Lecture 2. Analysis and Error

Lecture 2. Analysis and Error - What is Analytical...

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Unformatted text preview: What is Analytical Chemistry? 2nd Attempt: * Analytical chemistry is about (a) identifying what is in an unknown sample and (b) determining how much of each component is present. * Identifying what is in an unknown is called qualitative analysis. * Identifying how much is present is called quantitative analysis. 1 Quantitative vs. Qualitative Analysis Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Wiley 2 • Species: • Analyte: • Interfering species (interferent): 3 General Steps in Analysis: Step #1 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 4 Step #2 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 5 Select a Method Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 6 Step #3 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 7 Sampling Homogeneous vs. Heterogeneous Samples http://www.snickers.com/original_info.asp What other considerations are there? 8 Sampling Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2001. Freeman 9 Step #4 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 10 Sample Preparation Extracting Lipids Removing Residual Solids Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2001. Freeman 11 Step #5 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 12 Chemical Separations Selectivity and Sensitivity Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2001. Freeman 13 Step #6 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 14 Chemical Separations Selectivity and Sensitivity Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2001. Freeman 15 Analysis Selectivity And Sensitivity Dionex, Application note 225, Dionex, www.dionex.com, 2009. www.dionex.com 16 Report Results Standards and Calibration Curves What are the properties of a good Standard? What Standard Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2001. Freeman 17 Step #7 Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 18 Report the Results “A number without a confidence interval is number meaningless!” meaningless!” Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2001. Freeman 19 The Analytical Process Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Sons, 20 Chapter 3: Errors Daniel C. Harris, Exploring Chemical Analysis, 4th ed., W.H. Freeman and Company, New York, 2009. Company, 21 There is Error in Every Measurement Daniel C. Harris, Exploring Chemical Analysis, 4th ed., W.H. Freeman, New York, 2009. “An experimentally determined quantity without an An estimate of uncertainty is essentially meaningless!” estimate Izaak Maurits Kolthoff 22 “An experimentally determined quantity without an An estimate of uncertainty is essentially meaningless!” estimate I. M. Kolthoff 23 There is Error in Every Measurement 0.392 ± 2.001 g 0.392 ± 0.001 g “An experimentally determined quantity without an An estimate of uncertainty is essentially meaningless!” estimate Izaak Maurits Kolthoff 24 There is Error in Every Measurement Daniel C. Harris, Exploring Chemical Analysis, 4th ed., W.H. Freeman and Company, New York, 2009. Company, Spectronic 20 http://abacus.bates.edu/~ganderso/biology/resources/spec20.html 25 There is Error in Every Measurement Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2005. Company, 26 Random or Indeterminate Error Repeated measurements vary randomly around the Repeated true value. true Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. 27 Systematic (or Determinate) Error A consistent error over several measurements. Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. 28 ...
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This note was uploaded on 04/06/2011 for the course CHEM 2011 taught by Professor Buhlman during the Spring '10 term at Minnesota.

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