Using on-line solid phase extraction for simultaneous determination of ascorbic acid and rutin trihydrate by sequential injection analysis

This presented paper deals with a new methodology for the separation and simultaneous determination of two active substances in combined pharmaceutical formulation, composed of ascorbic acid (AA) and rutin trihydrate (RT). The methodology described is based on the sequential injection analysis (SIA) technique analysis coupled with a solid phase extraction (SPE) microcolumn. The SPE microcolumn was used for retention of RT, while the AA was eluted with the solvent front phase. Due to the different acidobasic and polarity properties of both compounds and the principles of reversed phase chromatography, it was possible to separate AA and RT with one eluting solution methanol/water (28:72), pH 2.5, flow rate 10 mul s(-1). The spectrophotometric detection of both substances was performed at 262 nm. Under the optimal conditions, the calibration was linear over the range 10-100 mug ml(-1) for AA with R.S.D. of 0.70% (n = 10) and 2-20 mug ml(-1) for RT with R.S.D. 0.40% (n 10), and was described by the following equations: A = 0.0098c + (-0.0005); r = 0.9995 and A = 0.0033c + 0.0080; r = 0.9987, for AA and RT, respectively. The sample throughput was 26h(-1). The proposed SIA-SPE method has been applied for the simultaneous assay and dissolution test of AA and RT in pharmaceutical formulation. (C) 2003 Elsevier B.V. All rights reserved.