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| Techniques and Methods 10–C2 |
(18O/16O)of Water: RSIL Lab Code 489 U.S. Geological Survey
By Kinga Révész and Tyler B. Coplen
Chapter 2
Section C, Stable Isotope-Ratio Methods
Book 10, Methods of the Reston Stable Isotope Laboratory
The purpose of the technique described by the Reston Stable Isotope Laboratory (RSIL) lab code 489
is to present a method to determine the δ(180/160), abbreviated as δ180, of water. This δ18O measurement of water also is a component of National Water Quality Laboratory (NWQL in USGS) schedules 1142 and 1172. Water samples are loaded into glass sample containers on a vacuum manifold to equilibrate gaseous CO2 at constant temperature (25°C) with water samples. After loading water samples on the vacuum manifold, air is evacuated through capillary to avoid evaporation, and CO2 is added. The samples are shaken to increase the equilibration rate of water and CO2. When isotopic equilibrium has been attained, an aliquot of CO2 is extracted sequentially from each sample container, separated from water vapor by means of a dry ice trap, and introduced into a dual-inlet isotope-ratio mass spectrometer (DI-IRMS) for determination of the δ18O value. There is oxygen isotopic fractionation between water and CO2, but it is constant at constant temperature. The DI-IRMS is a DuPont double-focusing mass spectrometer. It has a double collector. One ion beam passes through a slit in a forward collector and is collected in the rear collector. The other ion beams are collected in the front collector. The instrument is capable of measuring mass/charge (m/z) 44 and 45 or 44 and 46 by changing the ion-accelerating voltage under computer control. The ion beams from these m/z values are as follows: m/z 44=CO2=12C16O16O, m/z 45=CO2=13C16O16O primarily, and m/z 46 = CO2=12C16O18O primarily. The data acquisition and control software calculates δ18O values.
Forward
Conversion Factors
Acronyms, and Abbreviations
Summary of Procedure
Reporting Units and Operational Range
Reference Materials and Documentatione
Reference Materials Used, Storage Requirements, and Shelf Life
Documentation
Labware, Instrumentation, and Reagents
Sample Collection, Preparation, Analysis, Retention Times, and Disposal
Sample Containers, Preservation, and Handling Requirements
Sample Preparation and Time Requirements
Performing the Analysis and Time Requirements
Problematic Samples
Interferences
Troubleshooting and Bench Notes
Maintenance and Maintenance Records
Sample Retention Time and Disposal
Data Acquisition, Processing, Evaluation, Quality Control, and Quality Assurance
Laboratory Information Management System for Light Stable Isotope (LIMS-LSI)
Quality-Control (QC) Samples
Acceptance Criteria for all QC Samples
Corrective Action Requirements
Responsible Parties for All QA/QC Functions for Procedures Covered in RSIL SOPs
Data Management and Records
Health, Safety, and Waste-Disposal Information
Applicable Health and Safety Issues
Personal Protection
Electrical Hazards
Chemical Hazards
Gas Cylinder Handling
Specific Waste-Disposal Requirements
Revision History
References Cited
Apendixes
| A. | Step-by-Step Procedure to Log-in Samples to LIMS-LSI. |
| B. | Step-by-Step Procedure to Print a Template and a Samples-to-Be-Analyzed List. |
| C. | Step-by-Step Procedure to Prepare and Analyze Samples on the CO2 Equilibration Line. |
| D. | Step-by-Step Procedure for CO2 Mass Spectrometer Checklist. |
| E. | Step-by-Step Procedure to Determine and Apply Correction Factors and Evaluate Data. |
| F. | Step-by-Step Procedure to Leak Check Valves. |
| G. | Step-by-Step Procedure to Report Data. |
Révész, Kinga, and Coplen, Tyler, B., 2008, Determination of the δ(180/160), of water: RSIL lab code 489, chap. C2 of Révész, Kinga, and Coplen, Tyler B., eds., Methods of the Reston Stable Isotope Laboratory: U.S. Geological Survey Techniques and Methods, 10–C2, 28 p.
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