Uwe Oppermann and Dr Johannes Hesper examine one of the latest methods for the determination of hazardous substances.

The guidelines for WEEE (Waste of Electrical and Electronic Equipment) and RoHS (restriction of the use of certain hazardous substances in electrical and electronic equipment) have been integrated into national legislation in most of the European countries.

In Germany, the Electrical and Electronic Equipment Act (ElektroG) has been introduced on 24th March 2005. As of July 2006, lead, mercury, cadmium, chromium (VI), polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE) are prohibited in electrical and electronic equipment. 

In order to enforce the substances ban and the limitation or substitution of hazardous compounds, elemental analysis is obviously the most important control measure for monitoring limiting values. This requires precise analytical systems such as X-ray fluorescence, ICP-, UV-VIS-, FTIR-, GC-MS-, and atomic absorption spectrometers. 

X-ray fluorescence spectrometry

The threshold values according to RoHS have been set at 1000mg/Kg for lead, mercury, chromium and bromine and 100mg/Kg for cadmium and can be determined using an energy dispersive  X-ray fluorescence spectrometer such as the Shimadzu EDX-720 (Fig.1).

This system configuration with a large sample compartment (300mm diameter x 150mm height) allows a fast and non-destructive high precision screening , resulting in the highest level of reliability of analytical data in comparison to handheld instruments which are recently promoted for so called ‘quick tests’. The EDX-720 has been developed in order to meet all requirements of RoHS applications such as the determination of:

• Lead in solder of printed circuit boards, coatings, electro-ceramics, and glasses.

• Cadmium in NiCd batteries, synthetic, materials, electric arc contacts, sensors, galvanisings.

• Chromium (VI) in  metal coatings, undercoats for metal coatings, chrome plating, metallic synthetic surfaces.

• Mercury in batteries, fluorescent lamps, switches, sensors, relays.

The EDX-720 is equipped with a new set of filters and an improved count rate circuit resulting in a higher sensitivity as shown in Fig.2. High counting rates increase the intensity and improve resolution, whereas the new filter types reduce the background signal without appreciably decreasing peak intensities.

In addition to these two new features, the Measurement Time Reduction and the Switching Calibration Curves functions further contribute to the instrument’s success story. The Measurement Time Reduction function automatically controls measurement times according to the precision requirements of the user. This is, for instance, very useful for mixed samples as the measurement time can be greatly reduced this way. The latest version of EDX software features a multitude of fundamental parameter (FP) methods, enabling quantification of practically any type of sample without standards.

Applications

The EDX-720 is a very versatile instrument and is suitable for a wide range of elemental analysis applications. Instrument and software are easy to operate and very small sample preparation ensures fast and precise analytical results in the following segments:

• Analysis of toxic substances in electrical and electronic components according to RoHS and ELV in the electronics and automotive industry.

• Analysis of catalyser materials, pigments and dyes in the chemical industry.

• Quantification of nickel, vanadium and sulphur in oils and lubricants in petrochemistry.

• Quality control of ceramics, cements and glasses in the ceramic industry.

• Analysis of catalyst residues or contaminations in the medical-, agricultural-, and food industry.

• Determination of coating- and layer thicknesses and their composition in metallurgy.

• Quantification of bromine as an indicator of brominated flame-retardants in synthetic materials.

In order to identify the substances mentioned above, Shimadzu has developed the EDX-720 with improved specifications. The EDX-720 features improved detection sensitivity for lead and cadmium, the most significant elements in environmental analysis. In addition, the EDX-720 excels with new attractive functionalities such as the Auto Selection function for selection of a suitable calibration curve – for instance for PE or PVC – or the Auto-Reduced measuring function optimising the measurement time. The automatic Switching Calibration Curves function selects a suitable calibration for unknown samples. When both calibration curves (for example, PE and PVC) are stored, a calibration curve suitable for the synthetic polymer is selected based on the chlorine signal. In this way, polymer measurements based on incorrect calibration curves are a thing of the past.

Conclusion

A fast and precise system configuration has been used to demonstrate state-of-the-art technology for the determination of hazardous substances in electric and electronic equipment as well as electronic waste according to the WEEE and RoHS guidelines. The EDX-720 is a versatile tool for quality control of electric and electronic equipment and guarantees the proper monitoring within the maximum allowable concentration levels for cadmium, lead, mercury, chromium, and bromine according to RoHS. 

Dipl-Min Uwe Oppermann and Dipl-Chem Dr Johannes Hesper are with Shimadzu Europa GmbH, Duisburg, Germany. www.shimadzu.de