EPA-NERL: 547: Glyphosate in Water Using HPLC w/ Post Column Derivitization

Summary
Analytes
Revision
Data and Sites

Official Method Name

Determination of Glyphosate in Drinking Water by Direct-Aqueous-Injection HPLC, Post Column Derivitization, and Fluorescence Detection

Current Revision

July 1990

Media

WATER

Instrumentation

High Performance Chromatography with Post Column Derivitization and Fluorescence Detection

Method Subcategory

Organic

Method Source

EPA-NERL

Citation

Methods for the Determination of Organic Compounds in Drinking Water - Supplement I (EPA/600/4-90-020)

Brief Method Summary

An aliquot of a filtered water sample is injected into a cation exchange high performance liquid chromatography (HPLC) column. Separation is achieved by using an isocratic elution. After elution from the analytical column, the analyte is oxidized with calcium hypochlorite. The product (glycine) is then coupled with o-phthalaldehyde-2-mercaptoethanol complex at 38^oC to give a derivative fluorophor (post-column derivitization). The concentration of glyphosate eluted from the HPLC column is measured by detecting the fluorescence of the derivative with a fluorometer.

Scope and Application

This method determines glyphosate in 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) Reagent contamination: Use high purity reagents.

Quality Control Requirements

Initial demonstration of laboratory capability, followed by analysis of laboratory reagent blanks (LRBs), laboratory fortified matrix samples, laboratory fortified blanks (LFBs), and QC samples. Initial demonstration of laboratory capability includes analysis of LFBs at an analyte concentration of 250 ug/L. A MDL also must be determined.

Sample Handling

Collect samples in glass containers following conventional sampling practices. Dechlorinate samples with 100 mg/L of sodium thiosulfate. Store samples at 4^oC away from light until analysis.

Maximum Holding Time

14 days generally; up to 18 months for glyphosate in frozen samples.

Relative Cost

$201 to $400

Sample Preparation Methods

This method has 2 analytes associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Glyphosate(1071-83-6) Glycine, N-(phosphonomethyl)- Glyphosate Glyphosate (ANSI) Honcho M-(Phosphonomethyl)glycine N-(Phosphonomethyl)glycine, isopropylamine sal N-(Phosphonomethyl)glycine, isopropylamine salt Roundup	6.000 ug/L	96% Rec (SL)	9.10 % RSD (SL)			25.00 ug/L
Herbicides(E-12839) Herbicide formulations Herbicides	N/A	N/A	N/A

Precision Descriptor Notes:	Precision and accuracy values were determined using single laboratory data from eight replicate analyses of reagent water fortified with glyphosate.
Detection Level Note:	MDLs were determined using the standard deviation of replicate analyses of an analyte-fortified reagent water sample (25 ug/L of glyphosate) multiplied by the t-value for (# of samples - 1) degrees of freedom at the 99% confidence level. Detailed instructions for how MDLs are determined are found at 40 CFR part 136, Appendix B. NOTE: MDLs in ground water (GW) and dechlorinated tap water (TW) were also determined (GW = 9 ug/L, TW = 6 ug/L).

Precision Descriptor Notes:

Precision and accuracy values were determined using single laboratory data from eight replicate analyses of reagent water fortified with glyphosate.

Detection Level Note:

MDLs were determined using the standard deviation of replicate analyses of an analyte-fortified reagent water sample (25 ug/L of glyphosate) multiplied by the t-value for (# of samples - 1) degrees of freedom at the 99% confidence level. Detailed instructions for how MDLs are determined are found at 40 CFR part 136, Appendix B. NOTE: MDLs in ground water (GW) and dechlorinated tap water (TW) were also determined (GW = 9 ug/L, TW = 6 ug/L).

Revision	PDF/Link
July 1990

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EPA-NERL: 547: Glyphosate in Water Using HPLC w/ Post Column Derivitization

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