Determination of antibacterial quaternary ammonium compounds in lozenges by capillary electrophoresis

doi:10.1016/S0021-9673(97)00986-2

Journal of Chromatography A

Volume 798, Issues 1–2, 6 March 1998, Pages 335-343

https://doi.org/10.1016/S0021-9673(97)00986-2 Get rights and content

Abstract

A method for the specific determination of three quaternary ammonium compounds, benzalkonium chloride, cetylpyridinium chloride and dequalinium chloride, used as antibacterial agents in candy-based lozenges, is described based on capillary zone electrophoresis. It is shown that, following optimisation of buffer composition with respect to organic modifier concentration, pH and buffer concentration together with the inclusion of sodium dodecylsulphate as an ion-pairing agent in the case of dequalinium chloride, these analytes migrate in less than 5 min. The resultant electrophoretic peaks are sharp and readily quantified. The individual alkyl components of benzalkonium chloride can be resolved as can related impurities in dequalinium chloride lozenges. The quantitative characteristics of the assay method, based on peak areas normalised with respect to migration times, are reported and the method is compared with a previously published method based on liquid chromatography.

Introduction

The quaternary ammonium compounds benzalkonium chloride (BZK), cetylpyridinium chloride (CPC) and dequalinium chloride (DQC) are widely used as antimicrobial agents in the treatment of common infections of the mouth and throat. It has been shown that candy-based lozenge formulations are more effective in this respect than tablet preparations [1]. Classical methods of analysis of these compounds such as non-aqueous titration 2, 3and ion-pairing extraction followed by spectrophotometric estimation 4, 5, 6, 7, 8are unsuitable for the general determination of these compounds in single lozenges due to a lack of both selectivity with respect to excipients and also sensitivity. Assay methods for certain of these compounds have appeared in the literature based on various chromatographic techniques. Several methods including TLC [9], GLC [10]and HPLC 11, 12, 13, 14, 15, 16, 17, 18, 19have been published for BZK. Fewer methods have appeared in the literature for CPC or DQC 7, 20, 21, 22, 23, 24, 25. These include a method for identification of CPC and DQC in mouthwash by TLC and a method in which CPC and DQC were estimated by a volumetric procedure [24]. Methods have been reported for the determination of DQC in drug preparations (lozenge, ointment and tablet) based on ultraviolet [7]and infrared spectrophotometry [25]. LC methods for these compounds, because of their hydrophobicity, have required the use of cyanopropyl stationary phases or C₈ and C₁₈ with a very non-polar mobile phase. Of the LC methods in the literature only one has evaluated the technique for the determination of these three compounds in candy-based lozenges and it was found that the cyanopropyl stationary phase used was not adequately selective for the quantitative determination of BZK in the lozenges [26].

Capillary electrophoresis offers possible advantages over LC in terms of selectivity and also peak capacity as a result of the increased efficiency attainable with this technique. This potential for resolution has been demonstrated in several reports in the literature on the separation of diverse quaternary ammonium compounds 12, 27, 28, 29, 30, 31. In these reports the emphasis has been on using the resolving power of CE to separate individual compounds on the basis of their differing alkyl chains. A major difficulty in obtaining optimum peak shape and controlling migration times of such quaternary ammonium compounds has been attributed to their propensity for adsorption on the silica capillary and in the case of long alkyl chains for forming micelles, since the initial concentrations introduced into the capillary is often in excess of the critical micelle concentration. Both of these effects have been overcome by the inclusion of appreciable concentrations of tetrahydrofuran in the running buffer 27, 28. Subsequently the effect of adding other organic liquids on the separation of alkylbenzyl quaternary ammonium compounds was shown to be general in improving separation 29, 30. The application of both direct and indirect UV absorption for the determination of alkylbenzyl and alkyl quaternary ammonium compounds has been demonstrated and a comparison made between CE and LC for the determination of various important anionic, cationic and non-ionic surfactants [12].

Relatively few reports have appeared concerning the CE behaviour of the quaternary ammonium compounds used as antibacterial agents in lozenges. There has been one report on CPC in mouthwash [12]but no CE methods have been located for DQC. It is the purpose of the present work to describe a capillary electrophoresis method for the determination of BZK, CPC and DQC in commercial candy-based lozenges. It is intended to show the capability of capillary electrophoresis in resolving the active ingredient from the various other lozenge components and to compare the results obtained both in terms of resolution and quantitation characteristics with those obtained by the previously published method based on LC [26]. This is felt to be of some interest since CE is seen currently as the analytical method capable of providing an alternative to liquid chromatography.

Section snippets

Equipment

A Hewlett-Packard HP3D capillary electrophoresis system was used, fitted with an unmodified silica capillary 50 μm internal diameter of total length 275 mm and effective length 205 mm. Detection was by diode-array UV spectrophotometry. Detection wavelengths used were optimised for the individual compounds and were 210, 254 and 230 nm for BZK, CPC and DQC, respectively. The hydrodynamic injection mode was used for all measurements at a pressure of 50 mbar with an injection time of 10 s. The

Results and discussion

Fig. 2 shows the separation among the three alkyl benzyl components C₁₂, C₁₄ and C₁₆ of BZK and the internal standard diphenhydramine hydrochloride. Fig. 3 shows a representative electropherogram of a typical BZK lozenge sample and internal standard. Only the C₁₂ and the C₁₄ benzyls are seen to be present. This is consistent with other work concerning BZK in eye drops by HPLC [19]. The identities of the peaks were established by spiking with the appropriate species. Resolution between all

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Determination of antibacterial quaternary ammonium compound in lozenges and human serum by resonance light scattering technique
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A method for the specific determination of an antibacterial quaternary ammonium compound Dequalinium chloride (DQC) was described in this paper. At pH 0.5, the resonance light scattering (RLS) intensity of sodium dodecyl benzene sulfonate (SDBS) remarkably was enhanced by adding DQC. A RLS peak at 392.0 nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DQC in the range of 0.096–2.88 μg/mL. The detection limit was 2.98 ng/mL and the correlation coefficient was r = 0.9988 (n = 9). The method was applied to the analysis of DQC in lozenges and human serum. The results indicated that the method was sensitive, simple, practical and useful in the clinical assay.
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Determination of antibacterial quaternary ammonium compounds in lozenges by capillary electrophoresis

Abstract

Introduction

Section snippets

Equipment

Results and discussion

J. Pharm. Sci.

J. Am. Pharm. Assoc. Sci. Ed.

Int. J. Pharm.

J. Chromatogr. A

J. Chromatogr.

J. Pharm. Sci.

J. Chromatogr. A.

J. Chromatogr.

J. Chromatogr.

J. Pharm. Biomed. Anal.

J. Pharm. Sci.

Int. J. Pharm.

J. Pharm. Sci.

J. Chromatogr.

J. Chromatogr.

J. Chromatogr.