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Performance comparison of portable XRF instruments

N. W. Brand and C. J. Brand
Performance comparison of portable XRF instruments
Geochemistry - Exploration, Environment, Analysis (February 2014) 14 (2): 125-138

Abstract

Portable XRF instruments are effective tools to provide "fit for purpose" qualitative chemical data that are precise but typically very inaccurate. Under standardized test conditions, the analytical performance of portable XRF instruments varies significantly between individual instruments from the same manufacturer, and between manufacturers using similar instruments. The precision of the instruments to repeat a constant element concentration from a single sample is typically very good (<5 % RSD); however, the accuracy is generally poor to very poor with huge concentration differences in some elements. For example, Al measured from the same NIST standard reference material (NIST 2709a, an agricultural soil) by six Olympus-Innov-X Delta Premium instruments ranged from 2.56 to 7.93 % Al whilst two Thermo-Niton XL3t GOLD+ instruments gave values of 2.14 and 2.33 % Al against the certified value of 7.37 % Al.After two to five months, repeat analysis by the same instruments under the same conditions shows a measurable deterioration in element concentration, with elements of lower atomic number, Al and Si, the worst affected; for example, the Si response from the Olympus-Innov-X Delta Premium and Thermo-Niton XL3t GOLDD+ instruments deteriorated up to 43 % and 40 %, respectively. This deterioration in the instruments' performance was observed in all instruments evaluated.Lithium-ion battery packs, a key to the instruments' portability, can have a measurable effect on the precision and accuracy of the data with an instant 0.05 % concentration change in Fe (from 3.39 to 3.44 % Fe) during a routine battery pack change. Batteries' serial numbers should be recorded to monitor these effects and corrections applied.Each instrument provides uniquely individual data that should not be combined with data from any other units without appropriate post-processing or recalibration. To significantly improve the quality and value of the pXRF data, a calibration procedure appropriate to the material(s) being evaluated should be implemented with regular baseline data collected to ensure instrument and data stability. Over time, matrix calibrations need to be verified with the instrument undergoing a manufacturer's recalibration when control limits deteriorate significantly.


ISSN: 1467-7873
EISSN: 2041-4943
Serial Title: Geochemistry - Exploration, Environment, Analysis
Serial Volume: 14
Serial Issue: 2
Title: Performance comparison of portable XRF instruments
Affiliation: Geochemical Services, West Perth, West. Aust., Australia
Pages: 125-138
Published: 20140204
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
Number of pages: unpaginated
References: 12
Accession Number: 2014-019764
Categories: General geochemistryEconomic geology, general, deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 21 tables
Secondary Affiliation: Portable XRF Services, AUS, Australia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201413
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