HA PHN TCH THC PHMTS . PHM KIM PHNG Chuyen nganh Hoa Phan Tch

45 TIT L THUYT

Ni dung hc

-Cung cp nhng kin thc c bn trong phn tch nh tnh v nh lng. -Cung cp cc gii php xy dng phng php phn tch. -Cung cp k thut phn tch c in v hin i. -Cung cp nhng ng dng ca lnh vc ha hc phn tch trong nghin cu khoa hc v thc tin.

CHNG TRNH GING DY1/ I CNG HA PHN TCH 2/ CHUN AXT - BA Z3/ CHUN KT TA4/ CHUN OXY HA KH5/ CHUN PHC CHT6/ PHNG PHP O MAU7/ PHNG PHP PHN TCH QUANG PHOPhng php hp thu nguyn t 73 AASPhng php quang ph pht x Plasma ICP8/ L THUYT K THUT SC K9/ K THUT SC K KH11/ K THUT SC KY LNG

PHAN 1

I/ I CNG HA PHN TCH1/ NH NGHA TH NO L HA PHN TCH

2/ NH NGHA TH NO L HA PHN TCH THC PHM

3/ PHAN TCH NH TNH

4/ PHN TCH NH LNG

5/ NH GA PHNG PHP PHN TCH V S LIU PHN TCH

5.1/ O CHNH XAC, O UNG, O LAP LAI,TOC O PHAN TCH,O NHAY, PHNG PHAP AC TRNG , PHNG PHAP C CONG NHAN

6/ X LY THONG KE ( STATISTICAL ASSESSMENT OF QUAILITY OF DATA)

7/ CACH BIEU DIEN THANH PHAN DUNG DCH 7.1. chat chuan goc 7.2. cac nong o dung dch

9/ / DNG C O THU TINH CHNH XC V TNG I

1/ NH NGHA TH NO L HA PHN TCH

Hoa phan tch l mt ngnh khoa hc chuyen nghin cu cc phng php phn tch nh tnh v nh lng mt cht hay nhiu cht , mt nguyn t hay nhiu nguyn t c trong sn phm m mnh ang nghien cu . V d : Trong mt mu nc ung c b nhim d lng thuc tr sau hay khng ? Bc u tin chng ta phi nh tnh xem trong mu nc bao gm nhng cht g? Bc 2 : nh lng nhng cht c nh tnh Bc 3 : da trn cc mu chun tnh ton v cho ra kt qa cui cng

PHAN TCH THC PHAM

2/ Thc phm c p ng cc tiu chun ha hc v v sinh ? C b i thiu, h hng v bin thnh cht c hi hoc c cha nhng cht c do thi ra t bao b, ha cht cho thm vo

Kim nghim phn tch thc phm bng phng php ha hc ngoi ra cn phn tch trng thi cm quan, vi sinh vt

II/ TH NO L PHN TCH HA THC PHM

Thc phm l nhng thc n , nc ung l nhng cht dinh dng cn thit cho c th con ngi, vt nui .do vy p ng cc yu cu trn thc phm phi cn c kim nghim trc khi a ra th trng tiu th.Kim nghim ha hc thc phm ( Analytical Food) : nhm xc nh 1/ Thc phm c p ng cc tiu chun ha hc v phm cht v thnh phn dinh dng theo ng nh quy nh hoc c b gian di v ga mo hay khng?

oi tng cua Hoa phan tch thc pham la cac chat dinh dng nh am , beo, bot, ng co trong ca, tht sa, trng, nc uong

e nh lng cac chat dinh dng cac nguyen to hoa hoc hay nh danh cau truc thanh phan cua cac chat oi hoi phai co phng phap phan tch chnh xac va phu hp vi cac oi tng nghien cu.

PHAN TCH NH TNHPHAN TCH NH LNG Phan tch nh tnh : Giup cho nhan biet cac nguyen to hoa hoc, hay nhom nguyen to, cau truc, thanh phan co trong cac mau phan tch ( thc pham, mau at, khoang san, a chat, nc , tram tch ..) nh vao cac thiet b phan tch va cac phan ng hoa hoc ac trng oi vi nguyen to can xac nh

PHAN TCH NH LNG Xac nh so lng ga tr cua oi tng co trong mau. c the hien ga tr %, mg/kg,mg/l, g/kg, g/l

5/ CAC YEU CAU LA CHON PHNG PHAP PHAN TCH Khi chon phng phap va thiet b s dung e phan tch phai at c cac yeu cau sau :

-o ung va o chnh xac cao cua phng phap cung nh cua thiet b nh s dung cho phan tch

- Phng phap co tnh chon loc cao

- o nhay cao, cc tieu phat hien nho

-Thi gian phan tch nhanh, va co kha nang phan tch ong thi nhieu nguyen to - Giam chi ph phan tch

- Thiet b de s dung, de bao tr

ANH GIA PHNG PHAP

CHNH XC ( precision)

Bieu th qua o lap lai cua cac ket qua, s lap lai cang tot th o chnh xac cang cao. Tuy nhien ay chung ta phai hieu o lap lai cua ket qua co ngha la cac mau c x ly cung mot ieu kien nhng la cac mau oc lap nhau, ch khong phai mot mau ma o nhieu lan, neu trng hp mot mau o nhieu lan co ngha la thiet b o co o lap lai tot. Con neu mot mau c lam oc lap nhau thanh nhieu mau ma ket qua cho sai biet nhieu th phai xem lai qua trnh phan tch b sai sot do thao tac cua can bo phan tch, thiet b s dung a c hieu chuan cha, chat chuan

o ung ( Accuracy): Ket qua a ra gan ung vi so thc c bieu th qua gia tr trung bnh va gia tr thc va o lech chuan. o lech chuan cang nho th ket qua co c cang ung. Va cang ung hn na ngi phan tch phai tnh c o khong am bao cua phep o ( Uncertainty in measurement). o khong am bao cua phep o la phai tnh c o lech chuan bang phng phap thong ke, tnh c nguon sai so ngau nhien va sai so he thong

Sai so ngau nhien la sai so lap lai do thao tac cua ngi s dung dung cu nh can, the tch lay mau Sai so he thong la do cac nguyen nhan sau : Thiet b phan tch, dung cu s dung nh can , bnh nh mc, sai so do nha che tao, chng t hieu chuan, cac chat chuan tinh khiet ...

PHNG PHAP TNH X LY THONG KE1/ Tnh gia tr trung bnh cua cac phep o Xtb = xi /n2/ o lech chuan 2 = ( Xi Xtb )2/ n -1 3/ Tnh o bien ong cua ham lng ( RSD) RSD = 2 / X tb x100Khoan tin cay (CI) : CI = Xtb t p x /N

CHAP NHAN KET QUA1/ Ket qua c chap nhan khi : o bien ong cua ham lng phai nho hn 5% oi vi phan tch co ham lng % RSD 5%2/ Vi phan tch vet co ham lng: ppm,ppb co the chap nhan khi: RSD 10 %

O LAP LAI ( reproducibility)

Tng t giong nh o chnh xac nhng ket qua lap lai la do cac nha phan tch khac nhau hoac cac phong th nghiem khac nhau s dung cung mot quy trnh phan tch

YEU CAU PHONG TH NGHIEM THC HIEN QA/QC TRC KHI CHO PHAN TCHoi vi mot phep phan tch nao nhat la oi vi cac phan tch vet trc khi phan tch phong th nghiem phai thc hien chng trnh QA/QC cho tng phep th.

QA : Quality assurance am bao chat lng la khi phan tch cho mot ch tieu nao o th phai am bao rang co quy trnh phan tch co hieu lc cho ch tieu o, co chat chuan cua ch tieu o (chat chuan phai co giay chng nhan ISO cua ngi ban), ket qua phan tch phai co o tin cay cao. QA bao gom ca kiem tra chat lng (QC) va anh gia chat lng cua qua trnh phan tch (quality assessment)

QC: Quality control La phng phap a c hieu lc kiem tra bang cach them chuan vao mau, hoac phan tch mau chuan (material reference) t o tnh c recovery cua phng phap.

Quality assessment: Qua trnh phan tch c thc hien trong phong th nghiem thong qua cac anh gia noi bo va ngoai bo bi mot anh gia vien trng cua mot phong th nghiem khac hay noi cach khac anh gia phan tch bi cac lien phong th nghiem, kiem tra cheo gia cac phong th nghiem.

CAC BC THC HIEN QA/QC- Gii thieu nang lc cua phong th nghiem

- Thc hien QC ve o ung va o chnh xac cua phep phan tch

- Quy trnh lay mau

- Bao quan mau

- Phng phap phan tch

- Hieu chuan thiet b, hieu chuan phng phap theo nh ky - Thc hien QA,QC - Kiem tra cheo cac phong th nghiem ben ngoai va noi bo, anh gia ket qua - Bao cao ket qua

S la chon phng phap phan tchMoi oi tng lai co nhieu chat, nhng chat nay co the la ham lng en phan tram (%) cho en ham lng nho nh mg/kg , mg/l ( 10-6 hoac nho hn g/kg, g/l (10-9) hoac nho hn na 10-12 picrogam ( ppt) .

moi phep phan tch co nhng u va nhc iem rieng cua tng phng phap co ngha la co nhng phng phap thch hp cho phep xac nh ham lng ln, co phng phap phan tch cho phep xac nh ham lng nho v vay phong oan trc ham lng co trong mau e chon phng phap phan tch cho phu hp va giam s sai so trong qua trnh phan tch.

Vi ham lng ln va ban nh lng ngi ta thng dung cac phng phap hoa hoc co ien : Khoi lng, the tch, phan tch ban nh lng -Ham lng vi lng ( ppm ) va sieu vi lng ( ppb, ppt hoac nho hn ) phai dung cac thiet b phan tch hien ai e o nh AAS, ICP, ICP/MS, HPLC, GC, GC/MS,LC/MS, HRGC/HRMS .. Nhng thiet b nay thng s dung e o vet cac kim loai nang, cac d lng thuoc tr sau trong nc, at, thuy san, thc pham

6/ NH NGHA CHT CHUN GCCht gc C tnh n nh cao Bn vi mi trng ng lng ln Khi lng ng vi cng thc ha cht Phn ng nh lng H2C2O4.2H2O ; C6H5COOH Na2B4O7.10H2O K2Cr2O7 ; NaCl KMnO4ZnSO4.7H2O ; MgSO4.7H2O

NH NGHA CAC LOAI NONG ONH NGHA : Nong o la ai lng cua mot chat ( ion hoac phan t ) trong mot lng xac nh dung dch 1/ Nong o the tch cua mot chat long : la ty le the tch gia chat long o va the tch cua dung moi

V du : HNO3 1:3 co ngha la dung dch gom mot the tch HNO3 ac va 3 the tch nc HNO3 : HCl 1:3 cng toan 1th tch l HNO3 v 3 th tch l HCl

2/ Nong o % khoi lng Cho biet so gam chat tan co trong 100g dung dch C% = So gam chat tan (a) x 100%So gam dung dchV du : Hoa tan a gam chat tan vao b gam dung moi th nong o % cua dung dch la : C% = a .100 a + b Trong hoa phan tch, nong o % c coi la gan ung V du : Muon co dung dch KNO3 1% , th can 1g KNO3 hoa tan vao 100ml H2O

3/ Nong o mol/l : Cho biet so mol ( co the la ion hay phan t ) chat tan co trong 1lt dung dch, dung ch M hay mol/lCM (mol/l) = So mol chat tan (n) = n The tch dung dch V (l)

n : s mol cht tan n = m( chat tan) V : the tch, M M: phan t gamPhn mn : ( tc phn s mol) ca mt cht l t s gia s mol ca cu t chia cho tng s mol c trong dung dch XA = s mol cht A tng s mol

V du 1: Dung dch H2SO4 2M, la dung dch co cha 2 mol H2SO4 hay 2 x 98 = 196g H2SO4 trong 1 lt dung dch

V du 2: Tnh nng mol ca dung dch khi hoa tan 1,2g MgSO4 vao nc thanh 100ml

CM = n 1,2g = 0,1M 100 120 . 0,1

3/ Nong o ng lng gam ( lg) la so gam cua chat o ve mat hoa hoc tng ng vi 1mol Hydro hay 1mol Hydroxyt trong phan ng ma ta xet Trong cac phan ng hoa hoc, cac chat phan ng vi nhau vi cung so ng lng gam Lg khng phi l hng s nh s mol m ph thuc vo phn ng ha hc m cht tham gia CN = so ng lng gam chat tan (N)So lt dung dch (V)

4/ Nong o molan Cho biet so mol chat tan co trong 1kg dung moi

a/ Phan ng axt baz 1/ NaOH + HCl = NaCl + H2O 1 mol NaOH phn ng vi 1 ion H+ nen lgNaOH = MNaOH Tng t 1 mol HCl tng ng vi 1 mol OH- nn : lg HCl = MHCl

2/ NaOH + H3PO4 th tuy theo phan ng co khac nhau ve lg : - NaOH + H3PO4 = NaH2PO4 + H2O lgNaOH = MNaOH , lgH3PO4 = M H3PO4

2 NaOH + H3PO4 = Na2HPO4 + 2 H2O lgNaOH = MNaOH , lgH3PO4 = MH3PO4 2

3 NaOH + H3PO4 = Na3PO4 + 3 H2O lgNaOH = MNaOH , lgH3PO4 = MH3PO4 3

Vay lg cua axt bang khoi lng mol cua axt o chia cho so ion H+ ma 1 mol cua axt o tham gia phan ng lg cua baz bang khoi lng mol cua baz chia cho so ion OH- ma 1 mol baz o a tham gia phan ng

1.5. Nong o ng lngtrong phan ng ket tua Al2(SO4)3 + 3 Pb(NO3)2 = 2Al(NO3)3 + 3PbSO4 Trong phan ng nay lg cua cac chat tham gia phan ng bang khoi lng mol cua chat o chia cho so ien tch cua 1 mol chat o tham gia phan ng lg (Al2(SO4)3 = M (Al2(SO4)3 hay lg Al = MAl 6 3lg Pb(NO3)2 = M Pb(NO3)2 hay lgPb = Mpb 2 2

1.6. Nong o ng lng trong phan ng tao phc Trong phan ng tao phc phan ng xay ra phc tap cho nen e tnh lg cua cac chat tham gia phan ng tao phc ta phai quy c lg cua 1 chat roi t o tnh lg cua chat kiaV du: Ag+ + 2CN Ag(CN)-2Neu lgAg+ = MAg+ th lg CN = 2MCN

V du: Hg2+ + 4I- = HgI42-lg(Hg2+) = MHg2+ th lg (I-) = 4MI-

1.7 Nong o ng lng trong phan ng oxy hoa kh V 1 electron tng ng vi ion H+ nen lg cua chat oxy hoa hay chat kh bang khoi lng mol chia cho so electron ma 1 mol chat o cho hay nhan.2KMnO4 + 10 FeSO4 + 8 H2SO4 = 2MnSO4 + K2SO4 + 5 Fe2(SO4)3 + 8 H2O lg KMnO4 = MKMnO4 hay lg Mn = MMn 5 5lg FeSO4 = MFeSO4 hay lg Fe = MFe 1

2/ 3As2S3 + 28 HNO3 + 4H2O = 6H3AsO4 + 9 H2SO4 + 28NO As3+ - 2e- As5+ S2- - 8e- S6+ N5+ + 3e- N2+

lg(As2S3) = MAs2S3 , lgHNO3 = MHNO3 2 3

Nong o ng lng gam chat tan co trong 1 lt dung dch ky hieu : NTheo nh ngha ve ng lng g trong cac phan ng hoa hoc cac chat phan ng vi nhau theo so lg nh nhau va cac chat tao thanh sau phan ng cung tng ng vi nhau ve so lgV du: nA + mB pC + qDMac du he so n, m, p, q cac chat phan ng khac nhau nh so lg cua chat A phan ng bang ung so lg cua chat B. Chat C va D tao thanh sau phan ng cung co so lg nh nhau

CHUN T chun c biu din bng s gam (g) hay miligam (mg) hoc microgam (g) cht tan c trong 1ml hay 1L dung dch chun theo cht cn xc nh TA/B: c biu din bng s gam cht cn xc nh B tng ng vi 1ml dung dch chun cht AV d : Tnh chun ca dung dch KMnO4 0,02M theo Fe. 5Fe2+ + MnO4- + 8 H+ 5 Fe3+ + Mn2+ + H2O

Theo phan ng ta co : lg (MnO4) = MKMnO4 5Do o nong o ng lng cua dung dch KMnO4 la : 0,02 x 5 = 0,1N.

So mili ng lng gam KMnO4 co trong 1ml dung dch la 0,1 x 1= 0,1mlg.

Theo phan ng s mlg Fe phn ng vi 1ml dung dch KMnO4 l 0,1mlg vay so mg Fe tng ng vi 1ml dung dch KMnO4 la : 0,1 x 56 = 5,6mg Vay T KMnO4 / Fe = 0,0056g/ ml

PHA DUNG DCH T CHAT RAN 1/ Tnh toan lng can2/ Hoa tan3/ nh mc4/ Chuyen vao chai cha5/ Hieu chnh nong oMcan = CM . V. M 10. P%V : the tch tnhP% : o tinh khiet cua hoa chatM : phan t gamCM : nong o mol

V du : Tnh lng can NaOH co P = 96% e pha c 200ml dung dch NaOH 0,1Mmcan = 0,1. 200. 40 = 0,83g NaOH 10 . 96

Pha dung dch t chat long 1/ Tnh toan the tch can dung2/ Pha loang3/ nh mc4/ Chuyen vao chai cha5/ Hieu chuan lai nong o neu can

CM = C% . 10. d , V can lay = Ccan pha . Vcan pha M CM

V du : Tnh the tch H2SO4 98%, d= 1,84 can lay e pha 200ml dung dch H2SO4 co nong o 1MCM = 10. 98. 1,84 = 18,4 M 98 V can lay = 1. 200 = 10,87 ml 18,4

Moi lien he gia 3 loai nong oCM = C% . 10. d , CN = C% .10. d M

CN = M. CM , CM = so mol . chat tan(n) so kg dung moi M : khoi lng mol phan t chat tan : ng lng g chat tand : Ty trong rieng cua chat tan

CM = a gam chat tan. 1000ml dung dch M .VM: khoi lng phan t chat tan

5/ Nong o vi lng va sieu vi lng ppm ( mg/kg, mg/l) 10-6 ppb ( microgam / kg, microgam/l) 10-9ppt ( ng/kg, ng/l) 10-12

9/ DNG C O THU TINH CHNH XC V TNG I

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