A Simple and Rapid CZE Determination of Tiapride Hydrochloride and Related Impurities in Pharmaceutical Formulations 2009, 70, 293–297

Yuchun Wang1,3,&, Lei Zhou1,2, Yang Hui1,2, Xingguo Chen1,2,& 1 2 3

National Key Laboratory of Applied Organic Chemistry, Lanzhou University, 730000 Lanzhou, China Department of Chemistry, Lanzhou University, 730000 Lanzhou, China; E-Mail: [email protected] College of Petrochemical Technology, Lanzhou University of Technology, 730050 Lanzhou, China; E-Mail: [email protected]

Received: 31 December 2008 / Revised: 4 April 2009 / Accepted: 6 April 2009 Online publication: 17 May 2009

Abstract A simple, fast, inexpensive capillary zone electrophoresis method for the separation and determination of tiapride hydrochloride and its two related impurities in pharmaceutical formulations has been developed and validated. The successful separation of these compounds was achieved in less than 3 min using a fused silica capillary and photodiode array detector at 218 nm. The best conditions were obtained using a 10 mM sodium tetraborate (pH 8.0) as the running buffer. The linear responses covered the ranges from 1.0 to 100 lg mL-1 (R = 0.9989) for tiapride hydrochloride. The detection (LOD) and quantitation limits (LOQ) for tiapride hydrochloride were 2.7 and 9.0 lg mL-1, respectively. The intraand inter-day relative standard deviations for migration times and peak areas were less than 0.47 and 5.7%, respectively. The method was validated for the determination of tiapride hydrochloride in commercial tablets.

Keywords Capillary zone electrophoresis Pharmaceutical study Validation Tiapride

Introduction Tiapride (N-[(2-diethylammo)ethyl]-2methoxy-5-(methyl sulphonyl) benzamide hydrochloride) is a substituted benzamide and dopaminergic antagonist, which specifically blocks dopamine

Full Short Communication DOI: 10.1365/s10337-009-1140-x 0009-5893/09/07

receptors in the brain. It has been used successfully in the treatment of different neurologic and psychiatric disorders, including extrapyramidal motor disorders [1], tardive dyskinesia [2–5, 13], withdrawal symptoms [6–8], Tourettesyndroms [9–12], Huntington’s disease

[13–15]. Two kinds of synthetic impurities of tiapride (2-methoxy-5-(methylsulfonyl) benzoic acid and 2-methoxy-5methylsulfonyl benzoate) have been identified. The structures of tiapride hydrochloride and its two impurities are shown in Fig. 1. Reported methods for the determination of tiapride hydrochloride include nonaqueous titration [16, 17], stabilityindicating methods [18], LC methods [19–22], gas liquid chromatography [23, 24], spectrofluorimetric [25], capillary electrophoresis (CE) with electrochemiluminescence detection [26], gas chromatography/ion trap mass spectrometry [27], flow-injection chemiluminometric analysis [28] and membrane sensors [29]. Capillary electrophoresis is a rapidly developing analytical technique for the pharmaceutical analysis. It has been used as an attractive method for the determination of various pharmaceutical components with some advantages compared with the existing methodologies [30]. But, in the literature, there is only one paper [26] for the electrochemiluminescence determination of sulpiride and tiapride in human urine by capillary electrophoresis and no published capillary zone electrophoresis (CZE) method for the separation of tiapride hydrochloride from its two impurities and determination tiapride

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O

O CH3

C NH

S O

N

HCl

C

S O

OH

OCH3 Impurity A

O

O CH3

CH3

C2H5

OCH3 Tiapride hydrochloride

O

O

C2H5

C

S O

OCH3

OCH3 Impurity B

Fig. 1. Formulae of tiapride hydrochloride and its two impurities

hydrochloride in pharmaceutical formulations. The aim of the present work is to develop a simple and rapid CZE method for the separation of tiapride hydrochloride and its two impurities. The developed method was successfully applied to the determination of tiapride hydrochloride in pharmaceutical formulations.

P/ACE 5510 system (Beckman Coulter Instrument, Fullerton, CA, USA) equipped with a PDA detector. A fusedsilica capillary of 47 cm (40 cm effective length) 9 75 lm I.D.(Yongnian Photoconductive Fiber Factory, Hebei Province, China) was used. P/ACE station software was used for instrument control, data acquisition, and data analysis. The pH of the solutions was measured by a PHS-3B pH-meter (Shanghai, China).

Experimental Materials and Chemicals Standards of tiapride hydrochloride and its two impurities were purchased from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). Sodium tetraborate was obtained from Xi’an Chemical Reagent Company (Shanxi, China). b-CD was obtained from China Medicine Group (Shanghai, China) and other reagents used were obtained from Tianjin Chemical Reagent Factory (Tianjin, China). All chemicals were of analytical reagent grade and were used without further purification. Tiapride hydrochloride tablets (Batch NO.20070301, 100 mg tiapride HCl per tablet) was purchased from a local Pharmaceutical Company (Lanzhou, China).

Apparatus The optimization and validation of the CZE method were performed on a

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Solutions and Sample Preparation The stock solutions (1.0 mg mL-1) of each standard were prepared by dissolving precisely weighed compounds in water and stored at 4 °C. A mixture of tiapride hydrochloride and its two related impurities was prepared daily by mixing the stock solutions to appropriate concentrations in running buffer. The mixture containing 25 lg mL-1 of each compound was used for the method development and validation studies. The running buffer was prepared daily from 100 mM sodium borax and adjusted to pH 8.0 with 1 M or 0.1 M HCl. Twenty tiapride hydrochloride tablets were finely powdered and weighed. An accurately weighed quantity of the mixed powder containing an equivalent of 100 mg of tiapride hydrochloride was dissolved in water. The solution was then sonicated in an ultrasonic bath for 30 min, filtered through a 0.45 lm syringe filter and diluted to 100 mL with water. This solution was stored at 4 °C

protected from light and daily diluted to an appropriate concentration with running buffer.

Capillary Preconditioning New capillaries were treated by rinsing with 1.0 M NaOH for 30 min, distilled water for 30 min, 1.0 M HCl for 30 min, distilled water for 30 min, and finally buffer solution for 30 min. At the beginning of each working day, the capillary was rinsed with 0.1 M NaOH for 10 min, then with distilled water for 10 min and finally with running buffer for 10 min. Between injections, a rinse cycle, 0.1 M NaOH for 0.5 min, distilled water for 0.5 min, and running buffer for 3 min was employed.

Separation Conditions Detections were performed at 218 nm. Samples were hydrodynamically injected into the capillary for 2 s at 0.5 psi and a constant voltage of +30 kV was applied throughout analysis. The capillary was maintained at 25 °C in a cartridge. Optimized running electrolyte solution was 10 mM sodium tetraborate (pH 8.0). The pH was adjusted with 1 M or 0.1 M HCl, daily prepared and filtered with a 0.45 lm syringe filter.

Results and Discussion Optimization of Separation Conditions To optimize separation conditions, the influences of several parameters were investigated, which included the pH and concentration of the running buffer, the influences of additives, applied voltage, and the injection time.

Effect of Running Buffer The pH and concentration of the running buffer are two of the most important parameters for improving selectivity in CE. Firstly, the effect of pH on separation was investigated over different pH values

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ranging from 8.0 to 10.5 using 10 mM sodium tetraborate buffer. The migration times of all compounds varied slightly and the resolution of the compounds decreased with increasing buffer pH. At pH 10.5, tiapride hydrochloride and impurity B were even not resolved. Therefore, pH 8.0 was selected due to the optimum resolution. The effect of the concentration of sodium tetraborate solution on the separation was investigated in the range of 5-20 mM at a pH 8.0. In all investigating concentration ranges, three analytes could be separated and the resolution between the last two peaks (impurity B and impurity A) was good enough (always exceeded 12.0), so it was excluded from further considerations in the next experiments. With increasing sodium tetraborate concentration, migration times increased. The optimal buffer concentration was determined to be 10 mM, since it offered the best resolution between the first two peaks (tiapride hydrochloride and impurity B) with the shortest separation time. During the experiment, it was found that three analytes could be separated easily using sodium tetraborate solution, but the peaks were somewhat broadened. So the next experiment was performed to improve peak shapes.

Effect of Additives In an attempt to improve peak shapes of the analytes, several additives including methanol, ethanol, acetonitrile (ACN), SDS, and b-CD were evaluated at 10 mM running buffer (pH 8.0). It should be noted that, although these additives increased resolution significantly (except b-CD. Adding b-CD, the resolution between the last two compounds decreased.) they did not apparently improve the peak shape. A resolution increase was unnecessary, on the contrary, they increased analysis time drastically. So we thought it was useless to add these additives in our experiment.

Effect of Applied Voltage The influence of the voltage applied from 15 to 30 kV was also evaluated. When Full Short Communication

the voltage increased, the migration times of all compounds decreased and peak shapes were improved. Therefore, a voltage of 30 kV was used for further experiments due to the shortest migration time and an acceptable current.

Optimization of Injection Time In order to improve the sensitivity, the injection time was varied from 1 to 5 s using a 0.5 psi pressure of injections. The peak areas of all compounds increased but the peak shapes of all compounds were deformed with increasing injection time. Although short injection time had good peak shapes, very short injection time caused bad precision of the peak areas. For this reason, an injection time of 2 s was chosen as optimal value. Figure 2 shows an experimental electropherogram of tiapride hydrochloride and its two impurities standard mixture under the optimized conditions. From the molecular structures of tiapride hydrochloride and its related substances (tiapride hydrochloride is positively charged at basic pH, impurity A is negatively charged at basic pH, impurity B is neutral), it was anticipated that tiapride hydrochloride would have the fastest migration velocity and impurity A would be the slowest one. This was in correspondence with the experiment result. Li et al. [26] separated sulpiride and tiapride hydrochloride in 12 min. The migration time of tiapride hydrochloride is nearly ten times longer compared to the presented capillary zone electrophoresis method (less than 1.3 min). In the LC method [19], the retention time of tiapride hydrochloride was 10 min.

Fig. 2. Typical electropherogram of tiapride hydrochloride and its two impurities standard mixture. Conditions: borate buffer pH 8.0. applied voltage +30 kV; fused silica capillary 47 cm (40 cm effective length) 9 75 lm I.D, PDA detection 218 nm; capillary temperature 25 °C, pressure injection 2 s at 0.5 psi. Peaks: 1 = tiapride hydrochloride, 2 = impurity B, 3 = impurity A

different concentration levels of 1.0– 100 lg mL-1 and its related impurities standard at five different concentration levels of 2.5–50 lg mL-1. The peak areas of analysis compounds against their concentrations were used for plotting the graph. The calibration line was y = 1012.13 + 665.09x (R = 0.9989), y = 831.88 + 513.08x (R = 0.9996) and y = 807.58 + 479.15x (R = 0.9995) for tiapride hydrochloride, impurity A and impurity B, respectively. Acceptable regression coefficients indicated the linearity of the calibration curve for the method. Sensitivity

Method Validation The method was validated by the determination of the following parameters: linearity range, precision, accuracy, LOD, LOQ, specificity. Linearity

Linearity was investigated by injecting a standard tiapride hydrochloride at seven

The limit of detection (LOD) and the limit of quantitation (LOQ) can be estimated from a calibration graph by the following formula. LOD ¼

3r S

LOQ ¼

10r S

where r are the standard deviations (SD) of the intercept and S are the slope of the calibration line. The LOD was 2.7, 1.2 and 1.4 lg mL-1 for tiapride hydrochloride,

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Table 1. Repeatability of migration time, peak area Mode of precision

Intra-day RSD% (n = 5) Inter-day RSD% (n = 4)

Concentration (lg mL-1)

Tiapride hydrochloride Impurity A Impurity B Tiapride hydrochloride Impurity A Impurity B

12.5

25

Migration time

Peak area

Migration time

Peak area

Migration time

Peak area

0.27 0.42 0.32 0.35 0.47 0.30

3.9 4.3 5.7 3.5 5.0 2.6

0.39 0.44 0.38 0.35 0.34 0.26

2.9 3.5 2.2 2.0 2.3 3.3

0.23 0.15 0.18 0.16 0.15 0.13

1.7 1.6 1.5 2.1 0.94 2.1

as the percentage relative standard deviation (%RSD) are given in Table 1. As can be seen, for the precision of migration times, the intra-day repeatability of all analytes varied between 0.02 and 0.58% and the inter-day repeatability varied between 0.13 and 0.47%. It is obvious that both the intra- and interday reproducibilities of the presented method were fairly good. For the precision of peak areas, the intra-day repeatability of all analytes were between 0.2 and 5.4% and the inter-day repeatability varied between 0.94 and 5.0%. As an external standard method, the precision was therefore considered satisfactory. Accuracy and Recovery Fig. 3. Typical electropherogram of tiapride hydrochloride tablet. Conditions see Fig. 2

impurity A and impurity B, respectively. And LOQ was 9.0, 4.0 and 4.5 lg mL-1 for tiapride hydrochloride, impurity A and impurity B, respectively. Precision

The precision of the method was evaluated in terms of both the intra-day and inter-day reproducibility. The intra-day precision of peak areas and migration times for tiapride hydrochloride and its related impurities was studied with five successive injections of the standard mixture in the linear range (12.50, 25.00 and 50.00 lg mL-1) on the same day under the optimized conditions. The inter-day precision was assessed over four consecutive days at each concentration level (12.50, 25.00 and 50.00 lg mL-1). The results, expressed

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To evaluate the accuracy of the method, recovery studies under the optimum conditions were performed by standard addition procedures. The sample solution containing 12.68 lg mL-1 tiapride hydrochloride was spiked with low, medium and high concentrations equivalent to 12.5, 25 and 50 lg mL-1 of tiapride hydrochloride standard solution and was analyzed for three replicates at each concentration. The mean recovery of tiapride was 98.26, 101.36, and 116.36% respectively. Specificity

The specificity studies were performed by taking 5 mL of sample solution, transferring this to three individual 10 mL volumetric flasks, adding 4 mL 0.1 M NaOH, 4 mL 0.1 M HCl, 2 mL 0.1% KMnO4, and maintaining these at 80 °C in a water bath for 2 h. Then they were cooled to room temperature, adjusted to

pH = 7 and diluted to volume with water. In addition, about 100 mg of a tiapride hydrochloride tablet was accurately weighed and maintained at 120 °C for 2 h. Then it was treated as described in the procedure for sample preparation to prepare solution for analysis. These solutions were filtered through a filter paper before use. 30 lL of these solutions were diluted with running buffer to 0.4 mL and then introduced into the capillary electrophoresis system. Neither the alkali nor acid reagents resulted in interference and the electropherogram of the tiapride hydrochloride sample from the oxidation study showed that the oxidation compounds were 2-methoxy5-(methylsulfonyl) benzoic acid and 2-methoxy-5-methylsulfonyl benzoate. The electropherogram of the tiapride hydrochloride from the high-temperature damaged sample showed that there were no significant changes in tiapride hydrochloride at high temperature.

Determination of Tiapride Hydrochloride in a Tablet Formulation Commercial tiapride hydrochloride tablets were assayed using the proposed CZE method. When assaying impurities, the stock sample solution was directly injected without dilution. A typical electropherogram of sample is shown in Fig. 3. The peak of tiapride hydrochloride was not interfered by any of the matrix compounds of the formulations and the impurities A and B were not found in the samples. The assay results (101.4 mg) correspond well with the label claim (100 mg).

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Conclusion A simple and rapid capillary zone electrophoresis method for the separation of tiapride hydrochloride from its two impurities has been developed and applied to the detection of tiapride hydrochloride in pharmaceutical formulations. It can be considered as an alternative to the LC method and can be used for the determination of tiapride hydrochloride in pharmaceutical preparations. Compared to previous methods described in the literatures, the advantage of the proposed method is a short analysis time for determination tiapride hydrochloride and this is the first time for separation of tiapride hydrochloride from its two impurities.

References 1. Grass H, Gottschaldt M (1983) Psychiatr Neurol Med Psychol (Leipz) 35:222–229 2. Pere´nyi A, Arato´ M, Bagdy G, Frecska E, Szu¨cs R (1985) J Clin Psychiatry 46:229– 231 3. Pollak P, Gaio JM, Hommel M, Pellat J, Perret J (1985) Psychopharmacology (Berl) 85:236–239. doi:10.1007/BF00428422 4. Soares KV, McGrath JJ (1999) Schizophr Res 39:1–16. doi:10.1016/S0920-9964(99) 00021-3 5. Murphy DJ, Hughes G, Shaw GK (1982) Psychopharmacol Bull 18:13–16

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6. Presslich O, Loimer N, Aschauer G, Fodor G, Pfersmann D, Muller K, Pakesch G, Lieber A (1989) Psychiatr Prax 16:179–181 7. Peters DH, Faulds D (1994) Drugs 47:1010–1032. doi:10.2165/00003495199447060-00009 8. Bobolakis I (1995) Eur Psychiatry 10:110–111. doi:10.1016/0924-9338(96) 80322-1 9. Mu¨ller-Vahl KR (2007) Nervenarzt 78:264–271. doi:10.1007/s00115-0062131-x 10. Robertson MM, Stern JS (2000) Eur Child Adolesc Psychiatry 9:160–175. doi: 10.1007/s007870070020 11. Swain JE, King RA, Leckman JF (2005) In: Tarazi FI, Schetz JA (eds) Neurological and psychiatric disorders, from molecules and cells to symptoms and management. Humana Press Inc., Totowa, pp 151–169 12. Swain JE, Leckma JF (2003) Curr Treat Options Neurol 5:299–308. doi:10.1007/ s11940-003-0036-6 13. Roos RAC, de Haas EJM, Buruma OJS, de Wolff FA (1986) Eur J Clin Pharmacol 31:191–194. doi:10.1007/BF00606657 14. Norman T, Chiu E, James RH, Gregory MS (1987) Eur J Clin Pharmacol 32:583– 586. doi:10.1007/BF02455992 15. Dose M (2005) Treatment options in Huntington’s sisease. In: Danek A. Neuroacanthocytosis syndromes. Springer, Netherlands, pp 243–250 16. British pharmacopoeia (2001) Her majesty’s stationary office. London, p 1611 17. Wu B, Lu M, Wang Y, Fang X (1985) Yaowu Fenxi Zazhi 55:20–25 18. Metwally FH, Abdelkawy M, Abdelwahab NS (2007) J AOAC Int 90:1554–1565

19. Norman TR, James RH, Gregory MS (1986) J Chromatogr Biomed Appl 375:197–201. doi:10.1016/S0378-4347(00) 83711-1 20. Duan G, Lu M, Wu B (1986) Yaoxue Xuebao 21:39–43 21. Chiba R, Ogasawara A, Kubo T, Yamozaki Y, Umino M, Ishizuka Y (2003) Anal Sci 19:785–792. doi:10.2116/analsci. 19.785 22. Jin SE, Ban E, Kim CK (2004) J Pharm Biomed Anal 35:929–936. doi:10.1016/ j.jpba.2004.02.024 23. Kamizono A, Inotsume N, Miyamoto K, Ueda K, Miyakawa T, Arimoto H, Nakano M (1991) J Chromatogr Biomed Appl 567:113–120. doi:10.1016/0378-4347 (91)80315-4 24. Sa´nchez de la Torre C, Martı´ nez M, Almarza E (2005) Forensic Sci Int 155:193–204. doi:10.1016/j.forsciint.2004. 12.007 25. Buna M, Aaron JJ, Prognon P, Mahuzier G (1996) Analyst (Lond) 121(1111):1551– 1556. doi:10.1039/an9962101551 26. Li J, Zhao F, Ju H (2006) J Chromatogr B Analyt Technol Biomed Life Sci 835:84– 89. doi:10.1016/j.jchromb.2006.03.017 27. Plossl F, Giera M, Bracher F (2006) J Chromatogr A 1135:19–26. doi:10.1016/j. chroma.2006.09.033 28. Aly FA, Alarfaj NA, Alwarthan AA (2001) Talanta 54:715–725. doi:10.1016/ S0039-9140(01)00320-4 29. Metwally FH (2007) Yakugaku Zasshi 127:1267–1273. doi:10.1248/yakushi.127. 1267 30. Holzgrabe U, Brinz D, Kopec S, Weber C, Bitar Y (2006) Electrophoresis 27:2283– 2292. doi:10.1002/elps.200600016

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