User's Manual

8
Advanced Settings
Tools Menu Options
156 Niton XL2 Analyzer User’s Guide Thermo Scientific
Switch Library (Main)
Selecting the Switch Library button from the Tools Menu will swap the currently loaded
library with the other library on the analyzer. Selecting Switch Library again will switch them
back.
Enable/Disable Al
Normally, the collective amount of unquantifiable light elements in alloy analysis - the
"balance" - is assumed to be aluminum and labeled as such in the analysis. Selecting the
Disable Al button from the Tools Menu will delete this "aluminum" from the analysis results,
showing only the quantified elements. Selecting the Enable Al button, the default state, will
label this "balance" as "aluminum".
Thickness Correction
Plastics, and polymers in general, unlike metals or soil, are very weak absorbers of X rays. This
is because polymers are composed mainly of very light elements such as carbon and hydrogen.
While just half a millimeter of steel will completely stop 23.1 keV energy X rays of cadmium,
for example, it takes at least 10mm of plasticized PVC and as much as 100mm of
polyethylene (PE) to do so. Fortunately, polymers that may contain cadmium (Cd), lead (Pb)
and other restricted elements would also contain considerable quantity of elements such as
antimony (Sb), bromine (Br), titanium (Ti), etc. Their presence results in much stronger
absorption of X rays which means that, instead of 100mm, it takes only about 15mm of
compounded PE to achieve saturation thickness for these X rays. If the thickness of analyzed
polymer sample is less than 5mm for PVC or less than about 9mm for a “typical” PE, the
measured intensity of X rays will be a function of both analyte concentration and sample
thickness. This is why measurements performed on thin samples (less than saturation
thickness) need to be corrected for thickness.
How to apply Thickness Correction.
In order for the instrument to apply thickness correction to the measured concentration
results, the user must be using the Thickness Correction screen and enter the thickness of the
analyzed plastic object expressed in [mm] before the measurement is initiated. The thickness
may be entered with precision to the second decimal place, although in practice only one
decimal place is sufficient for effective correction.