Page 61 - Quality control of pharmaceuticals (07-PA 704)

= 1.52
The equation for the regression line is thus:
Y = 1.93 × + 1.52

5. Limit of detection (LOD)

It is the lowest concentration of the analyte that can be detected but not necessarily
quantitated, under the stated experimental conditions. It is a parameter of limit test
which specifies whether or not an analyte is above or below a certain limit.
Procedures:

• In the current USP General Chapter <1225>:

Determination of LOD is described:
1. For instrumental methods

One determines the signal –to-noise ratio by comparing test results from samples
with known concentration of analyte with those of blank sample and establishes the
lowest concentration at which analyte can be reliably detected. A signal –to-noise
ratio of 2:1 or 3:1 is required.

2. For non-instrumental methods:

LOD is determined by the analysis of samples with known concentrations of analyte.
The minimum concentration at which the analyte can be reliably detected is the
LOD.

• The ICH approaches are:
1. Based on visual evaluation: by analysis of samples with concentrations of

analyte and establishing the minimum level at which the analyte can be
reliably detected. Practically, LOD can be measured by the serial dilution of
samples until the peak can no longer be observed.