Rapid preconcentration method for the determination of azadirachtin-A and -B, nimbin and salannin in neem oil samples by using graphitised carbon solid phase extraction

A simple and rapid method involving solid phase extraction and liquid chrom atography for the determination of azadirachtin-A and -B, nimbin and salann in at nanogram levels in neem oil samples is presented. The neem oil sample s are defatted and the compounds of interest extracted by mixing the sample with hexane and passing the hexane solution through a graphitised carbon b lack column. After washing the column with 2 mi of hexane, azadirachtin-A a nd -B, nimbin and salannin are eluted with 5 ml of acetonitrile and quantif ied using HPLC with UV detection. The recoveries of azadirachtin-A and -B, nimbin and salannin in fortified oil samples were 97.4-104.7%. The upper li mit of quantification is up to 100 mu g ml(-1) without any additional clean -up and with little interference from lipids during the analysis by HPLC. T he method was successfully applied to various neem oil samples collected fr om different locations in India.