Abraxis: 54004B: 2,4-D in water by Immunoassay, Coated Tube
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Official Method Name
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Abraxis 2,4-D Tube Kit (40T) PN 54004B |
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Current Revision
| 2007 |
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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 (0.50 mL) and an enzyme conjugate (enzyme-labeled 2,4-D) are added to a test tube pre-coated with antibodies against 2,4-D. Both the 2,4-D in the samples (if present) and the enzyme conjugate compete for antibody binding sites on the 2,4-D immobilized antibodies in proportion to their concentrations. At the end of an incubation period, the unbound molecules are washed and decanted from the tube. A substrate is added which is catalyzed by the enzyme and converted from a colorless to a blue solution. The reaction is terminated with the addition of 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 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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2.0 - 100 |
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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 3 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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