USGS OGRL: O-2141-09: Glyphosate, Aminomethylphosphonic acid, and Glufosinate, in Water by Isotope Dilution and Online SPE and LC/MS/MS.
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Official Method Name
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Glyphosate, Aminomethylphosphonic acid, and Glufosinate, in Water by Isotope Dilution and Online Solid-Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry |
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Current Revision
| 2009 |
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Media
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WATER |
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Instrumentation
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Liquid Chromatography with Tandem Mass Spectrometry |
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Method Subcategory
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Organic |
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Method Source
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Citation
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Meyer, M.T.; Loftin, K.A.; Lee, E.A.; Hinshaw, G.H.; Dietze, J.E.; Scribner, E.A., 2009, Determination of Glyphosate, its Degradation Product Aminomethylphosphonic Acid, and Glufosinate, in Water by Isotope Dilution and Online Solid-Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry: U.S. Geological Survey Techniques and Methods 5-A10, 33 p. |
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Brief Method Summary
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Water samples are filtered at the collection site using glass-fiber filters with nominal 0.70-um pore diameter to remove suspended particulate matter. In the laboratory, 10 mL of sample(s) are dispensed into two labeled, 19-mL, screw-capped plastic tubes. Then 200 microliter of internal standard solution is added to each sample, and pH is adjusted to 9 by adding borate buffer. After mixing, a solution of FMOC is added to all tubes. Derivatization is carried out in the dark in a water bath at 40oC. After 24 hours, the reaction is stopped and stabilized by adding 2% phosphoric acid. All tubes are stored in the dark until analyzed. A 5.5-mL aliquot of each derivatized sample and 5.5-mL of deionized-distilled laboratory water are added to glass autosampler vials that are capped and placed in the tray of the on-line SPE autosampler. The SPE cartridge is conditioned with 2 mL of acetonitrile and then 2 mL of DI water; 10 mL of the sample is then loaded onto the cartridge. The SPE cartridge is then rinsed with 500 µL of DI water and vials are capped, and placed into the flow path of the liquid chromatography (LC) mobile-phase stream. The conditions and gradient of the mobile phase are set to elute the compounds of interest and leave the excess derivatization reagent on the cartridge. The compounds are separated on a liquid chromatograph using a gradient separation and analyzed by liquid chromatography/tandem mass spectrometery (LC/MS/MS) with electrospray ionization in negative-ion mode using multiple reaction monitoring (MRM). The compounds are identified by comparing their retention times to the internal standards in each sample, and comparing the ratio of the quantitation MRM daughter-ion to the confirming MRM daughter-ion for each compound. The concentration of each compound is calculated by determining the ratio of the area response produced by the quantitation daughter-ion of the analyte to the area response produced by the quantitation daughter-ion of the corresponding internal standard. |
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Scope and Application
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This method is suitable for the determination of sub microgram per liter (µg/L) concentrations for glyphosate analysis, its degradation product AMPA, and glufosinate in water samples. Because suspended particulate matter is removed from the samples by filtration, the method only is suitable for analysis of these compounds in the dissolved phase. The quantitation range for the method is from 0.02 to 5.0 µg/L. |
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Applicable Concentration Range
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The quantitation range for the method is from 0.02 to 5.0 µg/L. If the concentration is greater than 5.00 µg/L and estimated to be less than 10 µg/L, a part of the original derivatized sample is diluted appropriately with DI water and reanalyzed; if the sample is greater than 10µg/L, the raw water |
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Interferences
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Samples and field collection equipment that are handled improperly might become contaminated; therefore, sample-collection protocols and cleaning procedures for field equipment should be followed closely. |
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Quality Control Requirements
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Duplicate samples, matrix spikes, DI blanks, DI spikes (reagent spikes). |
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Sample Handling
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Samples are filtered in the field through a 0.7-µm pore-size baked glass-fiber filter, using an aluminum plate-filter holder and a ceramic-piston fluid-metering pump with all Teflon tubing. Filters are leached with about 200 mL of sample before sample collection . The filtered water is collected in baked 4-oz amber glass bottles with Teflon-lined lids. Chill immediately and ship to laboratory. Keep chilled at 4oC until derivatized and analyzed. |
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Maximum Holding Time
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Holding times of 5 days for raw filtered samples would result in minimal loss of glyphosate and that derivatized samples are stable for at least 60 days. |
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Relative Cost
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Greater than $400 |
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Sample Preparation Methods
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