CHMB16H3 Chapter Notes -Standard Deviation, Analyte

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7 Dec 2013
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CHMB16 Notes
Chapter 0. Sections 0-2 and 0-3
0-2 The Analytical Chemist’s Job
Sampling
oFirst step in chemical analysis
oTo measure
oVarious samples of each type should be taken for a broader range
oHomogenous – same composition everywhere
a sample is pure if it remains in 1 phase/homogenous
oHeterogenous –composition differs; multiple phases of compound
Sample Preparation
oTransforming a sample into a state that is suitable for analysis
oNeed to eliminate the interferences
oPhysical and chemical changes used to extract pure sample (ie. decant)
oAnalytes –substances being measured; the “target” molecule
oQuantitative transfer is used to dissolve analytes for chemical analysis
oReplicate samples are made to extract the heterogenous sample to make it more
pure
The Chemical Analysis
oStandard Solution is determined for each of the analytes to measure the
concentration (calibration)
oUse of methods for detector results (ie. chromatography)
oQualitative analysis –identifies what the unknown/s is/are in a sample
oQuantitative analysis –determines the amount of specific compound present in a
sample
Calibration Curves
oAnalytes vary in detector responses
oCalibration curves are used to determine which response was produced by a
certain analyte
oConcentrations must be known for each analyte using a standard solution of pure
substances
oStraight lines drawn through the calibration points will determine the
concentrations of the analytes in an unknown sample.
Interpreting the Results
oTaking the results to formulate a conclusion, answering the questions posed
oStandard deviation determines how accurate the result is given that the more
identical the results are, the closer to 0 the deviation would be
0.3 General Steps in a Chemical Analysis
Begins with a question, translated into measurements and experiments, concluded with an
answer understood by the public BUT, results have limitations such as: uncertainty,
interferences, non-specific absorbed molecules that creates the matrix.
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