Experimental optimization of selective hydrazine detection in flow injection analysis using a carbon paste electrode modified with copper porphyrin occluded into zeolite cavity

A carbon paste electrode modified with copper porphyrin occluded into zeoli te cavity was developed for sensing hydrazine in flow system. The sensor pr esented a high sensitivity and selectivity for hydrazine concentration in t he flow system. The flow system was optimized by factorial design consideri ng a two level, three factor factorial design (the factors were applied pot ential, sampling volume and flow rate). The sensitivity and analytical freq uency were considered as the most important parameters for the system. The best condition for the system was sampling volume of 50 mu l, applied poten tial of 270 mV vs. SCE and a flow rate of 1 ml min(-1). In this optimized c ondition, the electrode can improve its stability, sensitivity and selectiv ity. The operational range was between 5 up to 60 mu mol l(-1), adjusted by the equation Y=1.9(+/-0.1)+0.20(+/-0.01)[hydrazine]-0.0014(+/-0.0001)[hydr azine](2), with a correlation coefficient of 0.9995 for n=8. The analytical frequency was about 70 determinations per hour and the system was stable f or at least two months in continuous use.