Calculations Involved for Quality Control in EPA Methods

Descriptions and examples of calculations required to determine compliance with EPA quality control criteria for chromatographic measurements are presented.

Calculations Involved for Quality Control in EPA Methods, Alltech Application Note #ANE003, 1997.

Descriptions and examples of calculations required to determine compliance with EPA quality control criteria for chromatographic measurements are presented.

The relative retention time (RRT) is the retention time in minutes of a target analyte relative to an internal standard. The RRT is calculated for all analytes and calibration levels.

The percent Relative Standard Deviation (RSD) of the relative response factor (RRF) for an analyte vs. that of a specified internal standard is also calculated for all analytes and calibration levels. Both the RRT and RSD are compared to preset limits to assess compliance for an initial calibration.

Once the initial calibration QC has been met, the Percent Difference between the RRF for an analyte in the initial calibration is calculated each day or according to some more frequent schedule and compared to preset limits.

The Percent Recovery is the concentration of a spiked analyte recovered vs. that of the spiked level expressed as a percentage.