Experimental study of ICP in O 2 –N 2 –H 2 mixtures for sterilization of bacterial spores O. Kyli´ an, P. Colpo, F. Rossi European Commission, Joint Research Centre, Institute for Health and Consumer Protection, Via E. Fermi 1, 21020 Ispra (VA), Italy e-mail: {ondrej.kylian, pascal.colpo, francois.rossi}@jrc.it Received 1 May 2006 The inductively coupled discharge in the ternary mixtures composed of O 2 ,N 2 and H 2 has been studied by optical emission spectroscopy. The intensities of all intense spectral lines and bands as well as intensity of UV radiation have been measured as a function of the initial mixture composition. According to the obtained results, the conditions allowing optimal sterilization of bacterial spores have been identified. PACS : 52.80.Pi, 52.70.Kz Key words : RF plasma discharge, optical emission spectroscopy, ternary mixtures 1 Introduction Non–equilibrium discharges in molecular gases and their mixtures are exten- sively studied due to their applicability in different areas of surface treatment such as cleaning, functionalization or plasma based sterilization and decontamination. This is mainly due to the fact that low–pressure discharges are potent sources of number of active particles as well as intense UV radiation interacting with treated surfaces and modifying their properties. However, the total efficiency of plasma treatment is often a result of the joint effect of different processes taking part dur- ing plasma processing. This is also the case of sterilization of bacterial spores for which the total efficiency of plasma treatment depends on several parameters. Firstly, it is generally accepted that the main agent responsible for bacterial spores killing in low–pressure discharges is UV radiation that penetrates through spores membranes and destroys their genetic material (DNA) (e. g. [1, 2, 3, 4]). However, in many cases the spores are stacked on the surface which implies that significant portion of spores is shielded from the direct UV radiation by other spores. The shielding material removal is therefore needed to help the UV direct view to the underneath layer. For this, it has been shown that fast erosion and/or removal of bacterial spores can be achieved under conditions providing high fluxes of atomic oxygen (e. g. [5, 6]). Moreover, it is well known that besides spores harmful itself, their residues can also cause significant complications after entering human body. This is in partic- ular the case of lipopolysaccharides (LPS), the major cell wall components of the bacteria, which are the fever–causing molecules and whose presence in the mam- malian blood stream can have drastic consequences such as fever or septic shock and ultimately can lead to the death. Therefore their deactivation or removal from surfaces that can come in the contact with human body is highly needed in medical B1250 Czechoslovak Journal of Physics, Vol. 56 (2006), Suppl. B