"Wellness" finish with Vitamin E - II

Robert Zyschka, Dr Ralf Bruckmann, Dr Bernd Kammerer and Hans Schreiber
(This is the second and concluding part of this article).

Transfer of Vitamin E into the skin model

By successfully showing the presence of vitamin E on the textile, it was possible to clarify the question if the active substance vitamin E passes over to the skin when the textile is worn. This information which is very important for the consumer can be found in different transfer techniques:

The collagen model turned out to be the most feasible examination method. The treated textile sample was brought into contact with a cosmetics nonwoven (collagen model). The textile was then stored similar to the colour fastness test under defined conditions (electrolyte content, fabric and air humidity, temperature, mechanical stress) as if worn in reality. The nonwoven collagen was then exposed to an enzymatic decomposition (trypsin impact after reduction and alkylation). The resulting liquid tryptical digest contains the transferred substances.

MALDI-TOF-Analytics of Vitamin E (a -Tocopherol)

For the selective and sensitive analytics of small molecules made of a complex biological matrix, the mass spectrometry has turned out to be the best choice. Besides the easy mass determination, structure information of analytic molecules about induced fragmentation processes or processes of a metastable state can be taken from this.

The individual mass spectrometry methods differ in three elements: ionisation mechanism, mass analyser and ion detection system, whereas these individual components of a MS system can be combined as desired.

Selection of the most suitable mass spectrometrical process for a certain analytic question depends on the request of the molecules which have to be examined, in particular the molecular stability and the ionisation properties. This yields in a certain limit of detection depending on the disturbing matrix.

The MALDI-TOF mass spectrometer has proven to be a method with very low limit of detection, in particular for non polar molecules. The MALDI-TOF mass spectrometry allows to record especially higher molecule compounds like proteins, glycoproteins or polymers, but also molecules in the mass range between 400 and 3500 DA can be well recorded in the so called Reflektron-mode. The ionisation method of the MALDI-TOF mass spectrometry (MALDI-TOF: Matrix Assisted Laser Desorption Ionization - Time of Flight) is based on the principle of laser-desorption of molecules which are embedded in a solid matrix.

The formed ions are then accelerated in an electric field with constant voltage and brought onto a field-free region. An exact measurement of time allows determination of the mass because after passing through of the same potential difference, various speeds of the ions result (according to equation 1). Flight time can be determined with the linear flight pipe as well as with a reflector flight pipe. The reflector geometry offers the advantage compared with linear arrangements that a focusing of the mass peak takes place and thus permits a particularly high resolution (on internal or external calibration). The detection system used is normally a secondary electronic multiplier (SEV).

Determination of vitamin E after the tryptic digestion of the nonwoven collagen was carried out with help of the MALDI-TOF mass spectrometry. For the MALDITOF measurements a matrix of 2.5 dihydroxybenzoic acid in a concentration of 5 mg/ml was applied. 1l of each matrix and sample solution were applied the MALDI target with the dried-droplet method, brought to crystallization and then immediately measured. The measurements were done in the positive modus as well as the linear and reflection modus. For ascertaining the determination limit of vitamin E, a concentration series with the vitamin E cyclodextrine was made and measured with the MALDI-TOF-MS as described above. The determination limit of the vitamin E in the described matrix is 10 ppm (Signal/Noise = 15/1). This conforms with an absolute quantity of 200 pg vitamin E. Without the presence of proteins, the vitamin E-CD-complex up to a concentration of 1 ppm can be proven.

Outlook

With the transfer proof of vitamin E from the textile into a skin model, a very important milestone has been set on the journey of introducing product ideas like in this report up to readiness for the market. The next challenge will be to confirm the transfer in real wearing results.

(Mr Zyschka and Dr Bruckmann are with CHT R Beitlich GmbH, Tubingen. Dr Kammerer is with Eberhard-Karls-Universitat Tubingen and Mr Schreiber is with ITV Denkendorf).