Microextraction by packed sorbent (MEPS) to analyze catecholamines in innovative biological samples

A new microextraction by packed sorbent (MEPS) procedure coupled to a high-performance liquid chromatographic method has been developed for quantitation of catecholamines (i.e. norepinephrine, epinephrine and dopamine) in innovative biological samples, namely dried plasma and urine spots. Analyses were carried out on a C18 reversed-phase column using a mobile phase composed of 2.5% methanol and 97.5% aqueous citrate buffer, containing octanesulfonic acid. Coulometric detection was used, setting the first analytical cell at -0.350 V and the second analytical cell at +0.400 V. Dried matrices were purified by means of a fast and feasible MEPS procedure, optimized on C18 sorbent and requiring only a small amount of biological sample. The availability of miniaturized procedures allowed satisfying specific requirements that ought to be considered during pre-treatment intended for catecholamine analysis. The extraction yield values were always higher than 85% and sensitivity was good, with a limit of quantitation of 100 pg mL(-1) for all the analytes. Satisfactory results were also obtained in terms of linearity, precision and accuracy. The method was successfully applied to dried plasma and urine spots derived from two socially diversified groups, namely psychiatric patients and poly-drug abusers, in comparison to healthy volunteers.