By Courage & Khazaka.

Scientific Devices

With the Invitro Tewameter^® VT 310 a probe for the TEWL measurement is available, which offers all benefits of the Tewameter^® and is perfectly suited to sit on a Franz cell.

The Measurement Principle

The open chamber measurement of the Tewameter^® is the only method to assess the TEWL continuously, which is necessary for most applications without influencing the skin surface. Numerous studies are available.

Measurements with the Invitro Tewameter® VT 310

The probe Tewameter^® VT 310 emulates completely the upper part (donor chamber) of a Franz cell (standard is 15 mm Ø, other sizes on request). Thus the probes sits exactly on the membrane of the Franz cell as it would sit on skin directly without needing further adapters.
The measured TEWL-value is expressed in g/h/m², the worldwide acknowledged absolute measuring value for skin.
No other probe offers this possibility.

If needed, the probe can also be used on a centerpiece of high quality Teflon, which fits exactly on the probe and the receptor chamber of the Franz cell without further fixing adapters. The thus measured TEWL has to be regarded relatively (no longer absolute figures as the distance between probe and membrane is changed).

In vitro TEWL measurements have a variety of different applications:

• inexpensive prescreening before in vivo tests (no ethic commission, no expensive volunteers)
• only way to study skin permeability and dermal absorption necessary for safety and efficacy testing
• in vitro tests are established in several worldwide acknowledged guidelines: WHO (World Health Organization), SCCS (Scientific Committee on Consumer Safety) and OECD (Organization for Economic Cooperation and Development.

Advantages of the Invitro Tewameter® VT 310

• The probe offers all advantages of the open chamber measurement of the Tewameter^®, the worldwide most used TEWL-measuring device (even in space, the probe has been used for measurements on the ISS). Hundreds of publications performed with the probe proof this fact
• The Invitro Tewameter^® probe can replace the donor chamber of a Franz cell completely. Thus it sits perfectly on the membrane, fully comparable to in vivo measurements. The results are expressed in absolute figures (TEWL = g/h/m²)
• No further inconvenient adapters are needed
• If preparations are applied to the membrane during the measurement, a special centerpiece emulating the donor chamber made out of high quality, material-resistent Teflon can be put between probe and membrane. The probe fits exactly to the centerpiece and further adapters are not needed
• The standard probe fits to a Franz cell of 15 mm Ø. Any other sizes can be custom made
• Up to 10 probes can measure simultaneously.
• Continuous measurements over very long time periods are possible
• During the measurement all TEWL values, averages and the standard deviations as well as the information on temperature and relative humidity of the two sensor pairs in the probe can be recorded and displayed
• With the open chamber measurement even higher waterloss values can be detected accurately as no water is collected inside the probe
• Accuracy of the probe can be checked anytime quickly
• As the probe is very light and convenient, it may also be considered for other applications (e.g. fixing the probe to the skin with double sided sticking rings for long-term measurements, measurements under movement, etc.).
• Offset function to compensate “aging effects” of the probe

The Invitro Tewameter^® VT 310 can be connected to the  MPA-systems.
Please ask for package prices for several Invitro Tewameter^®-probes with basic unit.

Please also read Frequent Asked Questions on the Tewameter^®.

Download Brochure

Technical Data

Probe:

Dimensions: Length: 6.5 cm, Measuring chamber:  Height: 2 cm, Inner Ø: 1.5 cm, Outer Ø: 3 cm,  Cable length:  1.3 m, Weight: approx. 60 g,
Teflon-centerpiece: Height:  2.5 cm, Inner Ø: 1.5 cm, Outer Ø: 3 cm

These data apply to the standard probe for a 15 mm Ø Franz cell, for customized sizes they will partly vary.

Resolution: relative humidity ± 0.01 % RH, Temp.: ± 0.01 °C,  TEWL: 0.1 g/h/m², Measuring area: TEWL 0-320 g/h/m²
Accuracy:
Rel. Humidity (RH): ± 1.8 %, Temperature: ± 0.2 °C
TEWL:
between 10 % and 80 % RH: ± 0.25 g/h/m² for TEWL values up to 5 g/h/m² and 5 % for values over 5 g/h/m²
0 -10 % and > 80 % RH: ± 1 g/h/m² for TEWL values up to 5 g/h/m² and 10 % for values under 5 g/h/m²

Technical changes may be made without prior notice.