Maria Filomena Camões is the co-ordinator of the environmental biogeochemistry research group CQE (Centro de Química Estrutural)-Ciências, developed over decades in the frame of the Department of Chemistry and Biochemistry of the Faculty of Sciences of the University of Lisbon, Portugal. Her research activity was initiated with the scientific paper ‘Enthalpy of Ionization of Water from Electro-motive Force Measurements’, Journal of the Chemical Society, Faraday Transactions I 69 (1973) 949, and the PhD project Calibration Procedures for Glass Electrodes, University of Newcastle-upon-Tyne, UK (October 1973). The former concerns physical chemistry of water – the universal solvent, whilst the latter addresses key issues of an analytical nature, such as that of measuring the acidity of aqueous solutions. This curious association has dictated an intense academic career that linked teaching and research in these broad fields and, more specifically, in electroanalytical chemistry, namely pH measurements, in which she plays a leading role.
Analytical chemistry differs from the other four main conventional branches of chemistry (inorganic chemistry, organic chemistry, physical chemistry and biochemistry) in the sense that while these are basically concerned with the investigation of the properties of matter of well-defined composition, the first uses this knowledge to ascertain such properties in samples of unknown composition. Hence, analytical chemistry is defined as a scientific discipline that develops and applies methods, instruments and strategies to obtain information on the composition and nature of matter in space and time, as well as on the value of these measurements, i.e. their uncertainty, validation and/or traceability to fundamental standards.
In addressing the identification and quantification of the various analytes present in the most diversified matrices, the analytical chemist deals with a vast range of scientific expertise, mastering both theoretical knowledge and practical skills.
Aqueous solutions, with the ubiquitous presence of hydrogen ions which define both the acidity of the media and the speciation of chemical elements through participation in multiple chemical reactions and equilibria, are of the highest relevance. This has led to a strong focus on pH measurements in both fundamental and applied issues, from the primary level to the end user.
In connection with development and test of models of electrolyte solutions, from dilute (ionic strength below 0.1 mol kg-1) to seawater, a complex saline medium (ionic strength ≈ 0.7 mol kg-1), the quality of pH values assessed at the end of a chain of measurement and calculation steps (‘The Measurement of pH – Definition, Standards and Procedures’, Pure Appl. Chem. 74 (2002) 2105-2136; Metrological challenges for measurements of key climatological observables. Part 3: Seawater pH, Metrologia 53 (2016) R26–R39) has turned out to be a major interest.
The fact that there are no pure substances, rather mixtures of major and minor components in a wide range of combinations and concentrations, from macro to trace levels, prone to significant interferences, is the biggest challenge which can be overcome by two basic routes: the choice of highly selective measuring methods and working conditions, and preceding measurements by separation, e.g. by chromatography.
Ions in solution are indicators of the composition of many material systems for which ion chromatography (IC) of aqueous solutions is an excellent analytical technique. Expertise in IC with conductimetric and spectrophotometric detections has been built with applications from human health to the environment, e.g. water quality and water soluble fraction of atmospheric aerosols (‘Ionic Composition of Seawaters and Derived Saline Solutions Determined by Ion Chromatography and its Relation to Other Water Quality Parameters’, Journal of Chromatography A, 1210, 1 (7 November 2008) 92-98; ‘Evaluation of the performance of the determination of anions in the water soluble fraction of atmospheric aerosols’, Talanta, 104 (2013) 10-16).
Measurement science in chemistry is implemented in all working areas, and concepts such as uncertainty, uncertainty traceability, fitness for the purpose and comparability have become everyday tools.
Participation in the Parent JRP project ENV05- Metrology for ocean salinity and acidity – the European Metrology (Geophysical Research Abstracts, Vol. 15, EGU2013-4665, 2013) led to the award of an EMRP Research Grant, REG2 – Novel Approach to Assess Concentration and Activity Coefficients of Chemical Species in Seawater – pH.
Aiming at contributing to recommendations on standards and procedures, current research is being conducted on the traceability of oceanic carbon cycle quantities, namely pH, CO2 and alkalinity, with assessment of their respective uncertainty budgets.
Work is developed in the frame of collaborations at national and international levels and in the scope of affiliation with organisations such as IUPAC (president Div. Analytical Chemistry, 2012-2013; chair of subcommittee on pH/SpH), Eurachem (chair, 2002-2004), BIPM/EAWG, IAPSO/SCOR/IAPWS, and COST.
Support is acknowledged from Fundação para a Ciência e a Tecnologia, namely through PEst-OE/QUI/UI0612/2013.