Chiang Mai Journal of Science

A study was undertaken to develop a method for carbofuran and carboxin residues analysis in cabbages (Brassica oleracea L. cv. white headed cabbage cruciferae) by HPLC equipped with UV detector. Cabbage samples were extracted with ethyl acetate followed by solid phase extraction (SPE) with florisil sorbent for cleaning up. The SPE condition was achieved by employing 3 ml of 70% acetonitrile/water as eluting solvent. The extracts were separated by reversed phase C18 column of HPLC-UV. The mobile phase used was 25% acetonitrile/water at 0.8 ml/min of the flow rate and detection wavelength at 205 nm. Linearity of the response was obtained with linear determination coefficients higher than 0.996. The lower limit of detection (LOD) value was in the range of 0.02-0.06 μg/ml. Percent recoveries for carbofuran and carboxin were 94.7% ± 0.7 and 90.0% ± 1.2, respectively. The method was employed for analysis of these two pesticide residues in 11 cabbage samples from various types of market. Five of those have safety labels and three of them are certified, while another six have no safety label. Carbofuran residue was not detected in any cabbage samples while the carboxin was found in three samples from both with and without safety label. Its residue was in the range of 0.054 to 0.414 mg/kg fresh weight. The samples were confirmed by HPLCfluorescence and GC-MS, for carbofuran and carboxin respectively. The selected analytical methods gave agreeable result with each others. The carboxin, which was first detected by HPLC-UV in some of the extracted sample, was also found by GC-MS at the same level.