Performance study of analytical method for ethoxyquin in fruit]

A performance study of an analytical method of ethoxyquin (ET) in apples and pears was conducted. In the proposed method, the sample was homogenized with thiourea and ET was extracted with acetone instead of hexane used in the official analytical method for ET, in order to improve the extraction efficiency. Furthermore, dibutyl hydroxytoluene was added in the test solution to prevent the decomposition of ET. For evaluation of the method, ET spiked into apples and pears at the level of 0.2 mug/g was determined in replicate in six laboratories. Mean recoveries from apple, pear and Japanese pear were 85.3, 83.0 and 83.9%, respectively. Repeatability relative standard deviation values were 3.8similar to4.7% and reproducibility relative standard deviation values were 7.8similar to11.3%. The detection limits were 0.001similar to0.025 mug/g in the six laboratories; this value may reflect instrument performance. ET spiked into apples and pears at the level of 0.2 mug/g was detected by both LC/MS and GC/MS.