Sulpha-drug sensitive electrodes: selectivity and potentiometric titration
Yao, S.Z.; Xiao, J.; Nie, L.H.
Yao Xue Xue Bao 22(12): 889-895
1987
ISSN/ISBN: 0513-4870 PMID: 3450133 Document Number: 290332
Sulpha-drug sensitive electrodes have been suggested for the potentiometric titration of sulpha-drugs using a standard sulphuric acid solution as titrant with distinct potential jump at the equivalence point and a maximum error of 0.7%. Direct potentiometry is also possible. No significant interferences are caused by commonly met inorganic anions. The selectivity of the electrodes toward different sulpha-drugs has been investigated in detail. It has been found that for all electrodes tested including cetyltrioctylammonium sulphathiazole, sulphadoxine and sulphadimethoxine electrodes, the logKij values for the sulpha-drugs can be expressed as a function of molecular connectivity index, pHa and the electronic charge at the ionizing nitrogen atom of the amide group according to the following equation: logKij = a.chi. - b pKa + c.rho. - d. The correlation has been shown to be significant. However, the correlations between log Kij and molecular connectivity index, pKa, electronic charge either separately or binarily are rather poor.