Effect of refractive index of sample solution on FIA with a spectrophotometric detector

The difference of refractive index between the sample solutions injected and the carrier solution (the reagent solution) causes problems in detection if an FIA system with a spectrophotometric detection is applied to various samples containing solvents or salts. To recognize this phenomenon, a dual channel FIA apparatus was designed and distilled water was delivered in both streams. Sample solutions were injected into the stream and flow signals were recorded. Several water miscible solutes such as NaCl, urea and dextrose were selected as samples, and Methyl Orange was used as a standard colored sample. The signal intensity changed depending upon the refractive index. Therefore, the effect of the matrix in sample solution should be considered.