The method of CHNS-analysis in combination with ³¹P NMR and UV-VIZ spectroscopy was used to study polyoxometallates and ionic liquids as components of liquid-phase catalytic systems. The composition of imidazolium and TBA salts of tungstоphosphate anions active in the olefin oxidation with H₂O₂ was determined. A method for quantification of [BMIm]Br, Bu₄NBr, Bu₄NHSO₄ in solutions using the C, N, S analysis is proposed. The capabilities of the technique with applying IL to an inert porous support are evaluated. Using the obtained results, the effect of ionic liquids in combination with a Pt/C catalyst and H₃PMo₁₂O₄₀ heteropolyacid in the oxidation of cyclohexane with О₂-Н₂ gas mixture was determined.