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Dosage-form testing

Franz Diffusion Cell (Vertical Diffusion Cell)

A two-chamber glass cell used to measure how fast drug is released from creams, gels and ointments, or permeates through skin. Drug passes through a membrane into a stirred receptor medium that is sampled over time.

  • Pharmaceutical (topicals and transdermals)
  • Cosmetics
  • Research and academia
Photo of a Franz Diffusion Cell (Vertical Diffusion Cell)
Photo: RuiCiencia, CC BY 4.0 (cropped), via Wikimedia Commons
OVERVIEW

What is Franz cell?

A Franz cell has an upper donor chamber and a lower receptor chamber separated by a membrane. The semi-solid product is applied on top of the membrane; the receptor chamber below is filled with a medium that is stirred and held at skin temperature (about 32 °C).

Drug released from the product passes through the membrane into the receptor medium. Samples are taken from a side arm at set times and analysed, usually by HPLC. Plotting the cumulative amount released per unit area against the square root of time gives the release rate.

In vitro release testing (IVRT) with synthetic membranes is used for quality control and to support changes to semi-solid products. In vitro permeation testing (IVPT) uses human or animal skin and is used in development and bioequivalence work.

Used for

  • In vitro release testing (IVRT) of creams, gels, ointments and lotions
  • Supporting post-approval changes to topical products
  • Comparing test and reference products during development
  • Skin permeation studies (IVPT) with excised skin
  • Transdermal patch release
AT A GLANCE

How it works

  1. 01

    Prepare receptor

    Degassed receptor medium is filled into the receptor chamber with no bubbles.

  2. 02

    Mount membrane

    A synthetic membrane is placed between the chambers and clamped.

  3. 03

    Equilibrate

    Cells are held so the membrane surface is at about 32 ± 1 °C, with stirring.

  4. 04

    Dose

    A known amount of product is applied evenly on the membrane in the donor chamber.

  5. 05

    Sample

    Aliquots are withdrawn from the sampling arm at set times and replaced with fresh medium.

  6. 06

    Analyse

    Samples are assayed and cumulative release per cm² is plotted against √time.

Read the full working principle

Advantages

  • Simple, well-understood design
  • Sensitive to changes in formulation and manufacturing
  • Small amounts of product needed
  • Can be automated with multi-cell stations and autosamplers

Limitations

  • Manual sampling is slow and operator-dependent
  • Air bubbles under the membrane reduce diffusion area and give low results
  • Cell-to-cell variability means several cells (commonly six) are needed
  • Membrane choice must be validated so it does not limit release
In LimsPulse · Calibration Management

Keep every Franz cell in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how