RESUMEN

On page 343, the abstract, the second line,with which octadecylsilyl silica (ODS), was impregnated with was studiedshould readwith which octadecylsilyl silica (ODS) was impregnated, was studied.

RESUMEN

Solid-phase extraction (SPE) of divalent metal ions with a lipophilic and potentially divalent hexadentate chelating reagent (H2L), with which octadecylsilyl silica (ODS), was impregnated with was studied to gain more insight into and develop the potential of this methodology. This is the first time to demonstrate that this reagent as well as other common nitrogen-containing reagents were retained both by adsorption due to hydrogen bonding between nitrogen atoms of the reagent and residual silanol groups in the ODS phase and by simple distribution into the hydrophobic space. An appreciably large amount of this reagent could be retained by the adsorption mechanism even with a relatively thin loading solution. The divalent metal ions of Mn(2+), Co(2+) and Zn(2+) were extracted as 1:1 neutral complexes ([ML]), while Ni(2+) and Cu(2+) as ion-pairs of 1:1 cationic complex ([MHL](+)) with anion in SPE with H2L. The extractability and selectivity were substantially the same as that in liquid-liquid extraction.

RESUMEN

Solvent extraction is a very effective method for the separation of metal ions. N,N'-bis(2-hydroxy-phenylmethyl)-N,N'-bis(2-pyridylmetyl)-1,2-ethanediamine derivatives have been researched for solvent extraction of metal ions. In this study. We synthesized a bis-ß-ketoester ligand and evaluated its selectivity in extracting divalent transition metal ions. The ligand, hexane-1,6-diyl bis (4,4,4-trifluoro-3-oxobutanoate) (H2hdfob or H2L) was synthesized in one step by transesterification of ethyl 4,4,4-trifluoroacetoacetate with 1,6-hexanediol. The multidentate ligand H2hdfob successfully extracted divalent transition metal ions into its organic phase. The relationship between logD, which is a distribution ratio (D), and pH or log[H2L]o exhibited linear relationships with slopes of approximately +2 and +1, respectively. Based on these results, we proposed a mechanism of extraction with H2hdfob. Extraction with tetradentate H2hdfob provides a new method for enhancing selectivity of divalent metal ions, in comparison to other bidentate ligands.

RESUMEN

An automatic flow-injection (FI) system including on-line separation by microdistillation and spectrophotometric detection has been developed for the determination of trace amounts of fluoride. This ion was separated from sample matrix by distillation in the presence of sulfuric and phosphoric acids, and was subsequently determined with spectrophotometry based on the mixed-ligand complex of lanthanum(III)-fluoride-alizarin complexone. The proposed FI system has high sampling frequency (20 samplesh(-1)), small sample size (600 microl) and the dynamic range of 0.05-15 mgl(-1) with relative standard deviations of below 1.2%. Interfering ions such as aluminum(III) and iron(III) was effectively eliminated. The method was successfully applied to the determination of fluoride in industrial drainage after water treatment.

RESUMEN

This investigation looked at the extraction ability of divalent transition metal ions onto an octadecyl silica gel (C18g) with a 4,4-trifluoro-1-(2-thienyl)-1,3-butadione (TTA) chelating agent. A method of retaining TTA onto C18g (TTA-C18g) was developed in order to adsorb the metal ions. The difference in the half-adsorption and half-extraction pH values between transition metals Ni2+-Co2+ was found to be 0.7 in this system. This is better than previously published results of 0.3 for the conventional extraction method using TTA in nitrobenzene. More than 96% of the metal ions in aqueous solution could be adsorbed onto TTA-C18g. Our system, which has no organic phase, can achieve a better removal or separation of transition metal ions than the conventional solvent-extraction methods using TTA in toluene or nitrobenzene.

Asunto(s)

RESUMEN

The X-ray crystal structure of the title complex, Co(Cl2bprpi) is described. In this complex the Co(II) center displays a distorted octahedral coordination geometry. The piperazine ring exhibits boat conformation, forming chelate rings and capping the Co atom. The N2-Col-N3 angle is 69.41(15) degrees, extremely smaller than 90 degrees. Because the small angle causes a large steric hindrance, the piperazine ring can be effective as an ion size-recognition site. The molecular structure is stabilized by intramolecular N-H...O hydrogen bonds and Cl...H contacts.

RESUMEN

Di-Schiff base ligand, N,N'-bis(2-pyridylmethylidene)-trans-1,2-diiminocyclohexane (trans-BPIC), having sufficient hydrophobicity acts as neutral bidentate ligand in ion-pair extraction of divalent metal cations into nitrobenzene with picrate anion. In present study, the effect of steric restriction by chemical structure around imine-N donor atoms in trans-BPIC analogs on their complexation with divalent metal cations in ion-pair extraction was investigated by using N,N'-bis(2-pyridylmethylidene)-cis-1,2-diiminocyclohexane (cis-BPIC) and N,N'-bis(2-pyridylmethylidene)-o-diiminobenezene (BPIB). The former was used to observe the effect by geometrical restriction and the latter was by conjugate restriction. In BPIB-NaPic system, the higher extractability was obtained than those in cis- and trans-BPIC systems, and this result seems to be led by the increase of steric distortion originated from conformational restriction. Namely, it is considered that the extractability can be controlled by steric restriction on the complexation.

RESUMEN

Structural control of Schiff base ligands for selective extraction of copper(II) was investigated by changing pendant arms and the distance between two imine-N donor atoms in ligands. Di-Schiff base ligands, N,N'-bis(2-quinolylmethylidene)-1,2-diiminoethane (BQIE), N,N'-bis(2-pyridylmethylidene)-1,3-diimino-2,2-dimethylpropane (BPMP) and N,N'-bis(2-quinolylmethylidene)-1,3-diimino-2,2-dimethylpropane (BQMP), were used as complexation reagents for ion-pair extraction of divalent transition metal cations into nitrobenzene with picrate anion. The pendant arms affected the lipophilicity of ligand to nitrobenzene, due to their polarity. The distance between two imine-N atoms, on the contrary, was a factor of controlling the extraction selectivity. BQMP has both 2-quinolyl pendant arms and trimethylene backbone structure; use of BQMP as a complexation reagent led to the selective extraction of Cu2+ in the system.