Analytical Chem istry - DePauw University

DRAFTChapter 7Chapter Overview7A7B7C7D7E7F7G7H7I7J7K7LCollecting andPreparing SamplesThe Importance of SamplingDesigning a Sampling PlanImplementing the Sampling PlanSeparating The Analyte From InterferentsGeneral Theory of Separation EfficiencyClassifying Separation TechniquesLiquid –Liquid ExtractionsSeparation Versus PreconcentrationKey TermsChapter SummaryProblemsSolutions to Practice ExercisesWhen we use an analytical method to solve a problem, there is no guarantee that our resultswill be accurate or precise. In designing an analytical method we consider potential sources ofdeterminate error and indeterminate error, and take appropriate steps to minimize their effect,such as including reagent blanks and calibrating instruments. Why might a carefully designedanalytical method give poor results? One possibility is that we may have failed to account forerrors associated with the sample. If we collect the wrong sample, or if we lose analyte whilepreparing the sample for analysis, then we introduce a determinate source of error. If we fail tocollect enough samples, or if we collect samples of the wrong size, then our precision may suffer.In this chapter we consider how collecting samples and preparing them for analysis affects theaccuracy and precision of our results.Copyright: David Harvey, 2009285