Analytical Chem istry - DePauw University

180 Analytical Chemistry 2.0605040S std 300.0 0.1 0.2 0.3 0.4 0.5Figure 5.12 Example of a normal calibration curve witha superimposed confidence interval for the analyte’s concentration.The points in blue are the original data fromTable 5.1. The black line is the normal calibration curveas determined in Example 5.9. The red lines show the95% confidence interval for C A assuming a single determinationof S samp .20100C stdPractice Exercise 5.4Figure 5.3 shows a normal calibration curve for the quantitative analysisof Cu 2+ . The data for the calibration curve are shown here.[Cu 2+ ] (M)Absorbance0 01.55×10 –3 0.0503.16×10 –3 0.0934.74×10 –3 0.1436.34×10 –3 0.1887.92×10 –3 0.236Complete a linear regression analysis for this calibration data, reportingthe calibration equation and the 95% confidence interval for the slopeand the y-intercept. If three replicate samples give an S samp of 0.114,what is the concentration of analyte in the sample and its 95% confidenceinterval?Click here to review your answer to this exercise.In a standard addition we determine the analyte’s concentration byextrapolating the calibration curve to the x-intercept. In this case the valueof C A isand the standard deviation in C A isC = bx =− 0-interceptAb1