estimation, and compliance with pharmacopoeial standards.

2. Scope

This SOP applies to the Analytical Method Development (AMD) department and covers the determination of A_1%^1cm values of APIs and related substances in compliance with pharmacopeial monographs and ICH guidelines.

3. Responsibilities

• Analytical Chemist: Prepares test solutions, performs spectrophotometric analysis, and calculates absorptivity values.
• Method Reviewer: Reviews and verifies calculated data and confirms system suitability.
• QA Officer: Ensures GMP-compliant documentation and adherence to procedural controls.
• Head – AMD: Approves the absorptivity data and method outcome.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring accuracy, traceability, and regulatory compliance of absorptivity determination processes within the AMD department.

5. Procedure

5.1 Principle

1. Absorptivity (A_1%^1cm) is defined as the absorbance of a 1% w/v solution measured in a 1 cm path length cuvette at a specified wavelength.
2. It is calculated using:

   A1%1cm = (A × 100) / C
   

   where A = measured absorbance, C = concentration in mg/mL

5.2 Wavelength Selection

1. Scan the UV spectrum of the test API (200–400 nm) using appropriate solvent.
2. Select λ_max (wavelength of maximum absorbance) with good molar absorptivity and no interference.
3. Document spectrum and chosen λ_max in Annexure-1: UV Scan Report.

5.3 Preparation of Standard Solution

1. Weigh 10 mg of API (accurately) and transfer to a 100 mL volumetric flask.
2. Dissolve using suitable solvent (water, methanol, ethanol, etc.), and dilute to volume.
3. This gives 0.1 mg/mL = 0.01% w/v solution.
4. Prepare additional concentrations as required.
5. Record preparation in Annexure-2: Standard Preparation Log.

5.4 Measurement of Absorbance

1. Blank the instrument with the same solvent used for dilution.
2. Measure absorbance of prepared standard solutions at λ_max using 1 cm quartz cuvettes.
3. Run absorbance measurements in triplicate for accuracy.
4. Log absorbance readings in Annexure-3: Absorbance Record Sheet.

5.5 Calculation of Absorptivity

1. Use the formula:

   A1%1cm = (A × 100) / C
   

   where A = average absorbance and C = concentration in mg/mL.

2. Example: A = 0.450, C = 1 mg/mL

   A1%1cm = (0.450 × 100) / 1 = 45.0
   

3. Compare with pharmacopeial value (if available) for compliance.
4. Record results in Annexure-4: Absorptivity Calculation Sheet.

5.6 System Suitability

1. Check absorbance repeatability (%RSD ≤ 1.0% for triplicates).
2. Verify blank shows negligible absorbance (< 0.005).
3. Ensure consistent path length (1.00 ± 0.01 cm).
4. Log suitability results in Annexure-5: System Suitability Log.

5.7 Documentation and Archival

1. Ensure that all raw data, scan files, calculations, and analyst/reviewer initials are captured in the worksheet.
2. Store printed spectra and logbooks for 5 years as per data retention policy.

6. Abbreviations

• UV: Ultraviolet
• API: Active Pharmaceutical Ingredient
• A_1%^1cm: Absorptivity (1% w/v, 1 cm pathlength)
• RSD: Relative Standard Deviation
• SOP: Standard Operating Procedure

7. Documents

1. UV Scan Report – Annexure-1
2. Standard Preparation Log – Annexure-2
3. Absorbance Record Sheet – Annexure-3
4. Absorptivity Calculation Sheet – Annexure-4
5. System Suitability Log – Annexure-5

8. References

• USP <857> – Ultraviolet-Visible Spectroscopy
• ICH Q2(R1) – Validation of Analytical Procedures
• Indian Pharmacopoeia / British Pharmacopoeia / USP Monographs
• Instrument Manual – UV-Vis Spectrophotometer

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: UV Scan Report

Sample ID	Solvent	Scan Range	λmax (nm)
API-092	Methanol	200–400 nm	265

Annexure-2: Standard Preparation Log

Sample ID	Weight (mg)	Solvent	Final Volume (mL)
STD-092	10.00	Methanol	100

Annexure-3: Absorbance Record Sheet

Replicate	Absorbance
1	0.451
2	0.448
3	0.450

Annexure-4: Absorptivity Calculation Sheet

Average Absorbance	Concentration (mg/mL)	A1%1cm
0.450	1.0	45.0

Annexure-5: System Suitability Log

Parameter	Observed	Limit	Status
%RSD (Absorbance)	0.33%	≤1.0%	Pass
Blank Absorbance	0.003	<0.005	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Updated calculation method and added replicates requirement	Annual SOP Review