Under the European REACH legislation, every chemical compound produced or used by industry must be tested to identify any potentially harmful effects on humans and the environment. Companies often join forces to this end in associations that focus on one specific chemical element. The association then hires a specialist laboratory to carry out tests on a list of chemicals. The association for the element antimony has approached VITO to conduct these tests.

Companies and industries from around the world have set up an association to focus on the element antimony: a heavy metal with the chemical symbol Sb. The association was established more than thirty years ago and has its headquarters in Brussels. ‘We identify the risks on behalf of all antimony manufacturers, users and distributors’, explains Caroline Braibant of the International Antimony Association. ‘These risk assessments then enable our members to comply with legislation such as the European REACH chemicals regulation.’

Antimony was traditionally used in lead alloys to make them harder and more sustainable – for instance in lead letters for printing works, to prevent shrinkage as a result of cooling. These days, however, the heavy metal is mainly used in batteries and LED lighting, flame retardants, and even as a catalyst in the production of PET bottles.

Red tape

‘In principle, companies are required to submit a separate file for each individual chemical compound to the ECHA, the European agency that coordinates REACH’, states VITO’s Kristof Tirez. This involves a whole load of red tape, so the industry works together on specific elements. The application for antimony includes around ten different compounds for which the International Antimony Association is responsible for dealing with the admin.’

Three years ago, the association hired VITO to carry out a study into the presence of antimony particles in the working environment and to develop a number of protocols for further qualitative research. ‘One of the key reasons for approaching VITO was its expertise in biomedical toxicology and liquid chromatography, a technique that allows a very precise distinction between different compounds’, Braibant explains.

Bioelution tests

The methods used to asses toxicity include bioelution tests. These tests examine how toxic, and therefore how hazardous, a metal can be when it is dissolved in a substance such as gastric acid. ‘In the case of metals, toxicity often goes hand in hand with solubility’, says Tirez. ‘If you ingest the substance and it dissolves, it spreads throughout the body.’ In cooperation with Hasselt-based chemical analysis company ECTX, VITO carried out leach tests on ten antimony compounds in a simulated gastric environment (characterised by a high level of acidity). The elution tests themselves were conducted in Hasselt, while VITO was responsible for identifying and accurately determining the concentration of the various ‘antimony groups’. As Tirez explains: ‘Antimony can bond with other elements in a number of ways. We distinguish between two major bonding configurations: antimony III and antimony V. This distinction is important, because it can lead to a difference in toxicity even at the same concentration.’

VITO uses a technique called liquid chromatography to identify the different compounds. This involves using miniscule columns to filter molecules from a mixture based on their chemical and physical properties. A mass spectrometer then identifies the compounds found in the mixture and their concentration. ‘As a routine laboratory, most of our assignments consist of solely analysing metals to measure the total content per element’, says Tony Brouwers of ECTX. ‘But recently there has been a growing demand for speciation analysis, which involves determining differences in toxicity depending on the bonding configuration. This requires additional, often very expensive equipment and special expertise. These types of analysis can only be carried out by specialist research centres like VITO.’

Transformations between configurations

On the instructions of the International Antimony Association, VITO produced a detailed report on the solubility of various antimony compounds in a simulated gastric environment. During this process, Tirez and his colleagues also looked for potential transformations between bonding configurations. ‘Do the antimony III compounds remain the same in an acid solution? Or do they become antimony V? These are important questions that need to be taken into account in the ECHA application.’

What is the next step? Tirez: ‘The antimony association will combine the results and proceed on the basis of a worst case scenario, in other words the compound with the highest solubility. This approach ensures efficiency and cost effectiveness, while reducing the need for experimental testing in animals. The research can then be used to help determine safety limits and threshold values for use in industry and distribution on the European commercial market.’

Tony Brouwers (ECTX) views the cooperation with VITO as a success, despite the fact that the companies were operating as two separate entities. ‘We were responsible for the bioelution tests, while VITO carried out the sample analyses. It might not sound like the ideal working method on paper because it can get complicated if things go wrong. But since I had already got to know VITO’s researchers, laboratories and set-up in recent years, I was confident that we could bring this big project to a successful conclusion.’

With this research, VITO has further enhanced its reputation as a specialist technology partner, this time in the field of chemical and biomedical analysis. ‘And it has done so by providing a niche service that is not available to the industry on the commercial market’, says Tirez.