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Key WordsColumn liquid chromatography Titania Ion-exchange behaviour SummaryTitania synthesized in this laboratory has previously been tested under reversed-phase conditions to assess its ion-exchange behaviour. Although in reversed-phase chromatography with acetic acid-sodium acetate buffer as mobile phase titania behaved as an anion-exchanger only, retention data suggested either that it behaved as a cation exchanger at higher mobile phase pH or that the retention of cationic solutes was inhibited under these conditions. The objective of our research was to clarify this point and to use titania as a packing material for ion-exchange separation. Glycine-NaCI-NaOI-I and glycine-NaOH buffers were used to investigate the retention behaviour of cationic solutes. When glycineNaCI-NaOH buffer was used to increase mobile phase pH a cationic solute was not retained. In the absence of NaC1 in the buffer the solute was strongly retained and its retention decreased with an increasing pH, implying that the retention of the solute was inhibited under these conditions. When dilute acetic acid-sodium acetate or bicine-NaOH buffers were used as mobile phase the titania acted as a anion-and cation-exchanger; it retained fluoride ion strongly under the range of conditions in which it acted as a cation-exchanger. We concluded that the titania had anion-and cation-exchange properties and that the material could possibly be used for simultaneous analysis of anions and cations and as a selective packing material for ion chromatography.

The development of a rapid assay for hydrogen peroxide has great practical potential because H2O2 is an important analyte in the fields of environmental chemistry, 1-3 clinical chemistry 4 and food chemistry. 5 Many chemiluminometric flow injection (FI) systems 1,[6][7][8] have been developed for the rapid detection of H2O2, because chemiluminescence (CL) reaction kinetics are sufficiently fast and the combination of CL with FI methods makes it possible to mix samples and reagents rapidly with a high degree of reproducibility. Further, the characteristics of the FI systems are better sensitivity, larger linear calibration range, and simpler optical system. Among them, FI systems based on an H2O2-dependent peroxidase (POD) catalyzed oxidation of luminol are suited for the rapid and sensitive detection of H2O2 because of the low background level with the CL reaction.9-11 Flow-through sensors packed with immobilized POD have been developed, 12-16 since the instantaneous CL that is emitted immediately after mixing of the reagents is monitored by the integration of the reaction and detection in a flow cell. Horseradish POD (HPOD) and microbial POD were immobilized on a glass-disk, 12 glass beads, 13 immuno-affinity membranes, 14 activated nylon membranes, 15 or vinyl polymer beads. 16 In the sensor systems, though the maximum sample throughput went up to 200 h -1 , 16 it was required to prepare a large quantity of reagent solution and to continuously deliver it into the flow cell. From the position of green chemistry, this is undesirable based on environmental and resource considerations.As an alternative to full-size FI systems, miniaturized systems that offer the promise of increased throughput, as well as lower sample and reagent consumption, have been developed. [17][18][19] Using micromachining techniques, flow cells having channels and hollows have been fabricated based on the silicon wafer. 20,21 An enhancement of the analytical performance can be achieved by an overall reduction in the dimensions of the flow channel.In the present work, a single-line chemiluminometric FI system using a luminol solution as a carrier solution was designed for the fast determination of H2O2, and a miniaturized flow-through sensor based on immobilized POD was fabricated by micromachining techniques.To obtain a higher performance, flow rate, sample and detection volumes and connecting capillaries were reduced. The sensor consisted of an anisotropically etched silicon chip and a glass plate. The chip had a spiral channel and two penetrated holes. To form the capillary, the chip was anodically attached to a glass plate. Microbial POD was covalently immobilized with 3-(trimethoxysilyl)propyldietylenetriamine (TSDT) and glutaraldehyde (GA) on the inner surface of the capillary; the microbial one was selected because of a higher maximum rate for the CL reaction than that of HPOD. A spiral capillary was placed in front of a window of a photomultiplier tube and used as a flow cell. This method was applied to the determination of H2O2 in ...

A chemiluminometric flow-through sensor for simultaneous determination of L-glutamate (Glu) and L-lysine (Lys) in a single sample has been developed. Immobilized uricase, immobilized peroxidase, support material, coimmobilized glutamate oxidase/peroxidase, support material, and coimmobilized lysine oxidase/peroxidase were packed sequentially in a transparent PTFE tube, and the tube was placed in front of a photomultiplier tube as a flow cell. A three-peak recording was obtained by one injection of the sample solution. The peak height of the first peak was due to the concentrations of urate and other reductants in the sample; the immobilized uricase was used to decompose urate, and the hydrogen peroxide produced was decomposed with a luminol-hydrogen peroxide reaction by immobilized peroxidase. The peak heights of the second and third peaks were free from the interferences from the reductants and were dependent only on the concentrations of Glu and Lys, respectively. Calibration graphs for Glu and Lys were linear at 40-1,000 and 50-1,200 nM, respectively. The sampling rate was 11/h without carryover. The sensor was stable for two weeks. The sensor system was applied to the simultaneous determination of Glu and Lys in serum.