Potentially
toxic substances in electrical and electronic equipment are increasingly regulated, yet there is little guidance regarding appropriate sample preparation and analysis for
compliance testing. Printed circuit boards are likely to contain regulated substances. Unfortunately, they are very difficult to break into homogeneous components of a mass allowing ready analysis by
X-ray fluorescence (
XRF)
spectrometry, instrumental
neutron activation analysis or dissolution-based techniques such as
inductively coupled plasma, yet they must be analyzed despite this
heterogeneity. Analysis of unprepared samples of circuit board using microspot, hand-held, benchtop and
polarizing XRF spectrometers results in unacceptable analytical precision. Shredding samples to < 0.5 mm improves analytical precision sufficientlyfor RoHS compliance screening. To improve analytical precision further, additional sample preparation by fine shredding or milling is required. Milling for 90 s using a puck and ring mill reduces
mean particle size to < 90 microm, which is sufficiently fine for
XRF analyses or acid
dissolution. Sample loss during milling
means that fine shredding is probably an optimal form of sample preparation.
