Thispaperreportsthedevelopmentandvalidationofanassayforthedeterminationofacetonitrileintherecycledmobilephaseusinghighperformanceliquidchromatography(HPLC).Themethodisbasedonthattheretentioninreversed-phaseliquidchromatographyincreaseswithdecreasingconcentrationoforganicphaseinthemobilephase.Thenaturallogarithmofthecapacityratioforagivensoluteislinearlyrelatedtothevolumefractionoftheorganicmodifierinthemobilephase.Fordimethylphthalateanddiethylphthalate,thelinearityrangeis30%―60%,andforbiphenylandterphenyl,therangeis60%―95%.Precisionvalues(RSD)wereboth<1%andtheaccuracy(RE)wasintherangeof±1%.Theassaywassuccessfullyappliedtothedeterminationofacetonitrileconcentrationofrecycledmobilephaseafterthedistillationofthecolumneluentinourlaboratory.
