Diquat and paraquat - Drinking Water

Laboratory Fee Schedule

Procedure: EZZ0094A

Synonym(s): DIQUAT and PARAQUAT in Water
Requisition Form G-22
Test Description Diquat and paraquat EPA method 549.2.
Pre-Approval Needed N/A
Supplemental Information Required N/A
Supplemental Form(s) N/A
Performed on Specimens from (sources) Environmental 
Sample/Specimen Type for Testing Drinking Water
Minimum Volume/Size Required Amber PVC high density plastic or salinized amber glass; 1 quart (1 L)
Storage/Preservation Prior to Shipping
  • Add 100 mg/L sodium thiosulfate to each container (to dechlorinate)
  • Open the tap and allow the system to flush until the water temperature stabilizes, at least 5 minutes. Turn flow down to a smooth, pencil thin stream.
  • Remove cap from the bottle, tilt, and place under stream.
  • Fill the container with sample water. Mix for one minute until the sodium thiosulfate is completely dissolved.
  • Add sulfuric acid (H2SO4) to achieve a pH < 2.
  • Iced (4°C)
  • Store samples in the dark. (Very light sensitive).
Transport Medium N/A
Specimen Labeling
  • Label each bottle with a waterproof marker. 
  • Pre-printing labels is acceptable.   
  • Sample identification must match information on submission form.
Shipping and Specimen Handling Requirements
  • Ship according to Dangerous Goods Regulations, IATA, and/or CFR 49.
  • Ship on ice (4°C).
Method EPA 549.2
Turn-around Time Samples must be extracted by the lab within 7 days of collection.
  • Sampling equipment must be free of plastic tubing, gaskets or other parts that may leach interfering analytes into the sample.
  • Interferences may be caused by contaminants that are coextracted from the sample. The extent of matrix interferences will vary considerably from source to source.
  • All of the glassware that comes in contact with analytes in method 549.2 must be salinized to prevent adsorption of the diquat and paraquat cations on the surface of the glass. 
  • Calcium and magnesium cations present in hard water interfere with the ion exchange process and cause low recovery of method analytes. 
Common Causes for Rejection Insufficient quantity, unacceptable specimen type or source, improper shipping conditions, expired media or collection container, discrepancies between specimen label and submission form and/or incomplete or missing submission form
Additional Information Contact the laboratory at (512) 776-7587 for currently supported analyte list.