---
type: "WebPage"
title: "Protein analysis using the CBQCA method"
description: "Your requirement: to analyse proteins using the CBQCA method The CBQCA (3-(4-Carboxybenzoyl)quinoline-2-carboxaldehyde) method is a fluorescence-based protein assay technique that offers significantly higher sensitivity than conventional colorimetric methods such as BCA or Bradford. Quantify your proteins with high fluorescent precision..."
resource: "https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-analysis-cbqca-method/"
tags: ["EN", "pll_68f9cd98e9120"]
timestamp: "2026-03-12T08:24:20Z"
published: "2025-10-24T11:33:48Z"
language: "en"
author: "Laure Durieux"
---

# Protein analysis using the CBQCA method

## Your requirement: to analyse proteins using the CBQCA method

The CBQCA (3-(4-Carboxybenzoyl)quinoline-2-carboxaldehyde)**method is a [fluorescence](https://filab.fr/en/our-technical-resources/x-ray-fluorescence-analysis-laboratory-xrf.md)-based** protein assay technique that offers significantly higher sensitivity than conventional colorimetric methods such as BCA or Bradford.

### Quantify your proteins with high fluorescent precision

In the [pharmaceutical](https://filab.fr/en/sectors-of-activity/analysis-industry-pharmaceuticals.md), [cosmetic](https://filab.fr/en/sectors-of-activity/laboratory-analysis-cosmetics.md), [chemical](https://filab.fr/en/our-services/our-analysis-services/chemical-analysis-laboratory.md) and [natural ingredients](https://filab.fr/en/our-services/our-analysis-services/chemical-analysis-laboratory/analysis-natural-ingredients.md) industries, **protein quantification** is an essential step in controlling the quality, compliance and performance of finished products.
The **CBQCA (3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde)** method enables **sensitive and** **specific quantification** of proteins, even at very low concentrations, through **fluorescence detection**.

### What is the CBQCA method?

The CBQCA method is based on a reaction between the CBQCA reagent and **the primary amine groups** of proteins and peptides, forming a **fluorescent complex** detected by spectrofluorimetry.

It is particularly suitable for **samples with low protein concentrations or containing optical interferences** that limit the use of conventional colorimetric methods (BCA, Bradford, Lowry).

### Our protein services

The FILAB laboratory offers a wide range of analytical services related to proteins. These specialised services are aimed at manufacturers wishing to characterise their proteins of interest in detail.

[Proteomic analysis](https://filab.fr/en/sectors-of-activity/biopharmaceutical/laboratory-proteomic-analysis.md)

[Analysis of protein purity](https://filab.fr/en/our-services/our-expertise-services/laboratory-analysis-deposit-contamination/purity-analysis-laboratory.md), [stability](https://filab.fr/en/sectors-of-activity/health-pharmaceutical-cosmetics/stability-testing-medications-and-active-ingredients.md) or [degradation](https://filab.fr/en/sectors-of-activity/health-pharmaceutical-cosmetics/forced-degradation-study.md)

[Method development](https://filab.fr/en/our-services/our-expertise-services/analytical-development.md) and [transfer](https://filab.fr/en/our-services/our-expertise-services/life-cycle-of-an-analytical-method-in-the-laboratory/analytical-method-transfer-laboratory-for-the-pharmaceutical-industry.md)

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

[Protein analysis using the BCA method](https://filab.fr/en/sectors-of-activity/biopharmaceutical/protein-analysis-bca-method.md)

[Detection and quantification of HCPs (Host Cell Proteins)](https://filab.fr/en/sectors-of-activity/biopharmaceutical/host-cell-protein-hcp-testing-analysis-laboratory.md)

[Protein identification or characterisation](https://filab.fr/en/sectors-of-activity/biopharmaceutical/biotherapeutic-recombinant-protein-characterization/protein-analysis.md)

[Validation of analytical method according to ICH Q2 (R2)](https://filab.fr/en/our-services/our-expertise-services/life-cycle-of-an-analytical-method-in-the-laboratory/laboratory-analytical-method-validation/validation-of-laboratory-analysis-methods-according-to-the-ich-q2-standard/)

[Training in LC technique](https://filab.fr/en/our-services/rd/laboratory-analytical-chemistry-training/lc-training-for-laboratories.md)

[Glycoprotein analysis](https://filab.fr/en/sectors-of-activity/biopharmaceutical/biotherapeutic-recombinant-protein-characterization/analysis-characterization-glycoproteins.md)

[Characterization of AAVs by GPC/SEC according to the MAM method](https://filab.fr/en/sectors-of-activity/biopharmaceutical/characterization-aavs-mam.md)

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

## FILAB performs protein analyses using the CBQCA method.

### Why choose FILAB for protein analysis using the CBQCA method?

At the FILAB laboratory, we provide pharmaceutical, cosmetics and chemical manufacturers with **comprehensive analytical expertise** for **protein quantification and characterisation**. FILAB offers tailor-made solutions for protein analysis: dosage, contaminant identification and structural characterisation, supported by [cutting-edge technologies](https://filab.fr/en/our-technical-resources.md) ([LC-MSMS](https://filab.fr/en/our-technical-resources/altis-lc-msms-analysis.md), [HPLC](https://filab.fr/en/our-technical-resources/laboratory-analysis-uplc.md), [UPLC-UV](https://filab.fr/en/our-technical-resources/high-pressure-liquid-chromatography-uplc-laboratory.md), etc.).

### What are the main advantages of the CQBCA method?

 Very high sensitivity
The CBQCA method can detect extremely low quantities of proteins — **down to a few nanograms per millilitre (ng/mL).**
Ideal for:

- diluted samples,
- low-concentration proteins,
- matrices with low protein content (pharmaceutical formulations, natural extracts, etc.).

 A major distinctive feature
The CBQCA reagent reacts only with **primary amine groups** in proteins and peptides.
This selectivity greatly reduces **interference** from other matrix components (detergents, buffers, solvents, etc.).

 Extensive compatibility with complex formulations
Unlike certain colorimetric methods that are sensitive to the composition of the medium, **CBQCA remains largely unaffected by additives:**

Compatible with salt-rich **buffers**,

Compatible with or**ganic solvents**,

Compatible with certain **detergents** used in purification processes.

 Signal reproducibility and stability
The fluorescent complex formed by the CBQCA-protein reaction is **stable over time**, ensuring **good reproducibility** of measurements and **increased reliability** when comparing samples.

 Adaptation to very small sample volumes
The method **requires little material** — a major advantage when working with rare, expensive proteins or those produced in limited quantities.

 Complementarity with other methods
CBQCA can be easily integrated into a multi-technique analytical strategy:

- Used in conjunction with **BCA** for different concentration ranges,
- In support of **HPLC** or **LC-MS/MS** for **precise quantification prior to characterisation**,
- As part of **method development and validation in accordance with ICH Q2 (R2)**.

## FAQ

 In what contexts should the CBQCA method be used?
Industrial teams use this analysis in several cases:

- **Production issues**: yield control, detection of protein loss, monitoring of a purification step.
- **Compliance control**: verification of a protein specification or validation of a dosage.
- **Process optimisation**: validation of an analytical method or technology transfer.
- **Failure investigation**: suspected degradation, interaction or contamination.
- **Regulatory requirements**: creation or updating of a dossier in accordance with ICH Q2 (R2).

 Which matrices can be analysed using the CBQCA method?
The FILAB laboratory applies the CBQCA method to a wide variety of matrices:

- **Pharmaceutical formulations**: recombinant proteins, vaccines, enzymes, monoclonal antibodies
- **Cosmetic products**: active ingredients, protein extracts, peptide-based formulations
- **Chemical and biotechnological raw materials**
- **Natural ingredients and extracts**: plant proteins, enzyme extracts, hydrolysates

 CBQCA vs BCA vs Bradford: which method should you choose?
| Method | Principle | Sensitivity | Matrix compatibility | Type of detection | Typical applications |
| --- | --- | --- | --- | --- | --- |
| **CBQCA** | Fluorescent reaction with primary amines | Very high (ng/mL) | Large (stamps, solvents) | Fluorescence | Diluted samples, high sensitivity required |
| **BCA** | Coloured Cu⁺–BCA complex | Medium to high (µg/mL) | Good (detergents)  | Absorbance | Production monitoring, quality control |
| **Bradford** | Coomassie complex–proteins  | Average (µg/mL)  | Limited (sensitive to additives)  | Absorbance | Rapid assays, initial screening |

Our engineers select the most appropriate method based on the nature of your sample, the target concentration range and the purpose of the analysis.

 À qui s’adresse ce service ?
- **R&D** teams exploring new molecules, formulations or processes.
- **Quality Control departments** ensuring batch release or compliance verification.
- **Production/Process departments** dealing with changes in scale, yields or production incidents.
- **Regulatory Affairs departments** required to document files or meet requirements.
- **Formulation/analytical project** managers who coordinate the transition from innovation to industrialisation.