Fate of Preharvest-Sprayed Dicofol in Date Fruits: Residue Analysis by HPLC-UV

Abstract

The fate of pre-harvest-sprayed dicofol (DCF) on date fruits has been investigated. Date palm trees, variety Sukkari, were sprayed with DCF (18.5%, EC) at the rate of 200 ml/100 L. DCF residues in date fruits were determined at different time intervals using high performance liquid chromatography (HPLC) with UV detection at 220 nm. The method was based on extraction with ethyl acetate. The results showed that the HPLC response was linear (r2 > 0.98) for DCF in the range of 0.0 to 2 mμg. The limits of detection and quantification were 0.24 and 0.80 ppm, respectively. The method was developed by using spiked date fruits at levels of 0.25, 0.50 and 1.0 ppm. Recovery percentage was satisfactory with a range of 77.2 to 103.6% and an RSD ranging from 6.33 to 11.84%. A biphasic model was assumed in order to carry out the statistical study of the loss of DCF from date fruits. The results showed that the initial deposit of DCF on date fruits was 11.22 ppm, while the residue value decreased to 1.90 ppm seven days after spraying, which is below the tolerance limit for fruits and vegetables (2 ppm). Also, the data indicate that there was a faster rate of DCF loss in the first phase than the second one. This is clearly reflected in the t1/2 values, where the half-lives of DCF were 1.35 and 38.52 days, for the first and second phase model, respectively. The described method is rapid and sensitive, with satisfactory recoveries and reproducibility.

Keywords

• date fruits, fate, dicofol, residue, limit of detection, half-life