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methanol-extracted solid (Solid III), Figures 2a and 3b, are identical to those observed by Sasuga and coworkers for pure sodium allyl sulfonate monomer (5). Prominent IR features are the bands at 920,998, and 3000-3100 cm"1, which are due to stretch and deformation motions associated with the allylic double bond in CH2=CH—CH2—iS03-. Additional confirmation for the monomer is provided by the NMR data, where the chemical shift signals at 3.61-3.70, 5.15-5.30, and 5.80-6.15 ppm are due to the protons at —CH2—SO3-, CHz=, and =CH-groups, respectively. The IR spectrum observed for the tacky gray-white solid (Solid II), Figure 2c, is identical to that obtained for the solid recovered from the ion-exchange column (Figure 2b). Moreover, these spectra are also similar to those obtained by Sasuga et al. (5) for a polymer they produced via high-energy radiation of sodium allyl sulfonate under pressure. The main spectral features that distinguish the polymer from the monomer are the absence of the bands due to the double-bond motions and a shift in the band at 660 cm -1 to 608 cm - 1 in the former. The NMR spectrum provided additional evidence that the fouling species is a large molecule, i.e., a polymer. Figure 3a, obtained from Solid I, contains some narrow peaks at 3.5-6.1 ppm, due to some residual amounts of the allyl sulfonate monomer. However, the main intense peaks, situated at 1-3 ppm, are extremely broad and are characteristic of a large molecule in which restricted tumbling motion is not rapid enough to average out the anisotropic nuclear magnetic interactions in it. Clearly, the spectral data strongly indicated that the foulant was a polymer, or more appropriately a polyelectrolyte of allyl sulfonate, -(CHj CH)jCH,—SO,Molecular Weight Distribution
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Some measure of the molecular weight distribution in the polymer was obtained from gel permeation chromatographic results. For this purpose small amounts of the gray-white residue (Solid II) and the white residue recovered from the ion-exchange elution (Solid I) were separately acidified with HC1 and dissolved in p-dioxane. Aliquots of solutions of the solids were analyzed on a Waters Associates AnaPrep chromatograph operating with p-dioxane as the solvent at 45 °C. A flow rate of 1 mL/min was maintained. Column arrangements consisted of
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How to switch HPLC columns using valves. Different analyses sometimes use different columns. But even when the same column can handle more than one kind of sample, many chemists dedicate a column to each analysis. This prolongs column life, reduces interferences, and eliminates equilibration delays. Rheodyne's Technical Notes 4 tells how to use switching valves to connect as many as five columns to a chromatograph. Any column can be selected, while the off-line columns remain sealed at each end. The effect on resolution is shown to be negligible in most cases.
Send for Tech Note # 4 For the well-illustrated tech note, contact Rheodyne, Inc., P.O. Box 996, Cotati, California 94928, U.S.A. Phone (707) 664-9050.
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