The Sequential Injection stop flow method is a powerful tool for automation of all reagent-based techniques. By stopping the flow, a selected section of mixed sample/reagent zone is arrested within in the optical path of a flow cell, [] while changes in absorbance or fluorescence are monitored due to chemical reactions taking place.
An increase in signal is recorded in the presence of ANALYTE, while in the absence of analyte, a horizontal line is recorded (BLANK). In the presence of reagent and/or sample background, this line is elevated compared to signal background. This feature eliminates tha background signal and thus allows spectrophotometric assays to be carried out on highly colored samples. Optimization of assay conditions is achieved by adjusting the reversal volume to select the most suitable sample (S) to reagent (R) ratio. Larger reversal volumes result in higher reagent/sample ratios in the flow cell, while smaller reversal volumes have the opposite effect. The reversal volume is defined from the turning point (TP).
Stop Flow Technique
2.2.9.
