Water Activated by Thermal Atmospheric Plasma of an Electrodeless Microwave Torch, Its Production Conditions and Chemical Composition

A thermal atmospheric plasma generated by an electrodeless microwave torch in an argon jet, which is placed within a protective nitrogen environment, is used to produce plasma-activated water (PAW). The aim is to prepare hydrogen peroxide and nitrous acid–based solutions for application in cancer and skin-disease therapy via indirect treatment methods. In these approaches, the activated water or the medium (PAM) prepared from it, which contains controlled concentrations of long-lived reactive oxygen and nitrogen species (RONS), can selectively affect transformed cells without injuring healthy ones. PAW produced by well-known non-thermal (cold) atmospheric plasma (CAP) sources based on electrode discharges typically contains metal impurities originating from the electrodes and moreover is produced only in limited quantities because of the low plasma density of such discharges. By contrast, PAW obtained using thermal atmospheric plasma has high purity and offers controlled levels of long-lived species, namely hydrogen peroxide (H2O2) and nitrite ions (NO2–), with concentrations exceeding 1 mM at pH ≈ 3. Batch volumes of 0.1–2 L can be produced with activation times up to 20 min.