Chemistry 155 Introduction to Instrumental Analytical Chemistry

Chem 155 Unit 1 Page 43 of 3131.11 Validation – Assurance of Accuracy:Calibration and linear regression optimizes theprecision of a calibration curve determination but acalibration curve can only be said to be accurate if:the analysis has been validatedAnother way of saying this is that a method is valid if:all significant sources of biashave been removedValidation addresses the various aspects of ananalysis that can ‘go wrong’ and give you a wronganswer.The table below lists some of the aspects of ananalysis that can be invalid, and suggests ways tovalidate them.Source of bias:Analyst erraticError in analysttechniqueCalibrationstandards are inerror (are not whatthey say the are)CalibrationmethodInstrumentfunction erraticInstrument driftPossible Solution(s):Analyst can repeat experimentDifferent analyst does same analysis andgets same result.Entire analysis Independent standardrepeated with measured periodically -indpendent called validation standardcalibration or QC standard (qualitystandard set control)Different calibration method used (standardadditions)Different instrument used (can be a differentkind of instrument)Periodically measure validation standard orinternal standardPage 43 of 313