Determination of daminozide residues in apples using gas chromatography with nitrogen-phosphorus detection

A method was developed for the determination of daminozide in apples using gas chromatography (GC) with nitrogen-phosphorus detection (NPD). Daminozide is hydrolysed to 1,1-dimethylhydrazine (UDMH) by alkaline digestion. The UDMH generated is distilled from the apple matrix, derivatized with 2-nitrobenzaldehyde and analysed by GC-NPD. The limit of detection (LOD) and the limit of quantitation (LOQ) for daminozide are 1.9 mu g/kg and 6.2 mu g/kg, respectively, in a 10-g sample. Average recoveries from apples spiked at the 12 and 60 mu g/kg level are between 88% and 108% with R.S.D.s less than or equal to 6.9%. Additives used by others, such as calcium chloride, titanium chloride or zinc, have no positive effect on the extraction of daminozide from samples with incurred residues. The repeatability for these samples, containing 0.018, 0.13 and 1.8 mg/kg daminozide, is 4.0%, 4.4% and 2.5%, respectively.