The kinetic of the hydroxyl radical is studied in N2/O2/H2O
mixtures with small amounts of acetone or isopropyl alcohol (0.5%). The
radical density is measured in absolute value in the afterglow of a
photo-triggered discharge, which generates an homogeneous transient
non-equilibrium plasma, using a time resolved absorption measurement method.
For dry mixtures, experimental results are compared to predictions of a
self-consistent 0D discharge and kinetic model. It is shown that
dissociation of the VOCs through quenching collisions of nitrogen metastable
states plays an important role in the production of OH. Measurements can not
be explained looking only at the oxidation of acetone or IPA by the oxygen
atom. This result is reinforced by experimental results about the OH density
in wet mixtures, with or without VOCs, compared to dry ones.