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231total caustic = total hydroxide content of the liquor2total soda = the sum of the total caustic and carbonate contents3H. L. Watts and D. W. Utley, Anal. Chem. 28, 1731 (1956)4E. Van Dalen and L. G. Ward, Anal. Chem. 45, 2248 (1973)AB-315Determination of free fatty acids (FFA) in edible oilsIn a titration, the titrant reacts with the analyte either exothermically(gives off heat) or endothermically (absorbs heat). TheThermoprobe measures the temperature change during the titration.When all of the analyte has reacted with the titrant the temperaturealteration of the reaction solution changes and this is visible as atemperature curve inflection.However, in some cases the inflection in the temperature curveis not sufficient to evaluate a thermometric titration. In a titration ofsamples containing very weak acids, e.g., in rape oil, the endpointof the titration is difficult to identify. In these cases, catalyticallyenhanced titrations are the key to success. They rely on a catalyzedindicator reaction to get a sharp inflection in the titration curve. Theendothermic hydrolysis of paraformaldehyde in the presence of excesshydroxide is an example for such a catalyzed indicator reaction.It is used for the determination of FFA in edible oils and requiresadding a small amount of paraformaldehyde to the sample solutionprior to titration. As soon as all acidic compenents of the reactionsolution have been neutralized, further addition of titrant leads toan excess of hydroxide ions which starts the endothermic hydrolysisof the paraformaldehyde. This results in a sharp inflection in thetemperature curve.Edible oils are dissolved in a mixture of toluene and 2-propanol(1:1) and titrated with a standardized solution of tetrabutylammoniumhydroxide dissolved in 2-propanol (c(TBAH) = 0.01 mol/L) toa catalytically enhanced endpoint.The respective tiamo method is capable of displaying theresults as a percentage of free fatty acids (% FFA) or alternatively as atotal acid number (mg KOH/g).AB-341Determination of TAN in engine oil with 859 TitrothermThe method for the determination of TAN in engine oil or othermineral oils is basically the same as for determining free fatty acidsin edible oils.The Total Acid Number (TAN) is the amount of base (in mg KOHper g oil) that is required to neutralize the acids contained in theoil. The TAN is a measure of the acidity of the oil resulting from thepresence of acidic compounds formed by oxidation, degradation ofadditives or the introduction of acids.INFORMATION | 2 | 2010-11