Methylene blue monga chizindikiro: zimene kusintha kwa mtundu kumasonyezadi

Katswiri wa labotale amathira methylene blue mu beaker, amasintha pH, ndipo amadikira kuti mtundu usonyeze kuchuluka kwa asidi. Palibe kusintha koonekeratu kumene kumachitika. M'malo mwake amathira dontho la madzi osungunula ascorbic acid, ndipo buluu amachoka. Amagwedeza flask mumlengalenga, ndipo buluu amabwerera. Utoto womwewo, koma makhalidwe awiri osiyana kwambiri. Chisokonezo chimenechi ndicho nkhani yonse ya nkhaniyi: methylene blue ndi chizindikiro cha redox chimene chimayankha kusamutsidwa kwa ma elekitironi, osati chizindikiro cha pH chimene chimayankha ma protoni. Kusiyana kumeneku kukamveka bwino, zina zonse zimakhala zomveka.

Lamulo lothandiza likhoza kufotokozedwa m'chiganizo chimodzi. Buluu amatanthauza kuti mawonekedwe otaya ma elekitironi alipo. Kusakhala ndi mtundu kumatanthauza kuti mawonekedwe olandira ma elekitironi, leucomethylene blue, alipo. Chilichonse chimene chimasamutsa ma elekitironi chikhoza kusintha mawonekedwewo. Ma asidi ndi ma besi okha sangathe, ngakhale kuti pH imasintha voteji imene kusinthako kumachitika.

Mitundu iwiri ya redox imene imayambitsa mtundu

Methylene blue yotaya ma elekitironi ndi methylthioninium cation, dongosolo lathyathyathya la phenothiazinium la mphete zitatu, limene limaperekedwa ngati mchere wa chloride, ndipo PubChem imalilemba kuti methylthioninium chloride. Ikakhala yosungunuka m'madzi mochuluka, monoma yake imayamwa kuwala pafupi ndi 664 nm, ndipo kuyamwa kumeneku ndiko kumapangitsa buluu amene diso limaona. Mnzake wolandira ma elekitironi, leucomethylene blue, ali ndi mafupa omwewo a molekyulu koma nayitrojeni wa mphete yapakati walandira protoni ndipo chromophore yasokonezeka. Choncho ili pafupifupi yopanda mtundu ndipo ili ndi gawo lamphamvu loyamwa kuwala kwa ultraviolet (zolemba za PubChem za mawonekedwe a leuco).

Reakeshoni yonse imasamutsira ma elekitironi awiri, koma chiwerengero cha ma protoni chimadalira pH chifukwa mawonekedwe olandira ma elekitironi amalandira ma protoni mu asidi. Kufotokozera kwa mu kuonetsa kemistri ya redox kumapereka potensholo yokhazikika pafupi ndi +0.53 V pa pH 0 ndi potensholo ya mikhalidwe yomwe yaikidwa pafupi ndi +0.011 V pa pH 7, poyerekeza ndi elekitirodi ya haidrojeni. Pakati pa mfundo zimenezi, potensholo imasuntha ndi pH. Voltammetry yamakono mu kafukufuku wa khalidwe la redox ndi potensholo za utoto imapeza pafupifupi 29.5 mV pa yuniti ya pH kuchokera pafupifupi pH 4 mpaka 10, mogwirizana ndi dongosolo la ma elekitironi awiri ndi protoni imodzi, komanso pafupifupi 88.5 mV pa yuniti ya pH pansi pa pH 4, mogwirizana ndi dongosolo la ma elekitironi awiri ndi ma protoni atatu. Choncho potensholo yotchulidwa popanda pH yake ilibe tanthauzo. Nthawi zonse funsani kuti kuchuluka kwa kusintha ndi elekitirodi yoyerekezera zomwe zikugwirizana ndi nambalayo ndi ziti, chifukwa manambala oyerekezedwa ndi ma elekitirodi a siliva sangathe kuyerekezedwa mwachindunji ndi manambala oyerekezedwa ndi sikelo ya haidrojeni. Kapangidwe ndi mikhalidwe yake ndiyo imakhazikitsa chromophore, ndipo tsamba lina logwirizana lofotokoza kapangidwe ka njira yowerengera redox limafotokoza mmene mitundu iwiri imeneyi imakhudzira kusankha zosakaniza.

Malo ake apakati pa sikelo ya potensholo ndi amene amapangitsa utotowu kukhala wothandiza. Pa pH 7 uli m'gulu la zinthu zofatsa zolandira ma elekitironi: uli ndi mphamvu zokwanira kulandira ma elekitironi kuchokera kwa opereka abwino monga ascorbate kapena NAD(P)H, koma ndi wofooka mokwanira kuwapereka kwa okosijeni wosungunuka kapena malo a ferric. Choncho umazungulira pakati pa mawonekedwe awiri m'malo mokhazikika pa amodzi. Kulandira ma elekitironi kumachotsa mtundu wake. Mpweya umaubwezeretsa ku mawonekedwe otaya ma elekitironi. Njirayo ndi yomweyo kumbali zonse ziwiri.

Chifukwa chake mafunso a pH amabwerezabwereza

Pali zinthu zitatu zoyambitsa chisokonezo zimene zimabwerezabwereza m'malabotale ndi m'makalasi, ndipo chilichonse chili ndi njira yomveka yochikonza.

Choyamba, pH imasuntha potensholo, ndipo zimenezi zimaoneka ngati kuyankha pH. Mukakweza pH, mitundu iwiri ya redox imakhala yosavuta kulandira ma elekitironi pa muyeso wa elekitirodi wosasinthidwa, motero wopereka yemweyo amachotsa mtundu wa utoto mofulumira. Koma kulandira protoni kokha sikumapangitsa kusintha koonekeratu kuchokera pa buluu kupita popanda mtundu mkati mwa malire anthawi zonse. Ndemanga yowunika mikhalidwe ya methylene blue ya 2025 imati malo apamwamba oyamwa kuwala a 665 nm amakhalabe pafupifupi osasintha kuchokera pa pH 2 mpaka 12, ndipo kuchuluka kwa kuwala koyamwa kumangosintha pang'ono. Ma protoni amakonza voteji. Ma elekitironi amasintha mtundu.

Chachiwiri, dzina la gulu m'dongosolo logawa zinthu limasocheretsa. PubChem panopa imatenga kufotokozera ntchito kuchokera ku ChEBI kumene kumatcha utotowu chizindikiro cha asidi ndi besi. Dzina limenelo siliyenera kutengedwa ngati umboni wakuti methylene blue imachita ngati phenolphthalein kapena methyl red. Pa ntchito zanthawi zonse za m'madzi, sichita zimenezo.

Chachitatu, chosakaniza cha Tashiro chimabwereka dzinalo. Chizindikiro cha Tashiro ndi chosakaniza cha methyl red ndi methylene blue, mmene methyl red imapereka kuyankha asidi ndi besi ndipo methylene blue imapereka mtundu wa buluu wakumbuyo. Izi zimasintha kusintha kuchokera pa wofiira kupita pa wachikasu kukhala kusintha koonekeratu kwambiri kwa mitundu yosakanikirana. Chosakaniza chimodzi cha Tashiro chogulitsidwa chimatchula pH 4.4 mpaka 6.2, pamene chosakaniza chodziwika bwino cha ITW Reagents chimatchula wofiira-vayolete pa pH 4.4 mpaka wobiriwira pa pH 5.8. Palibe malire amenewa amene ndi malire a kusintha kwa methylene blue yokha. Utotowu umathandiza kuti kusintha kuoneke, osati kuzindikira pH.

Mkhalidwe umodzi wapadera umafunika chenjezo. Pafupi ndi pH 13, mikhalidwe ya besi wamphamvu ingapange zinthu zofiira mpaka zapinki za mtundu wa methylene-violet kudzera mu hydrolysis yosasinthika kubwerera. Pinki ameneyo ndi kuwonongeka, osati malo omaliza a chizindikiro. Muutenge ngati chenjezo loti mutaye madziwo, osati kuti muwawerenge.

Kumene imagwira ntchito ngati chizindikiro cha redox

Ntchito yodziwika kalekale ndi titration ya Lane-Eynon ya shuga wopereka ma elekitironi. Madzi a Fehling otentha okhala ndi besi amayezedwa mwa kuwathirira shuga, ndipo methylene blue imawonjezedwa pafupi ndi malo omaliza; buluu wotsalayo amachoka pamene mphamvu ya shuga yopereka ma elekitironi yaposa imene ikufunika pa copper(II). Ndondomeko ya AOAC Lane-Eynon imasunga chosakanizacho chikuwira kuti nthunzi yotuluka ichepetse kubwezeretsedwa ku mawonekedwe otaya ma elekitironi ndi mpweya, nthawi zambiri ndi madontho ochepa a madzi a utoto. Kusintha kwa mtundu kumasonyeza kuti palibe mkuwa wotsala umene ungathe kulandira ma elekitironi. Umenewu ndi uthenga wa redox wokhudza zimene zili mu flask, osati uthenga wa pH.

Njira zakale zoyezera ndi titration zinagwiritsa ntchito mfundo yomweyo pa ntchito zina. Utoto wosungunulidwa kwambiri unkatha kulowa m'malo mwa sitachi mu ma titration ena a iodimetry pamene mowa unkapangitsa sitachi kukhala yosayenera, pa kuchuluka kogwiritsira ntchito pafupi ndi 0.05 g pa lita, ngakhale kuti utoto wochuluka kwambiri ungapange chinthu chophatikizana cha ayodini ndi utoto, monga Sinnatt anasonyezera mu 1912. Mabuku osonkhanitsa njira amatchulanso utotowu pa titanometry ndi iodometry. Njira ya ascorbic acid ya Gal ya 1936 inapatsa utotowo ma elekitironi pogwiritsa ntchito zotulutsa za vitamini C, kenako inayesa utoto wotsala ndi titration yobwerera pogwiritsa ntchito titanium trichloride. Njira imeneyo tsopano ndi ya mbiri m'malo mwa ntchito yanthawi zonse, koma imasonyeza dongosolo lake: wopereka ma elekitironi amasintha buluu kukhala wopanda mtundu, ndipo kuchoka kwa buluu ndiko malo omaliza.

Njira zoyezera okosijeni wosungunuka zimagwiritsa ntchito mitundu iwiri yomweyo mobwerera. Njira imodzi yofalitsidwa imayamba kupatsa utotowo ma elekitironi pogwiritsa ntchito glucose mu ethanol yosakanizidwa ndi madzi yokhala ndi besi, kenako imalola okosijeni wosungunuka kuti achotse ma elekitironi ku mawonekedwe a leuco opanda mtundu ndi kuwabwezeretsa ku buluu pafupifupi nthawi yomweyo. Kuwerenga kumachitika pafupi ndi 600 nm mpaka pafupifupi 13 micrograms pa milliliter, monga anafotokozera Okumura ndi Hashitani. Musasokoneze zimenezi ndi titration yachikale ya Winkler yoyezera okosijeni wosungunuka, imene imagwiritsa ntchito sitachi pa malo ake omaliza; SOP ya NOAA Winkler imatchula sitachi ya pafupifupi 1 percent. Njira za methylene blue zoyezera okosijeni ndi gulu lina lokhala ndi kusintha kwa mtundu kolowera mbali yosiyana.

Chionetsero cha botolo la buluu cha m'kalasi ndi mitundu iwiri yomweyo pa mlingo waung'ono: glucose m'madzi okhala ndi besi imapatsa utoto wa buluu ma elekitironi n'kuusintha kukhala wopanda mtundu ukasiyidwa osagwedezedwa, ndipo kugwedeza kumasungunula okosijeni amene amaubwezeretsa ku buluu pochotsa ma elekitironi. Ndondomeko yonse ndi njira zoilamulira zili pa chionetsero cha botolo la buluu, ndipo malo a magawo oyamwa kuwala ndi kusuntha chifukwa cha kusonkhana kwa mamolekyulu zili pa tsamba la sipekitira ndi zotsatira za kuchuluka kwa utoto. Nkhaniyi ikungofotokoza mmene zimachitikira, chifukwa ndondomeko ndi sipekitira iliyonse zimafunika mikhalidwe yake.

Tchati cha mtundu ndi mawonekedwe: mawonekedwe, mikhalidwe, malire

Tebuloli ndi cholozera choyambirira cha nkhaniyi. Werengani mzere wonse musanakhulupirire malo aliwonse omaliza.

Zinthu zosokoneza malo omaliza

Mpweya ndi chinthu choyamba chokayikiridwa nthawi iliyonse malo omaliza akamasuntha. Mawonekedwe a leuco amataya ma elekitironi mosavuta, makamaka m'madongosolo okhala ndi besi, choncho titration imene inafika popanda mtundu ingabwererenso ku buluu ikasiyidwa kapena ikazunguliridwa mwamphamvu. Letsani mpweya pamene kusungika kwa mawonekedwewo kuli kofunika, khazikitsani kugwedeza kofanana, ndipo werengani pa nthawi yokhazikika.

Kuwala ndi chinthu chachiwiri chokayikiridwa. Utotowu umachita ma reakeshoni chifukwa cha kuwala, ndipo kuwunikiridwa pamene opereka ma elekitironi alipo kungachotse mtundu kudzera m'njira zimene zimaphatikiza zinthu zomwe zataya magulu a methyl. Sungani madzi a utoto woyezera mumdima ndipo musayese malo omaliza pansi pa nyali zamphamvu za pa tebulo la labotale.

Kuchuluka kwa utoto ndi chinthu chachitatu. Cation yotaya ma elekitironi imasanjikana kukhala madima ndi magulu akuluakulu a mamolekyulu, okhala ndi gawo loyamwa kuwala losunthidwa kufupi ndi 610 mpaka 615 nm. Choncho madzi okhala ndi utoto wochuluka amaoneka ngati achoka pa malo apamwamba oyembekezeredwa ngakhale alibe zosafunika zosakanikirana nawo. Onjezerani madzi mpaka utotowo ukhale m'mawonekedwe a monoma musanaweruze sipekitira kapena malo omaliza.

Zinthu ziwiri zosawonekera kwambiri zosokoneza miyeso ziyenera kufotokozedwa chifukwa zimakhudza makamaka ntchito ya utoto wochepa kwambiri. Utotowu umamatirira pamalire a galasi ndi madzi mokwanira kuyezeka, zomwe zimasokoneza madzi oyezera osungunulidwa kwambiri ndi miyeso ya liwiro la reakeshoni; zotengera kapena ma cuvette a polima ndi njira yothetsera zimenezi pamene kulondola kuli kofunika. Komanso utoto wogulitsidwa ungakhale ndi zinthu zosafunika za thiazine zogwirizana nawo, kuphatikiza Azure B, zimene kafukufuku wakale woyeretsa anazichotsa mwadala. Choncho ntchito yoyezera iyenera kutchula giredi yake m'malo mongoganiza kuti botolo lililonse lolembedwa methylene blue lili ndi mankhwala ofanana ndendende. Mwatsatanetsatane, kusuntha kwa sipekitira chifukwa cha kusonkhana kwa mamolekyulu kwasiyidwa pa tsamba la sipekitira mwadala.

Mndandanda wachidule woti muwunike pa tebulo la labotale

Gwiritsani ntchito buffer kuti pH ya madzi ikhale yokhazikika, ndipo lembani pH pafupi ndi potensholo iliyonse ndi malo aliwonse omaliza. Khazikitsani mkhalidwe wa okosijeni: kuwira kokhala ndi nthunzi yophimba pa ntchito ya mtundu wa Lane-Eynon, kapena kuphimba ndi gasi wosachita reakeshoni kapena kugwiritsa ntchito nthawi yokhazikika pa ntchito zina. Gwiritsani ntchito utoto wosungunulidwa mokwanira kuti muone monoma, tetezani madziwo ku kuwala, sankhani zotengera za polima pamene utoto uli wochepa kwambiri, ndipo lembani giredi ya utotowo. Ngati cholinga chenicheni ndi pH, gwiritsani ntchito chizindikiro chenicheni cha asidi ndi besi kapena chosakaniza cha Tashiro chodziwika bwino, ndipo tchulani malire a chosakanizacho ngati malire a chosakaniza, osati ngati malire a methylene blue.

Mfundo yake imakhalabe yolondola potsatira malamulo amenewa. Methylene blue imasonyeza mawonekedwe a oxidation momveka kwambiri chifukwa mawonekedwe ake awiri amayamwa kuwala kooneka ndi maso mosiyana kwambiri. Tengani mtundu wake ngati kuwerenga kwa redox kochitika pa pH yotchulidwa, pansi pa mikhalidwe ya okosijeni ndi kuwala yotchulidwa, ndi giredi ya utoto yotchulidwa, ndipo imakhala yothandiza pa titration. Muigwiritse ntchito ngati litmus ndipo idzakusocheretsani mosasintha.