Determination of alkylphenols by GC/negative-ion chemical-ionization MS

An analytical method for the determination of potential endocrine disruptor s, seven alkylphenols including nonylphenol and 4-t-octylphenol, by gas chr omatography/mass spectrometry (GC/MS) with negative-ion chemical-ionization (NICI) has been developed. First, the detection limits by GC/MS-SIM with e lectron ionization (EI) and NICI were compared for the underivatized and pe ntafluorobenzyl (PFB) derivatives of alkylphenols. The NICI-SIM of PFB deri vatives used an (M-PFB)(-) ion as the monitoring ion. The reagent gas (meth ane) flow rate and the ion-source temperature were determined to be 2.5 ml/ min and 250 degrees C, respectively, for the optimized NICI-SIM conditions. In the case of EI-SIM, the sensitivities of PFB derivatives were 2.1 simil ar to 6.3 times higher than those of underivatized target chemicals. Furthe rmore, the sensitivities of PFB derivatives by NICI-SIM were 67 similar to 300 times higher than those of underivatized target chemicals by EI-SIM. Th e detection limits by NICI-SIM ranged from 1.0 pg/ml to 33 pg/ml. This meth od also provides good linearity of the calibration curve and repeatability. The correlation coefficients of calibration curve were > 0.9995 for all ch emicals in the concentration range from 1 pg/ml to 10 ng/ml. The relative s tandard deviations of the peak areas of the target chemicals were 3.6 simil ar to 6.8% for 10 pg/ml, 2.3 similar to 4.9% for 100 pg/ml and 2.4 similar to 3.5% for 1000 pg/ml. The recoveries of the target chemicals from a river -water sample spiked with standards at 10 pg/ml levels for 4-n-pentylphenol , 4-n-hexylphenol, 4-n-heptylphenol and 4-noctylphenol, 100 pg/ml levels fo r 4-t-butylphenol and 4-t-octylphenol and 5000 pg/ml levels for nonylphenol were 77.9 similar to 102%. The relative standard deviations were to be fro m 4.1 to 12%.