How do you test the Range and Linearity of your analytical method? Lets summarize it in brief:

**Range**

The range of the method is the interval between upper level and lower level of analyte that have been determined with acceptable accuracy, precision and linearity.

**Dissolution:**

- Should be performed from 10% to 150% of the working concentration.
- For multiple strengths 10% of the lower concentration and 150% of the higher strength concentration including the working range.
- For controlled release formulation, ±20% over the specified limit.

**Acceptable Criteria:**

- Response should be linear and correlation coefficient should be NLT 0.995

**Related Substances and Residual solvents:**

- API: LOQ to 150% of the limit concentration of Known and unknown impurities.
- Formulations: LOQ to 200% of the limit concentration of Known and unknown impurities.

**Acceptable Criteria:**

- Response should be linear and correlation coefficient should be NLT 0.99

**Assay and Content uniformity:**

- For Assay: 80% to 120% of the working concentration
- For content uniformity: 70% to 130% of the working concentration.

**Acceptable Criteria:**

- Response should be linear and correlation coefficient should be NLT 0.995

**Linearity**

Linearity is the ability of analytical procedure to obtain a response that is directly proportional to concentration (amount) of analyte in the sample within a given range.

- ICH guidelines recommend evaluating a minimum of five concentrations to assess linearity.
- The linearity solutions are prepared by performing serial dilutions of a stock solution. The response of the interested peak is plotted against the, corresponding actual concentration (use potency/purity).
- Each linearity solution prepared should be injected either in duplicate or triplicate.
- Brazil regulation requires linearity to be performed by preparing three individual stock solutions (triplicate stock) and serial dilution thereof at 5 different levels.

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**Resource Person:**Jairus Fernandes

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