The determination of ethoxylated non-ionic surfactants in wool grease.

Abstract

Abstract Surfactants in grease can be identified by dissolving the grease (5 g) in hexane-ethyl acetate (1: 1 v/v) and adding to silica gel (100–200 mesh), eluting first with solvent and then with 50% v/v aqueous ethanol, evaporating and extracting with acetone. After evaporation, the residue is heated at 130 °C for 2 h with the mixed anhydride of acetic acid and 4-toluene sulphonic acids (cleavage reagent) (3 ml) to give ethyleneglycol diacetate (EGD) and the corresponding acetate or phenolic derivatives of the hydrophobic portion of the surfactant. When cool, the mixture is diluted with water, added to Na2SO4 (anhyd.) neutralized with Na2CO3, extracted with ether, dried (Na2SO4), concentrated and a sample (3 μ1) gas chromatographed (glass column 1 m × 3 mm i.d., packed with 15% Carbowax 20M on Gas-Chrom Q, oven temp. 170 °C, inlet/outlet 210 °C, N2 carrier 30 ml min−1) and compared with g.c.s of known surfactants. Quantitatively, the grease (0·1-1·0g) is refluxed with cleavage reagent as above, cooled to 60 °C, distilled water (15 ml) added and the separated liquor centrifuged (3000 rev min−1, 5 min). The clarified liquor is added to Na2SO4 (anhyd.), neutralized and extracted with ethyl acetate and a sample (3 μl) chromatographed as above with oven temp. 150 °C. The concentration of surfactant can be determined from comparison of the height of the EGD peak (Rt 2.5 min) with heights from known amounts of the surfactant treated concurrently. The type of grease (commercial, lanolin B.P., and a methanol-soluble fraction of a commercial grease were examined) has no effect on the method.