---
type: "WebPage"
title: "Determining the Molar Extinction Coefficient in the laboratory"
description: "Molar Extinction Coefficient Determination: securing your protein assays The molar extinction coefficient (ε) is an essential parameter for accurately quantifying the concentration of a protein or nucleic acid in solution using the Beer-Lambert law.In the development of biomolecules (mAbs, recombinant..."
resource: "https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-molar-extinction-coefficient-determination/"
tags: ["EN", "pll_69b11fc6796af"]
timestamp: "2026-03-12T08:21:46Z"
published: "2026-03-11T08:01:59Z"
language: "en"
author: "Filab"
---

# Determining the Molar Extinction Coefficient in the laboratory

## Molar Extinction Coefficient Determination: securing your protein assays

The **molar extinction coefficient (****ε)**is an essential parameter for accurately quantifying the concentration of a protein or nucleic acid in solution using the Beer-Lambert law.

In the development of biomolecules ([mAbs](https://filab.fr/en/sectors-of-activity/biopharmaceutical/biotherapeutic-recombinant-protein-characterization/analysis-characterization-monoclonal-antibodies-mabs.md), [recombinant proteins](https://filab.fr/en/sectors-of-activity/biopharmaceutical/biotherapeutic-recombinant-protein-characterization.md)), an error in this coefficient leads to an incorrect assessment of yield and dosage, which can jeopardize stability studies and clinical trials.

**FILAB** laboratory offers a rigorous experimental determination of your molar extinction coefficient, moving beyond simple theoretical estimations based on amino acid sequences to account for the molecule’s tertiary structure and chemical environment.

### Our Extinction Coefficient Analysis Services

FILAB helps you establish the exact correlation between absorbance and mass concentration:

**Experimental (****ε)** **determination:** Direct measurement by coupling UV spectrophotometry with an absolute quantification method.

**Linearity validation:** Verification of absorbance response over a range of defined concentrations to ensure the reliability of your routine protocols.

[**Amino Acid Analysis (AAA):**](https://filab.fr/en/our-services/our-analysis-services/chemical-analysis-laboratory/analysis-amino-acids/study-amino-acids.md) The gold standard method for precisely quantifying protein mass after total acid hydrolysis, allowing for the calculation of the real extinction coefficient.

Physicochemical characterization requirements ([**ICH Q6B**](https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-characterization-ich-q6b-laboratory.md)).

## Our technical resources

 [### HPLC-UV](https://filab.fr/en/our-technical-resources/laboratory-analysis-uplc/hplc-uv-analysis-laboratory.md) [### Fluorometer](https://filab.fr/en/our-technical-resources/laboratory-fluorometer-analysis.md)
### Our other biopharmaceutical analysis services

[Intact mass analysis](https://filab.fr/en/sectors-of-activity/biopharmaceutical/intact-mass-analysis-laboratory.md)

[Peptide mapping](https://filab.fr/en/sectors-of-activity/biopharmaceutical/biotherapeutic-recombinant-protein-characterization/peptide-analysis-biopharmaceutical-services.md)

Identification and quantification of PTMs

Elemental impurities ([ICH Q3D](https://filab.fr/en/our-services/our-analysis-services/analysis-ich-q3d-context.md) and [USP 233](https://filab.fr/en/our-services/our-analysis-services/analysis-usp-233-laboratory.md))

Analysis according to ICH 6B guideline

Analysis and localisation of [disulfide bridge](https://filab.fr/en/sectors-of-activity/biopharmaceutical/disulfide-bridge-analysis.md)[s](https://filab.fr/en/sectors-of-activity/biopharmaceutical/disulfide-bridge-analysis.md)

[Analysis of HCP (Host Cell Protein)](https://filab.fr/en/sectors-of-activity/biopharmaceutical/host-cell-protein-hcp-testing-analysis-laboratory.md)

Protein analysis using the following methods: [BCA method](https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-analysis-bca-method.md), [Lowry method](https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-analysis-lowry-method.md), [CBQCA method](https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-analysis-cbqca-method.md), [Bradford method](https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-analysis-bradford-method.md)

### Why choose FILAB ?

- **Multidisciplinary expertise**: a team of PhDs and engineers specializing in analytical chemistry and biochemistry.
- **Dual chemistry / materials expertise**
- **ISO 17025 accreditation** by COFRAC.
- **5,200 m²** state-of-the-art analytical facility
- **GMP environment**