A low power analog frontend (AFE) for Ion-Sensitive Field effect Transistor sensor readout presented. The AFE is demonstrated with off-the-shelf components. It includes a biasing circuit to an ISFET sensor, a noise rejecting current readout circuit, and a igma-delta analog to digital converter. The digital output can be interpreted by a simple counter to acquire the ion-concentration in a drop of liquid on top of the calibrated ISFET sensor. A PH sensing experiment is performed validate the AFE. Total power consumption is less than 40 μW with 1.8 V supply.