Electroanalytical method of TCPP and its supramolecular system with cyclodextrins

In this paper, electroanalytical method of tetrakis (4-carboxylphenyl) porphyrin (TCPP) has been established. In a supporting electrolyte of KH2PO4–Na2HPO4 (pH 7.0), a sensitive second derivative reduction peak of TCPP was found by single-sweep oscillopolarography. The potential peak is −0.70 V (versus SCE).The relationship between peak height and the concentration of TCPP is linear from 1×10−7 to 2×10−5 mol l−1, the relative standard deviation (R.S.D.) was 0.41% (n=8), and the recovery of TCPP varied from 95.8–105.4%.The interaction of cyclodextrins (CD) with TCPP in NH3–NH4Cl (pH 8.0) has been studied by polarography. The TCPP can form the 1:1 inclusion complex with β-CD, γ-CD, hydroxylpropyl-β-CD, sulfurbutylether-β-CD and trimethyl-β-CD. “Current method” has been used to determine the formation constants of TCPP with five CDs. The result shows that the inclusion ability of hydroxylpropyl-β-CD is very strong. Moreover, modified β-CD has stronger inclusion capacity than native β-CD. The formation constant of TCPP with γ-CD is much greater than that of TCPP with β-CD, because the γ-CD has a bigger cavity that can match with the size of the meso-phenyl of TCPP. The supramolecular data will provide useful information for further application of TCPP.