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| Techniques and Methods 10–C11 |
(15N/14N) of Total Nitrogen in Solids: RSIL Lab Code 2893U.S. Geological Survey
By Kinga Révész and Haiping Qi
This report is available as a pdf.
15N/14N), abbreviated as 15N, of total nitrogen in solid samples. An Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total N in a solid sample into N2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines relative differences in the isotope-amount ratios of stable nitrogen isotopes (15N/14N) of the product N2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero-Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that contains an oxidant, where the combustion takes place in a He atmosphere containing an excess of oxygen gas. Combustion products are transported by a He carrier through a reduction tube to remove excess oxygen and convert all nitrous oxides into N2 and through a drying tube to remove water. The gas-phase products, mainly CO2 and N2, are separated by a gas chromatograph (GC). The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan ConFlo II interface, which also is used to inject N2 reference gas and He for sample dilution. The IRMS is a Thermo-Finnigan DeltaPlus CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle, capable of measuring mass/charge (m/z) 28, 29, 30, simultaneously. The ion beams from N2 are as follows: m/z 28 = N2 = 14N/14N; m/z 29 = N2 = 14N/15N primarily; m/z 30 = NO = 14N/16O primarily, which is a sign of contamination or incomplete reduction.
Forward
Conversion Factors, Acronyms, and Abbreviations
Summary of Procedure
Reporting Units and Operational Range
Reference Materials and Documentation
Reference Materials Used, Storage Requirements, and Shelf Life
Documentation
Labware, Instrumentation, and Reagents
Sample Collection, Preparation, Analysis, Holding 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 (or) 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 Generate an Excel Sample Workbook or to Print a Template and a Samples-to-Be-Analyzed List |
| C. | Step-by-Step Procedure for Weighing and Storing Samples |
| D. | Step-by-Step Procedure of Zero Blank Autosampler Operation |
| E. | Step-by-Step Procedure to Add Sample Information to Sequence Table |
| F. | Step-by-Step Procedure to Retrieve Data from ISODAT 2.0 for LIMS-LSI and for Data Back-Up |
| G. | Step-by-Step Procedure to Transfer Data to LIMS-LSI, to Transfer Data to Back-Up Computer, and to Reevaluate Old Data |
| H. | Step-by-Step Procedure to Determine and Apply Correction Factors and Evaluate Data |
| I. | Step-by-Step Procedure to Check Elemental Analyzer for Leaks |
| J. | Daily Checklist |
| K. | Changing the Insertion Tube |
| L. | Changing the Water Trap |
| M. | Changing the Reaction Tubes |
| N. | Step-by-Step Procedure to Report Data |
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| U.S. Department of the Interior, U.S. Geological Survey
Persistent URL: http://pubs.water.usgs.gov/tm10c11 Page Contact Information: Publishing Service Center Last modified: Tuesday, August 14 2007, 04:04:42 PM |
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