Yuzi Takayama

Preparation of deactivated metal capillary for gas chromatography

Abstract Research was conducted to prepare a deactivated metal (stainless-steel) capillary that is physically tough and thermally stable compared with a fused-silica capillary. A key step in the preparation is the formation of a silicon layer by the thermal decomposition of monosilane. The silicon formed on the metal surface is assumed to exist as large grains compared with that on the glass surface. Activation of metal capillary was observed, which is assumed to be due to the migration of silicon grains on the metal surface during the heating test of the capillary, thus exposing the metal surface. Such a phenomenon was not found with a glass capillary treated with monosilane. These observations suggest that the problem comes from the wettability of the metal surface with silicon. The problem was solved by oxidizing the metal surface prior to the monosilane treatment. As a consequence, it became possible to prepare a deactivated metal capillary (DMC) thermally stable even above 400°C. A column coated with a commercially available gum-like liquid phase could not withstand continuous heating at 280°C. On the other hand, a column coated with dimethylpolysiloxane by the in situ (in the capillary) condensation of oligomer prepared from dimethyldichlorosilane showed excellent thermal stability: the column withstood continuous heating above 400°C and also repeated heating by programming up to 450°C. Various advantages of DMC over a fused-silica capillary (FSC) were also made clear. Hence DMC, as a metal capillary of the second generation, should replace FSC.

Behaviours of siloxane polymers containing phenyl or silarylene as stationary phases for high-temperature gas chromatography

Abstract Several kinds of mechanisms have been proposed for the thermal degradation of methylphenylsiloxane and dimethylsiloxane—silarylene copolymer in an inert atmosphere. These polymers have been used as gas chromatographic stationary phases at temperatures as high as 370°C, but there is no report on the thermal stability of the polymers during prolonged use at high temperatures, especially above 400°C. In this work, the thermal stability of these stationary phases at temperatures as high as 420°C was examined using a deactivated metal capillary column, which is much more thermally stable than the fused-silica capillary columns. It was found that these phases degraded at 380–400°C by eliminating arylene-containing moieties, which led to cross-linking, and the peak shapes therefore deteriorated. With a column treated at 420°C, elution of solutes was considerably delayed and the elution order became unusual, which could not be rationalized from the behaviours of these medium-polarity and non-polar columns. It was concluded that the medium-polarity stationary phases in these columns finally became highly cross-linked dimethylsiloxane by losing arylene-containing moieties, thus giving poor peak shapes.

Preparation of silylated celite by a vapour-phase method

Abstract Celite was silylated with hexamethyldisilazane (HMDS) vapour to produce gas chromatographic supports. The deactivated Celite supports obtained were of the highest quality. The process of preparation is simple, in that no post-treatment of silylated Celite is required, and neither harmful vapours nor waste solutions are produced. It was confirmed that heating for a long period did not affect the quality of the product, in spite of the usual decrease in the concentration of surface hydroxyl groups. Reasons for this are proposed. Further, it was established that impurities in the HMDS, possibility amines, have no effect on silylation or on the quality of the Celite obtained.

Application of a metal capillary column in gas chromatographic determination of catechol-O-methyltransferase activity

The utility of a deactivated metal capillary column, Rascot, in the measurement of an enzymatic reaction, in this case measurement of rat catechol-O-methyltransferase activity, was examined. 3,4-Dihydroxybenzaldehyde, 3,4-dihydroxybenzylalcohol and 3,4-dihydroxybenzoic acid were used as substrates and the m- and p-O-methylated products were separated by using Rascot after derivatization. The peaks on the chromatograms were symmetrical. The data obtained were compared with those reported in previously published papers. Good agreement with previous results proved that Rascot is able to withstand practical use in biological materials.

Preparation of lightweight sheet molding compound using glass balloon filler: improvement of strength, and a novel balloon treatment for better adhesion with the matrix

Lightweight sheet molding compound (SMC) was prepared using glass balloon filler instead of granular CaCO3 etc. The low flexural strength of balloon-SMC was improved by decreasing the ratio of resin to glass balloon, thus eliminating resin rich portions. This resulted in SMCs that have flexural strength comparable with that of CaCO3-SMC. An integral hydrolysis blend method for hydrolysis of the glass balloon surface was developed, resulting in improved adhesion between the glass balloons and the resin. Further, it was demonstrated that hydrolytic formation of the silanol groups of the glass balloon surface can be monitored using Fourier transform infrared spectroscopy.