I-Methylene Blue Njengenkomba: Ukuziphatha Kwe-Redox Nemibuzo Ye-pH

Uchwepheshe ufaka i-methylene blue ebhikhani, alungise i-pH, bese elinda ukuba umbala ubonise ubu-asidi. Akukho okucacile okwenzekayo. Esikhundleni salokho, ufaka iconsi lesixazululo se-ascorbic acid, bese kunyamalala umbala oluhlaza okwesibhakabhaka. Unyakazisa iflaski emoyeni, bese umbala oluhlaza okwesibhakabhaka ubuya. Udayi ofanayo, kodwa ukuziphatha okubili okuhluke kakhulu. Yikho lokhu kudideka okuyisihloko sonke salesi sihloko: i-methylene blue iyinkomba ye-redox esabela ekudlulisweni kwama-electron, hhayi inkomba ye-pH esabela kuma-proton. Uma lowo mehluko usucacile, yonke eminye imininingwane iba sobala.

Umthetho wokuyisebenzisa ungafingqwa ngomusho owodwa. Umbala oluhlaza okwesibhakabhaka usho ukuthi kukhona isimo esenze i-oxidation. Ukungabi nambala kusho ukuthi kukhona isimo esenze i-reduction, i-leucomethylene blue. Noma yini edlulisa ama-electron ingashintsha isimo. Ama-asidi nama-base ewodwa awakwazi, nakuba i-pH ishintsha i-voltage lapho lolo shintsho lwenzeka khona.

Ipheya elibangela umbala

I-methylene blue esenze i-oxidation iyi-methylthioninium cation, uhlelo lwe-phenothiazinium oluyisicaba olunamasongo amathathu, oluhlinzekwa njengosawoti we-chloride, i-PubChem ewubhala njenge-methylthioninium chloride. Emanzini lapho ihlanjululwe khona, i-monomer imunca ukukhanya eduze kuka-664 nm, futhi yilokho kumunca okwenza iso libone umbala oluhlaza okwesibhakabhaka. Ilungu lepheya elenze i-reduction, i-leucomethylene blue, linohlaka olufanayo kodwa i-nitrogen esesongweni eliphakathi inezelwe i-proton kanti i-chromophore iphazamisekile, ngakho cishe alinambala futhi ibhendi yalo enamandla iku-ultraviolet (umbhalo we-PubChem ngesimo se-leuco).

Ukusabela okuphelele kudlulisa ama-electron amabili, kodwa inani lama-proton lincike ku-pH ngoba isimo esenze i-reduction samukela ama-proton endaweni ene-asidi. Incazelo eyisisekelo kokuthi ukwenza ikhemistri ye-redox ibonakale inikeza i-standard potential eseduze kuka-+0.53 V ku-pH 0 kanye ne-formal potential eseduze kuka-+0.011 V ku-pH 7, kuqhathaniswa ne-electrode ye-hydrogen. Phakathi kwalawo maphuzu, i-potential ishintsha ngokwe-pH. I-voltammetry yesimanje ocwaningweni lokuziphatha kwe-redox nama-potential odayi ithola cishe u-29.5 mV ngeyunithi ye-pH kusukela cishe ku-pH 4 kuya ku-10, okuhambisana nesimo sama-electron amabili ne-proton eyodwa, kanye no-88.5 mV ngeyunithi ye-pH ngaphansi kwe-pH 4, okuhambisana nesimo sama-electron amabili nama-proton amathathu. Ngakho i-potential ebikiwe ngaphandle kwe-pH yayo ayinancazelo. Buza njalo ukuthi yiliphi izinga lokushintsha kanye nokuthi iyiphi i-electrode eyireferensi okusekela lelo nani, ngoba amanani aqhathaniswe namareferensi esiliva awanakuqhathaniswa ngokuqondile namanani aqhathaniswe nesikali se-hydrogen. Isakhiwo nezakhiwo eziyisisekelo yizo ezinquma i-chromophore, futhi ikhasi elihambisanayo ngokuklama ukufundwa kwe-redox lidlulisela leli pheya ekukhetheni ukwakheka kwezixazululo.

Yileso sikhundla esiphakathi esikalini se-potential esenza udayi ube wusizo. Ku-pH 7 uphakathi kwama-oxidant abuthakathaka: unamandla anele okwamukela ama-electron kubanikeli abahle njenge-ascorbate noma i-NAD(P)H, kodwa ubuthakathaka ngokwanele ukuba uwadlulisele ku-oxygen encibilikile noma ezikhungweni ze-ferric. Ngakho uyajikeleza phakathi kwezimo esikhundleni sokubambeka. I-reduction iyawususa umbala. Umoya uphinde wenze i-oxidation. Indlela iyafana kuzo zombili izinhlangothi.

Kungani imibuzo ye-pH ilokhu ivela

Imithombo emithathu yokudideka ivame ukuvela emalabhorethri nasemakilasini, futhi ngamunye unokulungiswa okucacile.

Okokuqala, i-pH ishintsha i-potential, okubonakala njengokusabela ku-pH. Uma ukhuphula i-pH, ipheya liba lula ukwenza i-reduction lapho ukufundwa kwe-electrode kungashintshi, ngakho umnikeli ofanayo ususa umbala kudayi ngokushesha. Kodwa ukwamukela i-proton kuphela akubangeli ukushintsha okucacile kusuka kokuluhlaza okwesibhakabhaka kuye kokungenambala ebangeni elivamile. Ukubuyekezwa okubucayi kwezakhiwo ze-methylene blue kwango-2025 kubika ukuthi indawo yokumunca okuphezulu engu-665 nm ihlala ingashintshile cishe ngokuphelele kusukela ku-pH 2 kuya ku-12, kube nezinguquko ezincane kuphela esilinganisweni sokumunca. Ama-proton alungisa i-voltage. Ama-electron ashintsha umbala.

Okwesibili, ilebula yokuhlukaniswa kwemiqondo iyadukisa. I-PubChem njengamanje ingenisa indima evela ku-ChEBI ebiza udayi ngokuthi inkomba ye-asidi ne-base. Leyo lebula akufanele ithathwe njengobufakazi bokuthi i-methylene blue iziphatha njenge-phenolphthalein noma i-methyl red. Emsebenzini ojwayelekile wezixazululo zamanzi, ayiziphathi kanjalo.

Okwesithathu, ingxube ye-Tashiro iboleka leli gama. Inkomba ye-Tashiro iyingxube ye-methyl red ne-methylene blue lapho i-methyl red inikeza ukusabela kwe-asidi ne-base, kanti i-methylene blue inikeza umbala wangemuva oluhlaza okwesibhakabhaka, iguqule ukushintsha kusuka kokubomvu kuye kokuphuzi kube ukushintsha kwengxube okucace kakhudlwana. Enye ingxube ye-Tashiro ethengiswayo ibika i-pH 4.4 kuya ku-6.2, kanti ingxube echaziwe ye-ITW Reagents icacisa okusabubende ngokubomvu ku-pH 4.4 kuya kokuluhlaza ku-pH 5.8. Alikho kulawa mabanga eliyibanga lokushintsha le-methylene blue uqobo. Udayi uyisisebenzeli sokuguqula ukubonakala kombala, hhayi inzwa.

Isimo esisodwa esingajwayelekile sidinga isixwayiso. Eduze kwe-pH 13, izimo ezine-alkali enamandla zingakhiqiza imikhiqizo ebomvu kuya kepinki yohlobo lwe-methylene-violet nge-hydrolysis engenakubuyiselwa emuva. Lowo mbala opinki uwukuwohloka, hhayi iphuzu lokugcina lenkomba. Wuthathe njengophawu lokulahla isixazululo, hhayi njengento okufanele uyifunde.

Lapho isebenza khona njengenkomba ye-redox

Ukusetshenziswa kwakudala kuse-titration ye-Lane-Eynon yoshukela onamandla okwenza i-reduction. Isixazululo se-Fehling esishisayo esine-alkali senziwa i-titration ngoshukela, bese i-methylene blue ifakwa lapho kusondelwa ephuzwini lokugcina; umbala oluhlaza okwesibhakabhaka osele uyanyamalala lapho amandla kashukela okwenza i-reduction esedlula lawo adingekayo ku-copper(II). Inqubo ye-AOAC Lane-Eynon igcina ingxube ibila ukuze ukuphuma kwesitimu kunciphise ukuphinda kwenzeke i-oxidation ngenxa yomoya, ngokuvamile kusetshenziswa amaconsi ambalwa esixazululo sikadayi. Ukushintsha kombala kubonisa ukuthi akusekho i-copper engenziwa i-reduction, okuyisitatimende se-redox mayelana nokuseflaskini, hhayi isitatimende se-pH.

I-titrimetry yakudala yayisebenzisa umqondo ofanayo kwezinye izindawo. Udayi ohlanjululiwe wawungasetshenziswa esikhundleni sesitashi kwezinye izinhlobo ze-iodimetric titration lapho utshwala benza isitashi singafaneleki, kusetshenziswa ukugxila okuseduze kuka-0.05 g ilitha ngalinye, nakuba udayi oweqile ubeka engcupheni yokwakheka kwenhlanganisela ye-iodine nodayi, njengoba u-Sinnatt abonisa ngo-1912. Izincwadi zezikhombo ziphinde zibhale ukuthi udayi usetshenziswa ku-titanometry naku-iodometry. Indlela ka-Gal ye-ascorbic acid yango-1936 yayenza i-reduction kudayi ngezingcaphuno ze-vitamin C bese yenza i-back-titration kudayi osele nge-titanium trichloride. Leyo ndlela manje ingeyomlando kunokuba ibe umsebenzi ojwayelekile, kodwa ibonisa iphethini: umnikeli wenza i-reduction esusa umbala oluhlaza okwesibhakabhaka, futhi ukunyamalala kwalowo mbala kuyiphuzu lokugcina.

Izindlela ze-oxygen encibilikile zisebenzisa ipheya elifanayo ngendlela ephambene. Enye indlela eshicilelwe iqala ngokwenza i-reduction kudayi nge-glucose ku-ethanol enamanzi ne-alkali, bese ivumela i-oxygen encibilikile ukuba yenze i-oxidation eshintsha isimo se-leuco esingenambala sibuyele kokuluhlaza okwesibhakabhaka cishe ngokushesha, kufundwe eduze kuka-600 nm kuze kufike cishe ku-13 micrograms nge-milliliter, njengoba kuchazwe ngu-Okumura no-Hashitani. Ungakudidanisi lokhu ne-titration yakudala ye-Winkler ye-oxygen encibilikile, lapho iphuzu lokugcina lisebenzisa isitashi; i-NOAA Winkler SOP icacisa cishe u-1 percent wesitashi. Izindlela ze-oxygen ze-methylene blue ziyiqembu elihlukile lapho umbala ushintsha ngendlela ephambene.

Ibhodlela eliluhlaza okwesibhakabhaka lasekilasini lisebenzisa ipheya elifanayo ngezinga elincane: i-glucose esixazululweni esine-alkali yenza i-reduction eshintsha udayi oluhlaza okwesibhakabhaka ube isimo esingenambala uma ushiywe unganyakaziswa, futhi ukunyakazisa kuncibilikisa i-oxygen ephinde yenze i-oxidation iwubuyisele kokuluhlaza okwesibhakabhaka. Inqubo ephelele nezilawuli zayo kuchazwa ekubonisweni kokuhlola kwebhodlela eliluhlaza okwesibhakabhaka, kanti izindawo zamabhendi nezinguquko ngenxa yokuhlangana kwama-molecule kuchazwa ekhasini lama-spectrum nemiphumela yokugxila. Lesi sihloko sigcina indlela yokusebenza kuphela, ngoba inqubo nama-spectrum ngakunye kudinga izimo zakho ezichaziwe.

Ishadi lezimo zombala: izimo, izimo ezizikhiqizayo, imikhawulo

Leli thebula liyisikhombo sokuqala salesi sihloko. Funda wonke umugqa ngaphambi kokwethemba noma yiliphi iphuzu lokugcina.

Isimo	Ukubukeka	Isimo esisikhiqizayo	Esikubonisayo	Umkhawulo
I-monomer esenze i-oxidation, ihlanjululiwe, ayinayo i-asidi noma i-alkali eyeqile	Okuluhlaza okwesibhakabhaka okujulile, indawo yokumunca okuphezulu eduze kuka-664 nm	Isixazululo esigcwele umoya, akukho mnikeli okhona	Isimo sokuqala esilungele ukusebenza	Uma ukugxila kuphezulu, indawo yokumunca okuphezulu isondela ku-610 nm ngenxa yokwakheka kwama-dimer, ngakho hlola umthunzi wombala ngemva kokuhlanjulula kuphela
Isimo se-leuco esenze i-reduction, asinayo i-asidi noma i-alkali eyeqile	Akunambala	Kukhona umnikeli (i-glucose ku-base, i-ascorbate, i-dithionite, i-NAD(P)H ene-catalyst)	Amandla okwenza i-reduction adlule isidingo senkomba	Umoya uphinde wenze i-oxidation, ngakho umbala emaphuzwini okugcina ubuyela kokuluhlaza okwesibhakabhaka ngaphandle uma umoya uvinjelwe noma ukuchayeka kuwo kulinganisiwe
Isimo se-leuco, sine-asidi	Akunambala	Abanikeli abafanayo ku-asidi, kanye nokwamukela ama-proton engeziwe kwesimo se-leuco	Okufanayo nokungenhla ku-potential eshintshile	Izinga lokushintsha kwe-potential liyakhula ngaphansi kwe-pH 4, ngakho ukulinganisa kwaku-pH 7 akusebenzi lapha
Ingxube ye-Tashiro, ine-asidi	Okusabubende ngokubomvu	I-pH engaphansi cishe kuka-4.4 engxubeni ye-methyl red ne-methylene blue	Ubu-asidi, obuvela ku-methyl red	Ibonisa i-methyl red, hhayi i-methylene blue; ungakubiki njengebanga le-pH le-methylene blue
Ingxube ye-Tashiro, eduze kwe-pH 5.8 kuya ku-6.2	Okuluhlaza kuya kokumpunga ngokuluhlaza	Ingxube efanayo eduze komkhawulo ophezulu wokushintsha kwayo	Okufanayo nokungenhla	Kuncike ekwakhekeni kwengxube; hlola ibhodlela, ungathembeli enkumbulweni
Okuwohlokile, kune-alkali enamandla	Okupinki kuya kokubomvu	I-pH eseduze kuka-13, ukushisa, ukuchayeka ku-base isikhathi eside	I-hydrolysis engenakubuyiselwa emuva ekhiqiza imikhiqizo yohlobo lwe-violet	Akubuyiseleki ngokunyakazisa; kulahle bese wenza okusha
Umbala osuswe ukukhanya	Okuluhlaza okwesibhakabhaka okufiphele okune-spectrum eshintshile	Ukukhanya okubonakalayo okunamandla, ikakhulukazi uma kukhona abanikeli	Ukusabela okuseceleni okuqhutshwa ukukhanya, okuhlanganisa imikhiqizo ekhishwe amaqembu e-methyl	Vikela izixazululo zezilinganiso ekukhanyeni, njengoba umsebenzi we-photoreduction ngokukhanya okubonakalayo wabonisa

Izindlela zokwehluleka ezifiphaza iphuzu lokugcina

Umoya uyinto yokuqala okufanele isolwe lapho iphuzu lokugcina lishintsha ngokuhamba kwesikhathi. Isimo se-leuco siphinde senze i-oxidation kalula, ikakhulukazi ezinhlelweni ezine-alkali, ngakho i-titration esuke yaphela ingenambala ingaphinde ibe luhlaza okwesibhakabhaka lapho iyekiwe inganyakaziswa noma izungeziswa ngamandla. Vimbela umoya lapho kudingeka isimo sihlale singashintshi, yenza ukunyakazisa kufane njalo, bese ufunda ngesikhathi esinqunyiwe.

Ukukhanya yinto yesibili okufanele isolwe. Udayi uyakwazi ukubamba iqhaza ekusabeleni kwamakhemikhali okubangelwa ukukhanya, futhi ukuchayeka ekukhanyeni lapho kukhona abanikeli kungawususa umbala ngezindlela ezihlanganisa imikhiqizo ekhishwe amaqembu e-methyl. Gcina izixazululo zikadayi zokuhlaziya ebumnyameni futhi ungafundi amaphuzu okugcina ngaphansi kwamalambu etafula lokusebenza anamandla.

Ukugxila yinto yesithathu. I-cation esenze i-oxidation ihlangana ibe ama-dimer namaqoqo amakhulu, nebhendi eshiftile eseduze kuka-610 kuya ku-615 nm, ngakho isixazululo esigxilile sibonakala siphambukile endaweni evamile yokumunca okuphezulu ngaphandle kokuba singcolile. Hlanjulula kuze kubuse ama-monomer ngaphambi kokuhlola ama-spectrum noma amaphuzu okugcina.

Izinto ezimbili ezicashile ezichezukisa imiphumela zidinga ukunakwa ngoba zithinta ikakhulukazi umsebenzi wokugxila okuphansi. Udayi unamathela ngesilinganiso esingalinganiswa emngceleni wengilazi namanzi, okwenza izixazululo zezilinganiso ezihlanjululiwe nezilinganiso zejubane lokusabela zicheme; izitsha noma ama-cuvette enziwe nge-polymer ayisixazululo lapho ukunemba kubalulekile. Futhi udayi othengiswayo ungaba nokungcola okuhlobene kwe-thiazine, okuhlanganisa i-Azure B, izifundo zakudala zokuhlanza ezazikususa ngokuqondile, ngakho umsebenzi wokuhlaziya kufanele ucacise ibanga lekhwalithi kunokucabanga ukuthi wonke amabhodlela abhalwe ukuthi i-methylene blue ayafana ngokwamakhemikhali. Imininingwane ye-spectrum yokushintsha okubangelwa ukuhlangana kwama-molecule igcinwe ekhasini lama-spectrum ngamabomu.

Uhlu olufushane lokuhlola etafuleni lokusebenza

Sebenzisa i-buffer esixazululweni bese ubhala i-pH eduze kwayo yonke i-potential nalo lonke iphuzu lokugcina. Misa izimo ze-oxygen: ukubilisa ngaphansi kwesendlalelo sesitimu emsebenzini wohlobo lwe-Lane-Eynon, noma ukumboza ngegesi engasabeli noma ukusebenzisa isikhathi esinqunyiwe kwezinye izimo. Sebenza ngokugxila okuphansi ngokwanele ukuze ubone i-monomer, vikela izixazululo ekukhanyeni, khetha izitsha ze-polymer lapho ukugxila kuphansi, bese ubhala ibanga lekhwalithi likadayi. Uma umgomo empeleni kuyi-pH, sebenzisa inkomba yangempela ye-asidi ne-base noma ingxube ye-Tashiro echazwe ngokucacile, bese ubika ibanga lengxube njengebanga lengxube, hhayi neze njengebanga le-methylene blue.

Umqondo uhlala ucacile uma kulandelwa le mithetho. I-methylene blue ibonisa isimo se-oxidation ngokucaca okungavamile ngoba izimo zayo ezimbili zimunca ukukhanya okubonakalayo ngendlela ehluke kakhulu. Thatha umbala njengokufundwa kwe-redox okwenziwa ku-pH echaziwe, ngaphansi kwezimo ze-oxygen nokukhanya ezichaziwe, ngebanga lekhwalithi likadayi elichaziwe, bese iba nendawo yayo efanele ku-titration. Yithathe njenge-litmus, bese ikudukisa njalo ngaphandle kokuphambuka.