range, in accordance with ICH Q2(R1) guidelines.

2. Scope

This SOP is applicable to all analysts involved in method development activities within the Analytical Method Development department for determining the linearity and range of newly developed or optimized analytical methods for Active Pharmaceutical Ingredients (APIs), excipients, or finished pharmaceutical products.

3. Responsibilities

• Analytical Scientist: Prepares stock solutions, performs dilution, executes linearity studies, and records results.
• Team Leader: Verifies the experimental design, approves concentration range, and reviews raw data.
• QA Personnel: Ensures compliance of the linearity evaluation procedure with regulatory and internal standards.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring proper execution, data review, and documentation of linearity and range evaluation in accordance with regulatory expectations and internal SOPs.

5. Procedure

5.1 Selection of Concentration Range

1. Determine the target concentration (100%) of the analyte based on the sample specification or label claim.
2. Plan at least five concentration levels covering 50% to 150% of the target concentration, including:
   • 50%
   • 75%
   • 100%
   • 125%
   • 150%

5.2 Preparation of Standard Solutions

1. Prepare a stock solution of the analyte using suitable diluent ensuring solubility and stability.
2. Use calibrated pipettes and volumetric flasks to prepare each level of standard solution from the stock.
3. Filter and degas solutions as required by method protocol.

5.3 Instrument Setup and Method Parameters

1. Ensure the chromatographic or spectroscopic method parameters are finalized before initiating linearity evaluation.
2. Perform system suitability tests to confirm the readiness of the instrument.

5.4 Execution of Linearity Study

1. Inject or analyze each standard solution level in triplicate.
2. Record the average response (e.g., peak area, absorbance) for each concentration level.
3. Ensure the injection sequence includes a blank and system suitability standards.

5.5 Data Analysis

1. Plot a calibration curve of response (Y-axis) versus concentration (X-axis).
2. Use linear regression analysis to determine the slope, intercept, and correlation coefficient (R²).
3. Acceptance criteria:
   • R² ≥ 0.999 for assay methods
   • % y-intercept ≤ ±2.0%
   • Residuals randomly distributed around zero line

5.6 Range Justification

1. Justify the selected concentration range based on method application and intended use (e.g., assay, dissolution, content uniformity).
2. Ensure acceptable accuracy and precision within the range to establish it as valid.

5.7 Documentation

1. Document all preparation steps, instrument settings, and observations in Annexure-1: Linearity Evaluation Log.
2. Record the regression data and calibration curve in Annexure-2.
3. Attach chromatograms or spectral output for all concentration levels.

6. Abbreviations

• API: Active Pharmaceutical Ingredient
• R²: Coefficient of Determination
• ICH: International Council for Harmonisation
• LOQ: Limit of Quantification
• QA: Quality Assurance

7. Documents

1. Annexure-1: Linearity Evaluation Log
2. Annexure-2: Calibration Curve and Regression Analysis

8. References

• ICH Q2(R1): Validation of Analytical Procedures
• USP General Chapter <1225> Validation of Compendial Procedures
• FDA Guidance for Industry on Analytical Procedures

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Karan Patel	Sneha Reddy	Dr. Kavita Singh
Designation	Analyst	QA Reviewer	Head – AMD
Department	Analytical Method Development	Quality Assurance	Analytical Method Development

11. Annexures

Annexure-1: Linearity Evaluation Log

Level	Concentration (µg/mL)	Peak Area	Mean Response
50%	50	24876	25012
75%	75	37521	37489
100%	100	49832	49895
125%	125	62210	62156
150%	150	74589	74540

Annexure-2: Calibration Curve Summary

• Regression Equation: Y = 499.85X + 120.5
• Correlation Coefficient (R²): 0.9998
• Slope: 499.85
• Intercept: 120.5

Revision History

Revision Date	Revision No.	Description	Reason	Approved By
01/06/2025	2.0	Expanded scope and enhanced data logging templates	Annual SOP Review	Dr. Kavita Singh
20/09/2022	1.0	Initial SOP Release	New SOP	QA Head