Pulsed coulometric detection of carbohydrates at a constant detection potential at gold electrodes in alkaline media

A significant increase in the signal-to-noise ratio for the pulsed amperometric detection (PAD) of carbohydrates at gold electrodes is obtained by increasing the length of the current integration period (t_i) from the traditional value of 16.7 ms (i.e., $\text{1}\text{60}$ Hz). For t_i > 16.7 ms, the integrated response (q, coulombs) is plotted as the signal. This pulsed coulometric detection (PCD) is applied in a flow-injection system. For t_i = 500 ms, the detection limit with the instrumentation used is 1 μM (S/N = 2) for glucose which is a significant improvement on the value 35 μM found with PAD. The absolute detection limits for glucose and sucrose are ca. 50 pmol and 125 pmol, respectively, in 50-μl samples. Calibration plots (q_p vs. C^b) for PCD are linear over significantly larger dynamic ranges than those observed for PAD because of the lower detection limits.