Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 66–71

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Derivative spectrophotometric method for simultaneous determination of zofenopril and fluvastatin in mixtures and pharmaceutical dosage forms Mariusz Stolarczyk ⇑, Anna Mas´lanka, Anna Apola, Wojciech Rybak, Jan Krzek Department of Inorganic and Analytical Chemistry, Jagiellonian University Medical College, Faculty of Pharmacy, 9 Medyczna Street, 30-688 Kraków, Poland

g r a p h i c a l a b s t r a c t

 A new method was developed for the

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determination of zofenopril and fluvastatin.  The analytical method has been validated according to the ICH recommendations.  Our method was applied for the analysis of drugs in the mixtures and dosage forms.

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Article history: Received 3 June 2014 Received in revised form 18 March 2015 Accepted 27 March 2015 Available online 2 April 2015 Keywords: Zofenopril Fluvastatin Derivative spectrophotometry

a b s t r a c t Fast, accurate and precise method for the determination of zofenopril and fluvastatin was developed using spectrophotometry of the first (D1), second (D2), and third (D3) order derivatives in two-component mixtures and in pharmaceutical preparations. It was shown, that the developed method allows for the determination of the tested components in a direct manner, despite the apparent interference of the absorption spectra in the UV range. For quantitative determinations, ‘‘zero-crossing’’ method was chosen, appropriate wavelengths for zofenopril were: D1 k = 270.85 nm, D2 k = 286.38 nm, D3 k = 253.90 nm. Fluvastatin was determined at wavelengths: D1 k = 339.03 nm, D2 k = 252.57 nm, D3 k = 258.50 nm, respectively. The method was characterized by high sensitivity and accuracy, for zofenopril LOD was in the range of 0.19–0.87 lg mL 1, for fluvastatin 0.51–1.18 lg mL 1, depending on the class of derivative, and for zofenopril and fluvastatin LOQ was 0.57–2.64 lg mL 1 and 1.56–3.57 lg mL 1, respectively. The recovery of individual components was within the range of 100 ± 5%. For zofenopril, the linearity range was estimated between 7.65 lg mL 1 and 22.94 lg mL 1, and for fluvastatin between 5.60 lg mL 1 and 28.00 lg mL 1. Ó 2015 Elsevier B.V. All rights reserved.

Introduction

Abbreviations: ZOF, zofenopril; FLU, fluvastatin; ICH, International Conference on Harmonisation. ⇑ Corresponding author. Tel.: +48 12 620 54 80; fax: +48 12 620 54 05. E-mail address: [email protected] (M. Stolarczyk). http://dx.doi.org/10.1016/j.saa.2015.03.100 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

Zofenopril (ZOF), (2S, 4R)-1-((S)-3-(benzoylthio)-2-methylpropanoyl)-4 (phenylthio) pyrrolidine-2-carboxylic acid (Fig. 1), is a cardioprotective drug from angiotensin-converting enzyme inhibitors group, used in the treatment of hypertension. In

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a

b

comparison with older drugs of this group such as enalapril, captopril or perindopril, it is characterized by a higher hypotensive efficacy and fewer side effects. Fluvastatin (FLU), (3R, 5S, 6E)-7-[3-(4-fluorophenyl)-1-(propan2-yl)-1H-indol-2-yl]-3,5-dihydroxyhept-6-enoic acid (Fig. 1), belongs to a group of statins, selective inhibitors of 3-hydroxy-3methylglutaryl coenzyme-A reductase (HMG-CoA reductase). It is commonly used as one of the primary hypolipidemic drugs. Both, angiotensin converting enzyme inhibitors (ZOF) and statins (FLU) are recommended in the treatment of hypertension with concomitant dyslipidemia. The use of such pharmacological profile reduces the potential of the occurrence of changes in cardiovascular and respiratory system [1]. The development of simple and fast method for simultaneous determination of drugs from these pharmacological groups, seems to be useful. Review of the literature showed that UV spectrophotometry is mainly recommended for the determination of ZOF in pharmaceutical preparations, which is useless for the determination of ZOF in the presence of other components, e.g. FLU [2]. ZOF, similar to other substances from the group of angiotensinconverting inhibitors, is often used in the treatment of hypertension together with drugs characterized by diuretic action [3]. In such a form, it was determined in the presence of hydrochlorothiazide by reversed-phase liquid chromatography (RP-LC) [4]. For the determination of zofenopril and its active metabolite (zofenoprilate) in serum, LC–MS–MS was used [5]. TLC method was used in the analysis of zofenopril and fosinopril mixture [6]. For the determination of fluvastatin, a number of analytical methods were used. The most commonly used separation methods include: HPLC with spectrophotometric [7,8] or fluorimetric [9–11] detection, liquid chromatography (LC) [12] and capillary electrophoresis [13].

Fig. 1. Chemical structure (a) zofenopril (ZOF), and (b) fluvastatin (FLU).

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Fig. 2. Zero-order absorption spectra of ZOF (22.94 lg mL and mixtures with the same concentrations.

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Electroanalytical methods have also been widely used in the analysis of fluvastatin [13–17].

Procedures Standard and working solution

Experimental

ZOF – to a 10 mL volumetric flask, approximately 10 mg of zofenopril calcium was weighed using an analytical balance, and filled with methanol to a specified volume. FLU – to a 10 mL volumetric flask, approximately 10 mg of fluvastatin sodium was weighed using an analytical balance, and filled with methanol to a specified volume. For direct measurements, solutions were diluted with methanol in a 5 mL flask, to obtain concentrations between 7.65 lg mL 1 and 22.94 lg mL 1 for ZOF, and 5.6 lg mL 1 and 28.00 lg mL 1 for FLU, respectively.

Instruments Spectrophotometer UV–VIS Cary 100 (Varian), quartz cuvettes (l = 1 cm). Computer Dell Optiplex 755; Intel(R) Core(TM)2 Duo CPU; E4500 @ 2.20 GHz; 1.18 GHz, 1.95 GB Ram (Microsoft Office 2010, Statistica 10 edition 2012). Chemicals Zofenoprilum calcium – Chengdu Sino-Strong Pharmaceutical Co., Ltd. (Chengdu, PR China), Fluvastatin sodium – USP Rockville, MD LOT F0F015. Reagents of analytical grade quality: methanol.

Spectral characteristics of ZOF and FLU In the first stage of the study, absorption spectra for ZOF (22.94 lg mL 1), FLU (28.00 lg mL 1) and mixtures of these substances at given concentrations were recorded in quartz cuvettes (l = 1 cm), in the presence of methanol as a reference solution in the UV range. Recorded absorption spectra were characterized by little variation. Lack of well-defined absorption maxima and a clear interference of recorded spectra, especially in the range of 200– 270 nm, was observed. This fact hampers the determination of the substance directly using zero-order spectra (Fig. 2). Conversion of zero-order spectra into derivatives causes their significant variation. Applying ‘‘zero-crossing’’ method, zeros of function for one of the compound were determined on the curve

Pharmaceutical formulations Two pharmaceutical preparations were used for determinations: ZOFENIL 30 manufactured by Berlin-Chemie AG, Berlin, Germany. Each ZOFENIL 30 mg tablet contains 30 mg of zofenopril calcium as 28.7 mg of zofenopril. LESCOL 40 manufactured by Novartis Pharma GmbH, Nürnberg, Germany. One capsule contains 42.12 mg fluvastatin sodium equivalent to 40 mg fluvastatin free acid.

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Fig. 4. The first D1, second D2 and third D3 derivative values for standard solutions of ZOF (—) and FLU (- - - -) (lg mL

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of derivatives. For quantitative analysis, the following wavelengths were selected: D1 k = 270.85 nm, D2 k = 286.38 nm, D3 k = 253.90 nm for ZOF, and D1 k = 339.03 nm, D2 k = 252.57 nm, D3 k = 258.50 nm for FLU, respectively. Recorded curves of derivatives for increasing concentrations of determined substance together with D1, D2, D3 plots against concentrations, are shown in Figs. 3 and 4.

5.60–28.00 y = 0.000056x 0.00002 0.9993 2.244 – 0.972 (0.903) 1.224 (0.349) 1.18 3.57 100.59 ± 1.193 101.89 1.19

M. Stolarczyk et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 66–71

Three concentrations of each analyte (7.50 lg mL 1, 15.00 lg mL 1, and 22.50 lg mL 1), repeated three times for each concentrate. Three concentrations of each analyte (12.00 lg mL 1, 15.00 lg mL 1, and 18.00 lg mL 1), repeated three times for each concentrate. a

b

5.60–28.00 y = 0.000572x 0.000243 0.9995 2.155 – 0.951 (0.750) 0.026 (0.883) 1.03 3.13 100.35 ± 1.064 99.85 1.06 7.65–22.94 y = 0.000016x 0.000002 0.9999 3.424 – 0.901 (0.382) 0.513 (0.526) 0.25 0.75 101.97 ± 2.005 101.52 1.97 7.65–22.94 y = 0.000041x + 0.000088 0.9993 3.019 1.645 (0.20) 0.949 (0.733) 0.231 (0.664) 0.87 2.64 98.77 ± 2.288 100.95 2.31 7.65–22.94 y = 0.000531x + 0.000325 0.9999 2.925 1.210 (0.27) 0.903 (0.39) 0.008 (0.93) 0.19 0.57 103.19 ± 1.573 102.70 1.52 Linearity range (lg mL 1) Regression equation Correlation coefficient (r) Durbin–Watson test Lagrange’s test (p) Shapiro–Wilk test (p) Mandel’s test (p) LOD (lg mL 1) LOQ (lg mL 1) Accuracya (%) Precisionb (%) RSD%

D1 (k 339.03 nm) D2 (k 286.38 nm)

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Fluvastatin sodium

Laboratory prepared mixtures containing different ratios of ZOF and FLU (selectivity) To a series of 5 mL volumetric flasks, different amounts of working solutions were accurately transferred and filled with methanol to a specified volume, obtaining mixtures at concentrations of 13.60 lg mL 1, 17.00 lg mL 1, 20.40 lg mL 1 for ZOF, and 11.52 lg mL 1, 14.40 lg mL 1, 17.28 lg mL 1 for FLU. For such mixtures of the active compounds, absorption spectra in the range 200–400 nm were recorded. After converting spectra into derivatives of an appropriate order, the values of derivatives against experimentally determined wavelengths were read. The amount

Parameters

Limit of detection (LOD) and limit of quantitation (LOQ) LOD and LOQ were determined using standard error of the estimate (SY) and the slope of the calibration curve (a) and calculated according to the formulas: LOD = 3.3SY/a and LOQ = 10.0SY/a.

Table 1 Validation parameters of the proposed spectrophotometric methods.

Accuracy and precision The accuracy of the method was determined as a percentage of analyte recovery for the prepared solutions at three concentrations: 80%, 100% and 120%. The precision of the method was checked using the proposed procedure for the determination of solutions containing very specific analyte amounts at three concentrations: 50%, 100% and 150%. All measurements were repeated three times, accuracy and precision of the results were calculated using the appropriate regression equation.

Zofenopril calcium

Linearity Zero-order absorption spectra for methanol solution of ZOF were plotted within the range of 7.65 lg mL 1 and 22.94 lg mL 1 and for FLU between 5.6 lg mL 1 and 28.00 lg mL 1. After conversion of the absorption spectra into the D1, D2 and D3 curves of derivative, the value of derivative was read at an appointed wavelength. The graph of D1; 2; 3 = f(c) was plotted. In the tested concentration range, linearity was maintained. To evaluate the results, linear regression equation characterizing the intersection points, correlation coefficients, Mandel’s, Shapiro–Wilk, the Durbin–Watson and Lagrange tests were used. In the evaluation of the calibration method, linear and quadratic fit were tested. Both models were compared using Mandel’s test. The p-value

Derivative spectrophotometric method for simultaneous determination of zofenopril and fluvastatin in mixtures and pharmaceutical dosage forms.

Fast, accurate and precise method for the determination of zofenopril and fluvastatin was developed using spectrophotometry of the first (D1), second ...
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