Mj. Lydy et al., COMPARISON OF GAS-CHROMATOGRAPHY MASS-SPECTROMETRY AND IMMUNOASSAY TECHNIQUES ON CONCENTRATIONS OF ATRAZINE IN STORM RUNOFF, Archives of environmental contamination and toxicology, 31(3), 1996, pp. 378-385
Gas chromatography/mass spectrometry (GC/MS) and enzyme-linked immunos
orbent assay (ELISA) techniques were used to measure concentrations of
dissolved atrazine in 149 surface-water samples. Samples were collect
ed during May 1992-September 1993 near the mouth of the White River (I
ndiana) and in two small tributaries of the river. GC/MS was performed
on a Hewlett-Packard 5971A(1) with electron impact ionization and sel
ected ion monitoring of filtered water samples extracted by C-18 solid
phase extraction; ELISA was performed with a magnetic-particle-based
assay with photometric analysis. ELISA results compared reasonably wel
l to GC/MS measurements at concentrations below the Maximum Contaminan
t Level for drinking water set by the U.S. Environmental Protection Ag
ency (3.0 mu g/L), but a systematic negative bias was observed at high
er concentrations. When higher concentration samples were diluted into
the linear range of calibration, the relation improved. A slight posi
tive bias was seen in all of the ELISA data compared to the GC/MS resu
lts, and the bias could be partially explained by correcting the ELISA
data for cross reactivity with other triazine herbicides. The highest
concentrations of atrazine were found during the first major runoff e
vent after the atrazine was applied. Concentrations decreased througho
ut the rest of the sampling period even though large runoff events occ
urred during this time, indicating that most atrazine loading to surfa
ce waters in the study area occurs within a few weeks after applicatio
n.