L. Maric et M. Siroki, EXTRACTION OF 4-(2-PYRIDYLAZO)RESORCINOL AND 4-(2-THIAZOLYLAZO)RESORCINOL WITH CHLOROFORM AND TETRAPHENYLARSONIUM AND PHOSPHONIUM CHLORIDES, Analytica chimica acta, 318(3), 1996, pp. 345-355
The extraction of 4-(2-pyridylazo)resorcinol (PAR) and 4-(2-thiazolyla
zo)resorcinol (TAR) with chloroform alone and in the presence of tetra
phenylarsonium or tetraphenylphosphonium chloride (Ph(4)XCl) was studi
ed. In the optimum pH range 3.5-5 for PAR and 1.5-5 for TAR, 94-95% of
the reagents was extracted into chloroform. In the presence of Ph(4)X
Cl in 10-100-fold excess 95-98% of PAR and TAR were extracted within t
he pH range 3.5-10 and 1.5-10, respectively. The species extracted wit
h chloroform alone were estimated to be H(2)R molecules. A quantitativ
e interpretation of PAR and TAR distribution between aqueous solution
(mu=0.33) and chloroform was made. Distribution constants for H(2)R we
re determined as 14.9 for PAR and 19.2 for TAR. In the presence of Ph(
4)XCl as extractant H(2)R molecules were predominantly extracted up to
pH 4; between pH 4 and pH 8 two species H(2)R and Ph(4)X(+)HR(-) were
transferred to the chloroform phase. Above pH 8 the Ph(4)X(+)HR(-) io
n pairs were the only extracted species. They were studied in solution
and by characterization of solid compounds isolated from the organic
phase and aqueous solution.