The detection limit for an analytical technique can be determined from the calibration curve.
Data required:
(1) calibration sensitivity = slope of line through the signals of the concentration standards, including blank solution (no material present)
(2) standard deviation for the analytical signal given by the blank solution
detection limit concentration =
= (3 * (standard deviation of signals for the blank solution)) / (slope of signals for concentration standards)
Notes:
(1) This assumes that the data is linear.
(2) The mean values are based on multiple replicate values (preferably 20-30) done over a period of time.
(3) 3 is a commonly used multiple of the standard deviation. Higher multiples can be used, but there is little perceived benefit.
(4) The equation above is derived from the minimal distinguishable analytical signal, which equals (mean blank signal) + (3 * (standard deviation of signals for the blank solution))
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