Acta Poloniae Pharmaceutica ñ Drug Research, Vol. 70 No.1 pp. 51ñ58, 2013 ISSN 0001-6837 Polish Pharmaceutical Society PURITY DETERMINATION OF GYNALGIN BACTERICIDAL TABLETS WITH HPLC METHOD WANDA BIA£ECKA1*, ANNA KULIK1, MARZENA PODOLSKA1, BARBARA KWIATKOWSKA- PUCHNIARZ1 and ALEKSANDER MAZUREK1,2 1Department of Basic and Applied Pharmacy, National Medicines Institute, 30/34 Che≥mska St., 00-725 Warszawa, Poland 2Department of Drug Chemistry, Medical University of Warsaw, 1 Banacha St., 02-097 Warszawa, Poland Abstract: The study was aimed at developing a simple HPLC method for the determination of the content of impurities in Gynalgin, a two-component preparation. A satisfactory separation was performed on 250 ◊ 4.6 mm Symmetry C8 column in a gradient elution system: mobile phase A ñ acetonitrile/buffer, pH 5.5 in 10:90, v/v proportion, and mobile phase B ñ acetonitrile/buffer, pH 5.5 in 75:25 v/v proportion. Two wavelengths: 250 nm and 315 nm were used for detection. Validation confirmed that the method was linear in a required con- centration range. The values of correlation coefficients for specific drug substances and the related impurities were as high as 0.999. The results of the purity tests proved that the method was sufficiently selective and pre- cise. Keywords: chlorquinaldol, metronidazole, 2-methyl-5-nitroimidazole, 2-aminophenol, HPLC method The combined action of multiple drug sub- method (1). On the other hand, many papers refer to stances improves therapeutic efficacy, and therefore, metronidazole tested in medicinal products (1ñ8, the number of multi-component drugs available on 10ñ13, 17, 19) or biological material (9, 14ñ16, the market has been continuously increasing. 18ñ21). A variety of methods has been applied in the Gynalgin preparation is available as vaginal tablets tests of metronidazole: spectrophotometric method and contains two drug substances: chlorquinaldol (2ñ6), NIR spectroscopy (7), voltammetric method and metronidazole. Chlorquinaldol is a derivative of (8, 9), HPTLC (10, 11), HPLC (12ñ16), UPLC-MS 8-hydroxyquinoline exhibiting bactericidal, fungi- (17, 18), NMR (19) and LC-MS (20, 21). In a num- cidal and antiprotozoal activity; metronidazole is a ber of papers, metronidazole is reported to be meas- derivative of 5-nitroimidazole with antiprotozoal ured in parallel to other drug substances. and bactericidal activity against anaerobes. No purity determinations of chlorquinaldol and The aim of the study was to develop the easiest metronidazole in medicinal products have been possible HPLC method to separate and determine reported using a single chromatographic system the content of impurities in Gynalgin medicinal (HPLC). product. Isocratic HPLC method for the purity test of EXPERIMENTAL tablets containing metronidazole is described in British Pharmacopoeia (B.P.2011). Materials Tests of purity of the substance can be found in ● Drug product: GYNALGIN ñ vaginal tablets con- B.P.2001, Ph.Eur.7.0, and Polish Pharmacopoeia taining 100 mg of chlorquinaldol and 250 mg of VIII. Neither tests of purity of chloroquinaldol metronidazole; manufactured by ICN Polfa tablets nor of the substance were found in the same RzeszÛw S.A.; batch number: 010506; expiry documents, yet the corresponding TLC tests were date: May 2009. inserted in an older source, Polish Pharmacopoeia ● Reference standards: Chlorquinaldol manufac- VI. Only one paper dealing with chloroquinaldol tured by ICN Polfa RzeszÛw S.A. batch number: was found, with the use of spectrophotometric C4011209; 2-aminophenol (impurity of chlor- * Corresponding author: e-mail: [email protected] 51 52 WANDA BIA£ECKA et al. quinaldol) manufactured by Acros Organics batch Standard solutions number: A0266307; metronidazole manufactured A methanol standard solution (mix 0.5%) was by Farchemia, batch number: 06548740; 2- prepared, 1 mL of which contained: 0.05 mg of 2- methyl-5-nitroimidazole (impurity of metronida- methyl-5-nitroimidazole, 0.05 mg of metronidazole zole) manufactured by CRS BP, batch number: (0.5% as compared to metronidazole concentration 2474. in the sample), 0.02 mg of 2-aminophenol, and 0.02 mg of chlorquinaldol (0.5% as compared to the con- Reagents and instrument centration of chlorquinaldol in the sample). ● High-purity HPLC reagents. ● Computer-controlled liquid chromatograph by Sample solutions Shimadzu, fitted with UV-VIS SPD-10AVVP One gram of pulverized tablets was weighed detector, LC-10ATVP pump system, DGU-14A and transferred to a 25 mL volumetric flask, then 15 sample degassing unit, SCL-10AVP controller, mL of methanol was added to the sample. It was and SIL-10ADVP automatic sample feeder. ultrasonicated for ca. 15 min then, agitated on a ● Chromatographic columns: Symmetry C8, 250 ◊ mechanical shaker for approx. 30 min, made up to 4.6 mm, by Waters, and Kromasil 100-5C8 250 ◊ volume with the solvent and filtered through a filter 4.6 mm, by AKZO NOBEL. with 0.45 µm mesh size. Table 1. Calibration curve parameters, correlation coefficients, detection limits (LOD) and quantitation limits (LOQ) of the analyzed sub- stances. Substance Calibration curve parameters LOD LOQ determined y = ax + b [ µg/mL] [ µg/mL] ∆ a ± a = 45745 ± 857; Sa= 333 b ± ∆b = 50136 ± 73949; S = 28768 Metronidazole b 4.30 13.02 Sy= 59567 r = 0.9999 ∆ a ± a = 134406 ± 4528; Sa= 1631 b ± ∆b = -268279 ± 109842; S = 39562 Chlorquinaldol b 1.23 3.74 Sy= 50294 r = 0.9997 ∆ a ± a = 48750 ± 726; Sa= 261 2-Methyl-5- b ± ∆b = 18635 ± 44358; S = 15977 b 1.37 4.17 nitroimidazole Sy= 20312 r = 0.9999 ∆ a ± a = 13775 ± 278; Sa= 99 b ± ∆b = 5052 ± 6446; S = 2322 2-Aminophenol b 0.71 2.14 Sy = 2954 r = 0.9999 a, b ñ regression coefficients; Sa, Sb ñ standard deviation of regression coefficients; Sy ñ standard error of the estimate; r ñ correlation coef- ficients. Table 2. Results of system precision tests. Substance Average Standard RSD determined peak area deviation [%] [a.u.] n = 6 Metronidazole 1992389 14419 0.72 Chlorquinaldol 1880307 28223 1.50 2-Methyl-5- nitroimidazole 2070600 17141 0.83 2ñAminophenol 219760 2585 1.18 Purity determination of gynalgin bactericidal tablets with HPLC method 53 Figure 1. Chromatograms of the mixture of standards at 250 nm and 315 nm wavelengh. Retention times: 2-methyl-5-nitroimidazole 5.3 min.; metronidazole 7.5 min.; 2-aminophenol 8.2 min.; chlorquinaldol 23.2 min The sample solution contained 10 mg/mL of parent drug substances. as well as peaks originating metronidazole and 4 mg/mL of chlorquinaldol . from the solvent and placebo. For the tests, the expired tablets were selected RESULTS AND DISCUSSION (1.5 years past their expiration date) with a new hav- ing more impurities. HPLC method development A variety of gradient elution systems were First, a specific HPLC system has been tested, along with numerous modifications of sought, which would provide sufficient separation mobile phases, flow rates and injection volumes. pH and quantitative determination of impurities origi- of the mobile phase influenced the 2-aminophenol nating from metronidazole and chlorquinaldol. It peak location. The following chromatographic sys- was necessary to separate 2ñaminophenol, 2- tem was finally selected for further tests with the aid methyl-5-nitroimidazole, and unidentified impuri- of gradient elution: Symmetry C8 column, 250 ◊ 4.6 ties developed in the course of stress tests from the mm; 40OC; mobile phase A ñ a mixture of acetoni- 54 WANDA BIA£ECKA et al. trile and buffer, pH 5.5 (10 : 90, v/v); mobile phase B ñ a mixture of acetonitrile and buffer, pH 5.5 (75 : 25, v/v); buffer, pH 5.5 ñ a mixture of 1,000 mL of water and 1 mL of 85% H3PO4 adjusted to pH 5.5 with 10% NaOH solution. Gradient elution: Time [min] Mobile phase B [%] 0 ñ 20 0 → 100 20 ñ 25 100 25 ñ 27 100 → 0 27 ñ 35 0 Mobile phase flow rate was 1.2 mL/min, injec- tion volume 20 µL, and detection wavelengths: 250 nm (to determine 2-aminophenol and unidentified impurities originating from chlorquinaldol) and 315 nm (to determine 2-methyl-5-nitroimidazole and other unidentified impurities originating from metronidazole) . The following system performance parameters were selected: symmetry coefficient (A10%)of metronidazole peak, which ought to be not higher than 1.5, and resolution (Rs) between the peaks for 2-aminophenol and metronidazole, not lower than 3.0. The parameters were measured with the mix 0.5% solution. Validation of the method Specificity In order to examine the method specificity, solvent, solution of excipients (placebo), solutions of identified impurities (2-methyl-5-nitroimida- zole and 2ñaminophenol) and unidentified impuri- ties (obtained in the course of stress tests) along with solutions of standard drug substances were injected onto the column. The recorded chro- matograms revealed that the peaks originating from the solvent, drug substances and excipients did not interfere with the peaks originating from Impurities originating Impurities originating from metronidazole [%] impurities.from chlorquinaldol [%] Linearity A dependence was examined between the peak areas on the chromatogram and the concentrations of specific substances and was found to be linear within the following concentrations: 0.01 mg/mL ñ 0.1 mg/mL for 2-methyl-5-nitroimi- dazole; 0.004 mg/mL ñ 0.04 mg/mL for 2-aminophenol; 1.75 0.14 0.74 0.28 1.21 0.64 13.75 12.59 1.89 3.03 0.2180.2180.2200.215 0.3070.219 0.3060.213 0.311 0.023 0.309 0.023 0.308 0.024 0.308 0.030 0.024 0.030 0.023 0.030 0.0230.01 0.061 0.030 mg/mL 0.060 0.030 0.061 0.030 0.060 ñ 0.060 0.639 0.1 0.061 0.637 mg/mL 0.646 0.634 0.066 0.638 for 0.058 0.641 metronidazole; 0.061 0.054 0.028 0.061 0.026 0.064 0.027 0.023 0.196 0.028 0.196 0.027 0.200 0.190 0.290 0.196 0.280 0.197 0.288 0.267 0.285 0.288 0.0038 0.0004 0.0002 0.0001 0.0007 0.004 0.0082 0.032 0.0036 0.01 RT 3.8 RT 4.7 RT 9.1 RT 9.2 RT 10.0 Total RT 24.4 RT 26.2 RT 28.8 Total 0.004 mg/mL ñ 0.04 mg/mL for chlorquinaldol.