Fighting Air Pollution: Tracking and Retaining Particulate Matter
Practical Retainer System for Filter Samples
A retainer system by which several folded or shredded filters can be digested was designed. Depending on the vessel type up to five filters can be easily managed. The retainer is manufactured from TFM-PTFE and thus chemically resistant. Due to the low porosity of the material, the risk of contamination or memory effects is significantly reduced. A consistent and complete immersion of the filters in the sample solution is ensured.
After digestion the retainer can be removed from the vessel and cleaned. The transfer of the sample solution to the volumetric flasks is therefore extremely straightforward. Filters that are not completely digested may be removed from the digestion vessel and rinsed out. The risk of a loss of samples is minimised.
Efficient Digestion for Reliable Particle Analysis
By adapting the existing norm, it is possible to digest several filter samples at the same time. This was proofed by the determination of the ERM CZ-120 reference material. The determined values are in good agreement with those of the analysis certification and were determined with sufficient precision.
The recovery rate of the elements examined lies between 90-113 %. According to DIN EN 14902, the minimum mean recovery rate specification is set at between 85-115 % for the elements Ni and As, between 90-100 % for Pb and between 90-110 % for Cd. The values thus conform to the specifications of the norm. This shows that the efficiency of digestion of the acid mixture, even with the addition of water, is still enough to be able to digest the elements sufficiently.
Determination of Cadmium and Lead
The Cd content found in the sample is 0.88 mg/kg ± 0.04 mg/kg. In spite of the limited concentration in the lower ppm range a good recovery rate of 97 % could be achieved. The recovery complies with the permitted range of mean recovery (90 – 100 %) stated in DIN EN 14902.