2000 Volume 49 Issue 3 Pages 181-187
An analytical method for determining potential endocrine disruptors(2, 4-dichlorophenol, pentachlorophenol, bisphenol A(BPA) and 17β-estradiol) by GC/MS with negative-ion chemical-ionization(NICI) has been developed.The target chemicals were derivatized with pentafluorobenzyl bromide(PFBBr) and the NICI of all derivatives produced an intense(M-PFB)- ion as the base peak.A trace analysis of the target chemicals was carried out on GC/MS-SIM using an (M-PFB)- ion.The effect of the reagent gas(methane) flow rate and ion source temperature on the ion abundance was examined for the optimized GC/MS condition.These were determined as follows:reagent gas-flow rate, 2.5ml/min;ion source temperature, 210°C.The detection limits of the method ranged from 0.4pg/ml to 12.5pg/ml.Good linearity of the calibration curve was obtained in the concentration range from 10pg/ml to 100ng/ml.The correlation coefficients were >0.9995 for all chemicals.The relative standard deviations of the peak areas of the target chemicals were 2.8∼9.3% for 20pg/ml, 6.2∼9.7% for 100pg/ml and 2.7∼8.6% for 1000pg/ml.The recoveries of the target chemicals from river water spiked with standards at the 10pg/ml level for 17β-estradiol, 100pg/ml level for chlorophenols and 1000pg/ml level for BPA were 91.4∼103.3%.The relative standard deviations were from 5.0 to 8.3%.When the detection limits of this method were compared with those obtained by electron ionization(EI) of the trimethylsilylated derivatives, the sensitivities of NICI were 6.5∼150 times higher than those of EI.
