Yoshifumi Akama

Extraction mechanism of Cr(VI) on the aqueous two-phase system of tetrabutylammonium bromide and (NH4)2SO4 mixture

An aqueous two-phase system of tetrabutylammonium bromide (TBAB) and (NH(4))(2)SO(4) mixture has been developed for the extractive preconcentration and separation of certain compounds. TBAB concentration in upper phase is much higher than that of bottom solution. This new aqueous two-phase system is proposed for the highly selective extraction of Cr(VI) from large amounts of Cr(3+). The Cr(VI) is found to be extracted into the TBAB-rich upper phase due to ion pair formation such as HCrO(4)(-) . TBAB(+). The Cr(VI) was sufficiently extracted into the upper phase in the pH range from 1 to 5. The proposed method has been applied to the determination of trace of Cr(VI) in wastewater samples with a coefficient of variation less than 3.2%. The recovery obtained was not lower than 90%. The determination limit for the Cr(VI) was found to be 60 mug l(-1) in 10 ml of sample solution.

Melatonin, a pineal secretory product with antioxidant properties, protects against cisplatin-induced nephrotoxicity in rats.

In an attempt to define the role of the pineal secretory melatonin and an analogue, 6‐hydroxymelatonin (6‐OHM), in limiting oxidative stress, the present study investigated the cisplatin (CP)‐induced alteration in the renal antioxidant system and nephroprotection with the two indolamines. Melatonin (5 mg/kg), 6‐OHM (5 mg/kg), or an equal volume of saline were administered intraperitoneally (i.p.) to male Sprague–Dawley rats 30 min prior to an i.p. injection of CP (7 mg/kg). After CP treatment, the animals each received indolamine or saline every day and were sacrificed 3 or 5 days later and plasma as well as kidney were collected. Both plasma creatinine and blood urea nitrogen increased significantly following CP administration alone; these values decreased significantly with melatonin co‐treatment of CP‐treated rats. In the kidney, CP decreased the levels of GSH (reduced glutathione)/GSSG (oxidized glutathione) ratio, an index directly related to oxidative stress. When animals were treated with melatonin, the reduction in the GSH/GSSG ratio was prevented. Treatment of CP‐enhanced lipid peroxidation in the kidney was again prevented in animals treated with melatonin. The activity of the antioxidant enzyme, glutathione peroxidase (GSH‐Px), decreased as a result of CP administration, which was restored to control levels with melatonin co‐treatment. Upon histological analysis, damage to the proximal tubular cells was seen in the kidneys of CP‐treated rats; these changes were prevented by melatonin treatment. 6‐OHM has been shown to have some antioxidative capacity, however, the protective effects of 6‐OHM against CP‐induced nephrotoxicity were less than those of melatonin. The residual platinum concentration in the kidney of melatonin co‐treated rats was significantly lower than that of rats treated with CP alone. It is concluded that administration of CP imposes a severe oxidative stress to renal tissue and melatonin confers protection against the oxidative damage associated with CP. This mechanism may be reasonably attributed to its radical scavenging activity, to its GSH‐Px activating property, and/or to its regulatory activity for renal function.

Pre-concentration of copper, cobalt and nickel with 3-methyl-1-phenyl-4-stearoyl-5-pyrazolone loaded on silica gel

3-Methyl-1-phenyl-4-stearoyl-5-pyrazolone loaded on to silica gel was used as a pre-concentration reagent for copper, cobalt and nickel prior to atomic absorption spectrometric determination. Both batch and column methods were used for the concentration of the above metals. These metals are quantitatively retained on the proposed adsorbent above pH 4. The adsorption-elution cycle can be repeated ten times with no observable decline in the efficiency of the adsorbent. As there are no observable effects due to changes in the volume of sample solution up to a volume of 1 l, a concentration factor of 40 can be achieved. The method has been applied to samples of sodium chloride solution and tap water.

Adsorption of chromium (VI) from aqueous solutions by cellulose modified with β-CD and quaternary ammonium groups

Cellulose powder was grafted with the vinyl monomer glycidyl methacrylate using ceric ammonium nitrate as initiator and was further derived with β-CD and quaternary ammonium groups to build Cell-g-GMA-β-CDN(+) adsorbent. Epoxy cellulose was made up of Cell-g-GMA and Cell-hydro-g-GMA, and was found to contain 3.71 mmol g(-1) epoxy groups. The adsorption process of the modified cellulose was described by the Langmuir model of adsorption well, and the maximum adsorption capacity of chromium (VI) reached 61.05 mg g(-1). The adsorption-desorption tests of β-CDN(+)-type cellulose derivatives exhibited that the reproducibility of the adsorbent was well and the adsorbent could be reused five times at least.

Selective separation of cadmium from cobalt, copper, iron (III) and zinc by water-based two-phase system of tetrabutylammonium bromide

An aqueous two-phase system of tetrabutylammonim. bromide (TBAB) and (NH(4))(2)SO(4)mixture is proposed for the selective extraction of trace Cd(2+) from large amounts of Co(2+), Cu(2+), Fe(3+) and Zn(2+). Transparent two-phase system is prepared by mixing 3 ml of 1.0 mol/l TBAB, and 2 ml of sample solution and 1.1g of (NH(4))(2)SO(4), the two-phase system thus obtained is of 1.5 ml upper phase and 4.1 ml bottom phase. TBAB was distributed between the upper and bottom phases respectively, but the concentration in upper phase is much higher than that of the bottom phase. The results showed that Cd(2+) is selectively extracted into the upper phase in the pH ranges 1.0-9.0, while Co(2+) Cu(2+) and Fe(3+) ions were little extracted (<1%) at pH 3.0. Zinc ion was extracted to upper phase by about 24%, but it did not interfere the extraction of Cd(2+). The interaction between CdBr(4)(2-) and TBA(+) plays an important role in the extraction process.

Selective preconcentration of Au(III), Pt(IV) and Pd(II) on silica gel modified with γ-aminopropyltriethoxysilane

Abstract Silica gel functionalized by reaction with γ-aminopropyltriethoxysilane was prepared and its adsorption characteirstics for metal ions were studied. This material selectively removes the Au(III), Pt(IV) and Pd(II) chloro complex ions from sample solutions containing Fe(III) and Cu(II) ions by ion exchange.

The study of the partitioning mechanism of methyl orange in an aqueous two-phase system.

An aqueous two-phase system of dodecyl triethylammonium bromide (C(12)NE, cationic surfactant) and sodium dodecyl sulfate (SDS, anionic surfactant) mixture is proposed for the extraction of some dyes and porphyrin compounds. Transparent two phase-systems are formed when the surfactant concentrations and C(12)NE/SDS ratios are in certain regions. In this study, the aqueous two phase-systems were prepared by mixing 0.1 mol l(-1) C(12)NE and SDS with a molar ratio of 1.7:1.0. The results showed that negatively charged chlorophyll (sodium copper chlorophyllin) and positively charged dye (methyl violet) were efficiently extracted into the upper phase. The negatively charged methyl orange (pH>7) was moved into the upper phase mostly while amphoteric methyl orange (pH<3) was distributed in the two phases uniformly. Except for hydrophobic force, charge interaction between solute and surfactant also play an important role in the extraction process.

Studies on extraction of copper(II) with 1-phenyl-3-methyl-4-acyl-5-pyrazolone

Abstract The extraction of Cu(II) with 1-phenyl-3-methyl-4-acyl-5-pyrazolone (HA), in different organic solvents has been studied. The extraction mechanism of Cu(II) and the composition of the extracted species has been determined. Cu(II) was extracted as CuA2, or in the presence of TOPO, as CuA2TOPO. The extraction constants do not change regularly with increasing the length of acyl chain in the 1-phenyl-3-methyl-4-acyl-5-pyrazolone derivatives. The effect of the temperature on the extraction of Cu(II) has also been investigated.

Aqueous two-phase system of cationic and anionic surfactant mixture and its application to the extraction of porphyrins and metalloporphyrins

Abstract Aqueous two-phase system is obtained when a cationic surfactant with bigger alkyl polar head groups such as dodecyltriethylammonium bromide (C12NE) is mixed with an anionic surfactant like sodium dodecyl sulfate (SDS) at certain surfactant concentrations and molar ratios. When C12NE is in excess, the top phase is opalescent and is a surfactant-rich micellar solution, while the bottom phase is transparent and is a dilute micellar solution. Such a new aqueous two-phase separation system is employed in extractive separation practice. Several dyes with different chemical structure like anthraquinone, methyl red and methylene blue partitioned in the two-phase system are investigated. Porphyrin compounds and metalloporphyrins, i.e., hematoporphyrin (hemato), uroporphyrin (uro), Cu-TPPS4 (tetraphenylporphine tetrasulfonic acid), Zn-TPPS4, Cu-T-4(TAP)P (tetrakis(p-trimethylammoniophenyl) porphine), are also extracted with the present two-phase system. It is found that hydrophobic as well as charge interaction between a substance partitioned in the system and the micelles are predominant factors that govern the extraction.

Raman spectroscopic study on keto-enol tautomers of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone

Abstract Raman spectral changes of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) were measured and its structural changes were studied when the crystal was heated continuously. The two peaks which appeared at 1599 and 1640 cm−1 for keto-PMBP were assigned to the intermolecular hydrogen bonded carbonyl (in the pyrazolone ring) and the free carbonyl (in the benzoyl group) groups, respectively. The keto form of PMBP changed into the enol form when it was melted. The peak at 1640 cm−1 disappeared at the same time. The structural change of keto-form PMBP was confirmed by the present continuous heating-Raman spectroscopic method.