We have created an asymmetric CCP plasma reactor that operates at 13.56 MHz for the purpose of large scale plasma treatment of sensitive samples such as textiles or seeds. In order to be able to optimise parameters for different treatments one should determine chemical composition of plasma in detail. Here we will present results obtained by optical actinometry that was used to determine concentration of oxygen atoms. In addition, mass spectrometry was used to estimate relative number of metastable and excited oxygen atoms and molecules.