A 1^st order current-mode continuous-time delta-sigma modulator architecture is presented for in-sensor-site readout in electrochemical sensor arrays. The electrode-to-electrolyte interface is used as integration capacitance, followed by a Current-Controlled Oscillator-based quantizer. A relaxation oscillator is optimized to meet the requirements of Cyclic Voltammetry. Two circuit realizations are presented and investigated by means of simulation. Both modulators achieve 30 dB/decade noise shaping and reach an SNDR of 67 dB and 62 dB, respectively, at a signal bandwidth of 10 kHz. The reported modulators are highly efficient regarding area and power, and immune to noise and supply voltage variations.