A tight control of acidity is needed for performing oxidation–reduction
reactions of organic compounds dissolved in liquid media, since the relevant
reactions often involve the occurrence of protons; the matching kinetics are
therefore acidity dependent. This feature holds for plasma treatments of
aqueous wastes which are intended to abate the concentration in organic
pollutants. Exposure of aqueous solutions to a gliding arc plasma in humid air
induces acid and oxidising reactions in the condensed phase. Acid effect
results from the occurrence of NO species formed in the plasma and leads to
the formation in water of nitrous and nitric acids, which are responsible
for a steep pH fall. Using selected buffers allows accurate controlling of
the acidity, which is necessary for most of the plasma-chemical or
plasma-biochemical reactions.