Technical Paper
Why the Limit of Detection (LOD) Value is Not an Appropriate Specification for Automotive Emissions Analyzers
2002-10-21
2002-01-2711
With the need for emission measurements of super ultra low emission vehicles (SULEV), analyzer manufacturers have been required to produce more precise and accurate analyzers. In order to compare analyzers, the customer must understand the different specifications used by the analyzer manufacturers. One specification that some manufacturers have used is the limit of detection (LOD) to indicate the reliability of the analyzer output at low concentrations. There are various methods for determining the LOD for a given analyzer. The authors will demonstrate how variations in methodology can produce different LOD values for a specific analyzer and what it means for the automotive emission analyzers. It is also demonstrated that the standard deviations of a zero signal, which is related to LOD, can be heavily influenced by data processing, such as data length in use and/or data smoothing. The LOD values obtained will be compared to the limit of quantification (LOQ) for that analyzer.