New Dynamic Method Developed to Measure Toxic Elements in PM10 Samples Using ICP-MS

Researchers at the University of Strathclyde in Glasgow, UK, have developed two dynamic versions of the simplified bioaccessibility extraction test (SBET) to measure the bioaccessible concentration of potentially toxic elements in PM₁₀ samples. The study was published in the Analytical and Bioanalytical Chemistry journal (1).

City fine dust | Image Credit: © ttlsc - stock.adobe.com

The dynamic versions of the SBET include an offline and online procedure coupled directly to an inductively coupled plasma–mass spectrometry (ICP-MS) instrument. The researchers applied batch, online, and offline procedures to simulated PM₁₀ samples prepared by loading NIST SRM 2711A Montana II soil and BGS RM 102 Ironstone soil onto 45-mm TX40 filters commonly used when monitoring air quality. They also used three real PM₁₀ samples for extraction.

PM₁₀ refers to particulate matter (PM) that has a diameter of 10 micrometers or less. These tiny particles can come from a variety of sources, including combustion processes, industrial activities, and natural sources like dust and pollen. PM₁₀ is considered hazardous to human health because it can be inhaled into the lungs and cause respiratory problems. As a result, PM₁₀ levels are closely monitored by air quality monitoring programs.

The SBET is a method to assess the bioaccessibility of potentially toxic elements in soils and dust. It simulates the conditions of the human gastrointestinal tract to estimate the amount of an element that could be absorbed into the body. The test uses synthetic stomach and small intestine fluids to extract the element of interest from the sample. The amount of the element in the extract is then measured and compared to the total amount in the sample to determine its bioaccessibility.

The extracts were analyzed using an Agilent 7700 ICP-MS instrument to determine the levels of arsenic, cadmium, chromium, copper, iron, manganese, nickel, lead, and zinc. The residual simulated PM₁₀ samples following the application of the SBET were subjected to microwave-assisted aqua regia digestion, and a mass balance calculation was performed with respect to digestion of a separate test portion of the SRM. Leachates were collected as subfractions for offline analysis or continuously introduced to the nebulizer of the ICP-MS for online analysis.

The researchers found that the mass balance was generally acceptable for all versions of the SBET. Recoveries obtained with the dynamic methods were closer to pseudototal values than those obtained in batch mode. However, offline analysis performed better than online analysis, except for lead. Recoveries of bioaccessible lead relative to the certified value in NIST SRM 2711A Montana II soil were 99%, 106%, and 105% for the batch, offline, and online methods, respectively.

The study demonstrates that dynamic SBET can be used to measure the bioaccessibility of potentially toxic elements in PM₁₀ samples. The researchers note that the dynamic methods are less time-consuming and less prone to sample contamination than batch mode. They suggest that the new method could help improve the accuracy of air quality monitoring and the assessment of health risks associated with PM₁₀ exposure.

Overall, the development of dynamic SBET represents an important advancement in air quality research, and the researchers believe that it could be further refined and adapted for other types of samples in the future.

Reference

(1) Alpofead, J. A. H.; Davidson, C. M.; Littlejohn, D. On- and off-line analysis by ICP-MS to measure the bioaccessible concentration of elements in PM₁₀ using dynamic versions of the simplified bioaccessibility extraction test. Anal. Bioanal. Chem. 2023, ASAP. DOI: 10.1007/s00216-023-04695-7