Glyphosate detection in water by enzyme-linked immunosorbent assay (ELISA) Presented by: Elaine Chen Session: Emerging Contaminants Issues Date: February 24, 2009 44 th Central Canadian Symposium on Water Quality Research Co-authors: Jaspal Parmar, James Li and Ching Lo
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Glyphosate detection in water by enzyme-linked immunosorbent assay (ELISA)
Presented by: Elaine Chen
Session: Emerging Contaminants IssuesDate: February 24, 2009
44th Central Canadian Symposium on Water Quality Research
Co-authors: Jaspal Parmar, James Li and Ching Lo
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Agenda
Background ObjectiveELISAResultsConclusions
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Background –
Glyphosate
N-(phosphonomethyl)glycineIntroduced 1974 by Monsanto Important and dominant herbicide worldwideNon-selective, broad spectrumIdeal herbicide
Unique as EPSPS inhibitorGood plant uptake and translocation to sites
Time and cost efficientPresence/absence testQuantification by LC-MS if present
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Objective
Determine suitability of ELISA for quantifying and/or qualifying glyphosate in water samples
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ELISA PrincipleGlyphosate toxin and enzyme-labelled glyphosatecompete for binding sites on immobilized antibodies
Unbound materials washed away
Concentration of glyphosate is inversely proportional to colour produced
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ELISA
Byer JD, Struger J, Klawunn P, Todd A and Sverko, E. 2008. Low cost monitoring of glyphosate in surface waters using the ELISA method: An evaluation. Environ. Sci. Technol. 42: 6052-6057
ELISA can be used in conjunction with wet chemistry methods to improve temporal and/or spatial monitoring
ELISA tube format used
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ELISA microplate
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ELISA Procedure
Derivatize standards, controls and samplesPerform ELISA:
Construct standard curve: plot %B0 of standard against its glyphosate concentrationInverse relationship between %B0 and concentration of glyphosate in sample
100% 0 ×=Control Negative of OD
Calibrator or Sampleof ODB
%B0 : used to measure concentration; equalizes different runs of an assay
OD = optical density
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ELISA
Data processing – calculation module
The module performs data manipulations, data reductions and results interpretationsCalculates Corrected AbsorbanceCalculates %B0
Draws calibration curve. Plots %B0 versus concentrationCalculates the concentration of glyphosate