Ask an Expert: Getting the best out of Omnian WDXRF semiquantitative analysis
X-ray fluorescence (XRF) analysis is a robust analytical technique that provides both qualitative (intensity-based) and quantitative (concentration-based) information about a sample. The combination of this ‘what?’ and ‘how much?’ information, also makes semi-quantitative analysis possible.
XRF quantitative analysis
In qualitative analysis, peak search and peak match are used to discover which elements are present in the sample. Peak search finds the peaks, and peak match determines the associated elements by referring to a database.
The usual procedure of quantitative analysis in XRF is to calibrate the spectrometer by measuring reference materials. The calibration determines the relationship between the concentrations of specific chemical elements and the intensity of the fluorescent lines of those elements. You can determine unknown concentrations of calibrated elements once the relationship is known. The intensities of the elements with unknown concentrations are measured, with the corresponding concentration being determined from the calibration. A typical limitation of an accurate XRF quantitative analysis is that unknown samples should be prepared in the same way as standards used for calibration, and in many cases to be of the same nature.
What is semi-quantitative analysis
A semi-quantitative analysis in XRF usually is a combination of both, qualitative and quantitative analyses. The semi-quantitative analysis determines the presence of all measurable elements. That is in contrast with “classic” quantitative analysis, which is calibrated only for specific elements present in the standards. Usually, a semi-quantitative analysis has one “universal” calibration that can be applied to specimens of samples of different origins. It can also make a relatively good estimate of concentrations of elements and compounds which weren’t even present in the original calibration.
Semi-quantitative analysis is basically the same for Energy Dispersive (ED) XRF and Wavelength Dispersive (WD) XRF. Both WD and EDXRF are used to identify and determine the concentrations of elements present in solid, powdered and liquid samples. The exact same mathematical methods can be used to calculate the composition of samples. The only difference is that in EDXRF the area of a peak gives the intensity, while in WDXRF the height of a peak gives the intensity.
Omnian Standardless analysis
Omnian is a Malvern Panalytical XRF application package that can provide (semi-)quantitative* chemical composition analysis of virtually any sample that one can place in an XRF spectrometer. Usually, we use it in situations where specific calibration standards are not available. Or we use it when samples are out-of-scope of normal laboratory routines.
When faced with non-routine samples or materials for which there are no certified reference materials, the software provides insight into the elemental composition. Its advanced fundamental parameters algorithm automatically deals with the analytical challenges posed by samples of widely differing types.
Get the best out of your Omnian analysis
Omnian is an “open” application package and users can make some changes to the default parameters to improve precision, accuracy, or Lower Limits of Detection in their measurements. It is a powerful tool but, are you making the most of it? If you want to make sure you know how to get proper analysis results out of it or have questions regarding your Omnian analysis, then join the next ‘Ask an Expert!’ webinar titled ‘Getting the best out of Omnian WD XRF semi-quantitative analysis’.
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