Methods

X-ray Fluorescence Analysis (XRF)

Two XRF instruments were available for the measurements of pigment powders. Most of the samples could be analyzed by using an energy dispersive system of Tracor Northern, type X-Ray Spectrace 5000. This instrument was equipped with a Rhodium (Rh) X-ray tube, different collimators and a Si(Li) detector cooled with liquid N2. The pigment powders were measured on a Mylar® foil. In order to characterize all elements in the best way, three different measurement parameters were chosen:

Tube voltage 8 kV 30 kV 50 kV
Tube current 0.35 mA 0.25 mA 0.20 mA
Filter - Aluminium Palladium-thin
Live time 100 s 100 s 100 s
Atmosphere Vacuum Air Air

The evaluation was done with the measurement software of Tracor.

   

X-Ray Spectrace 5000 of Tracor Northern is shown on the left and sample holder on the right.

For the analysis of the last set of approximately 100 pigment powders the energy dispersive and portable XRF instrument of XGLab (Bruker), type ELIO was used. The ELIO XRF was equipped with a 4 Watt Rhodium (Rh) X-ray tube, an SDD detector (active area of 25 mm2), a camera, and a positioning system including two laser pointers. The X-ray beam diameter applied was around 1 mm. All pigment powders were measured on a Mylar® foil. In order to characterize all samples in the best way, the following measurement parameters were chosen:


Tube voltage 40 kV
Tube current40 µA
Filter-
Measuring time60 s
AtmosphereAir

The evaluation of the XRF spectra was done in a qualitative way using the measurement software XGLab Elio 1.6.0.29.

   

XRF ELIO of XGLab (Bruker) is shown on the left and sample holder with white pigment powder on the Mylar foil® on the right.