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

5103 standardized methods versus universal

Info icon This preview shows pages 424–426. Sign up to view the full content.

View Full Document Right Arrow Icon
5.10.3 Standardized Methods Versus Universal Calibrations and Standardless Methods Universal calibrations and standardless methods based on fundamental pa- rameters can handle a wide range of elements and concentrations and do not require a complicated calibration process or the mixture of the sample with an internal standard. Such standardless methods can be optimized for a certain kind of matrix, e.g., for a light matrix consisting of H, C, and O with all the other elements in the trace range. The limits of detection and the reproducibility of such optimized standardless methods are similar to those of the standardized methods. On the other hand, all universal methods using fundamental parameters will require that all elements with a significant interelement effect are measured. In general, the criteria for a decision between a standardized method and a standardless method are as follows: A standardized method (ISO, ASTM, DIN) has to be used when required by legislation or the rules of the quality management system; If only a few elements have to be determined (or just one as in the case of S and Pb in petrochemistry), a standardized method may offer much shorter measurement times. A more universal method based on fundamen- tal parameters will not allow to skip the measurement of elements with a significant matrix influence; A universal calibration based on fundamental parameters is the best pro- cedure to be applied when no standardized method is available or when a higher number of elements have to be analyzed. 5.10.4 Summary Standardized methods are an important tool to ensure consistent results in X-ray fluorescence analysis. However, if these methods are too detailed in their technical specifications, they may delay innovations in hardware and software. For many applications, optimized standardless methods can ensure the same quality of results without the need for a special calibration process.
Image of page 424

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

View Full Document Right Arrow Icon
404 Symbols and Terminology Such methods are an option when a standardized procedure is not demanded by legislation or quality management, and when a longer measurement time does not matter. Symbols and Terminology i, j, k, . . . , n Subscripts for elements (or compounds) in any given sam- ple/specimen. Subscript i usually designates the analyte and j the remaining elements (or compounds) in the spec- imen (referred to as matrix elements or compounds). The subscripts are also used to indicate the (analyte or otherwise referred to) line of that element, or the absorp- tion edge belonging to that line S , St , s , u Subscripts for specimen (could be a reference standard, any specimen, or a specimen of unknown composition) Z Atomic number Σ n Summation of all elements, i = 1 , . . . , n , in a specimen Σ M Summation of all the matrix elements (also Σ j = i ) Σ J Summation over all lines of element j that cause indirect enhancement M i Term quantifying matrix effects on analyte i (also M i,St , etc.) λ Wavelength λ i Wavelength of a characteristic line of element i , usually the analyte line λ i, K α , λ i, KL2 Wavelength, element i
Image of page 425
Image of page 426
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