DETERMINATION OF FREE FATTY-ACIDS IN DAIRY-PRODUCTS BY DIRECT COUPLING OF A CONTINUOUS PRECONCENTRATION ION-EXCHANGE-DERIVATIZATION MODULE TO A GAS-CHROMATOGRAPH

A flow injection ion-exchange system coupled to a gas-liquid chromatograph was used for the determination of free fatty acids in dairy products. The pretreatment module permits isolation and preconcentration of free fatty acids on Amberlite IRA-400 and derivatization of eluted acids with acetyl chloride in methanol. The methyl esters are continuously injected via the injection port to prevent losses of the more volatile esters; they are quantified at the milligram per liter level with a FID detector. The method thus developed was applied to the determination of free fatty acids in milk, cream, and butter samples; fatty acids were also added to some samples to induce rancidity in order to assess the method performance.