Chromium Speciation Analysis: Overcoming Technological Limitations in CDV

In the field of environmental protection, the study of chromium is one of the most challenging disciplines. This is because it involves not merely determining the total metal content, but precisely distinguishing between its different forms—a process known as speciation analysis. It is precisely this task that has become the focus of Romana Michalicová’s work at the Transport Research Centre (CDV).

Health Risks and Instability of Chemical Forms

The primary reason for this analysis is the diametrically opposed effects of different forms of chromium on the human body. While trivalent chromium is essential in low concentrations, its hexavalent form is classified as a dangerous carcinogen. It is precisely hexavalent chromium compounds that are soluble in lung fluid and can penetrate through the alveoli directly into the bloodstream.

Romana Michalicová’s research focuses on the speciation analysis of chromium in airborne particulate matter, with an emphasis on transportation. However, a challenge lies in the instability of these forms, which can lead to the immediate conversion of one form into another during sample preparation, thereby disrupting the equilibrium and resulting in an incorrect interpretation of the obtained results.

Technical innovation that goes beyond the standards

During the year-long development of the methodology, the researcher encountered a major obstacle: systemic contamination. Standard analytical instruments contain metal components that release trace amounts of chromium. Romana Michalicová therefore contacted colleagues from the Department of Analytical Chemistry, Faculty of Science, Palacký University in Olomouc (UPOL), where, under the leadership of Tomáš Pluháček, methods for speciation analysis of trace concentrations of chromium species had been developed. Since the UPOL laboratory works with different matrices and equipment, their method had to be adapted for the needs of the CDV.

The first step was to replace the metal parts of the high-performance liquid chromatograph (HPLC) with plastic ones in order to prevent “system bleeding,” which increases the background noise for the element under study. The second challenge was the introduction of previously unused isotopically enriched standards of chromium species, specifically 53Cr³⁺ and 50Cr⁶⁺. The appropriate use of isotopically labeled standards contributes not only to the development of advanced methods based on the combination of liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS/MS), but also monitors and compensates for unwanted disturbances in the equilibrium between the studied chromium species throughout the entire preparation and analysis process. In addition to the aforementioned innovations in available instrumentation and methodological approaches, the development involved dozens of hours of work by the researcher to optimize ICP-MS/MS parameters, including plasma discharge parameters, sampling distance, gas flow rates, collision gas flow rate, and settings for the ion optics and detector.

From Validation to Environmental Impact

The effort paid off. Following successful validation of the method, 84 PM10 samples from three locations in Brno—specifically Lužánky Park, Kotlářská Street, and Velká Klajdovka—were processed under intensive conditions. Comparing data from different periods and locations with varying traffic volumes made it possible to assess the impact of traffic and estimate seasonal trends.

CDV will now use the developed methodology for unique monitoring in the tram tunnel in Brno-Bohunice. In these enclosed spaces, dust particles accumulate and are constantly resuspended (stirred up). Thanks to Romana Michalicová’s persistence, we now have a tool that can precisely identify the invisible risks in our mobility.