Polymer chip incorporated with anionic surfactant-ISFET for microflow analysis of anionic surfactants

An anionic surfactant ion-sensitive field-effect transistor (anionic surfactant-FET) based on a hydrophobic quaternary ammonium salt, tetrahexadecylammonium bromide was developed. The anionic surfactant-FET shows an almost Nernstian response to sodium dodecylbenzenesulfonate (NaDBS) ion in the concentration range from 1.0 × 10^-6 to 1.0 × 10 ^-3 M with a slope of 56.6 ± 3.3 mV/decade. The anionic surfactant-FET can be used in pH range of pH 3-10. The anionic surfactant-FET shows excellently selective for the DBS^- ion over small inorganic anions, but shows the similar selectivity to other anionic surfactants such as tetradecylsulfate and dodecylsulfate ions. The anionic surfactant-FET in a batch system and the two channel microchip incorporated with anionic surfactant-ISFET showed almost the similar performance in low detection limits, dynamic range of the calibration curve, the slope sensitivity and the stability of the potential response. From the results, the polymer-based microchip incorporated with ISFET, which is fabricated using polystyrene plates and stainless wires as a template of channel, can be useful in various kinds of applications for microflow analysis.