This paper presents a high sensitivity and high frame rate hydrogen ion image sensor in standard CMOS process for high accuracy and high throughput hydrogen ion monitoring. A novel ion-to-current-to-voltage sensing front-end using 2-transistor (2T) and a column capacitive transimpedance instrumentation amplifier (CTIA) enable high pixel density, high sensitivity and rapid response time. A column successive approximate register (SAR)-Single Slope (SS) dual-mode analog-to-digital converter (ADC) is employed as it outperforms SS ADC on quantization speed and power efficiency while occupies less chip area to be able to fit in a pixel column compared with SAR ADC. Due to the novel sensing front-end and dual-mode ADC employed, the proposed CMOS ion image sensor system achieves a simulated 191mV/pH sensitivity and 2219 fps frame rate.