Determination of Specific Migration of m-phthalic Acid and p-phthalic Acid in Food Contact Materials by Ultra High Performance Liquid Chromatography

A method was developed for the simultaneous determination of migration amount of m-phthalic acid and p-phthalic acid in food contact material of ethylene terephthalate (PET) by ultra high performance liquid chromatography (UHPLC). Parameters for migration test were as follows:① national standards of GB 5009.156-2016 and GB/T 23296.1-2009 were adopted as reference methods; ② 4% (volume fraction) acetic acid solution, 10% (volume fraction) ethanol solution, 20% (volume fraction) ethanol solution, 50% (volume fraction) ethanol solution and olive oil were used as simulant solutions; ③ migration temperature was 70℃, and migration time was 2 h. The obtained migration solution was analyzed by UHPLC. ShimSen-VD C₃₀ chromatographic column was selected as the stationary phase. The mixture of methanol and 7.5 mmol·L^-1 potassium dihydrogen phosphate-phosphate buffer solution (pH 3.0) at volume ratio of 40:60 was used as the mobile phase for isocratic elution, and the content of p-phthalic acid and m-phthalic acid was determined with DAD at 230 nm. Using phthalate as the internal standard, a series of mixed standard solutions were prepared with above 5 simulant solutions. The results showed that linearity ranges of p-phthalic acid and m-phthalic acid was found within 0.5-15.0 mg·L^-1, with detection limits (3S/N) in the range of 0.03-0.07 mg·L^-1. The spiked recovery test was made on the actual sample at three concentration levels, giving results of p-phthalic acid and m-phthalic acid in the range of 92.4%-106%, and RSDs (n=6) of the determined values (n=6) ranged from 0.17% to 5.0%. The PET samples were analyzed by the proposed method, and no migration of these two substances was found.