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Phan tich quang pho trac quang

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  • 1. Phn 1PHN TCH TRC QUANG11/04/131

2. Phn 1: PHN TCH TRC QUANGnh ngha Nguyn tc Phn tch trc quang l tn gi chung ca cc phng php phn tch quang hc da trn s tng tc chn lc gia cht cn xc nh vi nng lng bc x thuc vng t ngoi, kh kin hoc hng ngoi. Nguyn tc ca phng php trc quang l da vo lng nh sng b hp thu bi cht hp thu tnh hm lng ca cht hp thu.c11/04/132 3. Phn 1: PHN TCH TRC QUANG c trng nng lng ca min ph11/04/133 4. Phn 1: PHN TCH TRC QUANGc trng nng lng ca min ph nh sng c bc sng nh hn 200nm, b hp thu bi oxi khng kh, hi nc v nhiu cht khc, v vy ch c th o quang bc sng nh hn 200 nm bng my chn khng. nh sng c bc sng t 200 400 nm, c gi l nh sng t ngoi (UV), trong vng t 200 300 nm c gi l min t ngoi xa, cn vng t 300 400 nm gn min kh kin c gi l min t ngoi gn. nh sng c bc sng trong khong t 800 2000 c gi l nh sng hng ngoi (IR). S hp thu nh sng min ph ny t c s dng gii quyt trc tip cc nhim v phn tch, nhng c s dng rng ri nghin cu cu to ca phn t. 11/04/134 5. Phn 1: PHN TCH TRC QUANG c trng nng lng ca min ph nh sng vng UV c bc sng trong khong: 200 400 nm nh sng vng IR c bc sng trong khong: 800 2000 nm nh sng vng VIS c bc sng trong khong: 396 760 nm Trong phng php trc quang phng php hp thu quang hc, chng ta thng s dng vng ph UV VIS c bc sng t 200 800 nm11/04/135 6. c trng nng lng ca min ph Da camVngLc739 - 610610 - 590590 - 560560 - 510LamTm510 - 49011/04/13Chm 490 - 430430 - 4006 7. Lu Nhng hp cht mu l nhng hp cht c kh nng hp thu mt hoc mt vi mu ph ca nh sng t nhin, c th hp thu hon ton hoc mt phn cng ca mu ph. Nu ch hp thu duy nht mt mu ph, th mu ca dung dch chnh l mu b sung (t hp mu ph v mu b sung tr thnh khng mu) Th t11/04/131 2 3 4 5 6 7 8 9 10 (nm) 400 -430 430 480 480 -490 490 500 500 560 560 580 580 -595 595 650 650 730 730 760Mu phMu b sungTm Chm Chm lc Lc chm Lc Vng lc Vng Cam taVng lc Vng Cam ta Tm Chm Chm lc Lc vng Lc7 8. Phn 1: PHN TCH TRC QUANG Phn loi cc phng php trc quang Phng php hp thu quang: phng php ny da trn vic o cng dng nh sng b cht mu hp thu chn lc. Phng php pht quang: phng php ny da trn vic o cng dng nh sng pht ra bi cht pht quang khi ta chiu mt dng nh sng vo cht pht quang. Phng php o c: phng php o c da trn vic o cng dng nh sng b hp thu hoc b khuyt tn bi h keo c iu ch t cht cn phn tch 11/04/138 9. Phn 1: PHN TCH TRC QUANG Cc i lng c trng ca nh sng Bc sng l khong cch gia hai im dao ng ng pha gn nht, n v o l A0, m, , nm...(1nm=1m=10A0=10-9m).11/04/139 10. c Tn s sng = trong tc nh sng trong chn khng bng 3.1010 m/gy hoc 3.1017 nm/gy, khi v c n v cm thi n v ca l gy-1 S sng 1 = l s bc sng trn 1cm chiu di, n v l cm-1. Quang thng l nng lng nh sng bc x theo mi phng ca ngun im trong mt n v thi gian. Cng nh sng I l dng sng pht ra t ngun im trong mt n v gc khi l strian: I = 4 hc E= Nng lng bc x in t: Khi hp thu nh sng ni nng ca phn t tng t mc c bn E 0 n mc E1 cao hn. Phn nng lng hp thu l nng lng ca photon, n t l vi tn s nh sng 11/04/13 E = E1 - E 0 = h =hc 10 11. C s l thuyt ca phng php Nudung dch hp thu bc x vng t ngoi, nh sng trng truyn sut hon ton n mt, dung dch khng mu. Dung dch c mu khi cha cu t c kh nng hp thu bc x vng thy c, do khi nh lng bng phng php quang ph hp thu thy c cn c gi l phng php so mu hay o mu. Dung dch mu c nng cng cao, kh nng hp thu ca mu cng mnh, cng nh sng n mt cng yu, dung dch c mu cng sm. 11/04/1311 12. nh lut Bouguer Lambert Beer Chiu bc x n sc c bc sng I c cng I0 qua dung dch cha cu t kho st c nng C. B dy dung dch l l. Ti b mt cuvet o, mt phn bc x b phn x c cng IR, mt phn bc x b hp thu c cng IA. Bc x ra khi dung dch c cng I. 11/04/1312 13. nh lut Bouguer Lambert Beer IR I0IAIDo : I0 = IR + IA + I Chn cuvet o c b mt nhn, truyn sut IR = 0 I0 = IA + I11/04/1313 14. nh lut Bouguer Lambert Beer I0 log =A= .l.C I Trong : l mt hng s t l c tn hp thu phn t biu th hp thu ca dung dch c nng cht tan l 1M c ng trong bnh dy 1cm v c n v l l.mol-1cm-1. By gi ta c th p dng d dng nh lut Beer vo vic xc nh nng cc cht tan bng cch o hp thu A ca chng. 11/04/1314 15. Cng hp thu bc x ca cu t c xc nh bng 2 i lng truyn sut T (Transmittance) I I T = hay T% = 100 I0 I0 hp thu A (Absorbance) hay mt quang OD (optical density) I0 1 100 A = log = log = log = 2 - logT% I T T%11/04/1315 16. Nu o hp thu quang ca mt lot dung dch bng mt dng sng n sc (ti mt gi tr ) th A = f(l,C) l hm bc nht, ng biu din l mt ng thng, cn ng T = f(C) l mt ng cong. V vy trong phn tch trc quang ch dng ng A = f(C) m khng dng T =11/04/13 F(C).16 17. 100T (%)500 0A = lC11/04/1312C,l 3=10-lC17 18. Bng tm tt tnh cht cc i lng trc quang i lngT A (hay D)11/04/13Cng thcn vI T= I0Yu t khng ph thucGhi chKhng c tnh cng tnh,C,lcm2/molI0,C,lI0 A=lg IA = ClYu t ph thucI0C tnh cng tnh, bn cht cht mu, bn cht dung mi, t0I0,C,lc trng cho nhy v phn ng mu 18 19. ng dng tnh cht cng tnh ca A Tnh cng ca mt quang hay hp thu A A = AA + AB = 1lC1 + 2lC2Mt quang o c khi cht tan ho tan trong mt dung mi l mt quang tng cng ca dung dch . A = AX + Adm A phn nh ng AX th Adm rt nh ( 0). tho mn iu kin ny, ta nn chn dung mi c ph hp thu rt xa ph hp thu ca cht tan.Nu trong hn hp gm nhng cu t cng hp thu nhng chng khng ctng tc ho hc vi nhau. Ta c th xc nh c nng ca cc cu t theo h thc sau: A = 1lC1 + 2lC2 + + ilCi + + nlCn 11/04/1319 20. Dung dch mu tun theo nh lut hp thu c bn nu tho mn cc iu kin sau: C s trng kht cc ng ph - i vi cc dung dch c nng khc nhau. th biu din s ph thuc A C khi l = const l mt ng thng i qua gc to . Khi pha hai dung dch 1 v 2 sao cho C1l1 = C2l2 th cng t ta s c A1 = 1lC1 = A2 = 2lC2 Cc ng ph A - vi nng Cn khc nhau u c cng max th biu din mi quan h gia truyn qua T v lgC c im un nm gi tr T = 0.36811/04/1320 21. Cc nguyn nhn gy sai lch khi nh lut Beer Mc n sc ca nh sng ti. nh sng khng n sc thng dn n lch m. Cht mu hp thu cc i max v ch max mi c s tuyn tnh gia Aimax Ci v th Aimax Ci l mt ng thng, khi mt quang l cc i. Mc n sc cng ln, kh nng tun theo nh lut Lambert Beer cng ln. Nng ln ca dung dch kho st: Nng ca dung dch ln s xy ra tng tc in, i lng thay i, thng thng khi tng nng dung dch, gi tr gim. S sai lch khi nh lut Lambert Beer thng l sai s m.11/04/1321 22. S trng hp hoc kh trng hp phn t, s solvat ho hay hydrat ho xy ra khi thay i nng cht hp thu; s to thnh cc hp cht trung gian, phc ph, cc hp cht ng phn, to h keo hay s c mt ca cc cht in ly mnh, pH u c kh nng lm thay i hp thu ca dung dch, lm sai lch khi nh lut Beer. 11/04/1322 23. Ph hp thu ng biu din s ph thuc ca hp thu A hoc vo di sng (hay tn s sng ) gi l ph hp thu ca cht kho st. Ph hp thu ca phn t l ph m gm mt hoc mt s m hp thu, mi m u c dng ng phn b xc sut chun v khc nhau bi cng hp thu v bc sng cc i max ca m. Trong trng hp n gin phn t ch c mt tm mang mu th ph A = f() ch c mt gii ph c dng i xng hnh chung. 11/04/1323 24. 11/04/13max24 25. Phn tch nh lng bng phng php trc quang Nguyn tc v c s nh lng ca phng php Phng php ng chun Phng php thm chun Phng php vi sai Phng php chun trc quang Phng php so snh 11/04/1325 26. Nguyn tc v c s nh lng ca phng php Nguyn tc chung ca phng php phn tch trc quang -Chuyn cu t thnh hp cht c kh nng hp th nh sng.-o s hp th nh sng ca hp cht to thnh v suy ra hm lng cht cn xc nh X. Nguyn tc chung ca cc phng php phn tch nh lng -o quang ca dung dch mu.-So snh cng mu (hoc hp th quang) ca dung dch nghin cu vi dung dch chun.11/04/1326 27. C s nh lng nh lut Bougher-Lampere-Beer: khi chiu mt chm photon n sc qua dung dch th mc hp th ca dung dch t l thun vi cng sut chm photon v nng cc phn t hp th Cng thc: A = .l.C11/04/1327 28. Phng php ng chun QUI TRNH - Pha mt lot dung dch chun c Ctc tng dn mt cch u n. (thng 5 8 Ctc) (Cc dung dch chun phi c cng iu kin nh dung dch xc nh) - Tin hnh o A hoc T ca dy chun chn. - Dng th AX = f(Cx). Vit PTHQ tuyn tnh ca ng chun. - Tin hnh pha ch dung dch xc nh. - Do A hoc T ca mu. - Cn c vo PTHQ tuyn tnh ca dy chun v AX m xc nh nng ca cht X trong mu 11/04/1328 29. Phng php ng chun - th A = f(Ctc) tu theo cch o ta thu c 2 dng ng chun: + Dng 1: i qua gc ta + Dng 2: khng i qua gc ta - Khi chn vng nng xy dng ng chun phi ch : + Vng nng ca dy chun phi bao gm c CX + Vi vng nng chn dung dch phi tun theo nh lut Beer + Cc gi tr Atc ng vi nng chn phi sao cho khi o trn my c lp li cao v bo m s tuyn tnh A = f(C) 11/04/1329 30. Phng php ng chun U V NHC IM CA PHNG PHP U IM - Vi mt ng chun cho php phn tch hng lot mu. - Dung dch cng khng i hi phi tun theo nh lut Beer mt cch nghim ngt. NHC IM - chnh xc ca phng php khng cao. - Khng loi c nh hng ca nn mu 11/04/1330 31. Phng php so snh So snh 1 chun -Pha mt dung dch chun c Ctc. -Tin hnh o A hoc T ca dd chun so vi dd so snh (Atc) Theo nh lut Lambert Beer: Atc = lCtc. -Pha dung dch mu vi nng cn xc nh CX (cha bit) -Tin hnh o A hoc T ca dd mu so vi dd so snh (AX) Theo nh lut Lambert Beer: AX = lCX. Khi dung dch xc nh v dd chun c cng bn cht, c th xem A CX = X C tc nh nhau, v l = const. A tc 11/04/1331 32. nh lng Pb trong mu thc phm, ta tin hnh cn 5,000 g mu, ho tan thnh dung dch, sau tin hnh to phc vi thuc th dithizon, dng phc Pb ditizon tan trong CHCl3. Tin hnh chit bng CHCl3, dung dch sau khi chit c nh mc thnh 25 mL. Dung dch chun c chun b tng t nh mu, cha 10 g Pb2+ trong th tch dung dch em o l 20,00 mL. Mt quang ca chun v mu = 545 vi l = 1 cm ln lt l Ac = 0,320 v Am = 0,225. 11/04/1332 33. So snh 2 chunThc hin kh n gin, hm lng mu tun theo nh lut Beer. Chn cc dung dch chun sao cho C1 < Cx < C2 sau so snh cng dung dch xc nh vi cng dung dch chun.Cng thc tnh: Trong : C1, A1 l nng v mt quang ca bnh th 1. C3, A3 l nng v mt quang ca bnh th 3. CX, AX l nng v mt quang ca bnh cn kim tra. 11/04/1333 34. nh lng Pb trong mu thc phm, ta tin hnh cn 5,000 g mu, ho tan thnh dung dch, sau tin hnh to phc vi thuc th dithizon, dng phc Pb ditizon tan trong CHCl3. Tin hnh chit bng CHCl3, dung dch sau khi chit c nh mc thnh 25 mL. Dung dch chun c chun b tng t nh mu, vi m