Optimization of Dispersive Liquid-Liquid Microextraction of Irganox 1010 and Irgafos 168 from Polyolefins Before Liquid Chromatographic Analysis

A new dispersive liquid-liquid microextraction method has been established for extraction of two antioxidants, Irganox 1010 and Irgafos 168, from polyolefins. The extracts were analyzed by liquid chromatography. Carbon tetrachloride at microliter levels and acetonitrile at milliliter levels were used as extraction and dispersive solvents, respectively. Central-composite design and response-surface methodology were used as experimental strategies for modeling and optimization. The effects of experimental conditions on extraction were investigated by modeling extraction recovery as the response. The experimental design was performed at five levels of the operating conditions. Nearly the same results for optimization were obtained by using the one-variable-at-a-time and central-composite-design methods: sample size 5-10 mg, dispersive solvent acetonitrile (2 mL), extraction solvent carbon tetrachloride (200 mu L); extraction temperature 100 A degrees C, and extraction time 3 h. Under the optimum conditions the calibration plots were linear over the range 50-2,000 mu g L-1 in solution. The relative standard deviation of the method for six replicate experiments was 7.0 and 4.9% for Irganox 1010 and Irgafos 168, respectively.