Masaki Tachibana

Evaluation of titania as an ion-exchanger and as a ligand-exchanger in HPLC

SummaryThe chromatographic properties of titania have been compared with those of zirconia and alumina, by comparison of their relative Lewis acidities whenp-substituted benzoic acids were chromatographed with aqueous mobile phases. The retention behavior ofp-substituted benzoic acids on titania was found to be similar to that on zirconia; the slopes of plots of retention factors against solute pKa were approximately parallel for all pH values and the slopes obtained were similar to the average slope for zirconia. The shapes of solute peaks on titania were more symmetrical than on alumina and zirconia. The effect of calcination temperature on the chromatographic properties of titania was examined by use of titania prepared at different temperatures. The results obtained clearly showed that the preparation temperature affected the chromatographic properties of titania. It seemed, for example, that titania dried at 40°C behaved as a cation-exchanger, titania heated at 200°C behaved as an amphoteric exchanger, and titania calcined at 600°C behaved as an anion-exchanger in the pH range 4.1–6.5 It was found that the control of the preparation temperature enabled us to make effective use of titania.

Retention behavior of monosaccharides and disaccharides on titania

SummaryThe ability of titania to recognize the position of hydroxyl groups was previously found to result from the formation of a chelate ring between a titanium ion and the two oxygen atoms of the hydroxyl group and carboxylate anion of 2-hydroxycarboxylic acids. We investigated how titania could recognize the position of hydroxyl group of monosaccharides and disaccharides. The retention behavior of monosaccharides and disaccharides on titania was found to be characteristic. Thus, sucrose was eluted much faster than the other sugars, whereas D-ribose, D-fructose and L-sorbose were most strongly retained on titania of all of the sugars tested. It is apparent that the sugars strongly retained on titania have an axial hydroxyl group or neighboring hydroxyl groups of the same conformation.

Poly(allylamine) beads as selective sorbent for preconcentration of formaldehyde and acetaldehyde in high-performance liquid chromatographic analysis

Formaldehyde and acetaldehyde in water were determined by preconcentration with poly(allylamine) beads, derivatization with 2,4-dinitrophenylhydrazine (DPH) and analysis by HPLC. Poly(allylamine) beads (0.5 g) were used to adsorb formaldehyde and acetaldehyde at 1.2-150 microg l(-1) and 3.5-220 microg l(-1) from water (1 l). The concentration factor is 50 fold. The aldehydes were eluted and derivatized with 2 mM DPH in 0.5 M H2SO4 (10 ml). The time of analysis was 1 h. The detection limits (S/N=3) for formaldehyde and acetaldehyde were 0.6 and 2 microg l(-1), respectively.

Correlation Between Inclusion Formation Constant and DistributionCoefficient in a Liquid–Liquid Extraction System Consisting ofHydrocarbon Solvents and Aqueous Dimethyl Sulfoxide Solutions ofβ-Cyclodextrin

Carbazole was used as a fluorescence probe for the investigation of the correlation between the apparent formation constant (K f ) for an inclusion complex of β-cyclodextrin (CD) and the distribution coefficient (K d ) on liquid–liquid extraction. Single batch extractions of carbazole were performed at 25 ± 1 °C from three types of hydrocarbon solvents into an aqueous dimethyl sulfoxide (DMSO) phase containing CD or nothing. Both the K f and K d values for carbazole can be determined simultaneously under the same conditions on the basis of the extraction data. A plot of log K f versus log K d gives a straight line in both extraction systems of heptane and dodecane, with good correlations (0.9996 and 0.9992) and similar slopes (-0.675 and -0.672). The experimental results obtained from the cyclohexane–aqueous DMSO system suggest that the hydrocarbon used as the organic phase competes with carbazole for complexation with CD. The linear relationship is embodied in the form of an empirical equation, log K fOB = -0.673 log K d + log (K fCR /K fHY ), where K fOB is the observed K f value for a 1:1 carbazole–CD complex in the aqueous DMSO medium and K fCR and K fHY are the absolute K f values in water for the carbazole– and hydrocarbon–CD complexes, respectively.

Application of solvent extraction and synchronous spectrofluorimetry to the determination of the formation constant for a 1:1 complex of carbazole withβ-cyclodextrin in water-dimethyl sulfoxide medium

Extraction of carbazole in heptane was performed at 25±1°C with an aqueous dimethyl sulfoxide (DMSO) medium containing β-cyclodextrin (βCD) at consecutive concentrations in the range of 0–10 mM. The fluorescence intensity of carbazole remaining in the heptane phase was measured by synchronous scanning fluorimetry. The apparent formation constant (Kf) for a 1:1 carbazole: βCD inclusion complex in water-DMSO medium was determined by using a linear plot of the distribution ratio calculated from the fluorescence intensities vs. the β-CD concentration. The values thus obtained ranged from 477 M−1 in a 10% v/v DMSO medium to 12.1 M−1 in a 60% v/v medium. Good linear relationships were observed between logKf and the DMSO concentration ([DMSO]), and also between logKf and the logarithm of the distribution coefficient (Kd) for carbazole. The formation constant in 100% water was estimated to be approximately 1.0×103 M−1 on the basis of the logKf vs. [DMSO] and the logKf vs. logKd correlations.

Solvent extraction of acenaphthene from dodecane into aqueous β-cyclodextrin medium and application to synchronous spectrofluorimetric determination in kerosene

Acenaphthene can be selectively extracted from a dodecane phase into a water–dimethyl sulfoxide (20% v/v) medium containing β-cyclodextrin (10 mg cm–3), potassium iodide (300 mg cm–3) and sodium thiosulfate pentahydrate (15 mg cm–3) with a shaking time of 3 min. The distribution ratio for the solvent extraction was 0.292 with a relative standard deviation of 8.3% at 20 ± 1 °C. The amount of acenaphthene extracted from 1 cm3 of dodecane by three 8 cm3 successive batch extractions was 97.3% in calculations and 95.1% in practice. The extraction behaviours of several typical two- and three-ring aromatic compounds were investigated under the same conditions. Selective extraction based on complexation with β-cyclodextrin was applied to the synchronous spectrofluorimetric determination of acenaphthene in commercially available kerosene.

Selective synchronous spectrofluorimetric detection of acenaphthene in mixtures of three-ring aromatic compounds based on complexation with cyclomaltoheptaose (β-cyclodextrin) in the presence of iodide ion as quencher

Acenaphthene in a three-ring aromatic compound mixture can be selectively detected in a dimethyl sulfoxide–water (1 + 4) medium containing both cyclomaltoheptaose (β-cyclodextrin, β-CDx) and potassium iodide by synchronous fluorescence spectrometry. In this medium, synchronous fluorescence of acenaphthene was hardly quenched by iodide ion because of the inclusion complexation with β-CDx. According to Ksv values calculated from the simple Stern–Volmer plots, the fluorescence sensitivity to acenaphthene in the iodide-quenching state increased 364-fold in the presence of β-CDx, whereas those to other three-ring aromatics increased only 2–3-fold. Acenaphthene could be characterized by the double peaks at 322 and 328 nm in the synchronous fluorescence spectrum measured with Δλ= 7 nm. The method was applied directly to the selective detection of acenaphthene in mixtures of typical three-ring compounds, including dibenzofuran, fluorene, dibenzothiophene, carbazole, phenanthrene and anthracene, and in commercially available dibenzofuran.

Selective and simultaneous determination of trace amounts of 5H-benzo[b]carbazole and naphthacene in a variety of analogous chemical using the zone-melting technique and synchronous fluorescence spectrometry

5H-Benzo[b]carbazole and naphthacene can be selectively separated from analogous species by zone melting in a bibenzyl system because of the formation of solid solutions with distribution coefficients almost equal to unity. In practice, a uniform mixture of a polycyclic aromatic sample (10–100 mg) with bibenzyl containing 0.1% of 2,6-di-tert-butyl-4-methylphenol (3.6 g) was zone melted in a 4 mm i.d. glass tube. Only the first 0.2–0.4 fraction of the zone-molten ingot was cut off and the amounts of the two analytes in this fraction were simultaneously measured by using synchronous fluorimetry. Each content of the analytes in the original sample can be calculated from the resulting amount and other experimental data. The method was applied directly to the determination of parts per million levels of 5H-benzo[b]carbazole and naphthacene in commercially available chrysene, pyrene, carbazole and some other chemicals.

Measurements of Room-Temperature Phosphorescence Spectra of Polycyclic Aromatic Compounds Using Pullulan Films Containing β-Cyclodextrin and 2-Bromoethanol

A clear film was easily prepared by air-drying anaqueous solution of pullulan (6%w/w) containing β-cyclodextrin(CD, 1%w/w) and 2-bromoethanol (1%v/w). The resultingpullulan film was used as a substrate for simple measurements ofroom-temperature phosphorescence (RTP) spectra of polycyclicaromatic compounds (PACs). Only a drop (ca. 10 μL) of a 100 μgmL-1 sample solution in 95% ethanol was spotted onto the surfaceof the disk film (7–8 mm diameter) and the solvent wasallowed to evaporate at room temperature. The sample-spottedfilm was pasted on a glass plate (75 × 20 × 1 mm) with smallamounts of a starch glue. The plate was mounted into a solidsample holder, or alternatively inserted diagonally into a 1-cm cell holder.Without a dry gas flush during the measurements, RTPspectra based on the CD inclusion complexes of PACs wereobtained from six typical two- and three-ring compounds,including naphthalene, acenaphthene, fluorene, phenanthrene,carbazole, and dibenzofuran. Only anthracene did notproduce a discernable phosphorescence signal by the presenttechnique. This technique was directly applied to the spectralidentification of acenaphthene in commercially available kerosene.

Rapid spectrophotometric method for the determination of fluorene

Fluorene reacts rapidly with the sodium salt of 1,2-naphthoquinone-4-sulphonic acid in an alkaline dimethyl sulphoxide medium containing sodium methoxide and methanol to give a coloured product. The time necessary for this reaction was 30 s with continuous and thorough stirring. The intensity of the colour was measured spectrophotometrically at 655 nm following dilution with methanol. The apparent molar absorptivity is approximately 8.7 × 103 l mol–1 cm–1, and Beers law is obeyed over the concentration range 1–16 µg ml–1 of fluorene. The colour was stable if the product was kept in a tightly stoppered flask for at least 1.5 h in the presence of small amounts of 2,6-di-tert-butyl-4-methylphenol.