Clinical Chemistry, Vol 20, 1028-1042, Copyright © 1974 by the American Association for Clinical Chemistry

Photometric Errors in Equilibrium and Kinetic Analyses Based on Absorption Spectroscopy

¹ Department of Chemistry, Purdue University, Lafayette, Ind. 47907.

We report a detailed analysis of the effects of photometric errors in absorption spectroscopy. We show that photometric errors can be divided into five categories, each having a different effect on the relative concentration error for equilibrium and kinetic analyses. Error coefficients defined for each category are incorporated into mathematical equations that permit one to calculate both systematic and random components of the error. We show that the transmittance for minimum error depends largely on the types of errors that predominate, and equations are presented that can be used to predict the optimum point for any combination of systematic or random error coefficients. These equations are applied successfully to one commercial spectrometer for which data were published recently and to two custom-designed spectrometers with very different performance characteristics. We think that this error analysis can be applied successfully to virtually any spectrometer currently used in clinical laboratories and that the results of the analysis will identify the nature and origin of the major sources of error. We believe this to be an essential step in any program aimed at improving reliability of analytical results.

Submitted on March 18, 1974
Accepted on April 28, 1974