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Advanced analytical chemistry for determining metal species and their interactions in environmental and biological systems

Final Activity Report Summary - ACE-METALS (Advanced analytical chemistry for determining metal species and their interactions in environmental and biological systems)

The research objectives of the ACE-METALS team were the following:
Objective 1: Development and application of tandem mass spectrometric methods for the identification and quantification of known arsenic, selenium and antimony species in a variety of biological and environmental samples, i.e. method development for targeted analysis.
Objective 2: Development of analytical methods for the detection and characterisation of novel arsenic, selenium and antimony species.
Objective 3: Development of mass spectrometric methods and techniques for investigating the interaction of metal(-loid) compounds with various biomolecules.

Arsenic speciation:
High performance liquid chromatography (HPLC) -electrospray (ES)- selected reaction monitoring (SRM) methods were developed for the determination 50 organoarsenic species. These methods were applied for the quantification of As species in extracts of marine reference materials. Their application also resulted in the first report on the detection and quantification of arsenobetaine (AB) in extracts of marine algae. It was demonstrated that the application of HPLC-ES-SRM provides improved performance for the detection of low amounts of AB accompanied by high amounts of arsenosugars. The methods developed were also used for the MS identification of novel arsenosugars in marine bivalves and algae. This was the first time that the detection of thioarsenosugars in marine algae was reported. More specifically the presence of two novel thioarsenosugars in marine bivalves and marine algae was demonstrated. The analytical techniques developed were further demonstrated to be suitable for the comprehensive mapping of all As species present in marine organisms. Similar analytical approaches were developed and applied to characterise synthetic seleno-arsenic compounds. These new compounds and methods are potentially suitable for probing metabolic interactions between the two elements. Also developed were HPLC-ES-SRM and HPLC ICP-MS methods suitable for the sensitive and selective identification of four As-Glutathione (GSH) complexes. These analytical methods were applied to carry out a preliminary investigation of the role of As-GSH complexes in the methylation of arsenite by methylcobalamin in the presence of GSH. For the first time, the As-GSH complexes were detected as products of this reaction.

Antimony speciation analysis:
MS identification and characterisation of Sb complexes with ribose containing biomolecules (sugars, DNA, RNA) was carried out using ES-MS. These analytical methods were also used to detect and characterise for the first time a Sb-citrate complex present in citrus juices stored in polyethylene terephthalate (PET) containers.

Pentavalent antimonials:
Despite their long clinical use, their metabolism in mammals, mode of action, toxicity and resistance are not yet completely understood. For this purpose, a series of HPLC-ICP-MS and HPLC-ESI-MS/MS methods were developed that allow for the detection and quantification of the Sb species present in such drugs as well as their metabolites.

Selenium speciation analysis:
Tandem MS methods for the determination of selenosugars in crude human urine were developed. These were used to detect and quantify slenosugars in crude human urine. Subsequently, improved quantitative measurements were carried out using the isotopically (82Se) labelled standard selenosugars as internal standards.

Development of other analytical for metal speciation:
The direct coupling of nanoelectrospray (nES) ion mobility spectrometry (IMS) with ICP-MS was demonstrated. Technical challenges involving the coupling of the air-based nES-IMS with the argon-based ICPMS were addressed and overcome. The resulting novel hyphenated technique has so far been used to determine the elemental composition of nanoparticles resulting from electrospraying solutions containing inorganic salts and acids.