Research Article A novel RP-HPLC method for simultaneous determination of potassium sorbate and sodium benzoate in soft drinks using C 18 -bonded monolithic silica column Potassium sorbate and sodium benzoate are food additives that are generally employed for prevention of food spoilage originating from bacteria, molds or yeasts. Although these compounds were generally recognized as safe due to their low risk of acute and chronic toxicity, they have limitations of usage to protect human health. Development and vali- dation of a novel RP-HPLC method, in which a C 18 -bonded monolithic silica column was used as stationary phase to assay these compounds, is described for the first time. Aliquots of 10 mL of samples were injected into chromatograph and eluted using phosphate buffer (0.025 M, pH 2.0)–water–acetonitrile (50:45:5, v/v/v) solution, which was pumped at the rate of 3.0 mL/min. To sharpen the peaks, 10 mM octylamine was added to the mobile phase. Potassium sorbate and sodium benzoate were detected at about 12 th and 14 th min, respectively, and quantified at 230 nm using photodiode array detector. A total of 41 samples were prepared by simply filtering through 0.45 mm filters after sonication, and injected into the system without any pre-treatment steps. Applicability of the method was demonstrated by performing total procedure on samples of different brands and types, and their compliance to official regulations was assessed. Keywords: Direct sample injection / Food analysis / Monolithic column / Potassium sorbate / Sodium benzoate DOI 10.1002/jssc.201100172 1 Introduction The importance of food and diet quality has been attracting public attention more than ever for the last two decades, especially due to the increase in the incidence of diseases that was directly or indirectly related to nutrition habits. As a natural outcome, analysis of food additives came into focus, especially for the assessment of their harmful potentials and quantitative or qualitative value of risks related to their use. Food additives are generally added to processed foods for a specific purpose such as prevention of spoilage, conservation or fortification of color, flavor, texture, or control of pH, moisture, crispness etc. Sodium benzoate (Na-BEN) and potassium sorbate (K-SOR), as being highly preferred food preservatives, work well in acidic media to inhibit yeasts, molds and bacterial growth. They exist in a variety of products, such as pharmaceuticals and cosmetics, but more frequently in foods, e.g. non-alcoholic drinks, jams and fruit juices. The chemical structures of Na-BEN and K- SOR are given in Fig. 1. These compounds are effective in acidic media as preservative, and are not recommended to use in environments above pH 6.5. Briefly, Na-BEN (also coded as E-211) naturally exists in cherry, clove, cinnamomum and European cornel. Physiologically, it irri- tates gastric mucosa, stimulates bronchoalveolar secretion and promotes histamine discharge and allergic reactions. It has an acceptable daily intake of 5 mg/kg. On the other hand, K-SOR (also coded as E-202), whose name comes from Sorbus aucuparia (rowan), is also recognized as a safe additive and has limited adverse reactions such as promo- tion of pseudo-allergic reactions; and its acceptable daily intake is 25 mg/kg. The use of food additives is limited by regulatory authorities in different countries, and Na-BEN and K-SOR also have limitations of usage to protect human health. The Food and Drug Administration regulates the usage of Na- BEN and K-SOR as food additives in the United States of America. The Food and Drug Administration lists Na-BEN and K-SOR as substances that are generally recognized as safe with a maximum permitted concentration of 0.1% in Nafiz O. Can Goksel Arli Yigit Lafci Department of Analytical Chemistry, Faculty of Pharmacy, Anadolu University, Yunusemre Campus, Eskisehir, Turkey Received February 28, 2011 Revised April 1, 2011 Accepted April 1, 2011 Abbreviations: ICH, International Conference on Harmonization; K-SOR, potassium sorbate; Na-BEN, sodium benzoate; USP, United States Pharmacopeia Correspondence: Dr. Nafiz O. Can, Department of Analytical Chemistry, Faculty of Pharmacy, Anadolu University, Yunu- semre Campus, Eskisehir 26470, Turkey E-mail: nafizoc@anadolu.edu.tr Fax: 190-222-3350750 & 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com J. Sep. Sci. 2011, 34, 2214–2222 2214