Case 2.Linearity demonstrated from 50% of the ICH reporting limit to 150%
oftheshelflifespecificationofrelatedsubstance.Nosignificanty-intercept
is observed (Figure 3.7). In this case, a high–low calculation is more suitable, as
the response is linear only up to the shelf life specification level. Drug substance
concentration in sample solution (high concentration) should be diluted to the
linear range to obtain the low-concentration solution. Therefore, the response
of drug substance in low concentration will be within the linearity range and
suitable for calculation. Alternatively, a single-point external standard calibration
of concentration within the linearity range can also be used. |
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