A portable, self-contained medical diagnostic system is provided for assessing urinary function. In accordance with one embodiment of the invention, the fuel cell is used to either recharge a battery, or to power an application device, when the AC source andor the DC source are unavailable. The first wheeled component comprises a unit for screening the metal scrap-contaminated soil into at least a coarser fraction and a finer fraction. The determined compensation voltage is compared to calibration data relating to a compensation voltage for transmitting the at least a first type of indicator ions through the analyzer region at the given asymmetric waveform voltage in the presence of each of a plurality of different known trace amounts of the vapour mixed with the first gas.