Development of amperometric ion sensor array for multi-ion detection

We have successfully integrated an amperometric ion sensor array on an Si chip which simultaneously detects potassium ion (K+) and sodium ion (Na+). The sensor array has two kinds of selective electrodes which exhibit high sensitivity for K+ over Na+ (K+-selective electrode) and for Na+ over K+ (Na+-selective electrode), respectively. Ion transfer voltammetry method was adopted for the detection of these ions utilizing ionophore-doped PVC (polyvinyl chloride) membrane because it is difficult to detect these ions using redox reaction. K+- and Na+-selective electrodes have sensitivity of -5.1 and -4.0 nA/μM, respectively, while the differences in the sensitivity were 2.83 and 1.54 times in the K+- and Na+-selective electrodes, respectively. Consequently, selectivity on detection of multiple ions was demonstrated by an integrated sensor array on a Si chip, leading to miniaturized amperometric ion sensor array systems.