An analytical method for the determination of twelve pesticides in river wa
ter with liquid chromatography/mass spectrometry (LC/MS) has been developed
. Under reversed-phase liquid-chromatographic conditions, twelve pesticides
were analyzed using electrospray ionization(ESI) with a simultaneous acqui
sition of positive ions and negative ions. The effects of the liquid-chroma
tographic mobile phase on the separation of pesticides, the fragmentor volt
age and the capillary voltage with ESI oil the sensitivity of pesticides we
re examined. The maximum sensitivities for all pesticides in simultaneous a
cquisition were accomplished by setting the capillary voltage at 2500 V. La
rge volumes of river-water samples were directly injected into the precolum
n, and then twelve pesticides were separated by an analytical column with a
column-switching technique. The limit of detection (LOD) of these pesticid
es ranged from 0.7 to 2.1 pg/ml. The overall recoveries of pesticides were
from 83.4 to 109.4% (RSD(n = 5) were from 1.1 to 7.2%) for drinking water.