This paper describes a simple and sensitive method for determining alkylphenols namely 4-tert-octylphenol (4-t-OP) and the isomers of 4-nonylphenol (4-NPs) present in various types of baby-food purees. The method involves extracting a sample with n-hexane for 1 h using a modified Nielson-Kryger steam distillation extraction system and then identifying and quantitating the alkylphenols using a gas chromatography-mass spectrometry (GC-MS) operated in the selected ion monitoring (SIM) mode. The extraction conditions were evaluated at various values of pH of the sample solution. The limits of quantitation for this method were 0.2 ng/g from 1.0 g (wet weight) samples of 4-t-OP and the 4-NPs. The intra- and interbatch precisions and accuracies were also determined. The precision, in terms of the relative standard deviation (RSD), were less than 8%. Most of the recoveries of the alkylphenols from various spiked samples exceeded 60%, while the values of RSD ranged from 1% to 10%. Alkylphenol residues were detected in baby-food purees at concentrations of up to 19 ng/g (wet weight) for 4-t-OP and up to 21 ng/g (wet weight) for the 4-NPs.
- GC-MS analysis
- Steam distillation extraction