How to calculate LOD & LOQ in HPLC Validation Method
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Answer Posted / bhupalreddy
Limit of Detection (LOD):
• Based on visual limitation
– Visual evaluation may be used for non-instrumental
methods but may also be used with instrumental methods.
– The detection limit is determined by the analysis
of samples with known concentrations of analyte and by
establishing the minimum level at which the analyte can be
reliably detected.
• Based on signal-to-noise
– This approach can only be applied to analytical
procedures which exhibit baseline noise.
– Determination of the signal-to-noise ratios is
performed by comparing measured signals from samples with
known low concentrations of analyte with those of blank
samples an establishing the minimum concentration at which
the analyte can be reliably detected. A signal-to-noise
ratio between 3 or 2:1 is generally considered acceptable
for estimating the detection limit.
• Based on the standard deviation of the response
and the slope
– The detection limit = 3.3 s / S
– Where s is the standard deviation of the response
and S is slope of the calibration curve.
– The estimate of S may be carried out in a variety
of ways, for example:
• Based on the standard deviation of the blank
• Based on the calibration curve
Limit of Quantification (LOQ):
• Based on visual limitation
– Visual evaluation may be used for non-instrumental
methods but may also be used with instrumental methods.
– The quantification limit is determined by the
analysis of samples with known concentrations of analyte
and by establishing the minimum level at which the analyte
can be quantified with acceptable accuracy and precision.
• Based on signal-to-noise
– This approach can only be applied to analytical
procedures which exhibit baseline noise.
– Determination of the signal-to-noise ratios is
performed by comparing measured signals from samples with
known low concentrations of analyte with those of blank
samples an establishing the minimum concentration at which
the analyte can be reliably quantified. A typical signal-to-
noise ratios is 10:1.
• Based on the standard deviation of the response
and the slope
– The quantification limit = 10s / S
– Where s is the standard deviation of the response
and S is slope of the calibration curve.
– The estimate of S may be carried out in a variety
of ways, for example:
• Based on the standard deviation of the blank
• Based on the calibration curve
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