Internal Standard—Friend or Foe?

Abstract

Internal standardization is a calibration technique that is commonly used to correct for procedural errors associated with quantitative analysis, thereby improving the accuracy of data. The commonly used protocol for internal standardization, presented through all analytical chemistry text books, relies upon a single point calibration for the compound that is used as the internal standard. Therefore, if the analyst is unaware of the linear range of the internal standard and uses a concentration that is outside the linear range, a severe loss of accuracy will occur. The severity is demonstrated through an example and precautions to prevent this problem are suggested. An alternative protocol for internal standardization that does not rely upon a single point calibration is also presented.

Keywords:

• Internal standard
• single-point calibration
• ion suppression
• electro-spray MS