Error-budget considerations in diagnostic instrumentation

摘要

Abstract: Analytical instrument systems present assemblies of components which each introduces its won contribution to the overall system precision. Combining realistic models of detector response with a Beer's Law model for absorbance (A) provides a prediction for the overall system uncertainty. For the constant detector uncertainty model, reasonable values of sample parameters lead to substantial increases in the absorbance at minimum relative concentration error (RCE), the value of the RCE and the limits of the range of A values for best RCE. Similar effects follow from the square root detector model. In both detector models these effects are increased by concentration uncertainty. Assay chemistry factors dominate the system RCE at low A, making high precision difficult at low A. For fluorescence measurements, since analyte concentration is nearly proportional to detected signal, the same detector models indicate no minimum in RCE. !15