Analyte quantification

Analyte quantification - context
Quantification of analyte
Quantification and standards
     External standard (ES) calibration
           advantage - disadvantage
                 Signal drift and ES calib.
                 Matrix effects and ES calib.
                 Analyte loss and ES calib.
     Internal standard (IS) calibration
           advantage - disadvantage
                 Signal drift and IS calib.
                 Matrix effects and IS calib.
                 Analyte loss and IS calib.
     Calibration by standard addition
Working range of the detector
Noise of the detector
Limit of detection and quantitation
Analyte recovery
Evaluation of an analytical method
Spike-recovery experiments using SS
End of lesson
  

External standard (ES) calibration

advantage: very simple calibration method

disadvantage: high susceptibility to systematic errors

 

There are more elaborate calibration methods, which are less susceptible to systematic errors, are required in environmental trace analysis:

  • internal standard calibration
  • calibration by standard addition

 

three most common sources of systematic errors:

(i) signal drift
temporal changes in the response of the detector to a constant analyte concentration

     

(ii) matrix effects
components of the sample matrix (e.g., dissolved organic matter) suppress the response of the detector;
this effect is not accounted for by calibration with external standards, which are prepared in pure solvents
     

(iii) analyte loss
loss of analyte during sample preparation is not accounted for by calibration with external standards,
unless the standards are also carried through the sample preparation steps