Marcelo Blanco,^a Manel Alcalá,^a Josep M. González^b and Ester Torras^b
aUniversitat Autonoma de Barcelona, Department of Chemistry, Analytical Chemistry Unit, E-08193 Bellaterra, Spain. E-mail: marcel.blanco@uab.cat, manel.alcala@uab.cat
^bLaboratorios Menarini SA, c/ Alfons XII 587, E-08918 Badalona, Barcelona, Spain