[Simultaneous determination of ammonium and six alkylamines in cosmetics by ion chromatography]

A method for the simultaneous determination of ammonium and six alkylamines in cosmetic products by ion chromatography (IC) was developed. The sample pretreatment process and the separation resolution of chromatography were investigated. The samples were extracted by 100 mmol/L acetic acid-20% (v/v) acetonitrile solution at room temperature, and then solid phase extraction (SPE) column was used to eliminate the interferences. The influences of pH value, organic solvent and coexisted ions were investigated. The separation was carried out on IonPac CS17 (250 mm x 4 mm)analytical column and IonPac CG17 (50 mm x 4 mm)guard column using 1.5 - 15 mmol/L methanesulfonic acid and 0.5% - 5% (v/v) acetonitrile gradient elution at a flow rate of 1.0 mL/min at 24 degrees C, coupled with suppressed conductivity detector. Under the optimum conditions, a measurement could be completed less than 26 min. The linearity ranged from 0.3 to 15 mg/L, the detection limits and the quantification limits were in the ranges of 2.1 - 7.9 mg/kg and 7 - 26 mg/kg, respectively. The method was successfully employed for the determination of ammonium, methylamine, dimethylamine, trimethylamine, ethylamine, propylamine and butylamine in samples including cleaning, body lotion, skin-bleaching, sun block, marcel, hair dye and pilatory cosmetics with the recoveries of 80.2% - 109.2% and the relative standard deviations (RSDs) of 0.5% - 3.1%. The method offered high selectivity, sensitivity, and gave satisfactory results for real sample analysis.