Resolution of an intense sweetener mixture by use of a flow injection sensor with on-line solid-phase extraction

摘要

An integrated solid-phase spectrophotometry-FIA method is proposed for simultaneous determination of the mixture of saccharin (1,2-benzisothiazol-3(2H)-one-1,1-dioxide; E-954) (SA) and aspartame (N-L-alpha-aspartyl-L-phenylalanine-1-methyl ester; E-951) (AS). The procedure is based on on-line preconcentration of AS on a C-18 silica gel minicolumn and separation from SA, followed by measurement, at lambda=210 nm, of the absorbance of SA which is transiently retained on the adsorbent Sephadex G-25 placed in the flow-through cell of a monochannel FIA setup using pH 3.0 orthophosphoric acid-dihydrogen phosphate buffer, 3.75x10(-3)mol L-1, as carrier. Subsequent desorption of AS with methanol enables its determination at lambda=205 nm. With a sampling frequency of 10 h(-1), the applicable concentration range, the detection limit, and the relative standard deviation were from 1.0 to 200.0 mu g mL(-1), 0.30 mu g mL(-1), and 1.0 (80 mu g mL(-1), n=10), respectively, for SA and from 10.0 to 200.0 mu g mL(-1), 1.4 mu g mL(-1), and 1.6 (100 mu g mL(-1), n=10) for AS. The method was used to determine the amounts of aspartame and saccharin in sweets and drinks. Recovery was always between 99 and 101. The method enabled satisfactory determination of blends of SA and AS in low-calorie and dietary products and the results were compared with those from an HPLC reference method.