Survey of Total Tetrahydrophthalimide in Baby Foods Using Both Enzyme-Linked Immunosorbent Assay and Gas Chromatography/Mass Spectrometry: A Comparative Study

An enzyme-linked immunosorbent assay (ELISA) method was compared with a gas chromatographic/ mass spectrometric (GC/MS) method for determining the concentration (in parts per million) of the combination of captan and its degradation product tetrahydrophthalimide (THPI) in 13 fruit samples and in a survey of baby foods. Ninety baby foods (49 fruits, 28 juices, and 13 vegetables) from 2 different suppliers were sampled. All captan in the samples was converted to THPI before each analysis. None of the samples contained a concentration of combined captan and THPI that violated the maximum residue limit of 5.0 ppm. Eight samples of baby food tested positive for THPI at levels ranging from 0.019-0.041 ppm by the GC/MS method, whereas 20 samples tested positive in the ELISA assay. All samples that tested positive with the GC/MS method also tested positive with the ELISA method. Thirteen percent of the baby food samples tested false positive with the ELISA method. The ELISA assay also gave higher values than the GC/MS method. The ELISA method can be effectively used as a primary screening tool to select samples testing positive for THPI. The concentration of THPI in these samples can then be verified using the GC/MS method.