Rapid Separation Technique for Mono- and Disulfonic Acids M. W. Scoggins and John W. Miller Research Dicision, Phillips Petroleum Co., Bartlescille, Okla. 74003
THEEVALUATION of synthesis processes for both alkyl- and polycyclic arylsulfonic acids requires a rapid method for the separation and determination of mono- and disulfonic acids. Procedures are available for inorganic sulfate-organic sulfonate mixtures ( I , 2), but the only direct method for organic sulfonate-disulfonate mixtures is that of Skelly (3), who developed a continuous electrophoresis procedure for the separation of 4-biphenylsulfonic and 4,4’-biphenyldisulfonic acid; the individual acids were measured by ultraviolet spectrophotometry. However, this approach is limited to ultraviolet absorbing materials. A rapid separation and analysis of both alkyl- and arylsulfonic-disulfonic acid mixtures has been developed. The successful approach reported here is based on column chromatography with Rohm-Haas Amberlite XAD-2 resin ( 4 ) . This resin is an insoluble, cross-linked polystyrene designed t o adsorb selectively water-soluble organic compounds by attraction of their hydrophobic portion to the surface of the porous resin. Hydrophilic substances have little affinity for the resin and are not adsorbed. The adsorbed watersoluble organics are eluted with a polar solvent such as methyl alcohol. EXPERIMENTAL Preparation of Column Bed. Borosilicate glass columns, 1.2 X 25 cm, fitted with a stopcock are filled t o a height of 15 cm with Amberlite resin slurried in water. After washing with 5 to 6 bed volumes of water to elute inorganic materials, the resin is washed with methyl alcohol until the absorbance of the eluate, measured at 260 mp (1-cm cell), is less than 0.10. This treatment removes low-molecular-weight resin which would interfere with subsequent ultraviolet measurements on eluted fractions. Finally, the resin bed is washed with water to remove the alcohol completely. The resin bed is stored under water. Procedure. Dissolve a weighed sample containing 2-3 meq of alkylsulfonic acids or 0.5 meq of arylsulfonic acids in water and dilute t o 100 ml. Pipet a suitable aliquot t o the resin column and just as the solution enters the resin bed add aqueous eluent, either salt solution or water, depending on the type of sulfonic acid mixture. Collect 100 to 200 ml of eluate in 10-m1 fractions at a flow rate of 1.5-2.0 ml/min. Continue the elution with methanol and collect 100 ml in 10-ml fractions. Calculate the total acidity in each fraction from a titration with standard base in the case of alkylsulfonic acid mixtures. Alternately, determine sulfate ion with a potentiometric lead titration ( 5 ) and alkylsulfonic acid salts with a cationic titration (6). Measure polycyclic arylsulfonic acid concentrations in the fractions by ultraviolet spectrophotometry. ( I ) E. H. Griffin and E. W. Albough, ANAL.CHEM., 38,921 (1966). (2) S. D. Kullbom, W. K. Pollard, and H. F. Smith, ibid., 37, 1031
(1965). (3) N. E. Skelly, ibid., p 1526. (4) Rohm and Haas Co., Bulletin IE-89-65. ( 5 ) I . M. Kolthoff and N. H. Furman, “Potentiometric Titrations,” Wiley, New York, 1931, p 331.
(6) American Society for Testing and Materials, Philadelphia, Standard Test Method D-1681-62, ASTM Standards, January 1967, Part 22.
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