Triethoxysilane determination

Although the biocompatibility and biodegradability of these materials were rapidly determined, the bioactivity of Si02-PCL hybrid materials was not studied until recently [99]. In order to provide bioactivity to Si02-PCL hybrid materials, Rhee prepared triethoxysilane end-capped poly(s-caprolactone) which was then cocondensed with tetraethyl orthosilicate and calcium nitrate via the sol-gel method. The Ca-containing PCL/silica hybrid so obtained showed in vitro bioactivity and biodegradability. The hybridization procedure between the a,co-hydroxyl PCL and silica phases was proposed to be as follows ... 

The pre-distillate fraction, which accumulates in reactor 5 after several syntheses, is sampled to determine the content of unreacted allylamine and triethoxysilane, and then loaded into reactor 3. In this case the loading of raw stock for synthesis is re-calculated depending on the quantity and composition of the pre-distillate. 

After the reactive mixture has been introduced, it is kept in the reactor at 150-160 °C for 6-8 hours and sampled to determine the phenylethoxysi-lane content. The content of phenylethoxysilanes (equivalent to phenyl-triethoxysilane) should not be less than 65%. After the synthesis the reactive mixture is cooled to 40-60 °C by sending water into the jacket of the apparatus. The cooled mixture of phenylethoxysilanes, the so-called phenyl paste, is sent into hydrolyser 14 to hydrolytic cocondensation. 

Adsorbed films of ethykriethoxysilane and vinyltriethoxy-silane were formed on silica and alumina by retraction from hydrocarbon solution and their wettabilities and water-stabilities determined. The vinyltriethoxysilane films were generally more oleophobic, more hydrophobic and more resistant to contact with water than the films formed by the ethyl analog. Neither adsorbate formed stable films on a-alumina. The addition of low molecular weight organic acids or bases to the adsorbate solution resulted in both the ethyl and vinyl compound forming hydrophobic and water-stable films on silica and ot-alumina. Films of p-chloro-phenyl-ft-ethyltrichloro, -trimethoxy, and -triethoxysilane were also studied and found to be water-stable and to have wettabilities characteristic of a surface comprised of closely-spaced p-chlorophenyl groups. 

The presence of surface OH groups or H2 O molecules can play a primary role in adsorption. For example, a microcalorimetric study of the adsorption of stearic acid, from heptane solution, on ferric oxide (Husbands et al., 1971) revealed that preadsorbed water enhanced adsorption of stearic acid. When adsorption takes place from a dry organic liquid, residual surface water may act as special agent. This was shown for the adsorption of a silane coupling agent (y-amino-propyl-triethoxysilane) on silica covered with water molecules for 6 < 1 (Trens and Denoyel, 1996). By the simultaneous determination of adsorption isotherms and the enthalpies of displacement (of heptane by various silanes) it was demonstrated that the amine function was able to displace some of the surface water and make it available for the hydrolysis of the silane into trisilanol, whereas the residual water was able to promote the formation of siloxane bonds between the trisilanol molecules and the surface. 

R.S.S. Murthy and D.E. Leyden, Quantitative Determination of 3-Aminopropyl Triethoxysilane on Silica Gel Surface Using Diffuse Reflectance Infrared Eourier Transform Spectrometry, Anal. Chem., 58, pp. 1228-1234, 1986. 

Turkel taub et al have described gas chromatographic methods for the determination of ethanol in triethoxysilane. They used a column containing 20% of silicone PFMS-3 supported on firebrick with hydrogen or helium as carrier gas and a katharometer detector. Turkel taub et al have also described a method for the determination of ethanol in triethoxysilane based on chromatography of 25°C on a 200 cm column containing 2% of petroleum jelly on fire brick (particle size 0.025 to 0.050 cm previously dried at 150 to 200°C). A flame ionization detector was used and hydrogen was employed as carrier gas (25 ml per minute). 

Increased selectivity and prevention of passivation of the BDD surface may be also achieved by its modification. An enzyme-based amperometric sensor was proposed for detection of phenolic compounds by Notsu et al. BDD was anod-ically polarized for the introduction of hydroxyl groups onto its surface, then treated with (3-aminopropyl)triethoxysilane (APTES), and finally coated with a tyrosinase film cross-linked with glutaraldehyde. Tyrosinase catalyzes oxidadmi of phenol and various phenol derivatives to o-benzoquinone derivatives via catechol derivatives and thus the quinones generated are ready to be reduced electrochemically at an appropriate potential and obtained reduction currents serve as good analytical signals for the determination of the phenol derivatives. Bisphenol A and 17-/ -estradiol were detected at —0.3 V vs. Ag/AgCl with the detection limit of 1 pmol in FIA. However, the biosensor retained its activity only for a few days due to weak bonding of APTES to BDD surface. 

---