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Chapter 5

Jimmy
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Chapter 5

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    1. Chapter 5 Calibration Methods

    2. Calibration Methods Calibration Curve Standard Addition Internal Standards

    3. Calibration Curve Graphs the instrumental response to Standard Solutions Analyte solutions of known concentrations Blank Solution Solution that contains all reagents and solvents except the analyte Negates effects caused by impurities and interfering species

    4. Calibration Curve Construction and Use Prepare the standard solutions Varying concentrations of analyte Ideally incorporates the concentration of unknown Collect data for each of the standards 3 or more recommended discovery of inconsistent measurements Calculate the Corrected Absorbance value for each standard concentration Corrected Absorbance = standard solutions average absorbance - blank solutions average absorbance

    5. Calibration Curve Construction and Use Plot a graph of corrected absorbance values versus analyte concentration Obtain Calibration Curve Method of Least Squares Determinants

    6. Obtain Calibration Curve Method of Least Squares di2 = (yi - y)2 = (yi - mxi -b)2 Determinants

    7. Calibration Curve Construction and Use Find the Uncertainties associated with the slope, y-intercept, and y (corrected absorbance) d(bar) - 0 for best straight line 2 degrees of freedom are lost in determination of slope and y-intercept

    8. Calibration Curve Construction and Use Find the Uncertainties associated with the slope, y-intercept, and y (corrected absorbance)

    9. Calibration Curve Construction and Use Calculate the Uncertainty associated with the x-value Analyze the unknown

    10. Calibration Curve Example

    11. Standard Addition Method Unknown concentrations of analyte are determined via deduction obtained from the calibration curve resulting from adding quantities of known standards to unknown concentrations of analyte. Important when the sample composition is unknown or complex

    12. Standard Addition Curve Construction and Use Procedure 1 Prepare samples to be analyzed Add the same quantity of unknown to each of several volumetric flasks Add varying quantities of known standard to all but one of the volumetric flasks Dilute all volumetric flasks to their mark

    13. Standard Addition Curve Construction and Use Analyze the samples Construct a graph using the data obtained

    14. Standard Addition Curve Construction and Use Construct a graph using the data obtained x-intercept of the extrapolated line is the concentration of the unknown [X]f after it has been diluted to the final volume Method of Least Squares - construct the line uncertainty in x-intercept

    15. Standard Addition Curve Construction and Use Procedure - 2 Sample 1 Add a quantity of unknown to a volumetric flask Analyze the sample Sample 2 Add a quantity of known standard to sample 1 Analyze the sample Sample 3 Add a quantity of known standard to sample 2 Analyze the sample Additional Samples - repeat procedure for Sample 3

    16. Standard Addition Curve Construction and Use Calculation of the standard solutions and the unknown are completed using

    17. Internal Standard Compares the intensity of the absorbance of an internal standard compared to that of the analyte Important when instrument response may vary slightly from one run to the next

    18. Internal Standard Preparation Procedure Prepare a sample of unknown analyte concentration Add an amount of known standard to the solution Analyze the sample Compare the area under each signal - Response Factor

    19. Chapter 5 - Homework Problems - 2, 7, 18, 21, 22

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