Gas chromatographic/mass spectrometric determination of daminozide in high protein food products.

A gas chromatographic/mass spectrometric (GC/MS) method for determining daminozide in high protein products has been developed. Daminozide is hydrolyzed in the presence of a strong base to form unsymmetrical dimethylhydrazine (UDMH) which is then distilled from the food matrix. A stable derivative is formed by reacting UDMH with salicyladehyde to form salicyaldehyde dimethylhydrazone. This derivative is separated and quantitated by GC/MS using selected ion monitoring (SIM) of key ions in the fragmentation pattern: m/z 164 (molecular ion of hydrazone) and m/z 120 (C7H6ON). An internal standard, 4-nitroanisole, is monitored at m/z 153 (molecular ion) and m/z 123 (C6H5O2N). The limit of detection is 0.01 ppm daminozide in a 50 g sample; however, because of variation at low levels, the limit of quantitation is 0.1 ppm. Recoveries are 90% or greater from peanuts and peanut butter spiked at the 0.1-2 ppm level. Reproducibility of the method depends on the food matrix and is 26% RSD in the worst case. Data are compared for the GC/MS method and the official EPA colorimetric procedure. Results showed a high bias in the colorimetric method, especially when roasted peanut products were analyzed.