Flow injection determination of free fatty acids in vegetable oils using capacitively coupled contactless conductivity detection

Abstract

A single line flow injection analysis (FIA) method that incorporated a preconcentrator column packed with C 18 particles and capacitively coupled contactless conductivity detector (C 4D) was developed for the determination of free fatty acid (FFA) in vegetable oils. The carrier stream was methanol/1.5 mM sodium acetate (pH 8) 80:20 (v/v) at a flow rate of 1.0 mL min −1. Calibration curve was well correlated ( r 2 = 0.9995) within the range of 1–200 mg L −1 FFA (expressed as palmitic acid). Sampling rate of 40–60 h −1 was achieved. Good agreement was found between the standard non-aqueous titrimetry method and the proposed method when applied to the determination of FFA in palm (crude, olein, and refined, bleached and deodorised) and other vegetable (soybean, rice bran, walnut, corn and olive) oils. The proposed method offers distinct advantages over the official method, especially in terms of simplicity, high sampling rate, economy of solvents and sample, offering considerable promise as a low cost automated system that needs minimum human intervention over long periods of time.