Koichi Saitoh

Gel chromatography of acetylacetone and its metall(II, III) complexes in the merckogel or 2000-tetrahydrofuran system

Abstract The gel chromatographic behaviour of acetylacetone and its metal(II, III) complexes was studied, using the polyvinyl acetate gel (Merckogel OR-2000)-tetrahydrofuran system. Seven metal complexes, viz. , cobalt(III), iron(III), chromium(III), aluminium(III), copper(II), nickel(II) and beryllium(II), of acetylacetone were investigated. Experiments with some n -alkanes were also carried out for comparison. The elution characteristics, viz. , K av , HETP and skew ratio, were obtained with high precision with the aid of an on-line data processing system. The correlation between K av values and molar volumes of the solutes is discussed.

Reversed-phase high-performance thin-layer chromatography and column liquid chromatography of chlorophylls and their derivatives

Abstract The reversed-phase liquid chromatographic retention behaviour of chlorophylls-a and -b, pheophytins-a and -b and pheophorbides-a and -b has been studied on an octadecyl-bonded stationary phase with mobile phase solvents of different polarities, including alcohols, acetone, acetonitrile and mixtures of ethanol and water. The a type-of each chlorophyll derivative shows greater retention than the b type in every solvent tested. In both a and b series, the retention increases in the following order: pheophorbide

High-performance liquid chromatography of metal—tetraphenylporphyrin chelates on A C18-bonded stationary phase☆

The retention behaviour of meso-tetraphenylporphyrin (H2TPP) and its metal chelates with Mg(II), V(IV), Mn(III), Fe(III), Ni(II), Cu(II), Zn(II), Pd(H) and Cd(II) has been investigated on a C18-bonded stationary phase. The retention of the chelate depends on its central metal ion, increasing in the order Zn(II) < V(IV) < Fe(III) < Mg(II) ≈ Cd(II) ≈ (H2TPP) < Ni(II) ≈ Pd(II) < Cu(II) < Mn(III), although some irregulaties are found when using different solvents used. This retention sequence is approximately the reverse of those observed on silica gel and cellulose. The chelates of Mg(II), V(IV), Ni(II), Cu(II), Zn(II) and Pd(II) have been separated in ca. 8 min using a LiChrosorb RP-18 column (250 x 4 mm I.D.) with acetone–acetonitrile (40:60) as the mobile phase at a flow-rate of 1 ml/min.

Micellar electrokinetic capillary chromatography of haematoporphyrin, protoporphyrin and their copper and zinc complexes

Abstract The micellar electrokinetic chromatographic separation of haematoporphyrin IX (HP) and protoporphyrin IX (PP) in the forms of free acids and of metal complexes with zinc or copper is successful in a mixture of a micellar solution of sodium dodecyl sulphate (SDS) at pH 11 and dimethylformamide (10:2, v/v). All the porphyrins migrate in the direction of the electric field, i.e., from the positive end towards the grounded end of the capillary. The migration time of each porphyrin increases with increasing concentration of DMF in the carrier solution. The capacity factor calculated for the distribution of each porphyrin compound between the SDS micelles and the bulk solution varies nearly linearly with the concentration of the SDS micelles. The migration sequence, that is, the increasing order of migration time, for the porphyrins is Zn(HP)

Control of separation selectivity in micellar electrokinetic chromatography by modification of the micellar phase with solubilized organic compounds

On the basis of the data on the distribution of various neutral solutes between sodium dodecyl sulfate (SDS) micelles and water, the control of separation selectivity in micellar electrokinetic chromatography (MEKC) by modification of the micellar phase with organic additives has been proposed and applied to the separation of simple model compounds. It was found that the distribution constants between the micelles and water (Kd,mc), which were determined by means of MEKC, of the solutes possessing hydrophilic functional groups are much larger than those between heptane and water (Kd,hep), whereas the Kd,mc values of the solutes possessing no hydropholic groups are comparable to their Kd,hep values. This indicates that the former solutes are preferentially solubilized in the Stern layer of the micelles and that the latter are located in the hydrocarbon core. In MEKC separations of aromatic compounds and metal acetylacetonates, considerable changes in separation selectivity were caused by the addition of compounds possessing both hydrophilic functional groups such as alcohols, phenol and ketones to the SDS micellar solution. The variations of the retention factors of the analytes could be explained in terms of saturation of the solubilization sites in the Stern layer with the modifiers, specific interaction of the modifiers with the analytes via hydrogen bonding in the micelles, and expansion of the core volume with the hydrocarbon parts of the modifiers. Such effects of the micellar modification could improve the resolution as well as the selectivity of MEKC separations.

Separtation of metal tetrakis(p-tolyl)porphine complexes by reversed-phase high-performance liquid chromatography

SummaryThe feasibility of reversed-phase high-performance liquid chromatography for the separation of several metal complexes ofmeso-tetrakis(p-tolyl)porphine (TTP) is described. A combination of an octadecyl-bonded stationary phase with a non-aqueous polar mobile phase, such as an acetone-acetonitrile mixture, has proved effective for the separation. Thus, the TTP complexes of Mg, VO, Ni, Cu, Zn, and Pd and also TTP free acid were successfully separated in about 10min on a Li-Chrosorb RP-18 column (7μm, 250×4mm i.d.) with a 70∶30 (vol/vol) mixture of acetone and acetonitrile at a flow-rate of 1 mlmin−1.

High-performance thin-layer chromatography of metal complexes ofmeso-tetrakis(p-tolyl)porphyrin on cellulose and silica gel

SummaryThe migration behavior of metal complexes ofmeso-tetrakis(p-tolyl)porphyrin (TTP) are studied in HPTLC systems with cellulose and silica gel thin-layers and various organic solvents of relatively low polarity. The mobility of the metal complex tends to increase in the following orders of its central-metal elements: on cellulose, Mg(II)<Zn(II)<V(IV)<(H)<Pd(II)< Ni(II)≈Cu(II); on silica gel, Mg(II)<V(IV)<Zn(II)= (H)<Ni(II)≈Pd(II)⩽Cu(II). Recommendable phase system for the separation of metal-TTP complexes is a combination of silica gel thin-layer with a carbon disulfide-m-xylene mixture though the complexes of Ni, Cu and Pd are not completely resolved.

Gell Chromatography of β-diketones and their metal complexes : VI. Elution behavior of various β-diketones and their chromium(III) chelates on different gels☆

Abstract Seven β-diketones and their chromium(III) chelates were chromatographed on four gels with p-dioxan as eluent. Two poly(vinyl acetate) gels (Merckogel OR-PVA 500 and Merckogel OR-PVA 2000) and two polystyrene gel (Bio-Beads S-X8 and Poragel 60 A) were investigated. The distribution coefficients of each compound depend on the gel used. The increasing order of the distribution coefficients of the β-diketones and their chromium(III) chelates depend strongly on the gels, and cannot be simply correlated with the molecular weights of the compounds. The dependence of the distribution coefficients of β-diketones and their chromium(III) chelates on the gel is different from the of n-alkanes.

Control of selectivity in micellar electrokinetic chromatography by modification of sodium dodecyl sulfate micelles with organic hydroxy compounds

Modification of micellar phases with solubilized solutes was examined to control the separation in micellar electrokinetic chromatography (MEKC). The addition of organic hydroxy compounds (1-hexanol, cyclohexanol and phenol) as modifiers to a micellar solution of sodium dodecyl sulfate specifically decreased the capacity factor of some aromatic analytes possessing hydrophilic functional groups. The effect of phenol was different in selectivity to that of 1-hexanol and cyclohexanol. The effects of these modifiers were mainly explained in terms of the saturation of the micellar palisade layer with the modifiers and the hydrogen-bond interaction between the modifier and analyte molecules in the micellar phase. Such micellar modification were applied to improve the MEKC separation.

Distribution coefficients of acetylacetone and tris(acetylacetonato)chromium(III) in the Merckogel OR-2000-chloroform system☆

Abstract In order to clarify the mechanism of the separation of species containing metals by gel chromatography, the influence of column temperature and amount of sample on the distribution coefficient was studied. Acetylacetone and tris(acetylacetonato)-chromium(III) were selected as model compounds, and a chromatographic system consisting of Merckogel OR-2000 and chloroform was used. The distribution coefficient was influenced neither by the amount of sample nor by temperature, and the elution peak was symmetrical. It was concluded that the contribution of adsorption or partition was negligible and the sieving effect was the dominant factor in the separation mechanism. A new technique of packing, the “closed packing method”, was adopted successfully. It was a simpler and more reliable method than other methods for the column system used in the present work.