Applications of Quantitative XRF

Quantitative XRF is used in virtually every industry for almost any type of liquid or solid sample. XRF is used daily to analyze minerals, metals, paper, textiles, ceramics, cement, polymers, wood, environmental samples, food, forensic samples, cosmetics and personal care products, and more. Only a few examples will be given here. 

Petroleum hydrocarbon cracking catalysts usually contain more than 12 elements, including transition metals, rare earth elements (REEs), and alkali and alkaline earth elements at concentrations varying from 0.005 to 35 wt%. The composition of the catalyst can be determined accurately after fusion into borate beads the total analysis takes up to 1 h. The procedure and approach is described in ASTM D7085. Lubrication oil blenders use EDXRF to check their blends and ensure that control samples from lube shops are what the products claim to be (ASTM D6481 outlines the procedure). 

Used engine oil used to be monitored routinely for metal content, since the metal content indicated how parts of the engine were wearing away in use. The wear metals analysis indicated what parts needed to be replaced during maintenance. Analysis also enables extension of the oil life by verifying that there is still enough P, Ca, or Zn in the oil to function correctly. This analysis could be performed by XRF or by atomic emission spectrometry (e.g., ICP or DC plasma (DCP) emission). 

In metallurgy, alloy composition can be rapidly determined and unknown samples identified rapidly. XRF has an advantage over wet chemistry in that all the components can be measured due to the wide dynamic range of XRF. For example, in the analysis of nickel alloys, a wet chemical approach would measure all the other elements and calculate the Ni content as the balance. With XRF, the major element, nickel, as well as the minor and trace components can be measured accurately. For high-grade steel and alloys with multiple major components, WDXRF achieves better accuracy and repeatability than optical emission spectroscopy (OES). 

A limitation for XRF in a metallurgical application is the measurement of carbon in steel. The problem with carbon in this application is due to the small analyzed layer and the inhomogeneous distribution of carbon in steel. To ID the correct steel grade for low carbon steels, OES or combustion analysis is required. 

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