Intense Sweetener Mixture Resolution by Flow Injection Method with On-Line Monolithic Element

Abstract

A multi-analyte flow through method is proposed for the simultaneous determination of aspartame (AS), acesulfame-K (AK), and saccharin (SA) in several food and soft drink samples. The procedure is based on the transient retention of the three sweeteners in a commercial quaternary amine ion exchanger monolithic column, placed in its specific holder, and allocated in a monochannel FIA setup using pH 9.0 Tris buffer 0.03 M, NaCl 0,4 M, and NaClO4 0,005 M as carrier. In these conditions AS is very weakly retained, while AK and SA are more strongly retained, making it possible to measure the intrinsic UV absorbance of, first, AS and then AK and SA after desorption by the carrier itself. The applicable concentration range, the detection limit, and the relative standard deviation were the following: for AS, from 9.5 to 130.0 µg·mL−1; 2.87 µg·mL−1; 1.46% (at 65 µg·mL−1); for AK, between 2.2 and 600.0 µg·mL−1; 1.0 µg·mL−1, and 0.08% (at 300 µg·mL−1); and for SA, between 3.0 and 600.0 µg·mL−1; 0.9 µg·mL−1, and 0.09% (at 300 µg·mL−1). The method was applied and validated satisfactorily for the determination of AS, AK, and SA in foods and soft drink samples, comparing the results against an HPLC reference method.