analyte concentrations across a defined range in compliance with ICH Q2(R2).

2. Scope

This SOP applies to all quantitative analytical methods used in drug substance, drug product, excipient, and cleaning validation studies performed in the Analytical Method Development (AMD) department.

3. Responsibilities

• Analytical Scientist: Prepares the study design, performs linearity testing, and evaluates the regression statistics.
• Validation Analyst: Conducts preparation, injection, and data entry of standard solutions.
• QA Officer: Reviews the final report and ensures adherence to protocol requirements.
• Head – AMD: Approves the results and endorses the validation report.

4. Accountability

The Head of AMD is accountable for ensuring proper documentation, statistical accuracy, and compliance of linearity and range studies with international regulatory guidelines.

5. Procedure

5.1 Selection of Range

1. Define the working range as per the intended use of the method:
   • Assay methods: 80%–120% of target concentration
   • Impurities: LOQ to 120% of specification
2. Select a minimum of five concentration levels (e.g., 50%, 80%, 100%, 120%, 150%).
3. Each concentration must be prepared independently in triplicate.

5.2 Sample Preparation and Injection

1. Prepare solutions using accurately weighed and diluted standard material.
2. Inject each concentration level into the validated chromatographic system under consistent conditions.
3. Record peak area and concentration in Annexure-1: Linearity Raw Data Table.

5.3 Statistical Evaluation

1. Plot a calibration curve of concentration vs. response (peak area or absorbance).
2. Perform linear regression analysis to calculate:
   • Slope
   • Intercept
   • Correlation coefficient (R²)
3. Calculate %Y-intercept deviation and residual sum of squares.
4. Determine range as the interval between the lowest and highest concentration with acceptable accuracy and precision.
5. Summarize in Annexure-2: Linearity & Range Summary Report.

5.4 Acceptance Criteria

1. Correlation coefficient (R²) should be ≥ 0.998.
2. Deviation of Y-intercept should be ≤ ±2.0% of the response at 100% level.
3. Residuals must be randomly distributed and within ±2%.

6. Abbreviations

• R²: Correlation Coefficient
• SOP: Standard Operating Procedure
• LOQ: Limit of Quantification
• AMD: Analytical Method Development
• ICH: International Council for Harmonisation

7. Documents

1. Linearity Raw Data Table – Annexure-1
2. Linearity & Range Summary Report – Annexure-2

8. References

• ICH Q2(R2) – Validation of Analytical Procedures
• FDA Guidance – Analytical Procedures and Methods Validation
• Internal Quality Manual – Validation Practices

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Linearity Raw Data Table

Level (%)	Concentration (µg/mL)	Peak Area	Mean Area
50%	50	267534	—
100%	100	539870	—
150%	150	806334	—

Annexure-2: Linearity & Range Summary Report

Parameter	Result	Acceptance Criteria	Status
R²	0.9992	≥ 0.998	Pass
% Y-Intercept	1.4%	≤ ±2.0%	Pass
Range	50–150%	Defined range	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Incorporated statistical evaluation steps and updated annexures	Regulatory audit readiness