase contained the complex of Cu(II) with the optically active selector L-phenylalaninamide (L-PheA), and an ion-pair reagent, sodium 1-octanesulfonate. The effects of the concentrations of the Cu(II)–L-PheA complex and the ion-pair reagent, mobile phase pH, ionic strength, acetonitrile content, and column temperature were studied. Satisfactory resolution was achieved for three stereoisomers, RRR-, SSS-, and SRR-Oic.     

Use of unmodified silica with buffered aqueous mobile phase mixtures for selective chromatography of basic drugs

Summary The characteristic selectivity of unmodified silica using mixed aqueous-methanolic mobile phase systems for the separation of basic drugs was studied. It was found that low buffer concentration-high methanol eluents show increased chromatographic performance over mobile phase systems lower in methanol and higher in ion strength. Regarding an assumed ion-exchanger retention mechanism, the capacity factors of an amino group containing drugs is primarily dependent on the concentration of the cation and the pH-value of the eluent. By increasing the pH-value of the eluent, elution order of primary and secondary to tertiary amines is reversed. By only using eluents with buffering capability, a very high stability and reproducibility of retention of the basic drugs could be observed. Comparing three different brands of unmodified silica materials, with different pore size and specific surface area, only small differences in the selectivity for the tested drugs could be found.     

Influence of solvent strength in possible optimization of adsorption thin-layer chromatography

Considerations of TLC process optimization have been based on the thermodynamic theory of adsorption from multicomponent solvents using experimental and theoretical R_{M1, 2} = f (Φ₁) relationships. It was found that a relationship exists between the A_z parameter (log k where k is the partition coefficient of the substance chromatographed) of the above theory and pK_a values of substances as well as the solubility parameter δ of the mobile phase components. Analysis of the A_z values of substances shows that a slight variation therein is associated with lower selectivity of chromatographic separation.     

Thin-layer adsorption chromatography with mixed mobile phases. 1. Characterization of chromatographic systems showing energetic heterogeneity of adsorbent surfaces with regard to admolecules of solvents and solutes

Thin-layer adsorption chromatography with a multicomponent mobile phase is discussed. A new equation for predicting R_M-values in TLC with mixed mobile phases using the R_M-ValUeS obtained for pure solvents is proposed. This equation takes into account effects of energetic heterogeneity of the adsorbent surface with regard to adsorbed molecules of solvents and solutes. Experimental verification of this equation is presented for R_M-data obtained by TLC using a binary mobile phase.     

Retention behaviour of binaphthyl compounds in enantiomeric separation by microcolumn liquid chromatography with micellar bile-salt mobile phases

Summary Optical isomers of substituted binaphthyl, compounds such as 2,2-dihydroxy-1,1-dinaphthyl and 1,1-binaphthyl-2,2-diyl hydrogenphosphate are, separated by HPLC using micellar bile-salt mobile phases. Operating conditions which affect the optical resolution of these enantiomers are examined. The largest separation factor achieved for these enantiomers is 2.74. The elution order of the latter enantiomers changes with mobile phase composition.     

Optimization of a multisolvent composition in RP-HPLC: Convenient criterion for preliminary search for the best eluent strength

Summary Interpretive methods are very commonly used to direct the search for the optimum solvent composition. For multisolvent systems, the composition search space is often reduced to one straight line (ternary systems with two organic modifiers), three straight lines (three ternary systems with each possible pair of the organic modifiers of the tetrahedron) — or a plane delimited by a triangle (quaternary systems inside the solvent tetrahedron). In each case, the space is restricted by binary compositions of equal solvent strength, in such a way that through it, the analysis time remains approximately constant. This restricted space is defined without taking into account any selectivity criterion between peaks, and consequently, if a given pair of peaks is badly resolved with the considered binary solvents, the probability of any mixture of them improving the peak selectivity will be very low. The ability to calculate the retention models in a binary solvent system from two linear gradient runs, allows the prediction of the selectivity for each pair of solutes into each binary solvent system (ACN/Water, MeOH/Water, THF/Water) from six preliminary linear gradient runs, and then, to determine and eliminate all the sets of isoeluotropic binary compositions that will offer little hope of giving useful separation conditions with multisolvent systems and, at the same time, to select the most promising set of binary compositions. The selectivity and the total time of the chromatogram are the two parameters that are considered for this search. When several possiblities are found, priority is given to the simplest solvent system (binary rather than ternary and ternary rather than quaternary). Reducing the number of preliminary experiments and improving the accuracy of the predicted optimum are the two objectives of this approach. Its practical interest is discussed by comparing the results obtained for an illustrative separation to those obtained with another existing method.     

High performance liquid chromatography on the chiral stationary phase (R,R)-DACH-DNB using carbon dioxide-based eluents

Fast and efficient separations of chiral stereolabile compounds were obtained at very low temperature on a π-acid chiral stationary phase (R,R-DACH-DNB) using carbon dioxide-based mobile phases containing alcoholic polar modifiers. Furthermore, efficient separations of the newly discovered spherical carbon cluster buckminsterfullerene (C₆₀) and the related higher fullerenes (C₇₀, etc.) have been performed on the same stationary phase using eluents based on either n-hexane or carbon dioxide.