U.S. Geological Survey
Open-File Report 02-337

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Method of Analysis and Quality-Assurance Practices by U.S. Geological Survey Organic Geochemistry Research Group--Determination of Geosmin and Methylisoborneol in Water Using Solid-Phase Microextraction and Gas Chromatography/Mass Spectrometry

By L.R. Zimmerman, A.C. Ziegler, and E.M. Thurman

Abstract

A method for the determination of two common odor-causing compounds in water, geosmin and 2-methylisoborneol, was modified and verified by the U.S. Geological Survey's Organic Geochemistry Research Group in Lawrence, Kansas. The optimized method involves the extraction of odor-causing compounds from filtered water samples using a divinylbenzene-carboxen-polydimethylsiloxane cross-link coated solid-phase microextraction (SPME) fiber. Detection of the compounds is accomplished using capillary-column gas chromatography/mass spectrometry (GC/MS). Precision and accuracy were demonstrated using reagent-water, surface-water, and ground-water samples.

The mean accuracies as percentages of the true compound concentrations from water samples spiked at 10 and 35 nanograms per liter ranged from 60 to 123 percent for geosmin and from 90 to 96 percent for 2-methylisoborneol. Method detection limits were 1.9 nanograms per liter for geosmin and 2.0 nanograms per liter for 2-methylisoborneol in 45-milliliter samples. Typically, concentrations of 30 and 10 nanograms per liter of geosmin and 2-methylisoborneol, respectively, can be detected by the general public. The calibration range for the method is equivalent to concentrations from 5 to 100 nanograms per liter without dilution. The method is valuable for acquiring information about the production and fate of these odor-causing compounds in water.

CONTENTS

Abstract
Introduction
Analytical Method

Scope and Application
Summary of Method
Interferences
Apparatus and Instrumentation
Reagents and Consumable Materials
Standards and Controls
Sampling Methods
Extraction
Desorbtion
Calibration Curve
Evaluation of Mass Spectrometer Performance
Evaluation of Gas Chromatograph Performance
Calculation and Reporting of Results

Qualitative Identification
Quantitation
Reporting of Results

Method Performance
Quality-Control Data

Duplicate Samples
Laboratory Blank Samples
Calibration Verification
Surrogate Recovery

Conclusions
References Cited

Zimmerman, L.R., Ziegler, A.C., and Thurman, E.M., 2002, Method of Analysis and Quality-Assurance Practices by U.S. Geological Survey Organic Geochemistry Research Group--Determination of Geosmin and Methylisoborneol in Water Using Solid-Phase Microextraction and Gas Chromatography/Mass Spectrometry: U.S. Geological Survey Open-File Report 02-337, 12 p.

For additional information about the Organic Geochemistry Research Group, please visit their Web site at:

For additional information contact:

Betty Scribner
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, KS 66049-3839
Telephone: (785) 832-3564
Fax: (785) 832-3500
Email: scribner@usgs.gov