In this work new measurement techniques for the use in chemoresistors and electrochemical transistors are presented. The simultaneous two- and four-point measurement technique is used to discriminate between contact and bulk resistances in such sensors. By integrating two additional electrodes (reference and auxiliary) on the sensor chip, the possibility of electrochemical regeneration of conducting polymer based gas sensors is presented. By combination of an ion-selective electrode with an electrochemical transistor an ion-selective electrochemical transistor was introduced. In the second part new possibilities of creating conducting polymer metallic nanoparticle composites and a characterisation of such composites are presented. In the last chapter the use of graphene as a material for chemoresistor based gas sensors is evaluated. It is shown that modification of graphene by metallic nanoparticels leads to a higher sensitivity and selectivity of such sensors.