The determination of atrazine in estuarine waters in the presence of the common cross-reactants deethylatrazine, deisopropylatrazine, and simazine has been investigated using direct rapid pesticide immunodetection (RaPID) magnetic particle-based solidphase ELISA. Different parameters such as least detectable dose, 50% inhibition concentration, and percentage of cross-reactivity, determined by estimating the amount of compound required to displace 50% of the enzyme conjugate to the amount of atrazine, were calculated. Estuarine water samples containing various chlorotriazine herbicides from a pilot monitoring program (with levels varying from 0.008 to 0.326 ,ug/ L) were compared by using the RaPlD assay and gas chromatography-nitrogen/phosphorus detection (GC-NPD). Both analytical methods showed good correlation for atrazine and total chlorotriazines for most of the estuarine water samples analyzed. Gas chromatography/mass spectrometry (GC/MS) was used for confirmation purposes, and false positives were detected.
The disappearance of fenitrothion under real
environmental conditions was studied. Fenitrothion
was applied in the rice crop field of the Ebre Delta
(Tarragona, Spain) during July 1995 by helicopter spray
ing at a rate of 148 mL/ha Tionfos 50 LE (50% of pure
fenitrothion). For monitoring fenitrothion residues
in
water, two different analytical techniques were
used: enzyme-linked immunosorbent assay (ELISA)
and automated on-line solid-phase extraction (Prospekt) followed by liquid chromatography/diode array
detection (LC/DAD). The unequivocal identification
of fenitrothion, fenitrooxon, 3-methyl-4-nitrophenol, and
s-methyl isomer of fenitrothion was achieved by
liquid chromatography/mass spectrometry (LC/MS)
using an atmospheric pressure chemical ionization
(APCI) interface in the negative ionization (NI) mode.
The residue levels of fenitrothion in rice crop field
waters
varied from 119−178 μg/L down to 3.8−1.5 μg/L
after
48 h of helicopter application. The half-lifetimes
t
1/2
were calculated by both analytical techniques being
19.3 for ELISA and 11 h for LC/DAD after treatment, with
a disappearance rate of 0.036 and 0.063, respectively.
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