научная статья по теме DETERMINATION OF CETIRIZINE AND ITS IMPURITIES IN BULK AND TABLET FORMULATION USING A VALIDATED CAPILLARY ZONE ELECTROPHORETIC METHOD Химия

Текст научной статьи на тему «DETERMINATION OF CETIRIZINE AND ITS IMPURITIES IN BULK AND TABLET FORMULATION USING A VALIDATED CAPILLARY ZONE ELECTROPHORETIC METHOD»

ОРИГИНАЛЬНЫЕ СТАТЬИ

УДК 543

DETERMINATION OF CETIRIZINE AND ITS IMPURITIES IN BULK AND TABLET FORMULATION USING A VALIDATED CAPILLARY ZONE

ELECTROPHORETIC METHOD

© 2014 F. Sattary Javid, A. Shafaati, A. Zarghi

Pharmaceutical Chemistry Depratment, School of Pharmacy, Shahid Beheshti University of Medical Sciences 1360 Vali-e-Asr Ave., Niayesh Junction, Tehran, 1991953381 Iran Received 13.10.2011; in final form 04.12.2012

A stability indicating capillary electrophoretic method for separation and determination of cetirizine dihy-drochloride and its major impurities in bulk and a tablet dosage form was developed. The electrophoretic separation was performed in an uncoated fused-silica capillary (75 cm x 50 p.m i.d.) using 75 mM sodium phosphate (pH 2.8) as background electrolyte, with an applied voltage of +25 kV at 25°C and UV detection at 230 nm. Fexofenadine was used as internal standard. The proposed method was found selective for determination of the main drug and its major impurities. The regression data obtained from the calibration plots indicated linear relationship (r2 = 0.998) over the concentration range of 40—240 p.g/mL of cetirizine. Repeatability and reproducibility of the method, assessed as intra-day and inter-day variation and expressed as RSD (%), were 1.3 and 2.6, respectively. Stress tests on cetirizine under acidic, basic, oxidative and heat incubating at 80°C conditions revealed that no major compound was formed under the applied conditions and the proposed CE method is applicable for stability studies on cetirizine. Then, the method was successfully applied to the determination of cetirizine in bulk and a tablet dosage form.

Keywords: cetirizine, impurities, determination, capillary electrophoresis.

DOI: 10.7868/S004445021405003X

Cetirizine dihydrochloride is [(RS)-2-[2-[(4-chlo-rophenyl)phenylmethyl] piperazin-1-yl]ethoxy] acetic acid dihydrochloride (CTZ, Scheme 1), a carboxy-lated metabolite of hydroxyzine, belongs to the piper-azine class of second-generation of antihistamines. Compared with other antihistamines, the pharmacological effects of cetirizine are mediated through selective inhibition of the peripheral histamine H1 receptor; therefore, there are fewer central anticholinergic side-effects such as dry mouth and sedation [1].

Cl

O^COOH

Scheme 1. Chemical structure of cetirizine. Nitrogen (1) and (2) and carboxylic acid group (3) responsible for the ionization of the drug are marked.

A number of analytical methods for quantification of CTZ in bulk and/or pharmaceutical dosage forms can be found in the literature. High-performance liq-

uid chromatography (HPLC) with ultraviolet detection (UV) is the most widely used technique [2—9] along with liquid chromatography with mass spectro-metric detection (LC-MS) [10]. But, chromatograph-ic methods are known to be quite lengthy, consume large volumes of organic solvents and use expensive HPLC columns. Previously published methods also included gas chromatography (GC) [11], high-performance thin-layer chromatography (HPTLC) [12, 13], electrooxidation [14], spectrophotometric [15, 16] and titrimetric techniques [17].

Capillary electrophoresis (CE) is a powerful separation technique in that polar ionic compounds are separated due to their ionic character and aqua-ion size of the component [18]. Capillary electrophoretic methods for the determination of CTZ in pharmaceutical dosage forms are described using basic running buffers by which impurities of the drug are not detected [19—21]. In another report, a CE method described for determination of cetirizine in pharmaceutical formulations using an acidic buffer, but the method was developed specifically for the analysis of the drug itself [22]. None of the above-mentioned methods investigated possible interferences from degradation of CTZ by performing stability tests. There is also another paper reporting application of capillary electrophoresis

3

for determination of cetrizine in human plasma which is not suitable for the detection of the impurities [23].

The aim of this study was to separate CTZ from its structurally related impurities using a valid capillary electrophoretic method and to assess stability of the drug in solution and any possible interference from its degradation on the robustness of the method. Then, the method was applied to the determination of CTZ and its impurities in bulk and a tablet dosage form.

EXPERIMENTAL

Chemicals. Cetirizine 2HCl (CTZ), impurity A of cetirizine, intermediate impurity of cetirizine and fex-ofenadine (internal standard) were kindly gifted by Noor Research and Educational Institute (Tehran, Iran). All other chemicals were of analytical grade reagents and purchased from Merck (Darmstadt, Germany). Deionized water was used in the preparation of all samples, rinsing and buffer solutions.

Capillary electrophoretic conditions. All experiments were performed on a Prince-C650 CE (Emmen, the Netherlands) system equipped with UV/vis-ible detector Bischoff (Lambda 1010). Separation was performed on a bare fused-silica capillary, produced by Prince Technology company (Emmen, the Neath-erlands), with 75-cm total length (25-cm effective length) and 50 ^m I.D. The applied voltage was +25 kV at 25°C, and the migrant species were detected at 230 nm. The running buffer was a 75 mM phosphate buffer at pH 2.8, which was freshly prepared daily and filtered through a 0.45 ^m filter membrane. The elec-trophoretic integration was performed by Dax Data Acquisition Analysis software (version 8.0). The capillary was conditioned prior to the first use by rinsing with 1 M NaOH for 15 min, followed by 0.1 M NaOH, water and running buffer, respectively for 5 min each. Between runs, the capillary was flushed for 3 min with running buffer. Samples were introduced into the capillary by hydrodynamic injection for 12 s at 50 mbar.

Sample preparations. Standard stock solutions of each of CTZ and fexofenadine HCl (IS) containing 1 mg/mL of the compound was separately prepared by dissolving standard powder of each compound in water. Intermediate and working solutions were prepared by diluting stock solution of CTZ with water. Standard solutions for linearity studies and calibration were also prepared as described, in the range of 40 to 240 |g/mL CTZ. All CTZ solutions contained fexofenadine as IS, at a concentration of 200 |g/mL. The stock solutions were stored at 4 ± 2°C.

Method validation. The method was validated according to ICH recommendations Q2(R1) 2005 [24].

The specificity of the method was assessed by adding known amounts of each of CTZ, its impurities and the internal standard to the tablet placebo, separately. Then, all samples were extracted (as described below)

and the resultant solutions were subjected to CE. Any interference from the excipients was evaluated.

The response for the detector was determined to be linear over the range of 40-240 ^g/mL (40, 80, 120, 160, 200, and 240 ^g/mL) of CTZ. Each concentration was injected in triplicate to get reproducible response. The peak area ratios of the drug to IS were determined at six different CTZ concentration levels. The calibration curve was plotted as peak area ratios of cetirizine/fexofenadine versus concentration of CTZ at each level. The proposed method was evaluated by its correlation coefficient, and intercept value was calculated in the statistical study.

The precision of the method was examined as intra-and inter-day variation measurements at 3 concentration levels of CTZ (60, 140 and 220 |g/mL). Six replicate quality control samples at each concentration were assayed on the same day for intra-day variation assessment. The inter-day precision was evaluated on three different days.

Accuracy was determined by adding known amounts of the drug at concentrations of 60, 140 and 220 | g/mL to the excipients and measuring percent recovery of the drug from each sample in triplicate.

Detection and quantification limits (LOD and LOQ, respectively) for CTZ in the background solution were determined by analyzing serial dilutions of known concentrations of CTZ solutions and estimation of LOD and LOQ based on signal to noise (S/N) ratios of 3 : 1 and 10 : 1, respectively.

Stress degradation testing. Twenty mg of CTZ was

separately dissolved in 10 mL of each of 1M HCl, 1M NaOH and 3% H2O2 solutions and the solutions were kept in room temperature for 12 hours. For acidic and basic solutions, 1 mL of each solution was taken after 1, 4, 8 and 12 h, neutralized, and diluted to 100 | g/mL with water. For hydrogen peroxide containing solution for oxidation testing, 1 mL of the solution was taken after 1, 4, 8, and 12 h, then diluted to 100 |g/mL with water.

For testing the effect of temperature, 2 mg/mL aqueous solution of CTZ was allowed to stand in boiling bath for 12 h, and after 1, 4, 8 and 12 h 1 mL portion of the solution was cooled and diluted to 100 | g/mL by water. Then, CTZ content of each sample was determined and the results were compared with the original solution.

Analysis of the dosage form. A total of 20 tablets were weighed and finely powdered. A portion of the powder equivalent to 10 mg CTZ was weighed accurately into a 20 mL volumetric flask and suspended in 10 mL of deionized water. The flask was placed in an ultrasonic water bath for 10 min before the volume was made up to the mark with water. Then, 10 mL of the mixture was centrifuged (8000 rpm) for 10 min. The supernatant was filtered through a 0.45 micron pore size filter.

Then, 5 mL of this solution with the same volume of the internal standard was mixed and the obtained so-

lution was appropriately diluted with water to make 100 |g/mL of CTZ and 200 |g/mg of the IS solution.

Cl

(b)

Ph HO

Ph

OH

(c)

Scheme 2. Chemical structure of cetirizine impurities: (a) — intermediate impurity, (b) — impurity (a) and internal standard; (c) — fexofenadine.

RESULTS AND DISCUSSION

CZE separation. CTZ has a zwitterionic structure (Sc

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