I speictrophotim\u00e9adracht infheicthe, is f\u00e9idir ions\u00fa n\u00f3 tarchur substainte \u00e1irithe a chinneadh de r\u00e9ir an dath breathnaithe. Mar shampla, t\u00e1 cuma dhubh go teoirici\u00fail ar shampla r\u00e9itigh a ions\u00fann solas thar gach raon infheicthe (.i. n\u00ed tharchuireann aon cheann de na tonnfhaid infheicthe). Ar an l\u00e1imh eile, m\u00e1 tharchuirtear gach tonnfhad infheicthe (ie, nach n-ions\u00fann s\u00e9 rud ar bith), is cos\u00fail go bhfuil an sampla tuaslag\u00e1in b\u00e1n. M\u00e1 ions\u00fann sampla tuaslag\u00e1in solas dearg (~700 nm), feictear glas air mar is \u00e9 glas an dath comhl\u00e1ntach ar dearg. \u00das\u00e1ideann speictrifh\u00f3taim\u00e9adair infheicthe, go praitici\u00fail, priosma chun raon \u00e1irithe tonnfhad a chaol\u00fa (chun tonnfhaid eile a scagadh) ionas go n-aistr\u00edtear an l\u00e9as solais ar leith tr\u00ed shampla r\u00e9itigh.<\/p>\n\n
Gl\u00e9asanna agus meicn\u00edocht<\/h2>\n\n
L\u00e9ir\u00edonn F\u00edor 1 bunstrucht\u00far na speictreaf\u00f3taim\u00e9adair. T\u00e1 s\u00e9 comhdh\u00e9anta de fhoinse solais, collimator, monacr\u00f3mach, roghn\u00f3ir tonnfhad, cuvette le haghaidh r\u00e9iteach samplach, brathad\u00f3ir f\u00f3taileictreach, agus taispe\u00e1int digiteach n\u00f3 m\u00e9adar. D\u00e9antar cur s\u00edos ar mheicn\u00edocht mhionsonraithe th\u00edos. Taispe\u00e1nann F\u00edor 2 speictreaf\u00f3taim\u00e9adar samplach (M\u00fanla: Spectronic 20D).<\/p>\n\n
![\"\"](\"\/\/i0.wp.com\/qvarz.com\/wp-content\/uploads\/2022\/02\/spectrometry-1.png\" "\\"\\"")
<\/a>T\u00e1 speictreaf\u00f3taim\u00e9adar, go ginear\u00e1lta, comhdh\u00e9anta de dh\u00e1 fheiste; speictrim\u00e9adar agus f\u00f3taim\u00e9adar. Is gl\u00e9as \u00e9 speictrim\u00e9adar a th\u00e1irgeann, a scaipeann agus a thomhaiseann solas. L\u00e9ir\u00edonn f\u00f3taim\u00e9adar an brathad\u00f3ir f\u00f3taileictreach a thomhaiseann d\u00e9ine an tsolais.<\/p>\n\n
- Speictrim\u00e9adar<\/strong> : T\u00e1irgeann s\u00e9 raon inmhianaithe tonnfhad an tsolais. Ar dt\u00fas, tarchuireann collimator (lionsa) l\u00e9as d\u00edreach solais (f\u00f3t\u00f3in) a th\u00e9ann tr\u00ed mhonacr\u00f3mad\u00f3ir (priosma) chun \u00e9 a roinnt ina roinnt tonnfhad comhph\u00e1irte (speictream). Ansin n\u00ed tharchuireann roghn\u00f3ir tonnfhad (slit) ach na tonnfhaid at\u00e1 ag teast\u00e1il, mar a thaispe\u00e1ntar i bhF\u00edor 1.<\/li>
- F\u00f3taim\u00e9adar<\/strong> : Tar \u00e9is don raon tonnfhad solais at\u00e1 ag teast\u00e1il dul tr\u00edd an r\u00e9iteach sampla i cuvette, aims\u00edonn an f\u00f3taim\u00e9adar m\u00e9id na bhf\u00f3t\u00f3n a ions\u00faitear agus ansin cuireann s\u00e9 comhartha chuig galbh\u00e1naim\u00e9adar n\u00f3 taispe\u00e1int dhigiteach, mar a l\u00e9ir\u00edtear i bhF\u00edor 1.<\/li><\/ul>\n
![\"\"](\"\/\/i0.wp.com\/qvarz.com\/wp-content\/uploads\/2022\/02\/spectrometry-2.png\" "\\"\\"")
<\/a>F\u00edor 2: Speictreaf\u00f3taim\u00e9adar tonnfhad amh\u00e1in<\/figcaption><\/figure><\/div>\n\n Teasta\u00edonn speictrim\u00e9adar uait chun tonnfhaid \u00e9ags\u00fala a th\u00e1irgeadh mar is fearr a ions\u00fann comhdh\u00faile difri\u00fala ag tonnfhaid \u00e9ags\u00fala. Mar shampla, t\u00e1 an ions\u00fa uasta ag p-nitrophenol (foirm aig\u00e9ad) ag thart ar 320 nm agus is fearr an t-ions\u00fa p-nitrophenolate (bunfhoirm) ag 400nm, mar a thaispe\u00e1ntar i bhF\u00edor 3.<\/p>\n\n
![\"\"](\"\/\/i0.wp.com\/qvarz.com\/wp-content\/uploads\/2022\/02\/spectrometry-3.png\" "\\"\\"")
<\/a>F\u00edor 3: Ions\u00fa dh\u00e1 chomhdh\u00fail dhifri\u00fala<\/figcaption><\/figure><\/div>\n\n Ag f\u00e9achaint ar an ngraf a thomhaiseann ions\u00faiteacht agus tonnfhad, is f\u00e9idir pointe isosbestic a fheice\u00e1il freisin. Is \u00e9 is pointe isosbestic<\/strong> ann an tonnfhad ina bhfuil ions\u00facht dh\u00e1 speiceas n\u00f3 n\u00edos m\u00f3 mar an gc\u00e9anna. L\u00e9ir\u00edonn cuma phointe isosbestic in imoibri\u00fa NACH bhfuil idirmhe\u00e1nach ag teast\u00e1il chun t\u00e1irge a fhoirmi\u00fa \u00f3 imoibre\u00e1n. L\u00e9ir\u00edonn F\u00edor 4 sampla de phointe isosbestic.<\/p>\n\n
![\"\"](\"\/\/i0.wp.com\/qvarz.com\/wp-content\/uploads\/2022\/02\/spectrometry-4.png\" "\\"\\"")
<\/a>F\u00edor 4: Sampla de phointe isosbestic (CC BY-4.0; Heesung Shim tr\u00ed LibreTexts)<\/figcaption><\/figure>\n Ag tagairt ar ais go Figi\u00far 1 (agus F\u00edor 5), t\u00e1 an m\u00e9id f\u00f3t\u00f3n a th\u00e9ann tr\u00edd an cuvette agus isteach sa bhrathad\u00f3ir ag brath ar fhad an cuvette agus ti\u00fachan an tsampla. Nuair a bheidh d\u00e9ine an tsolais ar eolas agat tar \u00e9is d\u00f3 dul tr\u00edd an cuvette, is f\u00e9idir leat \u00e9 a cheangal le tarchur (T). Is \u00e9ard is tarchur ann an cod\u00e1n den solas a th\u00e9ann tr\u00edd an sampla. Is f\u00e9idir \u00e9 seo a r\u00edomh ag baint \u00fas\u00e1ide as an gcothrom\u00f3id:<\/p>\n\n
\\(Iompar (T) = \\dfrac{I_t}{I_o} \\)<\/p>\n\n
An \u00e1it a bhfuil m\u00e9 an d\u00e9ine solais tar \u00e9is don l\u00e9as solais dul tr\u00edd an gcuvette<\/sub> agus is \u00e9 I o<\/sub> d\u00e9ine an tsolais sula dt\u00e9ann l\u00e9as an tsolais tr\u00edd an gcuvette. Baineann tarchur le hions\u00fa ag an slonn:<\/p>\n\n
\\(As\u00fa (A) = – log(T) = – log(\\dfrac{I_t}{I_o} )\\)<\/p>\n\n
Nuair is ionann ions\u00faiteacht agus an m\u00e9id f\u00f3t\u00f3n a sh\u00faitear. Leis an m\u00e9id ions\u00fach\u00e1in at\u00e1 ar eolas \u00f3n gcothrom\u00f3id thuas, is f\u00e9idir leat ti\u00fachan anaithnid an tsampla a chinneadh tr\u00ed \u00fas\u00e1id a bhaint as Dl\u00ed Beer-Lambert. L\u00e9ir\u00edonn F\u00edor 5 tarchur solais tr\u00ed shampla. \u00das\u00e1idtear an fad \\(l\\) le haghaidh Dl\u00ed Beer-Lambert a bhfuil cur s\u00edos air th\u00edos.<\/p>\n\n
![\"\"](\"\/\/i0.wp.com\/qvarz.com\/wp-content\/uploads\/2022\/02\/spectrometry-5.png\" "\\"\\"")
<\/a>F\u00edor 5: Tarchur (CC BY-4.0; Heesung Shim tr\u00ed LibreTexts)<\/figcaption><\/figure><\/div>\n\n Dl\u00ed Beoir-Lambert<\/h2>\n\n
Deir Dl\u00ed Beoir-Lambert<\/a> (ar a dtugtar Dl\u00ed Beoir freisin) go bhfuil gaol l\u00edneach idir ions\u00fach\u00e1n agus ti\u00fachan sampla. Ar an gc\u00fais seo, n\u00ed f\u00e9idir Dl\u00ed Beoir a chur i bhfeidhm ach amh\u00e1in<\/em> nuair a bh\u00edonn caidreamh l\u00edneach ann. Scr\u00edobhtar Dl\u00ed Beoir mar:<\/p>\n\n
\\(A = \\ epsail\u00f3n{lc} \\)<\/p>\n\n
c\u00e1<\/p>\n\n
- Is \u00e9 \\(A\\) an tomhas ions\u00fach\u00e1in (gan aonaid),<\/li>
- Is \u00e9 \\(\\epsilon\\) an chomh\u00e9ifeacht d\u00edothaithe molar n\u00f3 an ions\u00faiteacht mh\u00f3lar (n\u00f3 an chomh\u00e9ifeacht ions\u00fach\u00e1in),<\/li>
- Is \u00e9 \\(l\\) fad an chos\u00e1in, agus<\/li>
- Is \u00e9 \\(c\\) an ti\u00fachan.<\/li><\/ul>\n
Tugtar an chomh\u00e9ifeacht d\u00edothaithe molar mar thairiseach agus athra\u00edonn s\u00e9 do gach m\u00f3il\u00edn. \u00d3s rud \u00e9 nach n-iompra\u00edonn ions\u00fach\u00e1n aon aonaid, n\u00ed m\u00f3r do na haonaid do \\(\\epsilon\\) na haonaid faid agus ti\u00fachana a cheal\u00fa. Mar thoradh air sin, t\u00e1 na haonaid ag \\(\\epsilon\\): L\u00b7mol -1<\/sup> \u00b7cm -1<\/sup> . D\u00e9antar fad an chos\u00e1in a thomhas ina cheintim\u00e9adair. Toisc go n-\u00fas\u00e1ideann speictrim\u00e9adar caighde\u00e1nach cuvette at\u00e1 1 cm ar leithead, glactar leis i gc\u00f3na\u00ed go bhfuil \\(l\\) comhionann le 1 cm. \u00d3s rud \u00e9 go bhfuil ions\u00fa, \\(\\epsilon\\), agus fad cos\u00e1in ar eolas, is f\u00e9idir linn ti\u00fachan \\(c\\) an tsampla a r\u00edomh.<\/p>\n\n
Sampla 1<\/strong><\/p>\n\n
T\u00e1 ions\u00faiteacht uasta de 275 nm ag Guan\u00f3is\u00edn<\/a> . \\( \\ epsilon_{275} = 8400 m^{-1} cm^{-1} \\) agus is \u00e9 1 cm fad an chos\u00e1in. Ag baint \u00fas\u00e1ide as speictreaf\u00f3taim\u00e9adar, aims\u00edonn t\u00fa an ceann sin \\(A_{275} = 0.70\\). Cad \u00e9 an ti\u00fachan guan\u00f3is\u00edn?<\/p>\n\n
R\u00e9iteach<\/strong><\/p>\n\n
Chun an fhadhb seo a r\u00e9iteach, n\u00ed m\u00f3r duit Dl\u00ed Beoir a \u00fas\u00e1id.<\/p>\n\n
\\[A lc \/><\/p>\n\n
0.70 = (8400 M -1<\/sup> cm -1<\/sup> )(1 cm)(\\(c\\))<\/p>\n\n
Ansin, roinn an d\u00e1 thaobh ar [(8400 M -1<\/sup> cm -1<\/sup> )(1 cm)]<\/p>\n\n
\\(c\\) = 8.33×10 -5<\/sup> mol\/L<\/p>\n\n
Sampla 2<\/strong><\/p>\n\n
T\u00e1 substaint i dtuaslag\u00e1n (4 g\/l\u00edtear). Is \u00e9 2 cm fad an cuvette agus n\u00ed tharchuirtear ach 50% den bh\u00edoma solais \u00e1irithe. Cad \u00e9 an comh\u00e9ifeacht ions\u00fa?<\/p>\n\n
R\u00e9iteach<\/strong><\/p>\n\n
Tr\u00ed \u00fas\u00e1id a bhaint as Dl\u00ed Beoir-Lambert, is f\u00e9idir linn an chomh\u00e9ifeacht ions\u00fach\u00e1in a r\u00edomh. Mar sin,<\/p>\n\n
\\(- \\log \\cl\u00e9(\\dfrac{I_t}{I_o} \\right) = – \\log(\\dfrac{0.5}{1.0}) = A ={8} \\eipeas\u00f3n\\)<\/p>\n\n
Ansin faighimid \u00e9 sin<\/p>\n\n
\\(\\epsilon\\) = 0.0376<\/p>\n\n
Sampla 3<\/strong><\/p>\n\n
I sampla 2 thuas, c\u00e9 mh\u00e9ad a tharchuirtear an l\u00e9as solais nuair a bh\u00edonn 8 g\/l\u00edtear ?<\/p>\n\n
R\u00e9iteach<\/strong><\/p>\n\n
\u00d3s rud \u00e9 go bhfuil \\(\\epsilon\\ ar eolas againn), is f\u00e9idir linn an tarchur a r\u00edomh tr\u00ed \u00fas\u00e1id a bhaint as Dl\u00ed Beer-Lambert. Mar sin,<\/p>\n\n
\\(\\log(1) – \\log(I_t) = 0 – \\log(I_t)\\) = 0.0376 x 8 x 2 = 0.6016<\/p>\n\n
\\(\\log(I_t)\\) = -0.6016<\/p>\n\n
Mar sin, \\(I_t\\) = 0.2503 = 25%<\/p>\n\n
Sampla 4<\/strong><\/p>\n\n
I sampla 2 thuas, cad \u00e9 an comh\u00e9ifeacht ions\u00fa molar m\u00e1 t\u00e1 an me\u00e1chan m\u00f3il\u00edneach 100?<\/p>\n\n
R\u00e9iteach<\/strong><\/p>\n\n
Is f\u00e9idir \u00e9 a fh\u00e1il go simpl\u00ed tr\u00edd an gcomh\u00e9ifeacht ions\u00fach\u00e1in a iolr\u00fa faoin me\u00e1chan m\u00f3il\u00edneach. Mar sin,<\/p>\n\n
\\(\\epsilon\\) = 0.0376 x 100 = 3.76 L\u00b7mol –<\/sup>1<\/sup> \u00b7cm –<\/sup>1<\/sup><\/p>\n\n
Sampla 5<\/strong><\/p>\n\n
Is \u00e9 an comh\u00e9ifeacht ions\u00fa de choimpl\u00e9asc glycogen-iaid\u00edn 0.20 ag solas 450 nm. Cad \u00e9 an ti\u00fachan nuair a bh\u00edonn an tarchur 40 % i cuvette 2 cm?<\/p>\n\n
R\u00e9iteach<\/strong><\/p>\n\n
Is f\u00e9idir \u00e9 a r\u00e9iteach freisin tr\u00ed \u00fas\u00e1id a bhaint as Dl\u00ed Beoir-Lambert. Mar sin,<\/p>\n\n
\\[- \\log(I_t) = – \\log(0.4) = 0.20 \\times c \\times 2\\]<\/p>\n\n
Ansin \\(c\\) = 0.9948<\/p>\n\n
Tagairt\u00ed<\/h2>\n\n
- Atkins, Peadar agus Julio de Paula. Ceimic Fhisiceach do na hEola\u00edochta\u00ed Beatha. Nua-Eabhrac: Oxford University Press, 2006.<\/li>
- Chang, Raymond. Ceimic Fhisiceach do na hEola\u00edochta\u00ed Bitheacha. SAM: Leabhair Eola\u00edochta na hOllscoile, 2005.<\/li>
- Gura, a Mhich\u00edl. Speictreaf\u00f3taim\u00e9adracht & Speictrifhluairim\u00e9adracht. Nua-Eabhrac: Oxford University Press, 2000.<\/li>
- Price, Nicholas agus Dwek, Raymond agus Wormald, Mark. Prionsabail agus Fadhbanna sa Cheimic Fhisici\u00fail do Bhithcheimiceoir\u00ed. RG Ratcliffe. Nua Eabhrac: Oxford University Press, 1997.<\/li>
- Irwin H. Segel, R\u00edomhaireachta\u00ed Bithcheimiceacha (Conas a R\u00e9it\u00edonn Fadhbanna Matamaitice sa Bhithcheimic Ghinear\u00e1lta), 2\u00fa eagr\u00e1n, John Wiley & Sons, 1975<\/li>
- http:\/\/www.nist.gov\/pml\/div685\/grp03\/spectrophotometry.cfm<\/a><\/li><\/ol>\n
Rann\u00edoc\u00f3ir\u00ed agus Tr\u00e9ithe<\/h2>\n\n
- F\u00f3taim\u00e9adar<\/strong> : Tar \u00e9is don raon tonnfhad solais at\u00e1 ag teast\u00e1il dul tr\u00edd an r\u00e9iteach sampla i cuvette, aims\u00edonn an f\u00f3taim\u00e9adar m\u00e9id na bhf\u00f3t\u00f3n a ions\u00faitear agus ansin cuireann s\u00e9 comhartha chuig galbh\u00e1naim\u00e9adar n\u00f3 taispe\u00e1int dhigiteach, mar a l\u00e9ir\u00edtear i bhF\u00edor 1.<\/li><\/ul>\n