Abraxis: 54003A: 2,4-D by Immunoassay, Microtiter Plate
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Official Method Name
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Abraxis 2,4-D Plate Assay Kit (96T) PN 54003A |
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Current Revision
| 2008 |
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Media
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WATER |
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Instrumentation
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Immunoassay |
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Method Subcategory
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Organic |
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Method Source
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Citation
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Brief Method Summary
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2,4-D is detected using a colorimetric immunoassay (ELISA) procedure. A sample (0.050 mL) and an enzyme conjugate (enzyme-labeled 2,4-D) are added to a microtiter plate well pre-coated with 2,4-D-specific antibodies. Both the 2,4-D in the sample and the enzyme conjugate compete for antibody binding sites on the wells in proportion to their concentrations. At the end of an incubation period, the wells are washed, and a substrate is then added which is catalyzed by the enzyme and converted from a colorless to a blue solution. The reaction is terminated with the addition of a dilute acid. The concentration of 2,4-D in the sample is determined by measuring its absorbance at a specific wavelength (450 nm) using a plate photometer, and comparing its absorbance to the absorbance of the calibrators. |
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Scope and Application
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This method determines 2,4-D in water (groundwater, surface water, well water). |
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Applicable Concentration Range
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2-80 |
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Interferences
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Cross-reactivity: 2,4-D acid; 2,4-D methyl ester; 2,4-DB; 2,4-D isopropyl ester; 2,4-DB butyl ester; and high concentrations of 2,4,5-T and MCPA produce false positive responses for 2,4-D. |
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Quality Control Requirements
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(A) Calibration with 6 standards and 1 blank, all analyzed in duplicate (B) Precision: 3 matrix samples with different levels in the range for quantitative analysis analyzed daily for 5 days with 5 replicates in each of 5 assays (C) Accuracy: 5 matrix samples spiked with the target analyte at 4 different levels in the range for quantitative analysis (D) Validation: Analysis of 4 positive and 4 negative samples by an independent method, for confirmation. |
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Sample Handling
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Samples are collected in glass containers with Teflon-lined caps; for compliance monitoring, samples should be held no longer than 14 days. If samples are held frozen, they can be held for longer periods of time. Immunoassay reagents are stored refrigerated until use. Samples containing gross particulate matter should be filtered using a 1 micron filter or centrifuged before use. Drinking water samples are typically dechlorinated with 0.008% sodium thiosulfate. |
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Maximum Holding Time
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14 days at 4 degrees C, longer if held frozen |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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