[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

Standardized procedures sometimes define each detail

Info icon This preview shows pages 422–424. Sign up to view the full content.

View Full Document Right Arrow Icon
Standardized procedures sometimes define each detail from instrument type to be used up to the reproducibility of the final results. Typically, the following items are included: Method, instrument and measurement process; Standard samples and sample preparation; Calculation methods; Precision of results. A closer look at typical specifications will help to understand the advantages and drawbacks of standardized methods. Method, Instrument, and Measurement Process A standardized method will specify X-ray fluorescence in general or, more specifically, an energy-dispersive (EDX) or a wavelength-dispersive spectrom- eter (WDX). Sometimes EDX or WDX is not stated explicitly, but follows from the description of the instrument details. Such instrument details can include the anode material and the minimum power of the X-ray tube, the analyzer crystal to be used in a wavelength- dispersive system or the specific kind of detector. The more detailed these descriptions, the higher is the risk to exclude new developments. For example, a modern medium-power wavelength-dispersive spectrometer with a sealed proportional detector may easily outperform old high-power instruments, but will possibly not fulfill the specifications of a minimum tube power and a flow proportional counter. For future standardized methods, it may be more ap- propriate to define parameters, which are directly relevant for the quality of the results, e.g., the minimum counting statistical error or the minimum reso- lution of a detector instead of technical specifications subject to innovations. Standardized methods typically specify the X-ray line to be used and spe- cial measurement parameters like the energy or wavelength for background measurements. Sample Preparation and Standard Samples Typically, an X-ray spectrometer sees only some milligrams of material close to the surface of the specimen. As an important precondition for reliable results, this volume has to be representative of the material to be analyzed. Therefore, all standardized methods describe sample preparation in detail including, e.g., the purity of reagents to be used.
Image of page 422

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
402 K.-E. Mauser Many standardized methods deal with the analysis of liquid samples or materials prepared as fused beads. For these applications synthetic standards can be used. The standardized methods prescribe in detail how to mix these standards by using pure reagents. When such synthetic standards are prepared exactly as defined, various laboratories will base their calibrations on exactly the same kind of standards and therefore ensure consistency of results. Sometimes certified reference materials are an option or have to be used. These materials have to be acquired from a national standards body or an accredited supplier.
Image of page 423
Image of page 424
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern