Quality control is crucially important in the arena of chemical analysis. Reference materials are essential for calibration and quality control processes, and for verification of the accuracy and reliability of the analytical results obtained. Owing to the complexity of their manufacture, reference materials for chemical agents occurring at workplaces are expensive and available only on a limited scale and for a small number of substances. Therefore, their cost-effective and fast production is an important aim. The Institute for Occupational Health and Safety (IFA) of the German Social Accident Insurance (DGUV) currently pursues different strategies for the production of reference materials. One strategy entails the use of a piezoelectric micro-dispensing system for non-contact spiking of extremely small quantities of substances with high reproducibility. The dispensing system is coupled to a semi-automated assembly unit for loading high numbers of samples. It is used for spiking phosphoric and sulphuric acid onto quartz fibre filters. Comparison of the results obtained on different days shows higher variability than results observed on the same day. However, after daily adjustment of the number of droplets to the current droplet volume, highly reproducible series with an adequate number of samples (>500) could be realized. The results of the internal quality control were verified in an interlaboratory comparison. Furthermore, storage stability was investigated systematically over a period of 2 years. The samples produced are suitable for use as reference materials for both inorganic acids.
Die Quantifizierung gesundheitsschädlicher Substanzen an Arbeitsplätzen wurde in den letzten Jahrzehnten immer wichtiger und ist auch weiterhin von großem Interesse. Die Rahmenbedingungen für Gefahrstoffmessungen am Arbeitsplatz haben sich gleichzeitig aufgrund des technischen Fortschritts und fortwährender Grenzwertabsenkungen geändert. Somit ist es essenziell, die analytischen Methoden diesen Änderungen anzupassen. Das Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA) bietet zur Qualitätssicherung für Messstellen verschiedene Ringversuche für gesundheitsschädliche Stoffe am Arbeitsplatz an einer dynamischen Prüfgasstrecke an. Im Zuge kontinuierlicher Verbesserung wurden Online-Messmethoden in den Prozess der Prüfgasherstellung implementiert. Der Einsatz eines Online-Gaschromatographen ermöglicht die selektive Quantifizierung der Substanzen im Prüfgasgemisch und sichert somit die Qualität des Prüfgases, z. B. während der Ringversuche für organische Lösemittel und flüchtige organische Verbindungen.
For the production of filters coated with metal oxides an aqueous metal salt solution is injected into a hydrogen/oxygen flame of a particle generator leading to the pyrolysis of the metal salts into nano-scaled metal oxide dust. The particles are introduced into a large sampling chamber (20 m³) via a dust tunnel (20 m). So far, the system was tested for Zn, Cu, Pb, Co, Ni, Mn and In but it should be suitable with all metals obtainable as soluble metal salts. For sample generation an eight-fold sampling system was developed for the GSP sampler. The constancy of the flow rate is assured by critical orifices. Up to fourteen of these systems can be operated to produce 112 samples in parallel. Nevertheless, for the production of a reference material a significantly higher number of samples will be needed. To achieve this aim the environmental conditions of the dust generation have to be stabilized for consecutive runs. The major problem was the temperature rise of the dust channel during the particle generation due to the heat of the flame. An additional heater was installed to work at a constant temperature of 30 °C. Three consecutive filter series were manufactured. The achieved temperature constancy of 30± 0.5 °C makes it possible to combine the successive filter series. The loadings of the combined series were Cobalt: 3.25±0.058 µg/filter, Nickel: 13.78±0.23 µg/filter, Lead: 109.5±3.0, Copper: 9.65 ±0.18 µg/filter and Zinc: 32.66±0.72 µg/filter.
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