In chiral and non-chiral electrophoretic resolution of basic drugs, adsorption of analytes to negatively charged capillary wall could lead to poor repeatability of migration time and peak area. In addition, chiral resolutions of basic drugs are commonly performed in low pH buffers.Therefore, longer analysis time due to suppression of electroosmotic flow (EOF) is another dilemma. In this work the improvement effect of polybrene (PB), a cationic polymer, on chiral separation of a model basic drug, amlodipine (AML), was investigated. PB both as a semi-permanent coating agent and as an additive in the running buffer was utilized. Better results were obtained with PB as a buffer additive. Compare to untreated bare silica without using PB in running buffer, addition of 0.0005% PB to buffer decreased analysis time downed to 3 folds; efficiency improved up to 5 folds; limit of detection (LOD) and limit of quantification (LOQ) downed to 8 folds and within-day migration time and peak area repeatabilities, in terms of relative standard deviations (RSD) downed to 5 and 20 folds, respectively.

One of the problems encountered in CE separations of basic compounds is the adsorption of analytes in negatively charged capillary wall which could lead to poor repeatability of migration time and peak area. Additionally, separation of enantiomers of chiral of basic drugs is commonly carried out in low pH buffer which contributes to strong ionic interaction of the cationic drug ions with negatively charged chiral selectors. The two phenomena results in poor ENANTIOSEPARATIONs. To overcome the problems associated with chiral separations of basic drugs by CE, the effect of guanidine (GU) on the improvement of chiral separation of a modelbasic drug, fluoxetine (FLX), was investigated. In the present study, GU was used as a cationic additive to the running buffer containing a chiral selector, sulfated beta cyclodextrine. Better results obtained with GU as the buffer additive in ENANTIOSEPARATION of FLX.

Background and the purpose of the study: The use of highly sulfated cyclodextrins (HS-CDs) as chiral selectors in capillary electrophoresis (CE) has been examined for rapid and reproducible ENANTIOSEPARATION of the model drug amlodipine, a calcium channel blocker. Materials and Methods: Fused silica capillaries with an inner diameter of 50 mm, and a total length of 45.5 cm (8.5 cm to the detector) were used. Capillaries were rinsed with polyethylene oxide (PEO) once daily. A systematic method development approach was conducted by modifying selected parameters such as the type and concentration of the chiral selector, the buffer pH and concentration of the background electrolyte.Results: Baseline separation was achieved at low (i.e. 0.05%w/v) concentrations of HS-aCD, but migration time and peak area repeatability were more than 4% and 25% of the relative standard deviation (RSD), respectively. At higher concentrations (>0.3%) of HS-aCD, amlodipine was transported to the anode by the carrier ability of HS-aCD. In carrier mode, the migration order of enantiomers was reversed, the migration time was reduced and the peak area repeatability of analysis was improved. The optimum electrophoretic conditions for the stereoselective analysis of amlodipine were obtained in carrier mode with 25 mM sodium phosphate buffer containing 1.25% w/v of HS-aCD at pH 2.5 with an applied voltage of +15 kV. Under these conditions migration time was less than 3 min and within-day migration time and peak area repeatability, were less than 0.4% and 2.1% RSD, respectively. Conclusions: Rapid ENANTIOSEPARATION was achieved with minimum variation in quantitative analysis. These optimized conditions are appropriate for the enantioselective analysis of amlodipine.

In recent years there has been considerable interest in the synthesis and separation of enantiomers of organic compounds especially because of their importance in the biochemistry and pharmaceutical industry. High-performance liquid Chromatography is a very useful method for the direct separation of enantiomers. However, about 30−40 years ago, commercially available chiral stationary phases were very limited. Researchers developed many novel chiral stationary phases for gas and liquid chromatography, and found these phases were effective practically to the separation and analysis of various chiral compounds. ENANTIOSEPARATION of drugs with multiple chiral centers is challenging. This review describes resolution of some drugs with multiple chiral centers using polysaccharide-type chiral stationary phases.

A new chromatographic procedure was proposed for the separation of propranolol (PRN)enantiomers based upon enantioselective chiral ligand-exchange chromatography. Theseparation was carried out on a short C8 column leading to considerably short separationtime. L-alanine and Cu2+ were applied as chiral selector and central bivalent complexing ion, respectively. It was found that the kind of copper salt could influence the ENANTIOSEPARATIONefficiency. The separation on the C8 stationary phase was more efficient than that on theC18 column. It was shown that the pH of mobile phase, organic modifier content of mobilephase, mole ratio of chiral ligand to bivalent ion and Cu (L-alanine) 2 concentration in themobile phase were important in ENANTIOSEPARATION efficiency. Water/methanol (70: 30) mixturecontaining L-alanine-Cu2+ (7: 1) was found to be the best mobile phase condition for PRNENANTIOSEPARATION. All effective parameters were optimized in order to improve the separationefficiency. The optimized HPLC method was utilized for analysis of propranolol enantiomersin spiked human blood plasma samples.

A common approach in resolving enantiomers of chiral basic drugs by capillary electrophoresis (CE) is to use cyclodextrins (especially their anionic derivatives) as chiralselector in the acidic buffer (pH£3) in normal or reversed (carrier) mode. Then, some organic modifiers are added to the buffer solution if the resolution is not satisfactory. In case of cetirizine (CTN), applying the same approach, i.e. a reversed mode capillary zone electrophoresis (CZE) method with an acidic buffer and sulfated-b-cyclodextrine (S-bCD) as chiral selector, was failed and no complete ENANTIOSEPARATION was achieved. Different organic modifiers, like urea and triethylamine HCl, were used to improve chiral resolution which led to partial resolution of the two peaks. Then, guanidine HCl at a concnetration of 100 mM was added to the running buffer and an acceptable resolution of the enantiomers of the drug was obtained. The method was successfully applied to determine optical purity of a levo -cetirizine (l-CTN) sample.