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.

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Our main target and concept was to develop a method for the determination of the most prescribed antilipemic drug, atorvastatin, together with its related substances, with a single sample preparation and during a single chromatographic run, in the shortest possible period of time, with the lowest possible mobile phase consumption. A new rapid, simple chromatographic method for the determination of atorvastatin and its main specified impurities was developed, using different chromatographic columns. With this new concept of a mobile phase and a powerful core–shell, or a superficially porous silica-based column, satisfactory results for targeted parameters, such as critical peak resolution, run time length, and column backpressure, were achieved. The analysis is performed within a run duration of less than 15 minutes, which is about six times shorter than the official European Pharmacopoeia method. The chromatogram performances suggests that the method limit of quantification (LOQ) can be about 7 times lower, and the limit of detection (LOD) about 20 times lower, using an injection volume of only 2 µl. This was confirmed by the performed method validation in accordance with the International Conference on Harmonization (ICH) guideline for the validation of analytical procedures Q2(R1), where the selectivity, linearity, accuracy, precision, limit of quantification, and limit of detection were tested and confirmed.

Fast, simple, accurate, and reproducible reverse phase‐high‐performance liquid chromatography method with direct ultraviolet measurement of memantine hydrochloride in tablets was developed, without any chemical derivatization pretreatment. Three main problems appear during chromatographic analysis of memantine: detection, achieving appropriate column retention, and limited choice of mobile phase components, as a result of memantine molecular structure. Among more than 35 tested columns, the best retention and peak symmetry yielded two C8 and three C18 columns with different characteristics, at a temperature of 30°C, mobile phase composed of 1%, v/v, acetonitrile and 99%, v/v, of 0.05–0.1% phosphoric acid or 2.5–5 mmol phosphate buffer, at flow rate of 1 mL/min and injection volume of 5 µL. The retention time of memantine was between 2.6 and 4 min. Both mobile phase concepts showed perfect linearity, precision, and accuracy. This is the first successful and reproducible direct reverse phase‐high‐performance liquid chromatography–ultraviolet quantification method for memantine.