No abstract

Simultaneous determination of drugs with different physicochemical properties necessitates thorough research and careful selection of high‐performance liquid chromatography conditions. In the present study, various concepts of high‐performance liquid chromatography method development for this aim have been discussed. Moreover, the work was motivated by the advantages of utilizing different chaotropic anions as a new promising approach to overcome the limitations of ion‐pairing agents commonly used for this purpose. Based on log P values, atorvastatin (log P = 6.36) and lisinopril (log P = –1.22) were chosen as representative examples for lipophilic and hydrophilic drugs, respectively. Several simple, economic, fast, and reliable high‐performance liquid chromatography methods were developed for their simultaneous analysis and are presented in a comparative manner, highlighting their advantages and limitations. Peak elution profile showed satisfying retentions and resolution about 3. Photo‐diode array calculations were exploited for identifying the molecules by their ultra‐violet spectra and peak purity, calculated and presented as rectangular‐shaped ratio grams. The linearity check showed excellent results and satisfactory system suitability parameters of both peaks. This confirms the investigation results and conclusions for the influence of the chaotropic salts on N‐containing molecules, by increasing their retentivities, and improving peak shapes, even on different quality columns without end‐capping and base‐deactivating of separation matrixes.

A fast, simple, accurate and robust reversed phase HPLC method for the simultaneous determination of two flavonoids, hesperidin and diosmin, in combined tablets was developed and validated. This method uses a short C8 column with dimensions of 75 mm × 4 mm with 5 µm particles thermostated at 30 °C, and a mobile phase composed of formic acid (pH 4.1 and 0.05%, V/V) and methanol (58:42, V/V), delivered at a flow rate of 1.2 ml/min, with UV detector signal monitoring at 280 nm and an injection volume of 5 µl. These chromatographic conditions yielded chromatograms with symmetric peaks of hesperidin, eluting at a ~2 min retention time, and diosmin, at a ~4.5 min retention time, with a total run time cycle of 6 min. The method validation parameters confirmed excellent values for accuracy, linearity and reproducibility. This method is suitable for routine analysis in pharmaceutical and food quality control laboratories.

Aim. We aimed to develop and validate fast, simple, accurate, robust and rugged chromatographic method for simultaneous determination of bisoprolol fumarate and enalaril maleate in solid pharmaceutical dosage form, with using chaotropic strong chaotropic perchlorate anions in composition of mobile phase. Materials and methods. Fast simple HPLC method for simultaneous determination of bisoprolol and enalapril in solid pharmaceutical dosage forms was developed, with perfect peak symmetries eluting at 4.7 and 5.2 miutes, with mobile phase composed of methanol and diluted perchloric acid pumped with 1ml/min on Zorbax Rx C8 250x4.6mm, 5um column thermostated at 42 °C, and monitored UV signal at 214nm. Mobile phase was composed of 55%methanol and 45% perchloric acid (0.07%v/v). Results. Usage of presence of perchloric anions showed very useful role in peak shape and chromatogram view, due to distinguished chaotropic characteristics of perchlorate anions on molecules containing nitrogen atoms in molecular structures of analytes, in acidic pH environment. Linearity was examined and proven at different concentration levels in the range of working concentration of bisoprolol (20–200 ug/ml) and enalapril (20–200 ug/ml). The methods achieved very good validation parameters, with determined LOQ about 0.032 mg/ml and LOD about 0.003 mg/ml for bisoprolol, and LOQ about 0.045 mg/ml and LOD 0.005 mg/ml for enalapril. The high value of recoveries obtained for bisoprolol and enalapril indicates that the proposed method was found to be accurate. Conclusion. A new fast and simple, but selective, accurate, precise and robust HPLC method for simultaneous determination of bisoprolol and enalapril in tablets was developed and many possible variations of the same were suggested. The developed method for the simultaneous quantification of bisoprolol and enalapril from solid dosage formulations offers simplicity essential for quality control of a large number of samples in short time intervals, which is necessary for routine analysis.

This review draws attention to the use of chiral monolithic silica HPLC columns for the enantiomeric separation and determination of chiral compounds. Properties and advantages of monolithic silica HPLC columns are also highlighted in comparison to conventional particle-packed, fused-core, and sub-2-µm HPLC columns. Nano-LC capillary monolithic silica columns as well as polymeric-based and hybrid-based monolithic columns are also demonstrated to show good enantioresolution abilities. Methods for introducing the chiral selector into the monolithic silica column in the form of mobile phase additive, by encapsulation and surface coating, or by covalent functionalization are described. The application of molecular modeling methods to elucidate the selector–selectand interaction is discussed. An application for enantiomeric impurity determination is also considered.