简介:TheelectrochemicalformationofMg-LialloyswasinvestigatedinamoltenLiCl-KCl(58-42mol%)eutecticmeltat723K.ThecyclicvoltammogramforaMoelectrodeshowedthattheelectroreductionofLi~+proceedsinasinglestepandthedepositionpotentialofLimetalwas-2.40V(vs.Ag/AgCl).ForMgelectrode,theelectroreductionofLi~+takesplaceatlesscathodicpotentialthanthatattheMoelectrodewhichwascausedbytheformationofMg-Lialloys.PhaseofthedepositedMg-Lialloyscouldbecontrolledbytheelectrolysispotential,andthesampleswerecharacterizedbyX-raydiffractionandscanningelectronmicroscopy.Theresultsshowedthatα-Mgandβ-Liphaseswereobtainedat-2.35and-2.55V,respectively.
简介:Arapidandeffectivemethod,solidphaseextractioncoupledwithhighperformanceliquidchromatography(SPE-HPLC),wasappliedtotheseparationandanalysisofginsenosides.WatersOASISHLBwasusedforconcentratingandpurifyingsamplesandAlltimaC_(18)(53mm×7mm,3μm)chromatographycolumnwasusedforseparatingginsenosideRg_1,Re,Rb_1,Rc,Rb_2andRd.Theseginsenosideswereanalyzedwithin20mininourgradientelutionprocessandtheequilibriumtimeofthechromatographycolumncostonly5min.Moreover,therewasnoobviousbaselinedriftinourexperiment.Thismethodwasusedtoanalyzethecontentsofginsenosidesindifferentginsengproductsforqualitycontrol.Fourginsengproductswerestudied,includingtwokindsofcapsules,onekindoftabletandonekindofinjection.Theresultsshowthatthemethoddevelopedinthispaperhadgoodaccuracy,linearityandprecision.Therefore,thismethodcouldbeappliedinqualitycontrolofginsengproducts.
简介:Inhibitorhydroquinone(HQ)wasaddedtothereactionsystemtopreparepolypropylene/polystyrene(PP/PS)blendpelletswithoutPSonthesurfaceduringdiffusionandsubsequentpolymerizationofstyreneinisotacticpolypropylenepellets.TheeffectsoftheamountofHQondiametricaldistributionofPS,surfacemorphologyofthepelletsandphasemorphologyinsidetheblendpelletswereinvestigated.
简介:Thefluorescencequenchingofnaphthalene(2)and1,3-di(α-naphthyl)propane(1)byRNAandbasesinmethanol-water(v:v=1:1)binarysolventsinthepresenceorabsenceofcyclodex-trin(CD)hasbeeninvestigated.Theresultsshowthatboththemonomerandexcimerfluorescenceof1canbequenchedbythesequenchers.Thequenchingandratesdependonthequencherandtem-perature.Itisshownthatthereisacriticaltemperature(Tc)foreachquencher.BelowTc,theexcimerfluorescencespectrashowvibrationalstructuresandtheStern-Volmerplotsarestraightlines(forura-cilandcytosine);whileabovetheTc,thevibrationalstructuresdisappearandtheStern-Volmerplotsdeviatefromlinearityandcurveupward.Theformerisastaticprocess;whilethelatterisamixtureofbothstaticanddynamicprocesses.Theadditionofα-CDhasnoeffectonthefinestructure,whereasβ-CDpreventstheappearanceofthisstructureefficiently.Thequenchingratesbothforthemonomerandexcimerof1bybasesexceptcytosineinthepresenceofβ-CDatambienttemperaturearenotchanged;thequenchingoffluorescenceof1byRNAinthepresenceofβ-CD,however,ishindered.Time-resolvedfluorescencestudyshowsthattheexcimerfinestructuresappearfromthezerotime.Theintensityoffinestructuresdependonthefractionofwater(φ)inbinarysolvents,anditisindependentofthepHvalueofthesolvents.ItissuggestedthatbasesandRNAinducedaggregates(perhapsmicrocrystal)areformed,inwhichthemotionofmolecules1islimited.