The residual caprylohydroxamic acid (CAP) in chicken and eggs was determined by gas liquid chromatography (GC) with an electron capture detector (ECD) of the derivative formed by reaction with pentafluorobenzoyl chloride (PFB-Cl).
The methanol extract of the sample was cleaned up by ion exchange column chromatography on Amberlite CG-400 (OH form) with 10% sodium chloride-methanol (1→10) mixture as an eluent.
CAP reacted quantitatively with PFB-Cl (20μl) in saturated sodium bicarbonate: methanol (1.5:0.5) solution in a boiling water bath for 2 minutes. The reaction product was subjected to GC after extraction with n-hexane.
GC was performed on a 2m glass column packed with 5% Thermon 1000 and 5% SP-2100 on Gaschrom Q (0.25+1.75). The column temperature was 190°C and the carrier gas (N2) flow rate was 20ml/min. Under these conditions, the retention time of the reaction product is about 12 minutes.
A linear calibration curve was obtained from 0.02ppm to 0.1ppm of CAP. The minimum detectable amount was 20pg of CAP and 0.01ppm in samples. The recoveries of CAP added to chicken and eggs were in the range of 90.7%-90.0%.