Development and Validation of an HPLC/UV/MS Method for Simultaneous Determination of 18 Preservatives in Grapefruit Seed Extract

Markus Ganzera,* Anita Aberham, and Hermann Stuppner
Institute of Pharmacy, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria
J. Agric. Food Chem., 2006, 54 (11), pp 3768–3772
DOI: 10.1021/jf060543d
Publication Date (Web): May 9, 2006
Copyright © 2006 American Chemical Society

Abstract

Grapefruit seed extracts are used in cosmetics, food supplements, and pesticides because of their antimicrobial properties, but suspicions about the true nature of the active compounds arose when synthetic disinfectants such as benzethonium or benzalkonium chloride were found in commercial products. The HPLC method presented herein allows the quality assessment (qualitative and quantitative) of these products for the first time. On the basis of a standard mixture of 18 preservatives most relevant for food and grapefruit products, a method was developed allowing the baseline separation of all compounds within 40 min. Optimum results were obtained with a C-8 stationary phase and a solvent system comprising aqueous trifluoroacetic acid, acetonitrile, and 2-propanol. The assay was fully validated and shown to be sensitive (LOD ≤ 12.1 ng on-column), accurate (recovery rates ≥ 96.1%), repeatable (σrel ≤ 3.5%), precise (intra-day variation ≤ 4.5%, interday variation ≤ 4.1%), and rugged. Without any modifications the method could be adopted for LC−MS experiments, where the compounds of interest were directly assignable in positive ESI mode. The quantitative results of several products for ecofarming confirmed previous studies, as seven out of nine specimens were adulterated with preservatives in varying composition. The samples either contained benzethonium chloride (2.5−176.9 mg/mL) or benzalkonium chloride (138.2−236.3 mg/mL), together with smaller amounts of 4-hydroxybenzoic acid esters, benzoic acid, and salicylic acid.

Keywords: Grapefruit; Citrus paradisi; pesticide; preservative; LC; LC−MS

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History

  • Published In Issue May 31, 2006
  • Received for review February 24, 2006. Revised manuscript received April 5, 2006. Accepted April 6, 2006.

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