Khoa Ha Trng H Khoa Hc T Nhin

LI CM N

Bng tm lng trn trng v bit n su sc, em xin chn thnh cm n thy giao ti v tn tnh hng dn em trong sut qu trnh thc hin seminar. Xin cm n qu thy c v cc bn sinh vin khoa Ha ng vin v gip em rt nhiu em c th hon thnh bi seminar ca mnh.

Tp. H Ch Minh, ngy.thngnm Sinh vin

GII THIU

Ra i t rt sm v pht trin cng vi lch s nhn loi, ngnh ha c xem l mt ngnh khoa hc c bn c xp ngang hng vi cc ngnh khoa hc khc nh vt l, sinh hc,Trong thi i cng nghip khoa hc k thut hin nay, ngnh ha hc cng tha k c nhng tin b cng ngh mi v c nhng bc pht trin to ln so vi trc y ng thi cc nhu cu t ra cho ngnh ha cng c nng cao. Ring i vi lnh vc ha hc phn tch, cc yu cu t ra cng kht khe hn buc phn tch ha hc phi lm vic i vi nhng hm lng rt nh ca cc cht. V th, cc phng php phn tch cng c ra i vi cc k thut tin tin cho php phn tch cc cht hm lng vt. Tuy nhin, cc phng php phn tch c nhy v chn lc gii hn nn cc nh phn tch ha hc phi hng n vic nghin cu phng php c c vt v tch chng ra khi cc nguyn t ca nn nhm m rng khong lm vic ca thit b phn tch. Vic tch chit v lm giu mu trc khi phn tch l vn ang c quan tm v n khng nhng ci thin c nhy ca php phn tch m nh hng ca cc yu t gy nhiu c th c khc phc bi vic tch cht nhiu ra khi cht phn tch. Hn na, vic c c cht phn tch cn cho php m rng khong lm vic ca thit b. Mc tiu ca bi seminar l ch trnh by s lc v k thut tch chit, lm giu kt hp vi phng php o ph nguyn t. Ni dung ca bi vit nhm th hin vai tr ca vic tch chit v lm giu mu ng dng trong php phn tch v nu ra nhng nh hng v yu t cn kho st khi tin hnh tch chit c th t c yu cu v sch phn tch, thu hi v h s lm giu cao.Do thi gian hn ch nn bi vit c nhng ch cn s st, mong qu thy c v mi ngi gp .

MC LCLI CM N1GII THIU2MC LC31.PHNG PHP PH NGUYN T YU CU CHIT TCH:31.1.Phng php ph nguyn t :[8]31.2.Cc yu t gy nh hng n kt qu thu c trong nn mu:[8]42.CHIT TCH LM GIU:52.1.Khi nim tch chit:[]52.2.Lm giu: []52.3.Vai tr ca chit tch v lm giu trong phn tch nh lng:62.4.C s ca phng php chit:62.5.1.Phng php cng kt:[10]82.5.2.Phng php chit lng-lng[7]122.5.3.Phng php chit pha rn (SPE- solid-phase extraction) [5]143.CC YU T NH HNG N QU TRNH TCH- CHIT:183.1.nh hng PH:[]183.2.Th tch thuc th:193.3.nh hng ca dung mi, cht gii chit:203.4.Thi gian chit, ra gii, tc ra gii:213.5.S ln chit:223.6.nh hng ca cc ion khc:224.TI LIU THAM KHO:26

1. PHNG PHP PH NGUYN T YU CU CHIT TCH:1.1. Phng php ph nguyn t :[8]Php o ph pht x hay hp th nguyn t l mt trong nhng phng php phn tch ha l quan trng, , ang c pht trin v ng dng rng ri trong nhiu ngnh khoa hc k thut, sn xut cng nghp, nng nghip, y dc, a cht, ha hc, Ph nguyn t tr thnh cng c c lc trong vic phn tch lng vt kim loi trong nhiu i tng khc nhau nh t, nc, khng kh, thc phm,v phng php ny c gii hn pht hin thp, nhy cao li t ra kh u vit khi phn tch hm lng vt. p dng phng php ph hp th nguyn t phn tch nhiu nguyn t c th t nhy 10-3 10-4 %, nu s dng trang thit b hin i c th t nhy 10-5 10-6 %, phn tch nhanh, chnh xc kh cao, v c kh nng phn tch hng lot cht trong mt mu m khng phi phn tch. Phng php ph pht x nguyn t cho chn lc v nhy tng i cao. Gn 60 nguyn t c xc nh trc tip bng phng php ny vi nhy 10-4 10-5 %. c bit, nu s dng k thut nguyn t ha khng ngn la c th t n 10-7 %.Tuy nhin, vic phn tch cc nguyn t cng gp nhng tr ngi bi cc loi nhiu quang ph, nhiu ha hc, nhiu vt l do dung dch mu phn tch em li. Mt nhc im ln ca phng php ny l ch cho ta bit v thnh phn ca cht phn tch trong mu ch khng cho bit trng thi ha tr ca nguyn t. V vy, vic tch chit l cn thit trong trng hp nn mu phc tp, nht cao,gy nh hng n kt qu o ph, hoc tch cc dng ca nguyn t trc khi a mu vo o ph trong trng hp ta mun bit hm lng tn ti ca tng dng. Mc d php phn tch ph nguyn t rt nhy nhng i khi vn phi lm giu mu hoc pha long mu nng nguyn t nm trong khong tuyn tnh v c th phn tch c m vn m bo chnh xc cao.1.2. Cc yu t gy nh hng n kt qu thu c trong nn mu:[6, 7, 8]Nhiu quang ph: Cc hin tng nn mu phc tp c th to ra nhng tn hiu trn ph gy chen ln, chng chp, thm ch che khut tn hiu ca nguyn t cn phn tch lm gim nhy ca phng php. c bit, phng php ph pht x nguyn t chu nh hng do cc hin tng ny nhiu v th cn phi tch cc nguyn t cn xc nh ra khi cc nguyn t c kh nng gy nh hng n vch ph o c. Tch chit cng l mt bin php loi tr nh hng ca cn nhiu ha hc. Ngoi ra , cn c cc loi cn nhiu quang ph khc i hi ngi lm phn tch phi tch cht phn tch nh: nhiu nn, nhiu do ph m, nhiu do hin tng tn x ca cc cht bn nhit c hnh thnh trong h thng nguyn t ha,cc loi nhiu quang ph ny do thnh phn mui, cc cht trong nn mu gy ra. Nu nng ca chng cao trong nn mu th nh hng gy ra rt ln. Yu t ha hc: S hnh thnh hp cht bn nhit, kh ha hi, kh nguyn t ha khi trong mu cha ion silicat, sunfat, photphat, florua lm gim ng k nhy ca phng php ph nguyn t. Nn mu ca dung dch nh hng ln n nhy ca phng php phn tch theo hai chiu hng: c li v c hi v n lin quan trc tip n qu trnh ha hi v nguyn t ha xy ra trong ngn la. Nu cht nn d bay hi th hiu sut ha hi cao, nng cao nhy. Nu cht nn kh ha hi , bn nhit th n chnh l nguyn nhn gy ra hin tng gim cng vch phCc hp cht bn nhit xut hin trong bung nguyn t ha gy ra hin tng tn x, cc ion c th ion ha thp c tc dng lm hn ch s ion ha nguyn t phn tch gip tng nhayV vy, nng cao nhy cng nh gii hn pht hin ca phng php, ta phi ch ng a vo trong mu phn tch nhng nhn t lm tng nhy v loi b nhng nhn t lm gim nhy kt hp vi qu trnh tch chit v lm giu mu. Vic chuyn nguyn t cn xc nh vo pha hu c cho php trnh khi nh hng khng mong mun ca cc mui thng c mt trong pha nc.Yu t vt l: nht v sc cng b mt ca dung dch mu nh hng n qu trnh phun sng v tc dn mu vo bung aerosol, cc yu t vt l ny gy nh hng trong c phng php AAS ln AES. Nguyn nhn chnh nh hng n sc cng b mt v nht l thnh phn nn mu v nng . Vic tch chit gip ta ch ng to ra s ging nhau v nng acid, loi acid, nng cht nn ca mu, thnh phn cht nn ca mu nhm to iu kin tng ng gia chun v mu gip gim sai lch do chun v mu iu kin khc nhau. nht cng nh cc tnh cht vt l khc cng c thay i theo theo chiu hng thun li cho vic phn tch khi chuyn cht cn xc nh t dung dch ban u n dch chit i phn tch. iu ny gip ci thin c iu kin phun sng ca cht, lm tng hiu sut phun sng, to ra nhng ht sol nh thun li cho qu trnh nguyn t ha mu. Ngn la: Vic ha hi, nguyn t ha tt v t hiu sut nguyn t ha cao ph thuc khng nhng vo qu trnh phun sng v thnh phn cc cht trong dung dch mu m chu s nh hng mnh ca nhit , n nh ca ngn la. Cc yu t trn khng nhng ph thuc vo nhin liu chy m cn ph thuc vo tnh cht ca dung dch mu trong dung mi mang tnh quyt nh do lng dung mi chim phn ln th tch mu. Nu thc hin chit tch th ta c th ci thin c tt vn ny v dung mi v thuc th thng dng l hp cht hu c d chy, hu nh l nhin liu. Do , nhit ngn la b gim i nh hn so vi trong trng hp dung dch nc, iu ny lm tng ng k cng pht x ca ngn la dn n tng nhy ca phng php phn tch ph vi ngn la l ngun kch thch.2. CHIT TCH LM GIU:2.1. Khi nim tch chit:[7]Tch chit l phng php phn chia da vo s phn b cu t ca hn hp gia hai pha, sau cc pha ny c tch c hc khi nhau.2.2. Lm giu: [1, 7]Lm giu l php c c c ng dng nhm lm tng nng cht phn tch. Trong ha hc phn tch, ta thng bt gp hai thut ng: c c tng i v c c tuyt i. C c tng i l lm giu cc nguyn t vi lng so vi cc nguyn t a lng. C c tuyt i l s chuyn cht t mt th tch ln vo th tch nh. Ngi ta c th dng cc phng php vt l da vo qu trnh bay hi ca dung mi, s bay hi ca cc thnh phn khc trong mu hay s bay hi cu chnh cht phn tch ra khi nn mu, s thng hoa ca nn mu hay phng php lc Cc phng php vt l t ra kh n gin tuy nhin cng gp phi kh khn v mt thit b, s phn hy cht phn tch, s mt mu, nhim bn vo mu phn tchHin nay, ti u ha quy trnh thc nghim, ngi ta thng kt hp vic lm giu mu ngay trong qu trnh tch chit bng cch chit cht phn tch t th tch mu ban u vo trong dung mi c th tch nh hn ng k, hoc c th la chn dung mi d bay hi vic lm bay hi dung mi d dng, to iu kin thun li cho vic lm giu mu. Vi k thut tch chit hin nay th vic lm giu tr nn d dng v hiu qu cao. Tuy nhin cn kim sot sao cho nng cht phn tch phi nm trong gii hn pht hin v gii hn nh lng ca phng php phn tch.2.3. Vai tr ca chit tch v lm giu trong phn tch nh lng:Nhim v t ra hin nay cho cc nh ha hc phn tch l xc nh lng hm lng rt b ca cht phn tch. Do cc nh khoa hc khng ngng nghin cu nhm lm gim gii hn pht hin v gii hn nh lng ca phng php. Mt mt, p dng tin b k thut hin i, mt khc nghin cu nhm tm ra cc quy trnh lm tng nng cht phn tch trong dung dch mu. Bng cch th hai, ngi ta c th ng dng hiu bit v ha hc ch ng nng cao nhy ca phng php m khng cn tc ng ln my mc. Bng cch ny, ngi ta c th xc nh c lng vt c nng b hn gii hn pht hin ca thit b o, xc nh c cht tn ti trong nn mu phc tp m khng cn phi dng my mc t tin. V d, khi xc nh vt kim loi ngi ta c th lm giu mu ri tin hnh phn tch bng phng php ph hp thu nguyn t va n gin, hiu qu li r tin hn cc phng php ICP-MS, kch hot notron,[7] loi tr nh hng ca cc cht cn tr vic xc nh cht phn tch ngi ta thng dng hai phng php c bn: thay i h nhm mc ch ngn nga s tham gia nh hng ca cc cht cn tr trong qu trnh o v tch vt l cht cn tr khi cht cn xc nh[8]. Trong ha hc phn tch hm lng vt kim loi cng nh phn tch ph nguyn t, ngi ta thng dng cc k thut tch chit sau khi v c ha mu v lm giu nguyn t cn phn tch.2.4. C s ca phng php chit:S phn chia cc cht[7]: Chit tch l qu trnh c thc hin da trn qu trnh chuyn chn lc cht mong mun t pha ny sang pha khc.c im ca qu trnh chit[7]: Hai pha khng trn ln vo nhau, cht tan chuyn t pha ny sang pha khc. Ty theo cht tan, ngi ta c th s dng cc dung mi chit cng nh cc tc nhn chit khc nhau.Gi s c mt cht M c ha tan trong hai dung mi (1) v (2) khng trn ln vi nhau th M c phn b gia hai pha: M(1) M(2).Thng thng, dung mi (1) l nc, dung mi (2) l pha hu c. Trong h chit, ta lun mong mun cht tan M chuyn hon ton t pha nc vo pha hu c.p dng nh lut tc dng khi lng cho cn bng trn, ta c:H s phn b:D= l nng cht tan M trong dung mi (2) l nng cht tan M trong dung mi (1)Xt i vi trng hp mt dng ca M phn b hai pha khc nhau ta c hng s phn b:KD=Thc t, trong hai pha chit, ty thuc vo nhiu yu t m cc cht c th khng tn ti ch mt dng duy nht m tn ti nhiu dng (hp cht trung ha in tch, hp cht tch in, bo ha s phi tr, cha bo ha s phi tr). Hn na, hng s chit ch c th gn ng iu kin dung dch rt long (c th b qua h s hot ). Do , h s phn b c trng cho kh nng phn chia ca cht v c ngha thc t hn so vi hng s phn b.Hng s chit:Cc ion kim loi Mn+ to phc vi phn t X- sau em chit bng dung mi hu c, cn bng chit xy ra nh sau:

Kex: hng s chit : hng s bn ca phc MXnDHXn : h s phn b ca phc HXnDMXn : h s phn b ca phc MXnKa : hng s phn ly ca acid HXnHng s chit c trng cho kh nng tch kim loi ra khi nc, hng s chit cng ln th kh nng chit cng tt. thu hi: c trng cho kh nng tch chit, ngi ta a ra khi nim thu hi Q. thu hi ca X (Y) c nh ngha l: t l gia lng cht X nhn c sau khi tch (x) vi lng cht X ban u khi cha tch (x0):Qx=Sai s xut hin trong qu trnh phn chia[7]Trong vic chit tch, iu m ta mong mun nht chnh l cht cn xc nh c chuyn hon ton vo dch chit v cc thnh phn khng mong mun khng c chit theo cht phn tch. Nu trong dung dch em tch c cu t X ng quan tm v yu t gy nhiu l Y, c 2 u cho tn hiu o t l vi hm lng ca n trong mu th vic tch khng hon ton s gy ra sai s khi o mu. Tht ng tic l s phn chia ch yu da trn cc qu trnh cn bng, do vy v nguyn tc khng th c s tch chit hon ton cc cht cn tr khi cht cn xc nh. Cht cn phn tch c th b mt trong qu trnh phn chia v cc cht khc vn tn ti trong dch chit vi mt lng nh. Gi s tn hiu thu c t l vi lng cht X v Y tn ti trong dung dch mu em o vi h s kx, ky tng ng:Mx= kx.x ; My=ky.y Tn hiu thu c khi o :M = Mx + My = kx.x + ky.y Tn hiu thu c nu trong dung dch ch cha mt lng x0 cht X v khng c cht gy nhiu Y :M0=kx.x0Sai s tng i: = = (Qx-1) + Vi: Qx =; Qy = , x0 v y0 l lng cht X v Y trong dung dch ban u, x v y l lng cht X,Y trong thu c trong dch chit. Trong biu thc sai s tng i trn th s hng th nht (Qx-1) phn nh sai s c lin quan n s mt cht X trong qu trnh phn chia, s hng th hai phn nh sai s do vic loi b khng hon ton cht Y trong qu trnh phn chia.T biu thc trn, ta thy: Sai s xut hin khi phn chia cng ph thuc vo nhy tng i ca php o i vi hai cht, c th hin qua t s: trong s hng th hai ca biu thc trn. Ngoi ra, t l gia lng ban u ca cht Y so vi X cng gp phn gy sai s trong php phn tch.2.5. Cc k thut chit tch:2.5.1. Phng php cng kt:[10]Cng kt l phng php kt ta cht cn phn tch bng cch a thm vo nhng cht kt ta ng hnh (cht gp) vo cc i tng phn tch cng kt cc nguyn t khi m hm lng ca chng rt nh. Cc cht gp thng dng l cc cht v c nh hidroxit kh tan (FeOH)3, Al(OH)3), mt s sunfur lm cht gp ngoi ra ngi ta cn s dng cht gp l hp cht hu c. Khi dng cht hu c cng chit th c th kt ta c nhng lng vt c hm lng 10-310-5 %. Vic dng cht hu c c u im hn so vi dng cht v c v cc kt ta d dng lc ra, phn t hu c d dng b phn hy khi nung nng kt ta nn nguyn t thu c trng thi c lm giu, tinh. Hn na, cht gp hu c c kh nng chn lc, cng kt c nguyn t cn phn tch khi c mt mt lng ln cc nguyn t khc.u im: n gin, hiu qu cao, nn mu phn tch c chuyn t phc tp sang n gin, nhiu ion phn tch c tch v lm giu ng thi t nn mu.Nhc im: tn thi gian nn t c s dng.ng dng: phng php cng chit c ng dng tt tch v c c nhiu nguyn t, thng c ng dng trong phng php ph hp th xc nh ng thi nhiu nguyn t.Bng di y thng k mt s phng php xc nh kim loi trong cc mu s dng phng php cng chit tch v lm giu ng dng trong phn tch ph nguyn t [3].Table1Preconcentration procedures using co-precipitation for the determination of metalAnalytescllectorrecoveryLODR.S.D(%)PFtechniquesamplereference(%)(gL-1)*(ngL-1)Se, Cu, Zn, sodium diethyldithiocarbamat>980.7(Zn, Cd), 1(Cu, Co)-40ICP-OESriver water [1]Cd, Fe, Co,7(Ni) Ni, Mn, Cr Sb, As, Cd,sodium diethyldithiocarbamat - 0.1-3.0--ICP-OESnature water [2] Fe, Cr,Cu, Pb, Mo, Ni, Ag, V, Zn.Cd, Pb,Nicopper diethyldithiocarbamat >95 0.23(Cd),3.2(Pb),1.4-2.2-F-AASnature water[3]2.2 (Ni)Fe, PbLanthannum phosphat>97-1.6(Pb)ICP-OESwater[4]Al, Cd,Mo,Manganese dioxide96-1051(Cd,Zn),5(Co,Cu,880F-AAS,groundwater[5]V, W,Ti, Ni, Pb)ICP-OESZn,Au, Bi, Co, Cu, Fe, Ni, Pb, PdPbManganese dioxide>953.25-ICP-OESriver water[6]Cd, Cu,PbAluminum hydroxide>956(Cd), 3(Cu),16(Pb)2-3-F-AASseawater[7]mineralwaterCu, Co,Pb,Cerium(IV) hydroxide>950.18(Cu),0.4(Cd),6.5-8.9-F-AASseawater,[8]Cd, Ni7(Pb),0.57(Co),drinkingwater1.56(Pb)sedimentCu, Mn, Co,Erbium hydroxide>950.11(Cu),0.25(Co),1-925F-AAStap water[9]Cr, Fe, Pb0.24(Pb)sedimentUrineAl, Ti, Cr,Gallium hydroxide-0.5(Pb),10-ICP-OESSea water[10]Mn, Co, Fe0.01(Cu, Zn)Ni, Cu, Zn, Y, PbCd, Co,Cr,Manganese hydroxide89-1000.08(Cd),0.14(Co)4.7-7.7-ET-AASDialysis [11]Cu, Mn, Ni,0.33(Cu),0.74(Ni)concentratePbCd,Fe,Co,Samarium hydroxide95-1001.1(Cu),3.1(Ni),0.2-10.2-ET-AASUrine,[12]Cr,Cu,Mn,4.5(Co),24.0(Pb)sediment,Ni,Pb0.4(Cd)DialysisConcentrates,Natural waterBe, Cr, Fe,Zirconium hydroxide-0.85(Co),0.88(Ni),