Concepts and principles for new rapid simple liquid chromatography method for quantification of antioxidants resveratrol, vitamin E, and coenzyme Q10 in capsules with high-performance liquid chromatography with a photo-diode array detector

Principles and problems in the development of simultaneous liquid chromatography (LC) analytical methods for potent antioxidative molecules resveratrol, tocopherol, and coenzyme Q10 in capsules, have been investigated and systematically compared and summarized. For these purposes, experiments within the full polarity spectrum of LC techniques. were tested and recorded. The whole range of polarities included: Alkyl C18 bonded reversed phase, phenyl, cyanopropyl, diol, and the most polar base silica-filled column matrixes have been used. The summarized results concluded that all mentioned LC techniques could be used for the determination of the mentioned group of the three analytes with different run characteristics and efficiency. These successes could be achieved after careful analyses of molecular physicochemical data of analytes. They are especially organic solubilities. The ultraviolet spectral absorption characteristics of each analyte and the mobile phase constituents for appropriate separation were very important to be known. The ultimate targets were the development method with the isocratic mode of separation yielding symmetrical peak shapes for the best sensitivity and accuracy, with the shortest run time and best reproducibility. From an analytical point of view important for LC, the three analytes have quite distinct characteristics that contribute to successful method development. These features are their organic solvent and water solubility, molecular polarities, and ultraviolet-absorption characteristics, like spectra and absorptivities. All these mentioned parameters were taken into account for solving complications appearing in the development of rapid LC methods for the simultaneous determination of three antioxidant molecules.

LC-MS/MS bioanalytical method for the quantitative analysis of nifedipine, bisoprolol, and captopril in human plasma: Application to pharmacokinetic studies

In this study, the development and validation of an accurate and highly sensitive LC-MS/MS method were performed for the estimation of nifedipine, bisoprolol and captopril in real human plasma. Liquid-liquid extraction using tert-butyl methyl ether was efficiently applied for extraction of the analytes from plasma samples. The chromatographic separation was carried out using an isocratic elution mode on the X-terra MS C18 column (4.6 × 50 mm, 3.5 μm). The mobile phase consisted of methanol-0.1% formic acid (95:5, v/v) for determination of nifedipine and bisoprolol and acetonitrile-0.1% formic acid (70:30, v/v) for determination of captopril with a flow rate of 0.5 ml/min. Acceptable results regarding the different validation characteristics of the analytes were obtained in accordance with US Food and Drug Administration recommendations for bioanalytical methods. The developed approach was linear over concentration ranges of 0.5-130.0, 50.0-4,500.0 and 0.3-30.0 ng/ml for nifedipine, captopril and bisoprolol, respectively. The method revealed a sufficient lower limit of quantification in the range of 0.3-50.0 ng/ml, as well as high recovery percentages, indicating high bioanalytical applicability. The proposed method was efficiently applied to a pharmacokinetic evaluation of a fixed-dose combination of the analytes in healthy male volunteers.

Application of salts of chaotropic anions in the development of hplc methods for the determination of meldonium in dosage forms

The aim of the work was to create an approach for the development of HPLC methods for the determination of meldonium in dosage forms with the usage of salts of chaotropic anions in mobile phases. Material and methods. Analytical equipment: Shimadzu UPLC system LC-40 PDA; Shimadzu Nexera-i LC-2040C 3D-Plus, controlled by software Lab Solution version 5.97, electronic laboratory balance RAD WAG AS 200/C, pH-meter I-160MI. Meldonium dihydrate (purity 99.3 %) was purchased from Sigma-Aldrich (Switzerland), and Vasopro capsules 500 mg were purchased from a local pharmacy. Chromatographic conditions: Agilent Zorbax C-18 SB 150 mm x 4.6 mm 3.5 μm column was used (Agilent Technologies, USA). Mobile phases: 1) 0.25 % KPF6 w/v – 0.1 % v/v 85 %H3PO4 95 % – 5 % ACN, 2) 0.3 % bis-(trifluoromethane)sulfonimide lithium salt 97 % w/v – 0.1 %v/v 85 % H3PO4 80 % – 20 % acetonitrile. Flow rate - 1mL/min, T=32 °C, detection UV=at 4 channels - 190 nm, 195 nm, 200 nm, 205 nm. Results and discussion. We have proposed two approaches using two different salts of chaotropic anions - potassium hexafluorophosphate and bis-(trifluoromethane)sulfonimide lithium salt – for the HPLC method development. The chaotropic effects of these anions toward meldonium strongly influenced the analyte migratory behaviour. Both mobile phases involved, in addition to the use of a chaotrope, also the use of acetonitrile and pH adjustment with 0.1 % v/v 85 % H3PO4 solution. The detection wavelength (190 nm, 195 nm, 200 nm, 205 nm) was selected experimentally. The results were obtained for 8 concepts. Parameters of the chromatographic system confirm the conclusions and results of this investigation for the influence of chaotropic salts on N-containing molecules in an acidic pH medium, by increasing their retentivity and improving peak shape and uniformity homogeneity, even on the column without end-capping and base-deactivating. Validation of the analytical method was carried out following the requirements of SPhU. Conclusions. HPLC methods for the determination of meldonium in dosage forms have been developed, using positive impacts of chaotropic salts on the molecules containing N-atoms in their molecule on their retentions and peak symmetries on the chromatogram. The validation of the analytical methods showed their suitability for pharmaceutical analysis

Development of the spectrophotometric method for the determination of metoprolol in tablets by using bromophenol blue

The aim of the work was to develop a simple, economical and eco-friendly spectrophotometric method for determining metoprolol tartrate in tablets based on the reaction with bromophenol blue (BPB). Material and methods: A double–beam Shimadzu UV-Visible spectrophotometer, with a spectral bandwidth of 1 nm wavelength accuracy ±0.5 nm, Model –UV 1800 (Japan), Software UV-Probe 2.62, and a pair of 1 cm matched quartz cells, was used to measure the absorbance of the resulting solution. All the chemicals were used in analytical reagent grade. Pharmacopeial standard samples of metoprolol tartrate and bromophenol blue (BPB) were provided by Sigma-Aldrich (≥ 98%, HPLC). The used dosage forms of metoprolol tartrate are tablets of Metoprolol 50 mg and 100 mg. Results and discussion: The method of spectrophotometric determination of the quantitative content of metoprolol tartrate based on its reaction with BPB in a methanol solution has been developed. The stoichiometric ratios of the reactive components as 1:1 were obtained by the methods of continuous changes and the saturation method. The developed method of quantitative determination of metoprolol tartrate was validated. The linearity regression equation was y = 0.0373x + 0.0038, and the obtained correlation coefficient was R2=0.9984. A linear relationship was found between absorbance at λmax and concentration of metoprolol tartrate in the range of 9.56-15.02 µg/mL. The LOD and LOQ values were calculated to be 0.81 µg/mL and 2.67 µg/mL. Conclusions. A simple, economical and eco-friendly spectrophotometric method has been developed for the quantitative determination of metoprolol tartrate in tablets based on the reaction with BPB. The developed method of quantitative determination of metoprolol tartrate was validated in accordance with the requirements of SPhU. We suggest our work with offered detailed and successful solutions for the mentioned aim with less sophisticated equipment for QC lab for routine manufacturing control

Synthesis of New 3-Morpholyl-Substituted 4-Aryl-2-Arylimino-2,3-Dihydrothiazole Derivatives and Their Anti-Inflammatory and Analgesic Activity

New 4-aryl-3-(morpholin-4-yl)-2-arylimino-2,3-dihydrothiazole derivatives 1.1-1.16 were obtained using the Hantzsch reaction by condensation of N-(morpholin-4-yl)-N'-arylthioureas with the corresponding α bromoacetophenones in alcohols. Synthesized hydrobromides 1.1-1.8 were formed as crystalline precipitates during the boiling of the reaction mixture. Bases 1.9-1.16 were obtained by neutralizing the corresponding hydrobromides with NH4OH solution. It has been proposed a possible mechanism of the reaction that is based on the study of the structure of the synthesized compounds. The structures of the synthesized compounds were confirmed by 1H NMR spectroscopy with its special techniques (NOESY and ROESY experiments). It has been shown the formation of the isomer 4-(4'-chlorophenyl)-3-(morpholin-4-yl)-2-(4'-chlorophenylamino)-2.3-dihydrothiazole on the basis of compound 1.14. Pharmacological screening of synthesized derivatives of 4-aryl-2-arylimino-2,3-dihydrothiazole compounds revealed the analgesic effect in the model of visceral pain caused by the introduction of acetic acid to white mice. The anti-inflammatory effect of the synthesized compounds was evaluated in vivo by reducing limb edema in rats with carrageenan-induced inflammation. Thus, the synthesized compounds have analgesic and anti-inflammatory activity.

Development of the spectrophotometric method for the determination of metoprolol tartrate in tablets by using bromocresol green

The aim of the work was to develop and validate a spectrophotometric method for determining metoprolol tartrate in tablets based on the reaction with bromocresol green (BCG). Material and methods. Analytical equipment: two-beam UV-visible spectrophotometer Shimadzu model -UV 1800 (Japan), software UV-Probe 2.62, laboratory electronic balance RAD WAG AS 200/C, pH-meter И-160МИ. The following APIs, dosage forms, reagents and solvents were used in the work: pharmacopoeial standard sample (CRS) of metoprolol tartrate (Sigma-Aldrich, (≥ 98 %, HPLC)), BCG (Sigma-Aldrich, (≥ 98 %, HPLC)), "Metoprolol" tablets 50 mg (Kyivmedpreparat, series 0035415), "Metoprolol" 100 mg (Farmak, series 30421), methanol (Honeywell, (≥ 99.9 %, GC)), ethanol (Honeywell, (≥ 99.9 %, GC)), chloroform (Honeywell, (≥ 99.9 %, GC)), acetonitrile (Honeywell, (≥ 99.9 %, GC)), and ethyl acetate (Honeywell, (≥ 99.7 %, GC)). Results and discussion. A spectrophotometric method was developed for determining metoprolol tartrate by reaction with BCG in a methanol solution using the absorption maximum at a wavelength of 624 nm. Stoichiometric ratios of reactive components were established, which were 1:1. The developed method for the quantitative determination of metoprolol tartrate was validated following the requirements of the SPhU. The analytical method was linear in the concentration range of 5.47-38.30 μg/mL. The limit of detection and quantification were 0.41 μg/mL and 1.24 μg/mL, respectively. According to the «greenness» pictogram of the analytical method using the AGREE method, the score was 0.79, which indicates that the proposed spectrophotometric method for the determination of metoprolol was developed in compliance with the principles of «green» chemistry.Conclusions. A spectrophotometric method for determining metoprolol tartrate in tablets based on the reaction with BCG in compliance with the principles of «green» chemistry has been developed and validated. Furthermore, the developed method for the quantitative determination of metoprolol tartrate was validated following the requirements of the SPhU. In summary, the developed method has a low negative impact on the environment and can be applied for routine pharmaceutical analysis

Development of the spectrophotometric method for the determination of atorvastatin in tablets by using bromothymol blue

The aim of the work was to develop a simple, economic, fast, reliable, and eco-friendly spectrophotometric method for the determination of atorvastatin in tablets based on the reaction with bromothymol blue (BTB). Material and methods. A double–beam Shimadzu UV-Visible spectrophotometer, with spectral bandwidth of 1 nm wavelength accuracy ±0.5 nm, Model –UV 1800 (Japan), Software UV-Probe 2.62 was used to measure absorbance of the resulting solution. Pharmacopeial standard sample of atorvastatin calcium and BTB were provided by Sigma-Aldrich (≥98 %, HPLC). The used dosage forms of atorvastatin: tablets Atorvastatin 10 mg and 20 mg. Results and discussion. The method of spectrophotometric determination of the quantitative content of atorvastatin calcium based on its reaction with BTB in ethyl acetate medium has been developed. The stoichiometric ratios of the reactive components as 1:1 were obtained by the methods of continuous changes and the saturation method. Linearity regression equation was y=0.0017x+0.0496 and the obtained correlation coefficient was R2=0.9993. The linear relationship was found between absorbance at λmax and concentration of medicine in the range 15.48–154.80 µg/mL. The LOD and LOQ values were calculated to be 4.85 µg/mL and 14.71 µg/mL respectively. Spectrophotometric method for the determination of atorvastatin in tablets using BTB was developed in accordance with GAC principles.  Conclusions. A simple, economic, fast, reliable and eco-friendly spectrophotometric method was developed for the determination of atorvastatin calcium in tablets based on the reaction with BTB and validated according to the standardized validation procedure by the standard method. It was proved that according to such validation characteristics as linearity, precision, accuracy, and robustness the proposed method met the requirements of SPhU

Study of the dissolution kinetics of drugs in solid dosage form with lisinopril and atorvastatin and intestinal permeability to assess their equivalence in vitro

Atorvastatin and lisinopril are a successful combination for the treatment of patients with chronic heart failure and hypertension. Study of the dissolution kinetics of drugs in solid dosage form with lisinopril and atorvastatin and intestinal permeability to assess their equivalence in vitro were described. In medium with hydrochloric acid pH 1.2, in the medium of acetate buffer solution with a pH of 4.5 and in the medium phosphate buffer solution with a pH of 6.8 for 15 min more than 85% of the active substance passes into solution, hence the dissolution profiles these drugs in these environments are similar, and the drugs in them are “very quickly soluble”. Among the in vitro models that make it possible to assess the degree of absorption of API, the most widely used culture of adenocarcinoma cells of the colon – Caco-2. The development of the analytical methodology and its validation is the final stage of both the dissolution study and the Caco-2 test, as well as the biowaver procedure. It plays the most important role in the reliability of the results for all the above procedures and tests. To study permeability, method LC-MS/MS was developed. According to the obtained results, atorvastatin and lisinopril showed low permeability. The values ​​of recovery of transport of test and control substances through the monolayer of cells of the Caco-2 line indicate that the results of the experiment can be considered reliable. The equivalence of the drugs “Lisinopril”, tablets of 10 mg and “Atorvastatin”, tablets of 10 mg, belongs to class III BCS proven by in vitro studies.

Non-extractive spectrophotometric determination of valsartan in pure form and in pharmaceutical products by ion-pair complex formation with bromophenol blue and methyl red

Two simple, rapid, green non extractive spectrophotometric methods are described for the estimation of valsartan in tablet dosage form. The determination is based on the ion-pair formation using the dyes, bromophenol blue (BPB) and methyl red (MR). Valsartan forms ion-pair complex selectively with the dyes, as indicated by the formation of a coloured complex with BPB at pH 5.5 with λmax at 424 nm and MR at pH 4.3 with λmax at 494 nm. For both methods, optimal spectrophotometric conditions were established. The linear relationship was found between absorbance at λmax and concentration of drug in the range 8–24 µg/mL for BPB and 4–20 µg/mL for MR. Regression analysis of Beer’s law plot at 424 nm yielded the regression equation, y = 0.0102x + 01636 (BPB) and at 494 nm y = 0.0222x – 0.0063 (MR). High values of correlations coefficient (R2 = 0.9988 (BPB) and R2 = 0.9991 (MR)) and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The LOD and LOQ values were calculated to be 1.03 µg/mL and 3.43 µg/mL respectively (BPB) and 0.68 µg/mL and 2.26 µg/mL respectively (MR). Intra-day and inter-day accuracy and precision, robustness were in acceptable limits. The proposed methods were applied for the quantification of valsartan in tablets pertaining to three commercial formulations. Analytical eco-scale for greenness assessment of the proposed spectrophotometric methods showed that both methods corresponds to excellent green analysis with a score of 89.

Spectrophotometric methods for the determination of lisinopril in medicines

Two simple, rapid and green spectrophotometric methods are described for the determination of lisinopril medicines. The determination is based on the reaction of the primary amino group of the lisinopril with ninhydrin in aqueous medium (Method I) and reaction on the carboxylic group of the lisinopril with copper (II) sulfate (Method II). For both methods, optimal spectrophotometric conditions were established. The linear relationship was found between absorbance at λmax and concentration of drug in the range 40–60 µg/mL (Method I) and 0.592–2.072 mg/mL (Method II). Regression analysis of Beer’s law plot at 400 nm yielded the regression equation, y = 7.4929x – 0.0545 (Method I) and at 730 nm y = 0.0443x – 0.0832 (Method II). High values of correlations coefficient (R2 = 0.9917 (Method I) and R2 = 0.999 (Method II)) and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The LOD and LOQ values were calculated to be 6.91 µg/mL and 23.01 µg/mL respectively (Method I) and 0.11 mg/mL and 0.36 mg/mL respectively (Method II). Intra-day and inter-day accuracy and precision were in acceptable limits. The proposed methods were applied for the quantification of lisinopril in tablets pertaining to three commercial formulations. Analytical eco-scale for greenness assessment of the proposed spectrophotometric methods showed that both methods correspond to excellent green analysis.

Chaotropic salts impact in HPLC approaches for simultaneous analysis of hydrophilic and lipophilic drugs

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.

Development and validation of a fast and simple HPLC method for the simultaneous determination of bisoprolol and enalapril in dosage form

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.

Method development for the quantitative determination of captopril from Caco-2 cell monolayers by using LC-MS/MS

Aim. Caco-2 cells are a human colon epithelial cancer cell line used as a model of human intestinal absorption of drugs and other compounds. Although compounds were used in the original Caco-2 cells monolayer assays, compounds have been replaced in most laboratories by the use of liquid chromatography-mass spectrometry (LC-MS) and LC-tandem mass spectrometry (LC-MS/MS). Mass spectrometry not only eliminates the need for compounds, but permits the simultaneous measurement of multiple compounds. The measurement of multiple compounds per assay reduces the number of incubations that need to be carried out, thereby increasing the throughput of the experiments. Furthermore, LC-MS and LC-MS-MS add another dimension to Caco-2 assays by facilitating the investigation of the metabolism of compounds by Caco-2 cells. A simple, rapid LC-MS/MS method has been developed for determination of captopril from confluent Caco-2 monolayers and from aqueous solution.

Materials and methods. Chromatography was achieved on Discovery C18, 50 × 2.1 mm, 5 μm column. Samples were chromatographed in a gradient mode (eluent A (acetonitrile – water – formic acid, 5 : 95 : 0.1 v/v), eluent B (acetonitrile – formic acid, 100 : 0.1 v/v)). The initial content of the eluent B is 0%, which increases linearly by 1.0 min to 100% and to 1.01 min returns to the initial 0%. The mobile phase was delivered at a flow rate of 0.4 mL/min into the mass spectrometer ESI chamber. The sample volume was 5 μl.

Results. Under these conditions, captopril was eluted at 1.42 min. A linear response function was established at 2 – 200 ng/mL. The regression equation for the analysis was y =0.0187x+0.000248 with coefficient of correction (r2) = 0.9993. According to the Caco-2 test results, captopril showed low permeability. It should be noted that the recovery value is 103.20%. The within-run coefficients of variation ranged between 0.321% and 0.541%. The within-run percentages of nominal concentrations ranged between 99.13% and 101.12%. The between-run coefficients of variation ranged between 0.314% and 0.663%. The between-run percentages of nominal concentrations ranged between 99.17% and 101.03%.The assay values on both the occasions (intra- and inter-day) were found to be within the accepted limits.

Conclusion. From results of analysis, it can be concluded that developed method is simple and rapid for determination of captopril from confluent Caco-2 monolayers and from aqueous solution. Acquired results demonstrate that proposed strategy can be effortlessly and advantageously applied for examination of captopril from Caco-2 cell monolayers.

Novel HPLC-UV method for simultaneous determination of valsartan and atenolol in fixed dosage form; Study of green profile assessment

Aim of this work was to develop the first simple, rapid, green, economical and selective HPLC method for simultaneous quantification of the cited drugs in their challenging binary mixture. The work was motivated by the global trends towards sustainable chemistry in designing eco-friendly mobile system without affecting the analysis parameters. The proposed method was subjected to a greenness profiles using some metrics as Eco-scale.

Materials and methods. This was accomplished under the following chromatographic conditions: HPLC column Discovery C18 (4.6 mm i.d. × 150 mm, 5 μm), column temperature 30 °C, flow rate 1.0 mL/min, mobile phase composed of 20% acetonitrile, 80% of 0.16% ammonium acetate and 0.2% of 1.5 M tetramethylammonium hydroxide (V/V) and signal monitoring at a wavelength of 225 nm and 237 nm.

Results. A conventional mixture of acetonitrile and 0.16% ammonium acetate was tried in different ratios, but the drugs were not well separated. The shortest aliphatic chain cationic ion pair reagent tetramethylammonium hydroxide should not be exchanged with other type similar with this, like tetramethylammonium hydrogen sulfate, it did not work to our experiments. Increasing salt concentration, ammonium acetate, more than 0.2%, pushes the peak of atenolol closer to dead volume, which is negative. Atenolol in their methods for multicomponent mixtures elutes in dead volume, or when retained longer, much stronger, hydrophobic mobile phase should be used if valsartan should be seen in same chromatogram at dissent time. The 237 nm can be chosen as compromise signal for nearly equal peaks height with high sensitivity is not essential. The 225 nm signal shows much higher sensitivity for atenolol and less increase for valsartan peaks, which can be used when higher sensitivities will be essential. Linearity was examined and proven at different concentration levels in the range of working concentration of valsartan (0.16–0.96 mg/mL) and atenolol (0.2–1.20 mg/mL). The high value of recoveries obtained for valsartan and atenolol indicates that the proposed method was found to be accurate. The results of proposed method found to be an excellent green analysis with a score of 84.

Conclusion. A new fast, simple and green, but selective, accurate, precise and robust HPLC-UV method for simultaneous determination of valsartan and atenolol in newly formulated dosage form was developed and many possible variations of the same were suggested. The developed method for the simultaneous quantification of valsartan and atenolol in their challenging binary mixture offers simplicity essential for quality control of a large number of samples in short time intervals, which is necessary for routine analysis. The method was subjected to greenness profile assessment.

Quality by design approach for simultaneous determination of original active pharmaceutical ingredient quinabut and its impurities by using HPLC. Message 1

Aim. The aim of study was to develop and validate a simple, highly robust (quality by design (QbD) approach), precise and accurate method using high performance liquid chromatography for the simultaneous determination of original active pharmaceutical ingredient Quinabut and its impurities.

Materials and methods. Experiments were performed on a Shimadzu LC-20 Prominence HPLC separation module, equipped with a quaternary gradient pump, temperature controlled column heater, sampler manager and diode array detector and LC-20 Chemstation for data analysis (Shimadzu Corporation, Japan). Same software was used for data acquisition and processing of results. X-Terra RP18 (4.6×150 mm, 5 μm) analytical chromatographic column provided by Waters Corporation (Milford, MA) was used for all optimization experiments. Mobile phase A: acetonitrile R. Mobile phase B: 0.025 M phosphate buffer solution. Samples were chromatographed in gradient mode. Flow rate of the mobile phase: 0.7 mL/min. Column temperature: 40 °С. Detection: at 233 nm wavelength. Injection volume: 50 μl.

Results. Screening of the influence of four chromatographic factors on different chromatographic responses was performed as the initial step of analytical method optimization. A randomized fractional factorial experimental design (24–1) of resolution IV with central point was used. Buffer pH, amount of acetonitrile in mobile phase A, the amount of phosphate buffer solution in mobile phase B and column temperature were selected as factors of interest, and were used to generate the fractional factorial experimental design. Linearity was established in the range of LOQ level to 0.2% having regression coefficients 0.9977. Calibration curve – y = 0.0132 + 0.9902. Since Δt for the content of quinabut is less than max δ, the technique is stable over time. The possibility of contamination of the sample by decomposition products by keeping it under stressful conditions (irradiation of the substance solution with UV light (UV irradiation with mercury lamp light); acid hydrolysis with 0.1 M hydrochloric acid solution; oxidative decomposition) was investigated. As a result of the irradiation with UV light, the impurity peaks for about 8.74 min (impurity C) and 12.68 min (impurity B) are additionally revealed. Their content exceeds the limits of normalization and is 0.6% and 3.7%, respectively. Therefore, the powder of the substance and its solutions should be stored away from direct sunlight. The column temperature and the speed of the mobile phase within ± 10% did not significantly affect the test results. The results were found to be within the assay variability limits during the entire process.

Conclusion. 1) The optimization of a new analytical method capable of simultaneous determination of quinabut assay and its impurities drug products was performed with a single fractional factorial experimental design. Only 11 experiments were needed for the optimization, while at least 16 experiments would be needed to cover the same analytical method operational region of the first optimization step with a traditional one factor at time (OFAT) approach. 2) HPLC method was developed and validated for the simultaneous detection and quantitation of quinabut and its impurities. 3) The final analytical method optimized with QbD approach was validated according to ICHQ2R1 guideline. The method proved to be sensitive, selective, precise, linear, accurate and stability-indicating. 4) The method was successfully applied to the analysis of demonstrating acceptable precision and adequate sensitivity for the detection and quantitation of quinabut and its impurities. So it may be reasonable to claim that the method can be extended to the analysis of drug formulations and stability samples as well. This optimization reflects in saving of time and resources since one stability study includes hundreds of samples tested during the product’s shelf life.

Method development and validation for the determination of residual solvents in quinabut API by using gas chromatography. Message 2

Aim. The aim of study was to develop and validate a simple, precise and accurate method using gas chromatography for analysis of residual solvents – acetone and 2-propanol – in quinabut API.

Materials and methods. All experiments were performed on a gas chromatographic system equipped with FID detector (Shimadzu GC System) using the DB-624 (30 m × 0.32 mm ID, 3.0 μm film sickness) column as stationary phase. Nitrogen was used as carrier gas with flow rate 7.5 mL/ min. Split ratio was 1:5, injector temperature was 140 °C, detector temperature was 250 °C, oven temperature was programmed from 40 °C (2 min) to 50 °C at 1 °C/min and then increased at a rate of 15 °C/min up to 215 °C; and maintained for 2 min. All solutions were prepared using water as diluent.

Results. This proposed method is assessed for separation of residual solvent from quinabut with quantification. The obtained results are compared with the corresponding specified limits of ICH standard guidelines. The method validation was done by evaluating specificity, limit of detection (LOD) and limit of quantitation (LOQ), linearity, accuracy, repeatability, ruggedness, system suitability and method precision of residual solvents as indicated in the ICH harmonized tripartite guideline. The separation between acetone and 2-propanol peaks is 2.07. Hence method was found to be specific. The linear relationship evaluated across range of 15 to 180% for acetone and 2-propanol of ICH specified limit of residual solvents. The graphs of theoretical concentration versus obtained concentration are linear and the regression coefficients ‘R’ for residual solvents were more than 0.9968. The values of LOD and LOQ were much less than the lower limit of the concentration range and cannot affect the accuracy of the test. The technique was characterized by high intra-laboratory accuracy at concentrations close to the nominal acetone and 2-propanol concentration. All solutions were stable in water for at least 1 hour when stored at room temperature.

Conclusion. A simple, specific, accurate, precise and rugged gas chromatography method was developed and validated for the quantification of residual solvents present in quinabut API through an understanding of the synthetic process, nature of solvents and nature of stationary phases of columns. The residual solvents acetone and 2-propanol were determined.

Efficient validated method of HPLC to determine amlodipine in combinated dosage form containing amlodipine, enalapril and bisoprolol and in vitro dissolution studies with in vitro/ in vivo correlation

Aim. A rapid and reproducible HPLC method has been developed for the determination of amlodipine in experimental combined dosage forms containing amlodipine, bisoprolol and enalapril and for drug dissolution studies.

Materials and methods. The separation was done using a column Phenomenex Polar Synergi, 5 μm, 4.6×50 mm and a mobile phase of methanol:phosphate buffer solution (65:35, v/v), flow-rate of 1.0 mL/min. The injection volume was 100 μL and the ultraviolet detector was set at 240 nm.

Results. The method was validated as per ICH guidelines. Under these conditions, amlodipine was eluted at 1.89 min. Total run time was shorter than 2.5 min. The linearity of the method had a good correlation with concentration and peak area. The correlation coefficient of amlodipine was found to be not less than 0.9991, which indicates good linear relationship over concentration range 0.625 mg/mL–5.000 mg/mL (1.250 mg/mL–5.000 mg/mL at pH 4.5). The % RSD values in intra-day and inter-day precision study were found to be less than 0.267 for amlodipine, which indicate method was precise. Hence, the present developed method was said to be suitable for the analysis of drugs in their pharmaceutical dosage form. Also, in vitro dissolution of amlodipine containing tablets were performed to validate the suitability of the proposed method. The dissolution pattern complies with the FDA standards, indicating suitability of the proposed method for the dissolution study of amlodipine. It will allow conducting comparative studies in vitro to confirm the equivalence of tablets containing amlodipine.

Conclusion. A simple and sensetive HPLC method was developed for the estimation of amlodipine in tablets containing amlodipine, enalapril and bisoprolol. The proposed method was applied successfully for quality control assay of amlodipine in experimental tablets and in vitro dissolution studies. In vitro / in vivo correlation of amlodipine has been conducted.

HPLC-MS/MS method development for the quantitative determination of nifedipine for Caco-2 permeability assay

Aim. Poorly water-soluble drugs such as nifedipineoffer challenging problems in drug formulation as poor solubility is generally associated with poor dissolution characteristics and thus with poor oral bioavailability (BCS class II drugs). Methods of quantitative determination of nifedipine by methods of spectrophotometry and chromatography are described in the scientific literature. However, methods are not developedfor examination of nifedipine from Caco-2 cell monolayers. Caco-2 cell monolayers have been extensively used for years as a tool to test permeability, assess the oral absorption potential and study the absorption mechanism of compounds. Therefore, the aim of this study was to develop and validate an efficient HPLC MS/MS method for determination of nifedipine from Caco-2 cell monolayers.

Materials and methods. Chromatography was achieved on DiscoveryC18, 50 × 2.1 mm, 5 μm column. Samples were chromatographed in a gradient mode (eluent A (acetonitrile – water – formic acid, 5 : 95 : 0.1 v/v), eluent B (acetonitrile – formic acid, 100 : 0.1 v/v)). The initial content of the eluent B is 0%, which increases linearly by 1.0 min to 100% and to 1.01 min returns to the initial 0%. The mobile phase was delivered at a flow rate of 0.4 mL/min into the mass spectrometer ESI chamber. The sample volume was 5 μl.

Results. Under these conditions, nifedipine was eluted at 1.83 min. A linear response function was established at 1 – 100 ng/mL. The regression equation for the analysis was Y = 0.0323x-0.00121 with coefficient of correction (R2) = 0.9987. According to the Caco-2 test results, nifedipine showed high permeability. The within-run coefficients of variation ranged between 0.331% and 0.619% for nifedipine. The within-run percentages of nominal concentrations ranged between 98.80% and 100.63% for nifedipine. The between-run coefficients of variation ranged between 0.332% and 0.615% for nifedipine. The between-run percentages of nominal concentrations ranged between 98.98% and 101.71% for nifedipine. The assay values on both the occasions (intra- and inter-day) were found to be within the accepted limits.

Conclusion. From results of analysis, it can be concluded that developed method is simple and rapid for determination of nifedipine from confluent Caco-2 monolayers and from aqueous solution. Acquired results demonstrate that proposed strategy can be effortlessly and advantageously applied for examination of nifedipine from Caco-2 cell monolayers.

HPLC MS/MS method development for the quantitative determination of verapamil hydrochloride from Caco-2 cell monolayers

Aim. An understanding of the role that transporters, in particular P-glycoprotein (P-gp), can play in the absorption, distribution, metabolism and excretion (ADME) of candidate drugs, and an assessment of how these processes might impact on toxicity and the potential for drug-drug interactions in the clinic, is required to support drug development and registration. It is therefore necessary to validate preclinical assays for the in vitro evaluation of candidate drugs as substrates or inhibitors of human P-gp. 2. A simple, rapid HPLC MS/MS method was developed for determination of verapamil hydrochloride from confluent Caco-2 monolayers and from aqueous solution.

Materials and methods. Chromatography was achieved on Discovery C18, 50 × 2.1 mm, 5 μm column. Samples were chromatographed in a gradient mode (eluent A (acetonitrile – water – formic acid, 5 : 95 : 0.1 v/v), eluent B (acetonitrile – formic acid, 100 : 0.1 v/v)). The initial content of the eluent B is 0%, which increases linearly by 1.0 min to 100% and to 1.01 min returns to the initial 0%. The mobile phase was delivered at a flow rate of 0.4 mL/min into the mass spectrometer ESI chamber. The sample volume was 5 μl.

Results. Under these conditions, verapamil hydrochloride was eluted at 1.08 min. A linear response function was established at 1 – 100 ng/mL. The regression equation for the analysis was Y = 0.0162x + 0.00391 with coefficient of correction (R2) = 0.9992. According to the Caco-2 test results, verapamil showed low permeability. It should be noted that the recovery value for verapamil hydrochloride is 102.69%. The within-run coefficients of variation ranged between 0.336% and 0.617% for verapamil. The within-run percentages of nominal concentrations ranged between 98.82% and 100.62% for verapamil. The between-run coefficients of variation ranged between 0.334% and 0.612% for verapamil. The between-run percentages of nominal concentrations ranged between 98.97% and 101.76% for verapamil. The assay values on both the occasions (intra- and inter-day) were found to be within the accepted limits.

Conclusion. From results of analysis, it can be concluded that developed method is simple and rapid for determination of verapamil hydrochloride from confluent Caco-2 monolayers and from aqueous solution. Acquired results demonstrate that proposed strategy can be effortlessly and advantageously applied for examination of verapamil hydrochloride from Caco-2 cell monolayers.

Bioanalytical method development and validation for the determination of metoprolol and meldonium in human plasma

Aim.The main purpose of this study was to develop a simple, precise, rapid and accurate method for the quantification of metoprolol and meldonium in human plasma.

Materials and methods. The resolution of peaks of metoprolol was best achieved with Discovery C18, 50 × 2.1 mm, 5 μm column and meldonium - ZORBAX HILIC Plus, 50 × 2.1 mm, 3.5 μm column. Samples of metoprolol were chromatographed in a gradient mode (eluent A (acetonitrile – water – formic acid, 5 : 95 : 0.1 v/v), eluent B (acetonitrile – formic acid, 100 : 0.1 v/v)). The initial content of the eluent B is 0%, which increases linearly by 1.0 min to 100% and to 1.11 min returns to the initial 0%. The mobile phase was delivered at a flow rate of 0.400 mL/min into the mass spectrometer ESI chamber. The injection volume was 5μl. Samples of meldonium were chromatographed in a isocratic using mobile phase water – acetonitrile – ammonium formate buffer 200 мМ, 20 : 75 : 5 v/v).

Results.The total chromatographic run time was 2.0 minutes and the elution of metoprolol, meldonium and IS occurred at ~1.39 and 1.18 minutes, respectively.A linear response function was established at 2 - 200 ng/mL for metoprolol and 50 -5000 ng/mL for meldonium in human plasma. The% mean recovery for metoprolol in LQC, MQC and HQC was 99.0%, 107.5% and 96.8%, for meldonium in LQC, MQC and HQC was 94.1%, 100.2% and 93.1% respectively. The lowest concentration with the RSD <20% was taken as LLOQ and was found to be 2.31 ng/mL for metoprolol, 47.70 ng/mL for meldonium. The % accuracy of LLOQ samples prepared with the different biological matrix lots were found 115.4% for metoprolol and 95.5% for meldonium, which were found within the range of 80.00–120.00% for the seven different plasma lots. % CV for LLOQ samples was observed as 12.8% and 7.7% respectively, which are within 20.00% of the acceptance criteria.

Conclusion.A rapid method was developed for simultaneous determination of metoprolol and meldonium in human plasma. The method was strictly validated according to the ICH guidelines. Acquired results demonstrate that proposed strategy can be effortlessly and advantageously applied for routine examination of metoprolol and meldonium in human plasma.

HPLC method for simultaneous determination of impurities and degradation products in Cardiazol

Aim. The aim of study was to develop a simple and accurate procedure that could be applied for the determination of impurities and degradation products in cardiazol.

Materials and methods. Separation in samples was carried out with Acquity H-class UPLC system (Waters, Milford, USA) equipped with Acquity UPLC BEH C18 column (2.1 × 50 mm, 1.7 μm) (Waters, Milford, USA). Xevo TQD triple quadrupole mass spectrometer detector (Waters Millford, USA) was used to obtain MS/MS data. Mobile phase A: 0.1% solution of trifluoroacetic acid R in water R; Mobile phase B: acetonitrile R. Samples were chromatographed in gradient mode (Table 1). Flow rate of the mobile phase: 1 ml / min. Column temperature: 30 °С. Detection: at 240 nm wavelength. Injection volume: 10 μl.

Results. The retention time of the main substance is about 18.5 minutes. The order of the peak, the retention times and relative retention times: impurity B (12.04, 0.65); impurity А (18.5; 0.98); Cardiazol (18.87; 1.00). The LOD and LOQ values obtained were in the range of 30 ng/mL to 100 ng/mL and 80 ng/mL to 310 ng/mL respectively (with respect to sample concentration of 2 mg/ml). Linearity was established in the range of LOQ level to 0.2% having regression coefficients in the range of 0.9996 to 0.9999. The change in the temperature of the column affects the degree of separation of cardiazol and the impurity A, and thus, with a decrease of 5 ° C, the degree of separation is (1.06), while with increasing this index (3.43). When changing the flow rate of the mobile phase, the degree of separation changes in the following order, with a decrease to 0.9 ml / min separation (1.90), with an increase in speed to 1.1 ml / min (2.45). When the number of mobile phase B decreases by 5%, the degree of separation varies by (2.65), with an increase of 5% (1.82). In comparison with the chromatogram of the tested solution, the substance is not resistant to the action of peroxide, alkaline and acid decomposition.

Conclusion. 1) HPLC method was developed and validated for the simultaneous detection and quantitation of impurities formed during the synthesis of cardiazol. 2) The method proved to be sensitive, selective, precise, linear, accurate and stability-indicating.