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Improving and Optimizing the Detection Method for Flow Injection Analysis Using Calibration Extension and External Data Comparison

Scott Smith
Illinois State Water Survey, Central Analytical Laboratory
2204 Griffith Drive, Champaign, IL 61820


Flow Injection Analysis is the method used by the National Atmospheric Deposition Program/Central Analytical Laboratory (NADP/CAL) to detect and quantify ammonium and orthophosphate in collected National Trends Network (NTN) and Atmospheric Integrated Research Monitoring Network (AIRMoN) precipitation samples. This quantification is determined through the use of a Beer’s law plot, in which standard solutions of known concentration are analyzed and the resulting peak areas are plotted linearly against the concentrations. By calculating the equation of the line running through these points, one can accurately determine the concentration of unknown samples based on peak areas. This method is only valid, however, within the range of the known standard concentrations. By adding additional standards throughout the curve, the range of detection can be extended and the accuracy of the extrapolated line can be improved as well.

Setting up a second FIA and reproducing the exact same run properties and conditions is another valid tool used to produce confidence in a detection method. Data comparisons can then be used to determine the reproducibility and validity of collected site data. This poster shows the results and procedures used to extend the FIA’s calibration range and to set up and use a second FIA for data comparison.