Page 62 - Quality control of pharmaceuticals (07-PA 704)

2. Based on the standard deviation of the response (S) and the slope (b):

Detection limit (LOD) =3.3 × ( ⁄ )
The S of the response can be determined from the SD of the blank, the residual S of
the regression lines, or the SD of the Y-intercepts of the regression lines.

6. Quantitation limit (LOQ)

It is the lowest concentration of analyte in a sample that can be determined with
acceptable precision and accuracy under the stated experimental conditions.
Procedures:

• The ICH approaches are:
1. Visual LOQ can be determined by analyzing successively diluted samples

until the requisite levels of accuracy and precision are achieved.
2. Based on the standard deviation of the response (S) and the slope (b):

Quantitation limit: LOQ = 10 × ( ⁄ )

Regardless of the method employed, it is recommended that the calculated LOQ be
confirmed by Appling samples prepared to contain the analyte at or near the LOQ.

• In the current USP General Chapter, for instrumental methods, signal –to –
noise ratio of 10:1 is used to determine LOQ.