or to rely on time resolved procedures such as chronopotentiometry or chronoamperommetry (see Figure ). When closer to the detection limit, chronopotentiometry can be once again used to look at the relationship between charge passed in the detection cell and fluorescence observed in the reporting cell. As shown in Figure , the fluorescent signal decreases as the charge passed is reduced, with charges as low as 5 pC observed by changing the current flowing through the working electrode. It should be noted that the exact value of the current applied to the working electrode is not known. According to the potentiostat's specifications, the galvanostatic control has a stated accuracy of ±1% of the current range and an additional ±10 pA. Whilst it is clear that the fluorescence decreases with applied current, for better accuracy it would be necessary to use potentiostatic control on even smaller electrodes (i.e. nanoelectrodes), or an analogue galvanostat composed of a stable voltage source and resistor of much larger resistance than the impedance of the studied cell in series. Currents below 1 pA were not applicable using galvanostatic mode, resulting in each signal below this current having the same fluorescence signal. This result suggests the leakage current value in the applied system is ca. 1 pA. In order to see if smaller charges could be observed, the time-scale of the chronopotentiometry could also be reduced.