Analytical Sciences

Experimental Optimization of Selective Hydrazine Detection in Flow Injection Analysis Using a Carbon Paste Electrode Modified with Copper Porphyrin Occluded into Zeolite Cavity

Silvia V. GUERRA*, Lauro T. KUBOTA* ⁺, Claudia R. XAVIER** and Shirley NAKAGAKI**

*Instituto de QuyõÊca-Unicamp, P. O. Box 6154, 13083-970 Campinas, SP, Brazil
**Departamento de QuyõÊca da Universidade Federal do ParantK Curitiba, Pr, Brazil

A carbon paste electrode modified with copper porphyrin occluded into zeolite cavity was developed for sensing hydrazine in flow system. The sensor presented a high sensitivity and selectivity for hydrazine concentration in the flow system. The flow system was optimized by factorial design considering a two level, three factor factorial design (the factors were applied potential, sampling volume and flow rate). The sensitivity and analytical frequency were considered as the most important parameters for the system. The best condition for the system was sampling volume of 50 ml, applied potential of 270 mV vs. SCE and a flow rate of 1 ml min -1 . In this optimized condition, the electrode can improve its sta-bility, sensitivity and selectivity. The operational range was between 5 up to 60 mmol l -1 , adjusted by the equation Y=1.9(±°.1)+0.20(±°.01)[hydrazine]-0.0014(±°.0001)[hydrazine]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 for at least two months in continu-ous use. (Keywords: Experimental optimization, modified zeolite, amperometric sensor, FIA, hydrazine determination)

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