Research topics
Use of secondary equilibria to enhance the chromatographic performance in reversed-phase liquid chromatography
The group started with this research line:
· based on a previous knowledge on the chemical equilibria with several publications and the determination of equilibrium constants
· based on a previous knowledge on micellar-enhanced spectrophotometry with several publications
· interested on doping control using micellar liquid chromatography, which could be benefited of the direct injection capability
Since 1990, the group has studied fundamental aspects in micellar liquid chromatography, including the proposal of retention models and retention mechanisms, and developed a number of methods to analyze pharmaceutical, clinical and food samples.
In 1996, the group began to be interested on the behaviour of ionisable compounds by proposing new models in micellar liquid chromatography. The research extended to classical RPLC in 2004.
In 2003, in collaboration with Prof. Alain Berthod the group began the work with ionic liquids.
In 2008, the group started with the research on high submicellar liquid chromatography
In 2011, the group was invited by Colin Poole to write a chapter on “Secondary equilibria” for the Handbook in Separation Science: Liquid Chromatography, published by Elsevier (Amsterdam, The Netherlands).
Modelling, treatment of signals in chromatography and optimisation
An optimisation in micellar liquid chromatography is particularly cumbersome, based on trial-and-error strategies due to the need of using two modifiers. In 1992, the group decided to apply interpretive strategies to improve the optimization of the experimental conditions in micellar liquid chromatography, proposing new perspectives to improve the reliability.
Since then, new models were proposed to include the effect of the organic solvent (in addition to the micelles) and the pH on the retention. Recently, this research has been extended to liquid chromatography with added ionic liquids and high submicellar chromatography.
Reliable optimizations require a reliable prediction of peak shape. This is also needed to improve the deconvolution of overlapped peaks or measure peak moments. Since 1996, the group has made an effort to improve the models to describe chromatographic peaks independently of their asymmetry or kurtosis. These models have been applied successfully to other fields were peaks are generated.
A big effort has been also made to improve the reliability of the optimization through a deep study of objective functions and the proposal of the peak purity to measure the resolution. This function considers both the peak retention and shape. Also, different optimization strategies have been developed, from which the search of complementary conditions and the peak count optimization can be highlighted.
The developed strategies have been applied to problems with one, two or three factors in diverse chromatographic modes.
Characterisation of chromatographic columns and combination of separation mechanisms
Classical methods to characterize columns are based on the retention and on the use of a selected group of compounds, which account to diverse properties affecting the retention and are chromatographed in selected conditions. The group is performing research on the validity of such approaches, extending the conclusions to a range of experimental conditions through similarity studies, and the measurement of the peak broadening and tailing through the proposal of the half-width plots.
Similarities of chromatographic columns have been examined in the absence and presence of diverse additives, and include monolithic columns and columns use for fast separations.
The combination of separation mechanisms have been approached through the use of complementary parallel columns, sequential coupling of columns and two-dimensional liquid chromatography
Development of methods for the analysis of pharmaceutical, clinical and food samples
All group members belong to the area of Analytical Chemistry in a Spanish university. They all have been involved in the development of methods for the analysis of diverse samples. The first methods used volumetric analysis, potentiometric analysis and spectroscopy (mainly spectrophotometry). Since 1990, a large number of publications deal with the analysis of pharmaceutical, clinical and food samples by micellar liquid chromatography.
Along the research, diverse advantages of the use of micellar mobile phases have been highlighted. A remarkable work has been done in the field of direct injection of samples to accelerate the analytical process.
Since 2005, most work on applied analysis has been developed by Samuel Carda-Broch in collaboration with Josep Esteve-Romero, who is also involve in the research on fundamentals of chromatographic techniques.