Direct loading of ethanol solution into high-power nitrogen–oxygen mixed gas microwave-induced plasma and the emission characteristics

A nitrogen–oxygen mixed gas microwave-induced plasma (MIP) with an Okamoto cavity was utilized as an atomization and excitation source for emission analysis when organic solvent samples are directly aspirated. Compared with the pure nitrogen plasma (excitation temperature of 5650 K), the excitation temperature in the nitrogen–oxygen mixed gas plasma (5100 K) was reduced, and thus, the detection sensitivity of ionic emission lines requiring higher excitation energy was degraded. However, nitrogen–oxygen mixed gases could produce the very stable microwave-induced plasma with a high robustness against the loading of ethanol solution. This effect might be because the organic solvent was completely burned in the oxygen-containing plasma. The excitation temperature was almost independent of the ethanol content in sample solutions, implying that the analytical performance was less effected by introducing organic solvent samples.