Preparation of electrotechnical products for reduction of hazardous substances compliance testing

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 sufficiently for 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 μm, 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.