Shigekazu Tsurubou

High-sensitivity extraction-spectrophotometric determination of iron with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine and tetrabromophenolphthalein ethyl ester

A sensitive extraction-spectrophotometric method for the determination of iron has been developed. Iron(II) forms a complex cation with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) in aqueous solution and may be extracted into 1,2-dichloroethane (DCE) with tetrabromophenolphthalein ethyl ester (TBPE) as an ion pair at pH 5–7.5. The maximum absorbance of the extracted species occurs at 610 nm. The calibration graph is rectilinear over the range 0–0.25 p.p.m. of iron(II) and the apparent molar absorptivity of the ion-association complex is 1.9 × 105 l mol–1 cm–1. The extracted species has a molar ratio of Fe(II): PDT : TBPE = 1:3:2. The method has been applied to the determination of iron in various sera and also to river and well waters.

Improved extraction-separation of alkaline earths and lanthanides with the aid of an ion size-selective masking reagent

A water-soluble macrocyclic compound, 4′-sulfobenzo-18-crown-6 (SB18C6), was prepared and utilized as an ion size-selective masking reagent with a view to establishing a highly selective extraction–separation system. In the synergistic extraction of alkaline earths with 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone and trioctylphosphine oxide in cyclohexane or benzene, the extraction of those with larger ionic radii shifted to a higher pH region when SB18C6 was added to the aqueous phase, giving improved separations. A similar result was achieved in the extraction of lanthanides into chloroform with bis(2-ethylhexyl)phosphoric acid. The distribution of SB18C6 into cyclohexane, benzene or chloroform was so low in comparison with that of 18-crown-6 (18C6) and cryptand[2.2.2] that the synergistic extraction with 18C6, which usually reduces the selectivity, was not observed.

Ion-pair extraction of some cinchona alkaloids with various chiral organic anions

Abstract Some cinchona alkaloids, the quinine/quinidine and cinchonine/cinchonidine pairs, are extracted by ion-pair formation with some chiral amino acids and d -camphorsulfonic acid. Their extraction behaviors are examined and the differences between the two isomers are compared. These alkaloids are extracted into chloroform in the pH range 4–7 as the 1:1 ion-pair with the organic acid. The relationship between the distribution ratio of the ion-pair and pH is discussed. In the pH range between the pKa1 and pKa2 values of these alkaloids, logarithmic plots of the distribution ratio are independent of pH. In this pH region, the extraction constants are determined and the differences caused by the ion-pair formation are discussed.

Quantitative extraction separation systems of alkali and alkaline earth metal ions using cryptands as ion-size selective masking reagents

Quantitative separation systems have been successfully developed in the synergetic extraction of alkali and alkaline earth metal ions with benzoyltrifluoroacetone (BFA) and tri-n-butylphosphate (TBP) or tri-n-octylphosphine oxide (TOPO) into cyclohexane in the presence of cryptand as an ion-size selective masking reagent. Diazapolyoxabicyclic ligands (cryptands) exhibit the possibility to separate alkali and alkaline earth metal ions. On adding cryptand to the aqueous phase, the extractions of metal ions with larger ionic radii were markedly reduced. Consequently, the separation of the metal ions was greatly enhanced. Since the masking effect by cryptands depends on the pH, it is desirable to select the extractants which have the pKa values in alkaline region. Cryptand[2.2.1] and [2.2.2] were selected as the masking reagents in order to get the quantitative separations of alkali or alkaline earth metal ions. Quantitative extraction separations between Mg and Ca, and Li and Na were achieved in the synergetic extraction with BFA and TBP or TOPO in the presence of cryptand[2.2.1]. Ca could also be quantitatively separated from Sr with BFA and TBP in the presence of cryptand[2.2.2]. The stability constants of alkali and alkaline earths with cryptand[2.2.1] and [2.2.2] were obtained.

Liquid-liquid extraction of cinchona alkaloids by using some metal complexes of optically pure usnic acids

Abstract Liquid-liquid extraction of cinchona alkaloids by using some metal complexes of zinc(II), cobalt(II) and copper(II) with (+)- and (−)-usnic acids was studied. The synergic effect of the chelates was studied by adduct formation with neutral Lewis bases such as tri- n -octylphosphine oxide and optically active isomers of cinchona alkaloids. It was possible to differentiate between the adduct formation of quinine and that of quinidine, and also of cinchonine and of cinchonidine, in the synergic extraction of zinc(II) and cobalt(II) with (+)- and (−)-usnic acids.

Improvement of separation in the solvent extraction of alkaline earths by the use of 18-crown-6 as a masking reagent

The improvement of separability among alkaline earths is shown to be achieved by employing 18-crown-6 as a masking reagent.

Stereoselective adduct formation of α-acylcamphorato-copper(II) chelates with some chiral Lewis bases

The formation constants of the mono-adducts of α-acylcamphorato-copper(II) chelates such as (+)-Cu(facam)2, (−)-Cu(facam)2, (+)-Cu(hfbc)2 and (−)-Cu(hfbc)2 with some chiral Lewis bases were determined spectrophotometrically in benzene. In order to compare the adduct formation constants obtained with the (+)- and (−)-forms, some pairs of chiral Lewis bases such as 1-amino-2-propanol [(R)(−), (S)(+)], 1-(α-naphthyl)ethylamine [(R)(+), (S)(−)], α-phenyl ethylamine [(R)(+), (S)(−)] and also quinine and quinidine were examined as neutral ligands. Although not very pronounced, the effects of combinations obtained for (+)- or (−)-Cu(II) chelates and (+)- or (−)-ligands indicate that formation constants obtained by the formation of adducts with the ligands having different directions of the optical rotation seems to be superior to those with the same direction.