Summar y A liquid chromatography/tandem mass spectrometric (LC/MS/MS) procedure for the determination of fungicide 1,1＇-[iminodi (octamethylene)]di-guanidine (iminoctadine) in water samples has been developed. A direct derivatization of iminoctadine in watetr samples with benzoyl chloride (C 6 H 5 COCl) was applied to the procedure for the quantitative detection, in order to prevent the loss of iminoctadine in analytical processes because of the absorption activities. Iminoctadines in a water sample were treated with C 6 H 5 COCl to form the benzoate derivative, and then the derivative was extracted into dichloromethane. The extract was cleaned up using a florisil cartridge column, and the eluate was exchanged to acetonitrile. The derivative of iminoctadine in acetonitrile solution was determined by LC/MS/MS. The method detection limit for iminoctadine was 0． 22 ng/L and the mean recoveries in water samples ranged from 80 to 101 % (c.v. 4． 0-8． 9 %). It was found that this method enables the reliable determination of iminoctadine residues in water samples at ppt level and is superior in sensitivity and reliability to the HPLC postcolumn derivatization fluorescence detection method which is the official analytical method for iminoctadine in Japan. Moreover, to clear the behavior of iminoctadine in aquatic environment, a river water sample was fractionated into hydrophobic and hydrophilic fractions, and recovery tests of iminoctadine added to the fractions were conducted using this determination method. The results showed that the behavior of iminoctadine in aquatic environment is affected not only by suspended substances but by aquatic fumic substances of humic and fulvic acids. Some of iminoctadine in aquatic environment are likely incorporated into aquatic fumic substances by hydrogen bond or combining with them to form amides.
