{"id":4448,"date":"2017-05-23T13:45:25","date_gmt":"2017-05-23T11:45:25","guid":{"rendered":"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/?p=4448"},"modified":"2017-05-23T13:45:25","modified_gmt":"2017-05-23T11:45:25","slug":"cromatografia-fulles-despinacs","status":"publish","type":"post","link":"https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/modul-a\/cromatografia-fulles-despinacs\/","title":{"rendered":"Cromatografia fulles d&#8217;espinacs"},"content":{"rendered":"<p><a href=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/download.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\" wp-image-4449 aligncenter\" src=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/download.jpg\" alt=\"download\" width=\"345\" height=\"461\" \/><\/a><\/p>\n<p>La separaci\u00f3 d\u2019un analit (subst\u00e0ncia que volem determinar) de les possibles interfer\u00e8ncies \u00e9s sovint una etapa molt important en els procediments anal\u00edtics. El m\u00e8tode m\u00e9s utilitzat per fer separacions anal\u00edtiques \u00e9s la <strong>cromatografia.<\/strong> En aquesta pr\u00e0ctica vam separar els pigments vegetals d&#8217;unes fulles d&#8217;espinacs per cromatografia sobre paper de filtre.<\/p>\n<p><!--more--><\/p>\n<p>Per entendre la pr\u00e0ctica primer hem de parlar de les bases sobre les que es fonamenta: Els cloroplasts de les fulles d\u2019espinacs deuen el seu color verd a un pigment denominat clorofil\u00b7la. Per\u00f2 lo que de veritat existeix en els cloroplasts \u00e9s una barreja de pigments representats principalment per dos tipus de clorofil.la (a i b), per B-carot\u00e8 i xantofil\u00b7la.<\/p>\n<p>Totes aquestes subst\u00e0ncies presenten un grau diferent de solubilitat, el que permet la seva separaci\u00f3 quan una soluci\u00f3 de la mateixa puja per capil\u00b7laritat per una tira de paper (paper de filtre), ja que les m\u00e9s solubles es despla\u00e7aran a major velocitat perqu\u00e8 acompanyaran f\u00e0cilment al dissolvent a mesura que aquest va pujant.<\/p>\n<p>Per a portar a terme aquesta pr\u00e0ctica vam necessitar: Un morter, placa de Petri, paper de filtre, embut, vas de precipitats, proveta, peu i suport d\u2019embut, fulles d\u2019espinacs i alcohol 96% (etanol).<\/p>\n<p><strong>PROCEDIMENT:<\/strong><\/p>\n<ol>\n<li>En primer lloc, agafem unes quantes fulles, traiem el nervi d\u2019aquestes, les tallem a trossets i les fiquem al morter.<\/li>\n<\/ol>\n<p>2. Agafem 20 mL d\u2019alcohol al 96% amb proveta a la campana extractora.<\/p>\n<p>3. Barrejem l\u2019alcohol amb les fulles que tenim al morter i triturem.<\/p>\n<p><a href=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/images.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4452\" src=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/images.jpg\" alt=\"images\" width=\"260\" height=\"194\" srcset=\"https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/images.jpg 260w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/images-200x150.jpg 200w\" sizes=\"auto, (max-width: 260px) 100vw, 260px\" \/><\/a><\/p>\n<p>4. Un cop triturades, les filtrem per l\u2019embut, que tindr\u00e0 un paper de filtre a dins, tamb\u00e9 en forma d\u2019embut i recollim el l\u00edquid en un vas de precipitats.<\/p>\n<p>5. Si falt\u00e9s l\u00edquid, continuar\u00edem triturant fulles, afegint alcohol i filtrant fins arribar als 20 mL. Hem d\u2019aconseguir que el l\u00edquid obtingut tingui un color verd molt fosc.<\/p>\n<p>6. Un cop tenim la soluci\u00f3, la transvasem a una placa petri.<\/p>\n<p>7. Col.loquem un paper de filtre doblegat en \u00e0ngle sobre la soluci\u00f3 i ho deixem en rep\u00f2s el temps necessari.<\/p>\n<p>8. D\u2019aquesta manera obtindrem les diferents bandes de color en el paper de filtre, representant els diferents pigments.<\/p>\n<p><a href=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/download-1.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-4454 aligncenter\" src=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/05\/download-1.jpg\" alt=\"download-1\" width=\"308\" height=\"251\" \/><\/a><\/p>\n<p>Despr\u00e9s d\u2019obtenir les diferents bandes de color al paper de filtre, mesurarem la dist\u00e0ncia entre bandes i aplicarem una f\u00f3rmula per tal de con\u00e8ixer el factor de despla\u00e7ament o \u00edndex de retenci\u00f3 de cada pigment.<\/p>\n<p style=\"text-align: center;\"><strong>Rf = Dist\u00e0ncia recorreguda pel front del solut\/Dist\u00e0ncia recorreguda pel front de l\u2019eluent.<\/strong><\/p>\n<p>Aplicant aquesta f\u00f3rmula vam concloure que aquells pigments amb una Rf m\u00e9s elevada s\u00f3n els m\u00e9s solubles i els que es desplacen a una velocitat major, ja que acompanyen al dissolvent a mesura que aquest avan\u00e7a.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>La separaci\u00f3 d\u2019un analit (subst\u00e0ncia que volem determinar) de les possibles interfer\u00e8ncies \u00e9s sovint una etapa molt important en els [&hellip;]<\/p>\n","protected":false},"author":158,"featured_media":4449,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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