Resins detection

The fraction of insoluble molecular aggregates in the produced resin, detectable by GPC/SEC analysis, is related to the particleboard performance. A larger amount of dispersed phase seems to lead to higher internal bond strength and lower formaldehyde emission. 

In pharmaceutical preparations, nicotinic acid can be separated from nicotinamide by TLC on silica gel, aluminum oxide, and ion-exchange resins detection of the spots can be made by examination of the plates under UV light or by specific detection reagents. For a table listing the values of water-soluble vitamins, consult Hengen and deVries (1985). Nicotinic acid can be separated from nicotinamide and other water-soluble vitamins by TLC on silica gel using the mobile phase acetic acid-acetone-methanol-benzene (5 5 20 70). Expected Rp values of water-soluble vitamins in this system are as follows B2, 0.3 nicotinic acid, 0.75 nicotinamide, 0.55 65, 0.13 C, 0.27 (Hengen and deVries. 1985). 

Fig. 6.9. Separation of some (A) divalent and (B) trivalent metal cations. Mobile phases (A) 1.5 mM ethylenediamine and 2.0 mM tartrate, pH 4.0 (B) 2 mM ethylenedi-amine and 2.0 mM tartrate, pH 4.5. Column 20-/tm, 350 mm x 2-mm i.d., sulfonated cationexchange resin. Detection conductivity. (Reprinted with permission from ref [2], copyright 1983 American Chemical Society.)...

Beckman Elutriation Method. The Beckman elutriation method uses a chamber designed so that the centrifugal effect of the radial inward fluid flow is constant (Fig. 3). The separation chambers are made of transparent epoxy resin which faciUtates observation of the movements of the cell boundary in strobe light illumination. This enables detection of the radius at which the cells are separating. When a mixture of cells, eg, mononuclear white cells, enters the chamber, separation can be achieved by fine tuning centrifuge speed and inward fluid flow to the specific cell group. This is a laboratory method suitable for relatively small numbers of cells. Chambers are available in sizes to handle 2-3 x 10 , 1 2 x 10 , and 1 x 10 ° cells. The Beckman chambers can be appHed to collect mononuclear cells from bone marrow aspirates. 

Gas chromatography (gc) has been used extensively to analyze phenoHc resins for unreacted phenol monomer as weU as certain two- and three-ring constituents in both novolak and resole resins (61). It is also used in monitoring the production processes of the monomers, eg, when phenol is alkylated with isobutylene to produce butylphenol. Usually, the phenoHc hydroxyl must be derivatized before analysis to provide a more volatile compound. The gc analysis of complex systems, such as resoles, provides distinct resolution of over 20 one- and two-ring compounds having various degrees of methylolation. In some cases, hemiformals may be detected if they have been properly capped (53). 

The use of an acidic solution of p-anisaldehyde in ethanol to detect aldehyde functionalities on polystyrene polymer supports has been reported (beads are treated with a freshly made solution of p-anisaldehyde (2.55 mL), ethanol (88 mL), sulfuric acid (9 mL), acetic acid (1 mL) and heated at 110°C for 4 min). The colour of the beads depends on the percentage of CHO content such that at 0% of CHO groups, the beads are colourless, -50% CHO content, the beads appear red and at 98% CHO the beads appear burgundy [Vdzquez and Albericio Tetrahedron Lett 42 6691 200]]. A different approach utilises 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald) as the visualizing agent for CHO groups. Resins containing aldehyde functionalities turn dark brown to purple after a 5 min reaction followed by a 10 minute air oxidation [Coumoyer et al. J Comb Chem 4 120 2002]. 

The presence of a COOH functionality on a polystyrene resin can be detected using a 0.25% solution of malachite green-oxalate in ethanol in the presence of a drop of triethylamine. Beads with COOH functionalities are coloured dark green or appear as clear gel beads [Attardi, Porcu and Taddei Tetrahedron Lett 41 7391 2000]. 

Greater range of detection systems to which the desorbed gas can be subjected (e.g. chromatography, infra-red and ultraviolet spectroscopy, colorimetry) Limitations Certain resins undergo degradation even below 250°C Test sample may be thermally unstable Not all compounds readily desorb ... 

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