EPA-NERL: 549.2: Diquat and Paraquat in Water Using HPLC/UV
|
Official Method Name
|
Determination of Diquat and Paraquat in Drinking Water by Liquid-Solid Extraction and High-Performance Liquid Chromatography with Ultraviolet Detection |
|---|---|
|
Current Revision
| Revision 1.0, June 1997 |
|
Media
|
WATER |
|
Instrumentation
|
High Performance Liquid Chromatography with Ultraviolet Detection |
|
Method Subcategory
|
Organic |
|
Method Source
|
|
|
Citation
|
|
|
Brief Method Summary
|
A 250-mL sample, is extracted using a C-8 liquid/solid extraction (LSE) cartridge or a C-8 disk which has been specially prepared for the reversed-phase, ion-pair mode. The LSE disk or cartridge is eluted with acidic aqueous solvent to yield the eluate/extract. An ion-pair reagent is added to the eluate/extract. The concentrations of diquat and paraquat in the eluate/extract are measured using high performance liquid chromatography (HPLC) system equipped with a UV absorbance detector. A photodiode array detector is utilized to provide simultaneous detection and confirmation of the method analytes. |
|
Scope and Application
|
This method determines diquat and paraquat in drinking water sources and finished drinking water. |
|
Applicable Concentration Range
|
Not specified in method. Range differs depending on matrix and instrumentation. |
|
Interferences
|
(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse. (B) Adsorptive loss on glass: Silanizing glassware will reduce adsorptive loss of diquat and paraquat. (C) Contamination of plastic ware: Detergent wash, rinse, and dry before use. (D) Reagent contamination: Use high purity reagents. (E) Extracted interferences: Interference from extracted non-target compounds, with retention times similar to target compounds, can be reduced by cleaning the extract. (F) Ion interferences: Ca+2 and Mg+2 lower recovery by interfering with the ion exchange process. |
|
Quality Control Requirements
|
Initial demonstration of laboratory capability, analysis of laboratory reagent blanks (LRBs), laboratory fortified matrix samples, and laboratory fortified blanks (LFBs). Initial demonstration of laboratory capability includes analysis of LFBs at analyte concentrations of 100 ug/L. A MDL for each analyte must also be determined. |
|
Sample Handling
|
Grab samples must be collected in amber PVC high density bottles or silanized amber glass bottles following conventional sampling procedures. Automatic sampling equipment must be as free as possible of adsorption sites which may extract the sample. Dechlorinate samples with the addition of 100 mg/L of sodium thiosulfate. Biologically active samples must be preserved to pH 2 with the addition of sulfuric acid. Store samples at 4oC away from light until analysis. |
|
Maximum Holding Time
|
7 days; extracts analyzed within 21 days. |
|
Relative Cost
|
$201 to $400 |
|
Sample Preparation Methods
|
