Potentiometric sensor for non invasive lactate determination in human sweat

The present work describes a non invasive lactate sensing in sweat during workout. The sensing system is based on a non-equilibrium potentiometric measure performed using disposable, chemically modified, screen printed carbon electrodes (SPCEs) that can be wetted with sweat during the exercise. The potentiometric signal, which is proportional to lactate concentration in sweat, is produced by a redox reaction activated by UV radiation, as opposed to the enzymatic reaction employed in traditional, blood-based measuring devices. The sensing system exhibits chemical selectivity toward lactate with linearity from 1 mM up to 180 mM. The dynamic linear range is suitable for measurement of lactate in sweat, which is more than 10 times concentrated than hematic lactate and reaches more than 100 mM in sweat during workout. The noninvasive measure can be repeated many times during exercise and during the recovery time in order to get personal information on the physiological and training status as well as on the physical performance. The device was successfully applied to several human subjects for the measurement of sweat lactate during prolonged cycling exercise. During the exercise sweat was simultaneously sampled on filter paper and extracted in water, and the lactate was determined by HPLC for method validation. The lactate concentration changes during the exercise reflected the intensity of physical effort. This method has perspectives in many sport disciplines as well as in health care and biomedical area.