Analysis of phenolic compounds in health care products by low‐pressure liquid‐chromatography with monolithic column and chemiluminescent detection

Abstract This paper presents a new application for monolithic columns with low‐pressure chromatographic separation using an flow injection analysis configuration with chemiluminescent detection for the determination of a mixture of phenolic compounds: phloroglucinol, 2,4‐dihydroxybenzoic acid, salicylic acid, methyl paraben and n ‐propyl gallate. The procedure consists of the separation of these compounds on a reverse‐phase ultra‐short monolithic column with pH 3.0 acetate buffer and 5% acetonitrile as carrier phase. The detection is based on a chemiluminescence measurement coming from Ce(IV)–Rhodamine 6G chemistry with the incorporation of two different chemiluminescent chemical conditions in the chromatographic setup in order to enhance the sensitivity for the different phenolic compounds. All separation and detection variables were optimized to propose a determination method. The analysis is performed in 280?s, with the sampling frequency being some 13 h −1 . The calibration function is a double reciprocal function obtaining good results within two orders of magnitude. The limits of detection were 8.8 × 10  −8   m (phloroglucinol), 2.7 × 10  −8   m (2,4‐dihydroxybenzoic acid); 2.3 × 10  −8   m (salicylic acid); 5.2 × 10  −8   m (methyl paraben) and 4.1 × 10  −6   m ( n ‐propyl gallate), and the relative standard deviations at a medium level of the linear range were 4.4% (phloroglucinol), 2.8% (2,4‐dihydroxybenzoic acid), 5.2% (salicylic acid), 3.6% (methyl paraben) and 6.8% (n‐propyl gallate). The method was applied and validated satisfactorily for the determination of these compounds in healthcare products, comparing the results against an HPLC reference method. Copyright © 2009 John Wiley & Sons, Ltd.