Determination of daminozide residues in apple pulp using HPLC-DAD-UV

This paper reports an HPLC-UV method to determine daminozide residues in apple pulps adopting the recently introduced EU limit of 0.01 mg/kg for baby food preparation (Commission Directive 1999/39/CE). The method is based on alkaline hydrolysis of daminozide to N',N'-dimethylhydrazine (UDMH), which is recovered by distillation and subsequently derivatizated with salicyl aldehyde to salicyl aldehyde-N,N-dimethylhydrazone under strongly basic conditions. The resulting solution was cleaned up with Extrelut 20 NT and dichloromethane as eluent, then analyzed by HPLC with a C18 column and a mobile phase programmed from 50:50 AcCN/H(2)O to 100% AcCN. The salicyl aldehyde-N,N-dimethylhydrazone was selectively detected through two diagnostic UV absorption maxima at 295 and 325 nm, which have strong molar absorbivities. Recoveries of daminozide at 0.01 mg/kg were above 80%. The limits of detection (LODs) of salicyl aldehyde-N,N-dimethylhydrazone expressed as daminozide concentration were 100 pg/microL at 295 nm and 150 pg/microL at 325 nm, and the limits of quantitation (LOQs) of daminozide were 0.0013 mg/kg at 295 nm and 0.0022 mg/kg at 325 nm.