Implementing infrared determination of quartz particulates on novel filters for a prototype dust monitor

Research by the National Institute for Occupational Safety and Health (NIOSH) has pursued quartz analysis for the specialized filter assemblies of a new worker-wearable personal dust monitor (PDM). The PDM is a real-time instrument utilizing a tapered element oscillating microbalance (TEOM). Standard fiberglass TEOM filters cannot accommodate the desired P-7 infrared analytical method used by the Mine Safety and Health Administration (MSHA). Novel filter materials were tested with the objective of demonstrating this type of analysis. Low temperature ashing and spectrometric examination were employed, revealing that nylon fiber candidate filters left minimal residual ash and produced no significant spectral interference. Avoiding titanium dioxide in all filter materials proved to be a key requirement. Fine quartz particulates were collected on prototype filters in a Marple chamber, either open-faced or through PDMs during test runs. The filters were then subjected to MSHA P-7 analysis and the spectrometrically based analytical results for quartz mass were compared to reference measurements. Also, PDM instrumental mass readings were compared to filter gravimetric measurements. Results suggest that the P-7 method is adaptable to variations in filter materials and that quartz dust analysis by the P-7 method when utilizing the new ashable PDM filters can have accuracy and precision within 10% and 4%, respectively. This is within the declared 13% accuracy and 7-10% precision of the P-7 method itself. Instrument mass readings had modest positive bias but met NIOSH accuracy criteria. Continued work with specialized PDM filters is merited, as they are a new type of TEOM sample amenable to ashing analysis of particulates.