ASTM D3712 Standard Test Method of Analysis of Oil-Soluble Petroleum Sulfonates by Liquid Chromatography
4. Summary of Test Method
4.1 The sample, except a sodium sulfonate product, is dissolved in ethyl ether and converted to sulfonic acid, using dilute hydrochloric acid. The sulfonic acid after extraction is converted to sodium sulfonate and the isolated sodium sulfonate and mineral oil are dissolved in chloroform. An aliquot of the chloroform solution, or a sample of a sodium sulfonate product, dissolved in chloroform, is placed on a silica gel column. The oil is eluted with chloroform, the sulfonate with ethyl alcohol, and both are determined gravimetrically. Average molecular weight is calculated from the average equivalent weight of the sodium sulfonate, which is determined by ashing a portion of the isolated sodium sulfonate.
4.2 Water is determined by Test Method D95. Base number is determined by Test Method D2896. Relative density is determined by pycnometer.
5. Significance and Use
5.1 This test method provides a means of determining sulfonate content and of classifying and characterizing natural and synthetic petroleum sulfonate products by sulfonate content and average molecular weight. Purity of sodium sulfonate products is measured by basicity and inorganic salt contents and the reserve alkalinity of alkaline earth sulfonates by the total base number.
