Sulfate groups, determination

Carboxyl and Sulfate Group Determinations. Conductimetric titrations of heparin (14) provided a convenient measure of sulfate and carboxylic groups. Sodium heparin was first converted into the acid form by elution of a known quantity of heparin, dissolved in neutral deionized distilled water, through a column of previously washed Amberlite IR-120 (H+) or bio-Rad AG 50W-X2 resin (i.e., 50-100 mg of heparin through a 7-mL column and diluted to a final volume of 150 mL to give a final concentration of 0.33 to 0.67 mg/mL heparin). The effluent was collected until onlv neutral water exited the column, and this then was diluted to a final volume of 150 mL. 

Methylation of free OH groups, followed by denitration, hydrolysis, reduction, and glc analysis has been suggested as a method for determining the location of nitrate (82). This method has been suggested for CP and CS (82) as the phosphate and sulfate groups are stable to methylation and can then be removed. Periodate oxidation has been used to determine the DS of CS (81). 

Evans studied the influence of the position of the sulfate group on the CMC at 40°C for a large number of sodium alcohol sulfates [92]. The results are given in Table 10. From these results it is possible to determine the constants A and B of Eq. (11) at 40°C as shown in Table 11. Observation shows a slight constant decrease of the slope (B) of the lines as the sulfate group is shifted toward the middle of the chain whereas the values of A are almost constant for all homologous series. 

An analysis of alcohol and alcohol ether sulfates should determine the anionic active matter, the unsulfated matter, the inorganic sulfate content, the chloride content, and water. Other more precise analysis must determine the alkyl chain distribution of the alcohol and in the case of alcohol ether sulfates the number of ethoxy groups and its distribution, as well as other more specialized determinations, such as the content of 1,4-dioxane and other impurities. 

The Ni and S contents on the catalyst series were determined after calcination at 600°C. As shown in Table 1, sulfate was only retained on the silica support when Ni was present. Infrared studies have previously shown that sulfate groups impregnated on pure silica are thermally unstable [13], Therefore, the S04/Ni molar ratios, close to unity, together with the colors resulting after calcining the silica-supported samples made us conclude that Ni was in the form of NiS04 On zirconia, the S04/Ni ratios were larger than one because the sulfate can be associated with both, Ni and the support. 

Polystyrene latexes have been prepared using persulfate initiator for many years, but only recently have methods been developed to determine the number and loci of the sulfate surface groups. To determine these surface groups, the latex is cleaned to remove the adsorbed emulsifier and solute electrolyte, then the surface sulfate groups in the H+ form are titrated conductometrically with base. The latexes can be cleaned effectively by ion exchange (2-5) or serum replacement (6) dialysis is not effective in removing the adsorbed emulsifier and solute electrolyte (3,5,6). +... 

One possibility is hydroxyl endgroups, which may be formed by a side reaction of sulfate ion-radicals to form hydroxyl radicals (9) or hydrolysis of the surface sulfate groups. To determine if hydroxyl groups were present, the ion-exchanged latexes were oxidized by heating with persulfate and 10 silver ion at 90°, then ion exchanged and titrated conductometrically to determine the carboxyl groups. Table II (9) shows that some sul-... 

To determine the effect of different polymerization conditions on the polymer endgroups produced, polymerizations were carried out using the standard bicarbonate buffer as well as other variations. Table V (13,16) shows that the use of the persulfate-bicarbonate combination with and without emulsifier gave latexes of final pH 7-8 with only sulfate groups. The addition of 10 5 silver ion gave a latex of pH 8.5, but with weak-acid groups, presumably because of oxidation of the sulfate groups. 

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