Erika Rosa Maria Kedor-Hackmann

Visible spectrophotometric and first-derivative UV spectrophotometric determination of rifampicin and isoniazid in pharmaceutical preparations.

Two methods are described for the determination of rifampicin and isoniazid in mixtures by visible spectrophotometry and first-derivative ultraviolet spectrophotometry. The absorbance at 475 nm in buffer solution pH 7.4 was employed to determine rifampicin after applying the three-point correction technique between 420 and 520 nm, while the amplitude of the first-derivative spectrophotometric spectrum at 257 nm in HCl 0.012 M was selected for the determination of isoniazid. The methods are rapid, simple and do not require any separation step. The recovery average was 99.03% for rifampicin and 100.01% for isoniazid. The methods were applied to determine the two compounds in commercial capsules and compared with the official method of the USP XXIII with good agreement between the results.

Development and Validation of Stability-Indicating HPLC Methods for Quantitative Determination of Pravastatin, Fluvastatin, Atorvastatin, and Rosuvastatin in Pharmaceuticals

Abstract High-performance liquid-chromatographic (HPLC) methods were validated for determination of pravastatin sodium (PS), fluvastatin sodium (FVS), atorvastatin calcium (ATC), and rosuvastatin calcium (RC) in pharmaceuticals. Two stability-indicating HPLC methods were developed with a small change (10%) in the composition of the organic modifier in the mobile phase. The HPLC method for each statin was validated using isocratic elution. An RP-18 column was used with mobile phases consisting of methanol–water (60:40, v/v, for PS and RC and 70:30, v/v, for FVS and ATC). The pH of each mobile phase was adjusted to 3.0 with orthophosphoric acid, and the flow rate was 1.0 mL/min. Calibration plots showed correlation coefficients (r) > 0.999, which were calculated by the least square method. The detection limit (DL) and quantitation limit (QL) were 1.22 and 3.08 µg/mL for PS, 2.02 and 6.12 µg/mL for FVS, 0.44 and 1.34 µg/mL for ATC, and 1.55 and 4.70 µg/mL for RC. Intraday and interday relative standard deviations (RSDs) were <2.0%. The methods were applied successfully for quantitative determination of statins in pharmaceuticals.

Determination of Ketoconazole in Pharmaceutical Preparations by Ultraviolet Spectrophotometry and High Performance Liquid Chromatography

Abstract The aim of this research was to study and to standardize an ultraviolet spectrophotometric (UVS) and a high performance liquid chromatographic (HPLC) method for the determination of ketoconazole in commercially available pharmaceutical preparations (tablets and creams). The UVS method was both standardized at 222 nm and 269 nm in 0.01M HCl. Beers law was obeyed in a range of concentration from 4.0 to 13.0 μg/mL at 222 nm and from 100.0 to 280.0 μg/mL at 269 nm. In the HPLC determination were used a Merck LiChrospherR 100 RP-18 (5 μm) in LiChroCARTR (125–4) column, a mobile phase consisting of diisopropylamine-methanol 1:500/ammonium acetate 1:200 (8:2) and UV detection at 225 nm. There was a correspondence in areas “versus” concentration in a range from 2.0 to 18.0 μg/mL.

Enantiomeric Separation and Quantitative Determination of Propranolol in Tablets by Chiral High-Performance Liquid Chromatography

The separation and quantitative determination of atenolol isomers by chiral high-performance liquid chromatography (HPLC) are described. Atenolol isomers were separated using a Chiralcel OD® column (250 × 4.6 mm,10 μm); the mobile phase was hexane-ethanol-diethylamine (75:25:0.1 v/v/v); ultraviolet detection was at 276 nm; and flow rate was 0.7 ml/min. The coefficient of variation and average recovery of (R)-isomer were 0.60% and 100.37%, respectively, for sample A and 0.69% and 100.63%, respectively, for sample B. The coefficient of variation and average recovery of (S)-isomer were 0.59% and 100.33%, respectively, for sample A and 0.63% and 99.78%, respectively, for sample B.

First-derivative spectrophotometric assay of timolol maleate in ophthalmic solutions

Abstract This research reports the application of derivative spectrophotometry to the determination of timolol maleate in ophthalmic solutions. A systematic approach developed for optimisation of the derivative order, graphical measurements and instrumental conditions led to the adoption of first-order spectrophotometry as a method with suitable precision and selectivity for the determination of timolol maleate in ophthalmic solutions without previous treatment.

Validation of a HPLC method for simultaneous determination of five sunscreens in lotion preparation.

The aim of this research was to develop and validate a high‐performance liquid chromatographic (HPLC) method for simultaneous determination of five sunscreens, namely benzophenone‐3 (B‐3), butyl methoxydibenzoylmethane (BM), octyl methoxycinnamate (OM), octyl salicylate (OS) and homosalate (HS). The separation and quantitative determination was made by HPLC at 40 ±1°C with a gradient elution from 10% to 100% mobile phase B in mobile phase A. The gradient liquid chromatographic system constituted of mobile phase A [acetonitrile : water (10 : 90 v/v)] and mobile phase B [acetonitrile : water (90 : 10 v/v)], at a flow rate of 1.0 mL min−1 and ultraviolet detection at 310 nm. The separation was obtained with two Waters® reversed phase columns: Novapack® C‐18 and Symmetry® C‐18 connected in series. All sunscreens were efficiently separated within 17 min. The coefficient of correlation and average recovery for B‐3, BM, OM, OS and HS were 0.9798 and 98.5%, 0.9672 and 98.8%, 0.9922 and 99.1%, 0.9961 and 98.9% and 0.9909 and 99.4% respectively. The relative standard deviations obtained were between 1.07% and 2.44%. The excipients did not interfere in the analysis. The results showed that the proposed method could be used for rapid and simultaneous determination of B‐3, BM, OM, OS and HS in sunscreen lotions with precision, accuracy and specificity.

First-derivative ultraviolet spectrophotometric and high performance liquid chromatographic determination of ketoconazole in pharmaceutical emulsions

First-derivative ultraviolet spectrophotometric (Method I) and reversed phase high performance liquid chromatographic (Method II) methods were developed. The validated methods were applied for quantitative determination of ketoconazole in commercial and simulated emulsion formulations. Quantitative first-derivative UV spectrophotometric determinations were made using the zero-crossing method at 257 nm, with methanol as background solvent. Liquid chromatographic analysis was carried out on a LiChrospher® 100 RP-18 (5µm) column. A mixture of triethylamine in methanol (1:500 v/v) and 0.5% ammonium acetate solution (75:25 v/v) was used as mobile phase at a flow rate of 1.0 mL/min with UV detection at 225 nm. The retention time of ketoconazole and terconazole were 3.9 min and 5.9 min, respectively, the later being used as internal standard. Analytical curves were linear within a concentration range from 5.0 to 30.0 µg/mL for Method I and 20.0 to 80.0 µg/mL for Method II, with correlation coefficients of 0.9997 and 0.9981, respectively. The relative standard deviation (RSD) was 0.56% and 0.41% for simulated and commercial emulsion formulations, respectively, using Method I. The corresponding values were 2.13% and 1.25%, respectively, using Method II. The percentage recoveries were above 100% for both methods. The excipients did not interfere in the analysis. The results showed that either method can be used for rapid ketoconazole determination in pharmaceutical emulsions with precision, accuracy and specificity.

Validation of a high performance liquid chromatography method for sunscreen determination in cosmetics.

The aim of this research was the development and validation of a high performance liquid chromatography (HPLC) method for the simultaneous and quantitative determination of benzophenone‐3, octyl methoxycinnamate and octyl salicylate contained in sunscreen emulsions. The separation and quantitative determination was achieved using a LiChrospher® 100 RP‐18 (5 µm) Merck column, a mobile phase constituted of methanol/water (85/15, v/v), a flow‐rate of 1.0 mL min−1 and UV detection at 310 nm. The correlation coefficients and percentage of recovery for benzophenone‐3, octyl methoxycinnamate and octyl salicylate were 0.9999 and 99.46%; 0.9995 and 98.85%; 0.9998 and 98.84%, respectively. The relative standard deviations (RSD) for commercial samples were between 0.50 and 0.70%.

Development and validation of a method for quantitative determination of econazole nitrate in cream formulation by capillary zone electrophoresis.

A simple, fast, inexpensive and reliable capillary zone electrophoresis (CZE) method for the determination of econazole nitrate in cream formulations has been developed and validated. Optimum conditions comprised a pH 2.5 phosphate buffer at 20 mmol L(-1) concentration, +30 kV applied voltage in a 31.5 cm x 50 microm I.D. capillary. Direct UV detection at 200 nm led to an adequate sensitivity without interference from sample excipients. A single extraction step of the cream sample in hydrochloric acid was performed prior to injection. Imidazole (100 microg mL(-1)) was used as internal standard. Econazole nitrate migrates in approximately 1.2 min. The analytical curve presented a coefficient of correlation of 0.9995. Detection and quantitation limits were 1.85 and 5.62 microg mL(-1), respectively. Excellent accuracy and precision were obtained. Recoveries varied from 98.1 to 102.5% and intra- and inter-day precisions, calculated as relative standard deviation (RSD), were better than 2.0%. The proposed CZE method presented advantageous performance characteristics and it can be considered suitable for the quality control of econazole nitrate cream formulations.

Determination of steroid hormones in oral contraceptives by high-performance liquid chromatography

ABSTRACT The aim of this research was to standardize a high-performance liquid chromatographic method for quantitative determination of steroid hormones, like ethinylestradiol (ETE), levonorgestrel (LEVO), and gestodene (GEST), in commercially available oral contraceptives (OCs). The combination ETE– LEVO was analyzed using a LiChrospher® 100 RP-8 column (5 μm, 125×4 mm) in LiChroCART®, with a mobile phase constituted of acetonitrile: water (60:40 v/v). Using the same column, ETE–GEST was analyzed with a mobile phase constituted of acetonitrile:water (50:50 v/v) at pH 7.5 adjusted with 0.02 M ammonium hydroxide. For both methods, a flow rate of 0.8 mL/min was utilized and detection was carried out at 215 nm. All analyses were performed at room temperature (24±2°C). Calibration curves for ETE–LEVO were obtained using solutions with concentration ranges from 2.40 to 60.0 μg/mL (ETE), and from 12.0 to 300.0 μg/mL (LEVO). Calibration curves for ETE–GEST were obtained using solutions with concentration ranges from 2.40 to 60.0 μg/mL (ETE), and from 9.0 to 160.0 μg/mL (GEST). Correlation coefficients obtained were from 0.9999 to 0.9990. Coefficients of variation for samples containing ETE–LEVO were 0.47% and 0.38%, respectively. For samples with ETE–GEST they were 0.39% and 0.44%, respectively. The average recovery for samples with ETE–LEVO was 103.46% and 100.78%, respectively. For samples containing ETE–GEST it was 100.89% and 101.03%, respectively.