Estimated Detection Limit or EDL
The lowest concentration that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operating conditions. The EDL is generally 5 to 10 times the MDL or for High Resolution GC/MS it is method specified as 2.5 times the signal to noise ratio (S/N). For many analytes the EDL analyte concentration is selected as the lowest non-zero standard in the calibration curve. Sample EDL’s are highly matrix dependent. The EDL’s in SW-846 are provided for guidance and may not always be achievable.
Signal to Noise Ratio (S/N) is a dimensionless measure of the relative strength of an analytical signal (S) to the average strength of the background instrumental noise (N) for a particular sample and is closely related to the detection level. The ratio is useful for determining the effect of the noise on the relative error of a measurement. The S/N ratio can be measured a variety of ways, but one convenient way to approximate the S/N ratio is to divide the arithmetic mean (average) of a series of replicates by the standard deviation of the replicate results. (Skoog & Leary 1992)