Envirologix: EP 020: DDT immunoassay

Summary
Analytes
Revision
Data and Sites

Official Method Name

DDT Microwell Plate Assay EP020 (EL 1999) http://www.envirologix.com/

Current Revision

1999

Media

SOILS/SEDIMENT

Instrumentation

Immunoassay

Method Subcategory

Organic

Method Source

Envirologix

Citation

Envirologix User Guides and Product Inserts

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 Concentration 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

Quality Control 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.

Maximum Holding Time

5 days at 4^oC until extraction and analysis

Relative Cost

Less than $50

Sample Preparation Methods

This method has 4 analytes associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
4,4'-DDD(72-54-8) 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethane 4,4'-DDD Benzene, 1,1'-(2,2-dichloroethylidene)bis[4-ch Benzene, 1,1'-(2,2-dichloroethylidene)bis[4-chloro- Dichloro-2,2-bis(p-chlorophenyl)ethane,1,1- Dichlorodiphenyldichloroethane Ethane, 1,1-dichloro-2,2-bis(p-chlorophenyl)- Rhothane TDE Tetrachlorodiphenylethane p,p'-DDD p,p'-Dichlorodiphenyl dichloroethane p,p'-TDE	0.023 ug/g	N/A	25.00 % RSD (SL)	6	0	0.05 ug/g
4,4'-DDE(72-55-9) 1,1'-(-Dichloroethenylidene)bis(4-chlorobenzene) 4,4'-DDE 4,4'-DDE, DDT, DDD Benzene, 1,1'-(dichloroethenylidene)bis[4-chlo Benzene, 1,1'-(dichloroethenylidene)bis[4-chloro- Ethylene, 1,1-dichloro-2,2-bis(p-chlorophenyl)- bis(p-Chlorophenyl)-1,1-dichloroethylene,2,2- p,p'-DDE p,p'-Dichlorodiphenyldichloroethylene	0.023 ug/g	N/A	25.00 % RSD (SL)	6	0	0.05 ug/g
Organochlorine pesticides(E-12851) Organochlorine pesticides Pesticides, organochlorine	N/A	N/A	N/A
p,p'-DDT(50-29-3) 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane 4,4'-DDT Benzene, 1,1'-(2,2,2-trichloroethylidene)bis[4-chloro- Chlorophenothane DDT Dichlorodiphenyltrichloroethane Ethane, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)- bis(p-Chlorophenyl)-2,2,2-trichloroethane,1,1- p,p'-DDT p,p'-Dichlorodiphenyltrichloroethane	0.023 ug/g	N/A	25.00 % RSD (SL)	6	0	0.05 ug/g

Precision Descriptor Notes:	Expect low recovery of DDT from soils in methanol extracts. Precision data from EnviroLogix: median within-sample precision at 0.05 ug/L RSD = 14%; median between-sample precision at 0.05 ug/L RSD = 25%. Percent false positives and false negatives from EPA Method 4042 Soil screening for DDT by immunoassay (EPA 1995): 6% false + at 0.2 ug/g; 0% false - at 0.2 ug/g. NOTE: Measurements in ug/g as the sum of p,p'-DDT, p,p'-DDD, and p,p'-DDE.
Detection Level Note:	spiked replicates: interpolation at 78% Bo, equal to 3 standard deviations from the mean of negative water samples

Precision Descriptor Notes:

Expect low recovery of DDT from soils in methanol extracts. Precision data from EnviroLogix: median within-sample precision at 0.05 ug/L RSD = 14%; median between-sample precision at 0.05 ug/L RSD = 25%. Percent false positives and false negatives from EPA Method 4042 Soil screening for DDT by immunoassay (EPA 1995): 6% false + at 0.2 ug/g; 0% false - at 0.2 ug/g. NOTE: Measurements in ug/g as the sum of p,p'-DDT, p,p'-DDD, and p,p'-DDE.

Detection Level Note:

spiked replicates: interpolation at 78% Bo, equal to 3 standard deviations from the mean of negative water samples

Revision	PDF/Link
1999

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Envirologix: EP 020: DDT immunoassay

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