Thesis
Analysis of geological materials by low dilution fusion at the Peter Hooper Geoanalytical Lab (Washington State University)
Washington State University
Master of Science (MS), Washington State University
2018
Handle:
https://hdl.handle.net/2376/101916
Abstract
The low dilution fused disks method used at the Peter Hooper GeoAnalytical Laboratory can produce and analyze ~5000 samples per year, measuring 34 major and trace elements using X-Ray fluorescence (XRF) spectrometry. Sample preparation begins by reducing the samples to fine powders using a hydraulic press, a steel jaw crusher, and shatterbox grinders with tungsten carbide grinding bowls. Powders are mixed with Lithium tetraborate, using a 2:1 ratio (flux:sample), fused at 1000°C in graphite crucibles, and ground and fused a second time to ensure sample homogeneity. A uniform grind is applied to the lower surface to finish. The, non-typical, low dilution, ratio (2:1) makes trace element analysis possible, and the second grind and fusion are sufficient to homogenize all geological samples regardless of their compositions. The speed and number of samples prepared is meaningless if the data produced is neither precise nor accurate. A significant portion of batches contain a repeat analysis which can be used to accurately estimate analytical precision. The Relative Standard Deviation for ~250 sample-repeat pairs were plotted against their average concentrations. As concentrations decreases, Relative Standard Deviations grow. These trends are well constrained by power function curves which can be used to calculate precision for samples with no repeat analyses. Methodology accuracy is determined by comparison of 19 CRM and RM samples with their certified and consensus values, and by cross-comparison of over 600 samples analyzed in-house by XRF and ICP-MS. Both techniques yield results that deviate by less than 5% from their "true" concentration for all elements, except for Y and Zr, with numerous elements deviating by less than ~2%. The result is a method capable of single digit or lower analytical precision and accuracy for 34 elements, with many at low parts per million concentrations, for geological samples with complex compositions.
Metrics
22 File views/ downloads
62 Record Views
Details
- Title
- Analysis of geological materials by low dilution fusion at the Peter Hooper Geoanalytical Lab (Washington State University)
- Creators
- Daniel Steven Kelly
- Contributors
- John A. Wolff (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525127101842
- Language
- English
- Resource Type
- Thesis