NEMI Method Summary

Method Summary Information

Method Number: EP020 Media: SOILS/SEDIMENT
Revision: 1999
Method Source: EnviroLogix, Inc
Subcategory: ORGANIC Analytes in this method
Official Name: DDT Microwell Plate Assay EP020 (EL 1999) http://www.envirologix.com/
Descriptive Name DDT immunoassay
Source Info: EnviroLogix Inc.
500 Riverside Industrial Parkway
Portland, ME, 04103-1418 USA
phone (207) 797-0300
FAX (207) 797-7533
www.envirologix.com
Citation: DDT Microwell Plate Assay EP020 (EL 1999) http://www.envirologix.com/
 
Brief Method
Summary:
 Inhibition immunoassay, with a colorimetric indicator for competitive binding of analyte and an enzyme-labeled conjugate to surface-immobilized antibodies. Colorimetric response is inversely related to the concentration of analyte in the sample or standard. Calibrated to determine sum of p,p'-DDT, p,p'-DDD and p,p'-DDE. Reagents are purchased in kits with manufacturers' instructions for sample preparation and analysis. Requirements: a supply of clean water and methanol, to extract soil and sediment samples, to dilute sample extracts, and to prepare standards; filtration equipment to remove particulates from water samples and soil extracts; an analytical balance, to accurately determine weights of soil and sediment samples after drying and extraction; a spectrometer, which accepts plate-kits (EL) for analyses at visible wavelengths (450 nm); equipment to automate sample preparation for large numbers of samples (prefiltration, measurement of uL volumes, plate washing, agitation), so that contact times with reagents are controlled as required; computerized data acquisition and processing. Expendable supplies - approximately $8 per determination.
Scope And
Application:
 Ambient and compliance monitoring. Can be used for Method 4042. Soil screening for DDT by immunoassay (EPA 1995).
Applicable
Conc Range:
 0.025 - 0.875 ug/g
Interferences: Sensitivity > DDT: p,p'-DDD. Sensitivity < DDT: p,p'-DDE. Sensitivity << DDT: DDA; o,p'-DDT; o,p'-DDE; o,p'-DDD; dicofol; chloropropylate; chlorobenzilate; methoxychlor; tetradifon; thiobencarb
QC Requirements: Recommended for a kit allowing 96 quantitative determinations: a. calibration with 3 standards and 1 blank, all analyzed in duplicate b. precision: all 44 samples analyzed in duplicate (repeats) c. accuracy: 3 matrix samples, spiked with the target analyte at different levels in the range for quantitative analysis. d. validation: analysis of 4 positive and 4 negative samples by an independent method, for confirmation
Sample Handling: Samples are typically collected in glass containers with Teflon-lined caps. Samples are held in a refrigerator at 4 oC. Immunoassay reagents and kits are stored in the dark at 4 to 8 oC until use.
Soil and sediment samples need to be dried, weighed, and extracted (methanol; clean water). Soil extracts generally need to be centrifuged or prefiltered to 0.2 um. Quantitative analysis requires dilution of highly concentrated samples, until they are bracketed by standards in the linear response range. Aliquots of sample extracts and reagents are accurately measured (uL) and mixed for required times, following manufacturer's instructions for use of the materials purchased.
Max Holding Time:
 5 days at 4oC until extraction and analysis
 
Relative Cost: Less than $50
URL to obtain ordering information for this method:
www.envirologix.com
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