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Techniques and Methods 5-B1

Prepared by the USGS Office of Water Quality
National Water Quality Laboratory

Determination of Elements in Natural-Water,
Biota, Sediment, and Soil Samples Using Collision/Reaction Cell Inductively Coupled
Plasma–Mass Spectrometry

By John R. Garbarino, Leslie K. Kanagy, and
Mark E. Cree

Chapter 1 of Book 5, Laboratory Analysis
Section B, Methods of the National Water Quality Laboratory

Abstract

A new analytical method for the determination of elements in filtered aqueous matrices using inductively coupled plasma–mass spectrometry (ICP–MS) has been implemented at the U.S. Geological Survey National Water Quality Laboratory that uses collision/reaction cell technology to reduce molecular ion interferences. The updated method can be used to determine elements in filtered natural-water and other filtered aqueous matrices, including whole-water, biota, sediment, and soil digestates. Helium or hydrogen is used as the collision or reaction gas, respectively, to eliminate or substantially reduce interferences commonly resulting from sample-matrix composition. Helium is used for molecular ion interferences associated with the determination of As, Co, Cr, Cu, K, Mg, Na, Ni, V, W and Zn, whereas hydrogen is used for Ca, Fe, Se, and Si. Other elements that are not affected by molecular ion interference also can be determined simply by not introducing a collision/reaction gas into the cell. Analysis time is increased by about a factor of 2 over the previous method because of the additional data acquisition time in the hydrogen and helium modes.

Method detection limits for As, Ca, Co, Cr, Cu, Fe, K, Mg, Na, Ni, Se, Si (as SiO2), V, W, and Zn, all of which use a collision/reaction gas, are 0.06 microgram per liter (g/L) As, 0.04 milligram per liter (mg/L) Ca, 0.02 g/L Co, 0.02 g/L Cr, 0.04 g/L Cu, 1 g/L Fe, 0.007 mg/L K, 0.009 mg/L Mg, 0.09 mg/L Na, 0.05 g/L Ni, 0.04 g/L Se, 0.03 mg/L SiO2, 0.05 g/L V, 0.03 g/L W, and 0.04 g/L Zn. Most method detection limits are lower or relatively unchanged compared to earlier methods except for Co, K, Mg, Ni, SiO2, and Tl, which are less than a factor of 2 higher.

Percentage bias for samples spiked at about one-third and two-thirds of the concentration of the highest calibration standard ranged from –8.1 to 7.9 percent for reagent water, –14 to 21 percent for surface water, and –16 to 16 percent for ground water. The percentage bias for reagent water spiked at trace-element concentrations of 0.5 to 3 g/L averaged 4.4 percent with a range of –6 to 16 percent, whereas the average percentage bias for Ca, K, Mg, Na, and SiO2 was 1.4 percent with a range of –4 to 10 percent for spikes of 0.5 to 3 mg/L. Elemental results for aqueous standard reference materials compared closely to the certified concentrations; all elements were within 1.5 F-pseudosigma of the most probable concentration. In addition, results from 25 filtered natural-water samples and 25 unfiltered natural-water digestates were compared with results from previously used methods using linear regression analysis. Slopes from the regression analyses averaged 0.98 and ranged from 0.87 to 1.29 for filtered natural-water samples; for unfiltered natural-water digestates, the average slope was 1.0 and ranged from 0.83 to 1.22. Tests showed that accurate measurements can be made for samples having specific conductance less than 7,500 microsiemens per centimeter (S/cm) without dilution; earlier ICP–MS methods required dilution for samples with specific conductance greater than 2,500 S/cm.

Contents

Abstract

Introduction

Purpose and Scope

Analytical Method

Application and Method Detection Limits

Interferences

Instrumentation

Sample Collection, Preservation, Shipment, and Holding Times

Calibration Standards and Other Solutions

Quantitation

Reporting of Analytical Data

Laboratory Quality Assurance/Quality Control

Results and Discussion of Method Validation Data

Summary and Conclusions

References Cited

Glossary

Appendix — Linear Regression Analyses of Elemental Results

Figures

1. The effect of increasing concentrations of chloride from two sources on the determination of arsenic at mass-to-charge ratio 75

2. The effect of increasing concentrations of chloride from two sources on the determination of vanadium at mass-to-charge ratio 51

3. The effect of increasing concentrations of dissolved organic carbon from two natural-water sources on the determination of chromium at mass-to-charge ratio 52

4. The variability in percentage recovery for selected elements extending the operational mass range as a function of increasing specific conductance

5. Sample-flow paths used with new collision/reaction cell inductively coupled plasma–mass spectrometric methods

6. Linear regression analysis of experimental concentrations for all elements in biological standard reference material digestates analyzed by collision/reaction cell inductively coupled plasma–mass spectrometry in relation to the certified concentrations

Appendix Figures

A1. — A58. Linear Regression Analyses of Elemental Results

Tables

1. Codes for elements in water, biota, and sediment and for arsenic species in water samples determined by collision/reaction cell inductively coupled plasma–mass spectrometry

2. Method detection limits for elements and species determined using collision/reaction cell inductively coupled plasma–mass spectrometry

3. Potential molecular ion interferences for elements determined using collision/reaction cell inductively coupled plasma–mass spectrometry

4. Effectiveness of using a collision/reaction cell gas for the elimination of molecular ion interferences

5. Typical operating characteristics for collision/reaction cell inductively coupled plasma–mass spectrometry

6. Long-term bias and variability of results from aqueous standard reference materials using collision/reaction cell inductively coupled plasma–mass spectrometry

7. Long-term bias and variability for the analysis of reagent water spiked with analyte concentrations in the lower one-third of the normal calibration range using collision/reaction cell inductively coupled plasma–mass spectrometry

8. Long-term bias and variability for the analysis of reagent water spiked with analyte concentrations at one-third and two-thirds of the normal calibration range using collision/reaction cell inductively coupled plasma–mass spectrometry

9. Long-term bias and variability for the analysis of surface water spiked with analyte concentrations at one-third and two-thirds of the normal calibration range using collision/reaction cell inductively coupled plasma–mass spectrometry

10. Long-term bias and variability for the analysis of ground water spiked with analyte concentrations at one-third and two-thirds of the normal calibration range using collision/reaction cell inductively coupled plasma–mass spectrometry

11. Linear regression results for filtered natural-water samples analyzed using collision/reaction cell inductively coupled plasma–mass spectrometry and other spectrometric methods

12. Linear regression results for unfiltered natural-water digestates analyzed using collision/reaction cell inductively coupled plasma–mass spectrometry and other spectrometric methods

13. Bias and variability of results for digested biological standard reference materials analyzed by collision/reaction cell inductively coupled plasma–mass spectrometry

This document is available in pdf format:

(Requires Adobe Acrobat Reader)

The citation for this report, in USGS format, is as follows:

Garbarino, J.R., Kanagy, L.K., and Cree, M.E., 2006, Determination of elements in natural-water, biota, sediment, and soil samples using collision/reaction cell inductively coupled plasma–mass spectrometry: U.S. Geological Survey Techniques and Methods, book 5, sec. B, chap. 1, 88 p.

For more information about the National Water Quality Laboratory, contact:

Laboratory Chief
U.S. Geological Survey
National Water Quality Laboratory (NWQL)
P.O. Box 25046, Denver Federal Center
Building 95, MS 407
Denver, CO 80225-0046

Or access the NWQL home page at:

http://wwwnwql.cr.usgs.gov/USGS


 

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