Historically, workplace exposure to the volatile inorganic acids hydrochloric acid (HCl) and nitric acid (HNO(3)) has been determined mostly by collection on silica gel sorbent tubes and analysis of the corresponding anions by ion chromatography (IC). However, HCl and HNO(3) can be present in workplace air in the form of mist as well as vapor, so it is important to sample the inhalable fraction of airborne particles. As sorbent tubes exhibit a low sampling efficiency for inhalable particles, a more suitable method was required. This is the first of two articles on "Evaluation of Sampling Methods for Measuring Exposure to Volatile Inorganic Acids in Workplace Air" and describes collaborative sampling exercises carried out to evaluate an alternative method for sampling HCl and HNO(3) using sodium carbonate-impregnated filters. The second article describes sampling capacity and breakthrough tests. The method was found to perform well and a quartz fiber filter impregnated with 500 μL of 1 M Na(2)CO(3) (10% (m/v) Na(2)CO(3)) was found to have sufficient sampling capacity for use in workplace air measurement. A pre-filter is required to remove particulate chlorides and nitrates that when present would otherwise result in a positive interference. A GSP sampler fitted with a plastic cone, a closed face cassette, or a plastic IOM sampler were all found to be suitable for mounting the pre-filter and sampling filter(s), but care has to be taken with the IOM sampler to ensure that the sampler is tightly closed to avoid leaks. HCl and HNO(3) can react with co-sampled particulate matter on the pre-filter, e.g., zinc oxide, leading to low results, and stronger acids can react with particulate chlorides and nitrates removed by the pre-filter to liberate HCl and HNO(3), which are subsequently collected on the sampling filter, leading to high results. However, although there is this potential for both positive and negative interferences in the measurement, these are unavoidable. The method studied has now been published in ISO 21438-2:2009.
Workers can be exposed to fume, arising from welding activities, which contain toxic metals and metalloids. Occupational hygienists need to assess and ultimately minimize such exposure risks. The monitoring of the concentration of particles in workplace air is one assessment approach whereby fume, from representative welding activities, is sampled onto a filter and returned to a laboratory for analysis. Inductively coupled plasma-atomic emission spectrometry and inductively coupled plasma-mass spectrometry are generally employed as instrumental techniques of choice for the analysis of such filter samples. An inherent difficulty, however, with inductively coupled plasma-based analytical techniques is that they typically require a sample to be presented for analysis in the form of a solution. The efficiency of the required dissolution step relies heavily upon the skill and experience of the analyst involved. A useful tool in assessing the efficacy of this dissolution step would be the availability and subsequent analysis of welding fume reference materials with stated elemental concentrations and matrices that match as closely as possible the matrix composition of welding fume samples submitted to laboratories for analysis. This article describes work undertaken at the Health and Safety Laboratory to prepare and certify two new bulk welding fume reference materials that can be routinely used by analysts to assess the performance of the digestion procedures they employ in their laboratories.
This work describes the deliberate failure of lithium-ion cells, and subsequent analysis of both the smoke and near field residue for the metals commonly found in battery cathodes.
ISO 16740:2005 specifies an ion chromatographic method for the determination of the time-weighted average mass concentration of hexavalent chromium in workplace air and is applicable to the determination of masses of 0,01 micrograms to 10 micrograms of hexavalent chromium per sample, without dilution. For a nominal 1 cubic metre air sample, this equates to a measurement range of between approximately 0,01 micrograms per cubic metre to 10 micrograms per cubic metre, suitable for assessing exposures in plating or weld shops. However alkaline extractants, required to liberate insoluble chromates from air samples collected in paint shops, can be contaminated with trace levels of chromium thereby negating the inherent sensitivity of this method. Work to address this issue, by sourcing and testing cleaner reagents, will be presented.
International Standard (ISO) 15202 describes methods for the determination of metals and metalloids in workplace air. Its development involved harnessing selected sample digestion procedures, promulgated in existing national standards, with additional method validation work carried out by HSE. In summary, requirements for air sampling (part 1); acid digestion procedures for dissolving air filter samples (part 2) and procedures for the analysis of digests (part 3) by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are described. Exposure limit values for many metals/metalloids are now reducing and consequently more sensitive analytical techniques such as ICP-MS (promulgated in ISO 30011) may well be required in occupational hygiene laboratories. Boosting the sensitivity of the ICP-AES technique through the use of high efficiency sample introduction systems (nebulisers) is however possible as described in this presentation.
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