Electrochemical sensors and biosensors for the detection of doping substances and methods

Francesco Botrč1, Francesca Buiarelli2, Franco Mazzei3

1: Dipartimento di Controllo e Gestione delle Merci e del loro Impatto sull’Ambiente

Universitą "La Sapienza", Roma

2: Laboratorio Antidoping, Federazione Medico-Sportiva Italiana, Roma

3: Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive

Universitą "La Sapienza", Roma

 

The detection of doping agents and of their metabolites in the athletes urines is generally performed by GC-MS techniques. These methods, although extremely powerful, require an extensive pretreatment of the urine, including a solid-liquid or liquid-liquid extraction step, enzymatic or chemical hydrolysis (when needed), preconcentration, and derivatization.

While for the confirmation analysis chromatographic techniques with mass spectrometry detection still represent the unique analytical option (also from a merely normative point of view), electrochemical sensors and biosensors could represent a faster, simpler and more economical alternative for the preliminary screening analysis of doping substances and methods.

Analytical methods involving the use of electrodes and bioelectrodes for the detection of pharmaceuticals and their metabolites in biological fluids can be divided into three main classes:

 

  1. combined chromatographic-electrochemical techniques, in which the electrochemical sensor or biosensor, assembled into a flow-through cell, constitutes the sensing element of the chromatographic detection unit;

  2. stand-alone electrochemical or bioelectrochemical cells, where the detection unit is employed for batch measurements on a pre-purified fraction of the biological fluid (urine) to be assayed;

  3. electrochemical immunosensors, where the immunological interaction between the sensor and the sample gives rise to a detectable change of a defined electrochemical parameter.

While the amounts of studies carried out on biosensors belonging to class 3 is still too limited to draw an even preliminary picture of the real potentiality of the relevant methods, sensors included in classes 1 and 2 have already been evaluated on real samples. More precisely, class 1 refers to HPLC methods with amperometric detection, whose advantage with respect to traditional HPLC-UV and also to GC-MS methods is given by a drastically simplified pretreatment procedure; while class 2 includes a wide variety of methods based on polarographic and voltammetric techniques, mainly adsorptive cathodic stripping voltammetry, cyclic voltammetry and differential pulse voltammetry.

An outline of presently studied methods is presented, focusing on those classes of doping substances (primarily b 2- agonists and corticosteroids) missing a reliable screening procedure in doping control analysis, as well as on specific compounds (e.g. some diuretics) whose detection by traditional GC-MS techniques can be affected by various experimental artifacts.

Depending on the specific class of compounds to be detected, the extent of the pre-purification process, the nature of the electrode and of the applied electrochemical technique, the lowest detection limit varies from 100-200 ng/ml down to few ng/ml, thus theoretically matching the sensitivity needed by an antidoping assay.

The possibility of employing some newly developed electrochemical methods for the "in vivo" monitoring of biophysiological parameters strictly related to the athletic performance is also discussed.

 

Keywords: Electrochemical sensors, voltammetry, doping analysis, beta agonists.