optimization conditions for determination of cosmetic preservatives using ion-exclusion chromatography

an ion chromatography (ic) method for simultaneous determination of benzoic, salicylic and sorbic acids was developed. in this method the samples were purified by solid-phase extraction. the analytes were then eluted with methanol from c18 cartridge. the separation was performed on ion-exclusion column by an isocratic elution with 0.25 mmol /l sulfuric acid solution containing 20% (v/v) acetone as elute. the calibration curves showed good linearity with suppressed conductivity detection.under this condition, separation of the three components was achieved in less than 23 min. the detection limit calculated as the concentration corresponding to three times the background noise, was 0.1, 0.15 and 0.2 mg/ l for benzoic acid, salicylic acid and sorbic acid respectively. the method was successfully applied to analysis of various cosmetic products.