EPA Method 8141B

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EPA Method 8141B:
Organophosphorus Compounds in Water, Soil, and Waste Samples by GC-FPD. Official Name: Organophosphorus Compounds by Gas Chromatography: Capillary Column Technique

Summary:
Samples are extracted and cleaned up (according to sample matrix) and the solvent appropriately exchanged. The samples are analyzed by direct injection into a gas chromatograph with a flame photometric or nitrogen-phosphorus detector.

Scope:
This method determines the concentration of organophosphorus (OP) compounds in water, soil, and waste samples by using fused-silica, open-tubular, capillary-column gas chromatography with either a flame photometric detector (FPD) or a nitrogen-phosphorus detector (NPD). Triazine herbicides can also be determined when the NPD is used.

Citation:
SW-846 Update IVB

Interferences:
A) Low recoveries: Some compounds have low yield recoveries when using either the Florisil Cleanup or Gel Permeation Cleanup and, therefore, are not recommended for all compounds. However, use of alternative cleanup procedures must demonstrate that the recovery of each analyte is not below 85 percent.(B) Flame photometric detector: Interferences from materials other than sulfur and phosphorus are minimized. If Method 3660 is used for sulfur cleanup, only the tetrabutylammonium (TBA) - sulfite option should be employed since copper and mercury may destroy OP pesticides. Recovery must not be less than 85 percent.(C) Halogen-specific detector: May be employed for halogen-containing compounds and for the determination of Chlorpyrifos, Ronnel, Coumaphos, Tokuthion, Trichloronate, Dichlorvos, EPN, Naled, and Stirophos only. Although many OP pesticides can be detected by electron capture detection (ECD), it is not as specific as NPD or FPD. ECD should only be used when previous analyses show that interferences will not adversely affect quantitation, and that the detector sensitivity is sufficient to meet regulatory limits.(D) Coeluting Compounds: Some compounds coelute, especially on 15-m columns. In which case, analysts should either use another column of different polarity for confirmation, use 30-m x 0.53-mm columns, or use 0.25-mm or 0.32-mm ID columns.(E) Analytical difficulties: The method describeds numerous analyte-degradation scenarios.(F) Method interferences: Contaminants in solvents, reagents, glassware, and other sample processing hardware may lead to elevated baselines and/or other interferences in the gas chromatograms. Routine analysis of reagent blanks should be performed as a check for method interferences.(G) NP Detector interferences: Triazine herbicides and other nitrogen-containing compounds may interfere.(H) Refer to Methods 3500, 3600, and 8000.

QC Requirements:
Refer to Chapter One and Methods 3500, 3600, 8000, and 8270 for specific QC procedures. Procedures include: analysis of mid-level check standards, validation of extraction, cleanup, and GC operation procedures, as well as, techniques for qualitative identifications and confirmations.

Maximum Holding Time:
Extract within 7 days of collection and analyze within 40 days of extraction.

Media:
VARIOUS

Subcategory:
Organic

Concentration:
Not Available.

Sample Prep:
8140, 3510, 3520, 3540, 3541, 3620, 3660

Precision:
-

Detection:
None.

Revision Number:
Revision 2, November 2000

Test Description:
Organophosphorus Pesticides by GC