Quality assurance and calibration methods (Lecture 17 ) Flashcards
What is sensitivity?
Sensitivity is the capability of responding reliably and measurably to changes in analyte concentration.
What is specificity/selectivity?
Specificity or selectivity means being able to distinguish analyte from from other species in the sample (avoiding interference).
What is the detection limit?
Detection limit is the smallest quantity of analyte that is significantly different from the blank. Must be lower than the concentrations to be measured.
What do blanks account for?
Blanks account for interference by other species in the sample and for traces of analyte found in reagents used for sample preservation, preparation, and analysis.
What is a method blank?
Method blank is a sample containing all components except the analyte and it is taken through all the steps of the analytical procedure.
What is a reagent blank?
Reagent blank is a method blank that has not been subjected to all sample preparation procedures.
What is a field blank?
Field blank is a method blank that has been exposed to the site of sampling.
What equations are associated with quantifying the detection limit?
ydl = yblank + 3s
ysample - yblank = m x sample conc
detection limit = 3s/m
quantitation limit = 10s/m
How are calibration curves made? What are they useful for?
Calibration curves are made by preparing a series of known solutions of analyte and making a graph of instrument response versus analyte concentration. General method for determining the concentration of an analyte in an unknown sample by comparing the unknown to a set of standard samples of known concentration.
What are external standards?
External standard: known solutions of analyte that do not involve the unknown solution.
What is standard addition?
Standard addition: known quantities of analyte are added to the unknown.
What is an internal standard?
Internal standard: known amount of a compound - different from analyte - that is added to the unknown.
