Phan Tich HS - Bai on Tap 1_ 1 Slide in 1 Page

Cc phng php phn tch Cc phng php phn tch ha sinh thc phm hin i

TS. Phan Ti HunKhoa Cng Ngh Thc Phm HNL TP.HCM

[email protected]

[email protected]

CNG CHI TIT MN HCChng trnh o to cao hc ngnh Cng ngh thc phm v ung

M S MN HC:M S MN HC:

TN MN HC: Cc phng php phn tch ha sinhhin i

(Advanced analytical biochemistry methods)

S N V HC TRNH: 3 TC (2, 1)

TN GIO VIN: TS. Phan Ti HunTS. Phan Phc Hin

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Gii thiu v phn tch ha sinh, xu hng pht trin K thut ly mu, x l kt qu phn tch

Ni dung mn hc

K thut ly mu, x l kt qu phn tch Cc phng php phn tch quang hc K thut sc k Phn tch thnh phn ho hc v cu trc i tng

nghin cu bng HPLC, GC, GCMS, Xc nh protein v acid nucleic bng phng php

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Xc nh protein v acid nucleic bng phng php in di v PCR

Ly tm cc phn t sinh hc Enzyme-linked Immunosorbent Assay (ELISA)

Gio trnh & ti liu tham kho: Phn tch ha hc thc phm, H Duyn T, Nh xut

bn Khoa hc v k thut 2009.

Ni dung mn hc

bn Khoa hc v k thut 2009. Food Analysis, S. Suzanne Nielsen, 4th Edition, Springer,

2010. Modern Techniques for Food Authentication, Da-Wen

Sun, Academic Press, 2008. Handbook of food analysis instruments, Semih tle,

CRC Press, 2008.(Google books)

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(Google books)

1- Gii thiu v phn tch ha sinh thc phm

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Phn tch thnh phn dinh dng m bo cht lng

Ti sao phi phn tch ha sinh?

m bo cht lng An ton thc phm Pht trin sn phm Chng minh tnh xc thc Gip truy xut ngun gc

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Nguyn vt liu: xc nh cht lng, thnh phn vtnh n nh ca nguyn vt liu.

Cc lai mu cn phn tch

Mu trong qu trnh ch bin: xc nh xem quytrnh ch bin nh hng nh th no n sn phm?

Thnh phm: sn phm c t yu cu? Mu sn phm b khiu ni: so snh vi mu t

chun.

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chun. Mu ca i th cnh tranh

Phn tch cc cht dinh dng chnh (cng b trnbao b thc phm).

Phn tch thnh phn g?

Phn tch cc Vitamin v khong cht. Phn tch cc d lng thuc tr su. Phn tch cc cht ph gia Phn tch cc amino acid, cc hp cht th cp Phn tch DNA

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Phn tch DNA

Nhng c quan, t chc chnh ban hnh cc lut linquan n thc phm

Trong nc:

Thc phm v Lut

Trong nc: Cc an tan v sinh thc phm Cc bo v thc vt Tng cc tiu chun o lng cht lngQuc t:

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Quc t: The Codex Alimentarius (Latin: "food code") Food & Drug Administration (FDA)

Food, Drug and Cosmetic Act (FFD&C) Nutrition Labeling Act 1990

Sch chuyn kho Cc phng php phn tch c chun ha

Cc ngun ti liu phn tch thc phm

Cc phng php phn tch c chun ha AOAC Intl: Association of Official Analytical Chemists

International: ngun thng tin v cc phng php phntch c thm nh s dng trn ton cu (bao gmhn 2700 phng php phn tch vi chnh xc v tincy cao.

Tp ch khoa hc chuyn ngnh

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Tp ch khoa hc chuyn ngnh Tp ch thng mi Catalog ca cc nh sn xut Trang Web

i vi ngi tiu dng Mi tng quan gia khu phn n v sc khe

Nhu cu v xu hng

Thnh phn dinh dng c s dng Cc thng co v sc khe quan trng

V d v thc phm gim bo Cn phng php phn tch chnh xc thnh phn cng

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b n ngi tiu dng Tm phng php phn tch cc cht thay th bo

i vi cng nghip thc phm Qun l cht lng t nguyn liu n thnh phm

Nhu cu v xu hng

Cc phng php phn tch bt buc phi c p dng La chn cc nh cung cp cho nguyn vt liu

T tin hnh phn tch m bo cc nguyn liu ca nh cung cp ng nh yu cu k

thut tha thun

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Thit lp mt phng php phn tch chun Ly mu

Cc bc trong phn tch thc phm

Ly mu Chun b mu trch ly Trch ly hp cht cn phn tch Phn tch, loi b nhng cht khc gy nh hngn kt qu phn tch

Pht hin, nhn dng hp cht cn phn tch

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Pht hin, nhn dng hp cht cn phn tch Xc nh v/hoc nh lng hp cht cn phn tch Lu tr thng tin

Thit lp phng php phn tch chun: Phng phpphn tch chun cn r rng, chnh xc, c kim


bi cc nh phn tch, v khi cn thit c th c lpli bi cc nh phn tch khc.

Cc tiu ch la chn phng php phn tch: ng ca phng php chnh xc ( lp li) ca phng php Tnh chuyn bit ca phng php

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Tnh chuyn bit ca phng php Kch c mu Trang thit b Tnh kinh t an tan v tnh c hi ca cht thi Tc v tnh n gin ca qu trnh phn tch

Ly mu: y l mt qu trnh chun b mt i dinca ton b thc phm cn phn tch. Nu cn phn


tch nh lng th thng thng s dng mt chtni chun (c tnh cht tng t vi cht cn phntch).

Chun b mu trch ly: Bc ny l thc thi ccqui trnh cn thit chun b mu nguyn bn snsng cho giai on trch ly, thng l i vi mu rn.

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sng cho giai on trch ly, thng l i vi mu rn.V d nh nghin th, tn mn hay l ly tm.

Trch ly: y l qu trnh trch cc hp cht cn phntch ra khi ngun mu th ban u. Dch trch c th


cha cc thnh phn khng mong mun. Kt qu thuc l mt dch trch c hm lng cht phn tchcao hn v t phc tp hn mu ban u.

Phn tch trc tip (khng cn trch ly). Trong trnghp cc cht phn tch c hm lng ln v khngb gy nhiu bi cc hp cht khc th ta c th phn

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b gy nhiu bi cc hp cht khc th ta c th phntch trc tip. V d nh mu lng trong HPLC, haytrong phng php phn tch to mu nh Biuret phn tch protein.

Phn tch: Thng c cp trong phng phpsc k. Mc tiu khng phi l loi b hoc trch


mt cht no m l tch ra cc thnh phn hnhp nhn dng v xc nh.

Pht hin nhn dng cht cn phn tch: nhn dngtrc tip bng thit b cm b cm bin (detector).

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Xc nh v/hoc nh lng: Thng qua tn hiu ghinhn c khi mt thnh phn ca mu c pht


hin trn ng chun. Ni dung tnh hiu s cchuyn ha thnh thng tin nh tnh hoc nh lng(trc tn hiu mu chun c thit lp vchun ha).

Ghi chp v lu tr kt qu phn tch.

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=> Ty c tnh mu v yu cu m chn v hiu chnhcc bc phn tch thch hp

2- Ly mu th nghim2- Ly mu th nghimTS. Phan Ti Hun

Khoa Cng Ngh Thc Phm HNL [email protected]

[email protected]

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Gii thiu chung Mt s khi nim chung

Ni dung

Mt s khi nim chung Phng php ly mu

Dng c ly mu Cc dng mu thng ly kim tra Chun b mu Bao gi, vn chuyn, bo qun mu

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Bao gi, vn chuyn, bo qun mu X l mu trc khi phn tch

Ly mu ng vai tr rt quan trong trong nh gicht lng l sn phm v mu phi phn nh chnh

Gii thiu chung

xc mi c im cht lng v phi c trng chothnh phn trung bnh ca l sn phm.

Ty vo c tnh ring bit ca sn phm m cnhng qui nh cho vic ly mu khc nhau. Kh cth a ra c nhng qui tc c nh c chpthun trong mi tnh hun, cho mi sn phm.

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thun trong mi tnh hun, cho mi sn phm.

Kim tra qu trnh sn xut Kim tra nghim thu

Mc ch ca vic ly mu

Kim tra nghim thu Xc nh c trng ca l (gi l tng th) tin hnh cc php th nh gi th trng

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Phng php ly mu

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Mu: l mt n v hoc nhm n v sn phm lyt mt tp hp (tng th) cung cp thng tin v c

Mt s khi nim chung

th lm c s a ra quyt nh i vi tp hp Php ly mu: th tc ly mu hoc to mu Tp hp (hoc tng th): l tan th cc n v sn

phm c xt. Ty theo trng hp tng th c thl mt l, mt s l hay mt qu trnh sn xut

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n v sn phm: i tng c th hoc mt lngvt cht xc nh trn tin hnh cc php th

n v ly mu: l n v sn phm m t ly ra

Mt s khi nim chung

n v ly mu: l n v sn phm m t ly ra phn tch. n v ly mu c th l mt hay mtnhm n v sn phm.

L hng (hay l sn phm): l lng hng nht nhc cng mt tn gi, cng mt hng cht lng, cngmt lai bao gi, cng mt nhn hiu (k hiu nhn),

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mt lai bao gi, cng mt nhn hiu (k hiu nhn),sn xut trong cng mt x nghip v cng mtkhang thi gian gn nhau, cng mt giy chngnhn cht lng, vn chuyn cng phng tin vgiao nhn cng mt lc

Mu ban u: l mt lng sn phm c ly cngmt lc t mt n v tng th (c bao gi hoc

Mt s khi nim chung

khng bao gi). Mu ring (hoc mu c s): l mu thu c bng

cch phi hp N mu ban u ly t mt tp hp lm i din cho tp hp .

Mu chung: l tp hp tt c mu ring ca mt tp

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hp. Mu trung bnh th nghim: l mu c chun b t

mu chung tin hnh phn tch, xt nghim.

Ch dn ban u: a im ly mu: ly mu ni bo qun, bc d hay

Phng php ly mu

a im ly mu: ly mu ni bo qun, bc d hayvn chuyn, ti tng im (hoc sau tng thit b)trong qu trnh sn xut, ti im nhp nguyn liuhoc xut thnh phm.

Kim tra s b sn phm: Trc khi ly mu cn kim tra tnh ng nht ca l

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Trc khi ly mu cn kim tra tnh ng nht ca lhng, nu khng t th phi chia l thnh nhiu phn ctnh cht gn nh nhau.

Cn xem xt bao gi ngai ca sn phm v trong chngmc c th xem xt bao gi ca tng n v sn phm.

Vi tr ly mu: c xc nh theo v tr ngu nhinnhng cn lm sch sn phm ly ra khng b dy

Phng php ly mu

bn. Trng hp dy bn ngu nhin:

Nu ngu nhin trn b mt sn phm b dy bn th phinh nhng b i.

Trng hp khi s dy bn nh hng n cht lng casn phm hoc lm thay i tnh cht ca sn phm th

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sn phm hoc lm thay i tnh cht ca sn phm thkhng c lai b m phi xem l 1 thnh phn casn phm

Cn s dng nhng dng c c kh nng ly cmu ban u t nhng dy bt k ca cc lp

Dng c ly mu

khc nhau ca l hng. Hnh dng, vt liu ch to v ln, di ca

dng c ly mu v dng c cha mu phi da vocc tiu chun ph hp cho tng lai sn phm ringbit.

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Cn chun b v gi dng c ly mu sch v kh

www.starqualitysamplers.com/seed.php

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Thng thng ty theo cc lai mt hng m quy nhmu sao cho ph hp, d i din, d phn tch.

i vi sn phm ng chai, ng hp nh nc

Cc dng mu thng ly kim tra

i vi sn phm ng chai, ng hp nh nckhang, nc gii kht, bia, sath n v mu lchai hoc hp.

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i vi sn phm ri nh trng, tri cy, bnhkoth n v mu l qu, thng hay n v khilng. Nhng i vi sn phm qu nh nh nho th


lng. Nhng i vi sn phm qu nh nh nho thn v mu l chm hoc kg.

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Ly mu sn phm c bao gi: Khi ly mu ban u lc tin hnh bc d hoc xp


Khi ly mu ban u lc tin hnh bc d hoc xpsn phm th phi ly mu u n, ngha l tinhnh trong khang thi gian gn bng nhau.

Nu vic bc d hay vn chuyn hng ha khngu th s lng bao gi phi ly vi lng gn bngnhau trong nhng khang thi gian khc nhau ty

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thuc vo tc vn chuyn. Mu ban u phi ly t cc v tr khc nhau ca bao

gi cc dy khc nhau ca l.

Ly mu cc sn phm lng, st, bt nho Cn khuy trn u cc sn phm trong thng ng


Cn khuy trn u cc sn phm trong thng ngnu thy cn thit. Nu sn phm phn thnh lp vkh khuy trn th phi ly t mi lp vi t l tngng vi lng sn phm ca lp .

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Trnh ly cht lng gn thnh ng, ti cc ch ungp v khng phn nh gi tr thc ca tng th. Cht


lng c nht qu cao thng khng u, v vy cth un nng hoc lm ng c ri p dng phngphp ly mu cht rn.

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Ly mu cht kh, c 3 trng hp: Kh dng ng: cn t ng ly mu vo gia dng


Kh dng ng: cn t ng ly mu vo gia dngkh. cho kh trong ng c thay th hang tanth ng phi ngn v xc nh ng thi gian.

Kh dng tnh (trong bnh): c th ly mu ti imbt k, nhng i khi cng cn kim tra t trng.

Kh trng thi na tnh: chng ta coi nh mu ng

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Kh trng thi na tnh: chng ta coi nh mu ngu nhng cn trnh ly ming bnh, ly nic coi l trn k.

Ly mu sn phm dng ri v khng bao gi (dng ht,dng cc)


C s khc bit v gi tr ca cc ch tiu gia htln v ht nh v vy cn to mu sao cho s phnb gia ht trong mu gn ging vi phn b giaht trong l.

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Trong sn xut hoc trong bo qun cc lai ht ccng kch thc v cng t trng thng tp trungvo mt ni


vo mt ni ly mu khi sn phm trng thi ng tng s lng mu ban u v mu ring

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Chun b sn phm dng lng, st, m, bt Tt c cc mu ban u cho vo bnh ng sch v

Chun b mu

Tt c cc mu ban u cho vo bnh ng sch vkh c np y kn.

Mu chung nhn c bng cch trn c trn cnthn thu c mt hn hp ng nht

Sau ly t hn hp mu chung to thnh mutrung bnh th nghim.

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trung bnh th nghim.

Chun b mu sn phm dng ht v cc Tt c mu ban u ly c cho vo mt dng c

Chun b mu

Tt c mu ban u ly c cho vo mt dng c(chai, ti ni lng hai lp) sao cho sn phm khng bdy bn hoc b ht m, bay hi nc).

Nu sn phm dng cc, nn nghin thnh cc nhhn ( sau khi nhn c mu chung cn trn u v tip tcnghin nh n kch thc yu cu (ty sn phm),v lc gim c mu trung bnh th nghim.

Mu trung bnh th nghim c ng trong ccdng c sch, tr trnh s nhim bn t bnngai, trnh lm h hng mu trong khi vn chuyn.

Bao gi, vn chuyn, bo qun mu TBTN

ngai, trnh lm h hng mu trong khi vn chuyn. Dng c cha mu phi c nim phong v gi

ngay n phng th nghim cng sm cng tt trnh h hng mu.

Mu lu phi c bo qun trong iu kin kh ro,sch s, thang mt nhit v m khng kh

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sch s, thang mt nhit v m khng khph hp vi tng lai sn phm.

V d mu ko bo qun 20C, =70%. hpng lnh th bo qun iu kin lnh ng. Thigian bo qun khng qu 6 thng.

X l mu trc khi phn tch

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Xc nh hp cht cn phn tch trong mu Cc pha cn xem xt

Lai mu

Pha kh: cc hp cht bay hi. Pha nc: cc hp cht phn cc (a nc). Pha dung mi hu c: cc hp cht khng phn

cc (k nc).

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Trch ly (chng ct): trch tch cc cht cn phn tchra khi mu.

Tinh sch: lai b cc hp cht gy nh hng: hp

Cc bc c bn trong phn tch

Tinh sch: lai b cc hp cht gy nh hng: hpph, phn b.

Ci bin: tng kh nng phn tch da vo kh nngphn ng ha hc ca cht phn tch.

nh lng: o hm lng cht phn tch bng cchso vi cht chun.

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so vi cht chun.

phn cc: lc lin kt ni phn t phn ln l do tnh phn cc

ca cc nguyn t v kh nng to lin kt hydr.

Nhng im lu v trch ly

ca cc nguyn t v kh nng to lin kt hydr. Cc ion:

Ion dng v ion m mang in v thng tan. V dNaCl, KCl, NH4Cl...

Cc phn t: Momen lng cc:

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Momen lng cc:

Tnh tan Dung mi phn cc: thng ha tan cc cht a

nc v mang in


nc v mang in Dung mi khng phn cc: thung ha tan cc cht

a bo hoc khng tan trong nc Hng s in mi []: m t tnh phn cc ca dung

mi. Hng s in mi o mc tc dng ca vt chtln tnh truyn in. Dung mi c phn cc cao

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ln tnh truyn in. Dung mi c phn cc caoth c hng s in mi cao.

Hng s in mi


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Hng s in mi l t s gia F/F Dung mi phn cc c xu hng nh hng cao

trong trng in v c hng s in mi cao


trong trng in v c hng s in mi cao Hng s in mi ca nc l 80,1. Dung mi khng phn cc th t c nh hng trong

trng in nn c hng s dung mi thp. Hng s in mi ca hydrocarbon l 1,89.

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Hng s in mi ca hydrocarbon l 1,89.

Dung mi Dung mi l mi trng cho cc phn ng ha hc

din ra.


din ra. Dung mi c s dng trch mt cch c chn lc cc

cht t hp cht phc tp. Dung mi c s dng phn tch v lm tinh sch cc

lai phn t. tan cho bit mc bao nhiu cht tan s tan

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tan cho bit mc bao nhiu cht tan s tanvo dung mi mt nhit c nh.

Dung mi thng phi p ng c cc ch tiu sau: Tr vi iu kin phn ng.


Ha tan c cc cht tham gia phn ng. D lai b cng an cui ca phn ng. Gi c va phi. Khng c hi.

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Cc yu t chnh nh hng n cc cht tan trong dungmi:

Nhit


Nhit Kch thc phn t Cc nhm ha hc chc nng pH

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Cc vt liu trong t nhin cha a dng cc nhmc phn cc khc nhau, do tch mt cchchn lc cc nhm cn phn tch th phi s dng


chn lc cc nhm cn phn tch th phi s dngdung mi ng lai phn cc hoc dng phngphp chng ct

V d: Hexane: lipit, sp, steroids MeOH: hp cht mu, alkaloids, tannins, flavonoids

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MeOH: hp cht mu, alkaloids, tannins, flavonoids Nc: cc lai mui, ng v protein


[ ][ ]aqueous

organicD A

AK =

H s phn b:

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=> Cn lm kh dung dch hu c (lai nc) trc khi phn tch (v d GC)

V d v tnh nng mt hp cht trong dung dchs dng h s phn b KD.


Xc nh lng caffeine trong tng phn lp canc:chloroform (100 mL v/v) nu bit tan cacaffeine trong nc v chloroform ln lt l 1,8g/100ml v 18 g/100ml.

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Nhit si

Nhng im lu v chng ct

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Lc lin kt ni phn t mt phn t c th di chuyn vo pha hi th phi

vt qua c lc lin kt ni phn t gi phn t


vt qua c lc lin kt ni phn t gi phn t trong pha lng

nh hng bi: Lin kt H Lin kt lng cc-lng cc Lin kt van der Waals

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Lin kt van der Waals Kch thc v hnh dng


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3- nh gi kt qu phn tch 3- nh gi kt qu phn tch TS. Phan Ti Hun

Khoa Cng Ngh Thc Phm HNL [email protected]

[email protected]

Kin thc ton hc c bn p dng trong nh gi kt qu phn tch th nghim.

Ni dung

qu phn tch th nghim.

nh gi ng chun .

Cc hng dn trnh by cc s liu nhm th hin tnh chuyn bit v tinh cy ca php phn tch.

lm tng ng v chnh xc cn phi phn tch lpli nhiu ln trn cng mt mu (3 ln).

V khng th xc nh c kt qu o no l chnh xc

nh gi xu hng t gi tr trung tm

V khng th xc nh c kt qu o no l chnh xcnht nn vic xc nh gi tr trung bnh l cn thit.

Trong : n

x

n

xxxx in =

++++=

...

x 321

Trong : x l gi tr trung bnh x1, x2l cc gi tr o (xi) n l tng s ln o

V d nh xc nh hm lng m ca mt sn phmhamburger thu c kt qu ca bn ln o ln lt


nh sau: 64,53%, 64,45%, 65,10% v 64,78%.

Hm lng m ca sn phm s l 64,72% (tc l gitr trung bnh). Quy c gi tr ny l gi tr c

(%) 64,724

64,7865,1064,4564,53x =

+++=

tr trung bnh). Quy c gi tr ny l gi tr clng tt nht ca hm lng m ca mu cn tm.

Cha cp n l gi tr o trung bnh thu c nyc chnh xc hay khng.

Chng ta cng c th s dng s trung v xc nhhm lng m ca hamburger trong v d trn. (?).


hm lng m ca hamburger trong v d trn. (?). S trung v ca tp l kt qu m so vi kt qu ny

th s cc kt qu vi gi tr nh hn v ln hn lnh nhau.

Trong trng hp l tng th gi tr trung bnh vtrung v phi trng nhau.

Trong phn tch ngi ta thng s dng gi tr trungbnh hn v y tht s l cng c hu dng clng kt qu sau cng.

v d trn chng ta ch xc nh c gi tr trungbnh m cha cp n tng kt qu o ring l.

Cu hi t ra:

tin cy ca php phn tch

Cu hi t ra: Liu cc kt qu ring l ny c gn ging nhau khng? Chng c gn vi gi tr thc khng?

=> tr li cc cu hi trn chng ta cn hiu 2 khinim: ng v lp li.

ng: th hin s ph hp ca gi tr nhn ci vi gi tr c chp nhn l gi tr thc v biu


i vi gi tr c chp nhn l gi tr thc v biuhin bng sai s.

Tr li v d v hamburger, nu nh gi tr ca hmlng m thc t l 65.05% th vi gi tr o trungbnh thu c (64.72%) th ta c th ni rng kt quo kh ng v 2 gi tr trn khng qu cch bito kh ng v 2 gi tr trn khng qu cch bitnhau.

xc nh c ng th chng ta cn bit cgi tr thc ca mu phn tch.


gi tr thc ca mu phn tch.Mua mt s mu c hm lng c xc nh chun cc trung tm o lng, kim nh c uy tn.

So snh kt qu ca chng ta vi kt qu ca ccphng th nghim uy tn khc (trn cng loi muphn tch). Lc chng ta mc nh kt qu ca ccphn tch). Lc chng ta mc nh kt qu ca cctrung tm phn tch ny l ng v chnh xc.

lp li ( chnh xc): l mc phn tn ca ccphp o lp li trn cng mt iu kin, c th hin


php o lp li trn cng mt iu kin, c th hinqua thng s lch chun (SD). Nu kt qu ca ccln phn tch lp li gn ging nhau th ta c th nil php phn tch c chnh xc cao.

=>Nh vy mc tin cy ca mt phng php phntch ph thuc vo ng v lp li.tch ph thuc vo ng v lp li.

ng + Chnh xc Khng ng + Chnh xc

ng chnh xc

ng + Khng chnh xc Khng ng + Khng Chnh xc

(Source: http://www.wellesley.edu/Chemistry/Chem105manual/Appendices/AccuracyPrecision.gif)

Mt phng php n gin xem xt dn trica kt qu phn tch l nh gi khong cch bit


ca kt qu phn tch l nh gi khong cch bitgia gi tr ln nht v nh nht. Tuy nhin phngphp ny t c x dng trong x l s liu v khngtht s hu dng.

Trong phn tch nh gi chnh xc ca s liuphn tch th lch chun c s dng thng dngnht v c ngha thng k nhtnht v c ngha thng k nht

lch chun xc nh dn tri ca cc s liu thnghim v l cng c hu ch ch ra xem tng kt quphn tch ring l c gn vi nhau khng.

lch chun ca mt tp hp rt ln (c cxc nh vi gi nh y l ton b sn phm cphn tch).

lch chun

phn tch).

Trong = lch chun

( )n

xi= 2

= lch chun xi= gi tr mu i = gi tr trung bnh tht s n = tng s mu nh gi

Trn thc t chng ta s khng xc nh c gi trtrung bnh tht s ca ton b sn phm

lch chun

trung bnh tht s ca ton b sn phm xc nh lch chun ca mu, k hiu l SD

(standard deviation)

Khi s lng mu em i nh gi 30 th ta c th

( )n

xxiSD = 2

Khi s lng mu em i nh gi 30 th ta c ths dng cng thc:

( )1

2

=

n

xxiSD

Nh vy kt qu phn tch ca hamburger s c ghinhn l 64,72% m vi lch chun l 0,2927.

lch chun & H s bin thin

T gi tr trung bnh v lch chun chng ta c thxc nh h s bin thin (CV, coeffiecient ofvariation), hay cn c gi l lch chun tngi (RSD, relative standard deviation).

%100= SDCV

V d Hamburger:

%100=x

CV

%453,0%10072,64

2927,0==CV

Gi tr CV cho chng ta thy lch chun trongtrng hp ny ch chim 0.453% so vi gi tr trung

lch chun & H s bin thin

trng hp ny ch chim 0.453% so vi gi tr trungbnh. V nh vy cho thy vic phn tch hamburgt gi tr chnh xc cao. Thng thng ngi ta chpnhn CV

68% gi tr s nm trong khang trung bnh 1, 95%nm trong khong 2 v 99,7% nm trong khong 3 .

Phn b chun

Xc sut tm ra gi tr trung bnh tht ca dn s snm trong khong tin cy CI (Confidence Interval)c xc nh thng qua lch chun.

Khang tin cy

c xc nh thng qua lch chun. i vi trng hp s lng mu ln, chng ta c th

xc nh khang tin cy dao ng xung quanh gi trtrung bnh bng cch s dng thng s thng k gil gi tr Z. Chng ta c th xc nh Z t bng thngk khi bit c xc sut tin cy.

nZxCI =

Xc sut tin cy, % Z50 0,67

Bng gi tr Z

50 0,6768 1,0080 1,2990 1,6495 1,9696 2,0096 2,0099 2,58

99,7 3,0099,9 3,29

Xc nh cc khang tin cy ca m hamburger(gi s lch chun v gi tr trung bnh l catan b 25 mu), xc sut tin cy 95% v 50%.

Bi tp

%115,072,6425

2927,096,172,64%)95( ==CI

tan b 25 mu), xc sut tin cy 95% v 50%.

%039,072,642927,067,072,64%)50( ==CI %039,072,6425

2927,067,072,64%)50( ==CI

Trong 100 trng hp c 50 trng hp gi tr trungbnh nm trong khang (64,681-65,759)% v 95trng hp nm trong khang (64,605 64,835)%.

Vi nhng trng hp s lng mu nh, khang tincy c xc nh thng qua bng thng k t.

Khang tin cy (lng mu nh)

Trong t c xc nh thng qua t do (n-1) vxc sut tin cy %.

n

SDtxCI =

n

Gi tr t cc xc sut tin cy khc nhau

Xt trng hp xc nh m hambuger ch vi 4ln phn tch nh trong v d trc y. Xc nhkhang tin cy xc sut tin cy 95%.

Bi tp

ln phn tch nh trong v d trc y. Xc nhkhang tin cy xc sut tin cy 95%.

Nh vy chng ta c th ni, xc sut tin cy 95%,

%465,072,644

2927,018,372,64%)95( ==CI

Nh vy chng ta c th ni, xc sut tin cy 95%,gi tr trung bnh tht s ca m hamburger s nmtrong khong 65.72% 0.465% hoc vo gia 65.185v 64.255%.

Mt phng php khc nh gi nhanh chnhxc l s dng lch tng i RD (Relative

lch tng i

Deviation ) khi ch phn tch 2 ln v lch trungbnh tng i RAD (Relative Average Deviation)vi s ln phn tch >2.

100=x

xxRD i

lch tng i

lch trung bnh tng i RAD (Relative Average Deviation)

xx

lch trung bnh tng i

Deviation)

S dng cc gi tr phn tch hm lng m hamburger, hy xc nh RAD.

1000

x

n

xxRAD i

=

hamburger, hy xc nh RAD.

/ 3,471000

64,724

0,060,380,270,19RAD OO=+++

=

Khi gi tr tht ca mu phn tch khng c bitn th chng ta ch c th tnh c chnh xc.

Sai s

chnh xc cng thp th cng kh xc nh gi trtht ca mu

Tuy nhin i khi chng ta c mu vi gi tr thtc xc nh trc v nh th chng ta c th sosnh vi kt qu phn tch. Trong trng hp ny,chng ta c th tnh sai s ca php o bng cch sochng ta c th tnh sai s ca php o bng cch sosnh vi gi tr tht v t thy c ng caphp o.

Sai s tuyt i (Eabs, absolute error): l hiu gia gitr quan st v gi tr thc (th hin sai s vi cng

Sai s

tr quan st v gi tr thc (th hin sai s vi cngn v o ca gi tr).

V d ng knh ca vin ko l 10.5 0.2 mm,trong 0.2 mm l sai s tuyt i.

= xEabs

trong 0.2 mm l sai s tuyt i. Sai s tuyt i khng phi l mt php kim tra tiu v gi tr khng th hin c tm quan trng cagi tr tht

Sai s tng i (Erel, relative error) th hin sai stuyt i dng phn s hoc phn trm.

Sai s

==

xEE absrel

%100%100% ==

xEE absrel

V d v vin ko: 0.2mm/10.5mm = 0.02= 2%. Nh vy knh ca vin ko l 10.5mm 2%, trong

2% l sai s tng i.

S dng s liu hm lng m ca hamburger, gi sl gi tr thc ca mu l 65,05%. Xc nh E

V d

l gi tr thc ca mu l 65,05%. Xc nh Erel

%507,0%10005,65

05,6572,64

%100%

=

=

=abs

relEE

Nh vy sai s tng i c gi tr m cho thy ktqu phn tch thp hn 0,507% so vi gi tr tht.

Sai s lun tn ti song song vi php o. C nhiu loi sai s:

Cc ngun sai s

Sai s ngu nhin (khng bit c nguyn nhn) Sai s h thng (do sai lch ca dng c phn tch, ha

cht, k thut) Sai s th

Sai s ngu nhin s khin cho kt quphn tch ca cc ln lp li khc nhaud kt qu trung bnh c th gn ging

Sai s ngu nhin

Nh vy kt qu phn tch vi loi sai s ny s kmchnh xc nhng thng vn ng.

V d nh c sai gi tr cn phn tch, phn on saiim kt thc trong chun acid, s dng pipette

d kt qu trung bnh c th gn ginggi tr thc.

im kt thc trong chun acid, s dng pipettekhng ng cch, ng nn ca thit b b nhiu.

Cc sai s ny c th l sai s dng hoc sai s m.Tuy sai s ny khng th trnh khi, nhng phn lnl sai s nh.

Sai s h thng

Sai s h thng s dn n mt kt qulun khc bit vi gi tr tht mtkhong c nh.

Rt kh v mt nhiu thi gian xc nh cnguyn nhn ca sai s ny bi v lin quan n kmchnh xc ca thit b phn tch hoc dng c o lng.

V d nh pipette xc nh mt th tch sai c nh scho ra kt qu phn tch chnh xc nhng khng ng.

khong c nh.

cho ra kt qu phn tch chnh xc nhng khng ng.Cc trng hp khc bao gm ha cht khng tinhkhit hoc do chnh phng php phn tch gy ra.

Thng thng chng ta khc phc sai s h thng bngcch cn chnh thit b, dng c.

Sai s th rt d b loi b v chng tac th nhn ra c. Kt qu phn tchvi sai s ny thng l b phn tn v

Sai s th

V d nh s dng sai ha cht, sai dng c hoc lng tc k thut phn tch cu th.

vi sai s ny thng l b phn tn vkhng gn vi gi tr chng ta trngi.

Sai s th d b pht hin v khc phc.

Tnh chuyn bit ca mt php phn tch c th cngha l c th cho php ch xc nh cht/nhm hp

Tnh chuyn bit ca php phn tch

ngha l c th cho php ch xc nh cht/nhm hpcht mong mun m thi.

Ty vo mc ch v loi hp cht cn phng tchm chng ta chn mt phng php phn tch tngqut hay chuyn bit.

V d: Phn tch lipit tng vs Phn tch ng lactose trong

kem.

nhy lin quan n mc thay i ca thit bo khi hm lng mt thnh phn no thay i.

nhy v gii hn pht hin tn hiu

o khi hm lng mt thnh phn no thay i. Trong bt k phng php phn tch no th cng c

mt gii hn m ti chng ta khng chc chnrng c tn ti mt cht hay khng.

Gii hn pht hin tn hiu (gii hn phn tch) lmc nng thp nht c th ph hin ra hp chtmc nng thp nht c th ph hin ra hp chtvi mt tin cy thng k cho trc.

Cc thit b phn tch c th gy ra nhng tn hiunhiu khng mong mun. Nguyn nhn l do s


chuyn ng nhit ca dng electron, do cc yu tmi trng tc ng ln.

phn tch c mu th hm lng cht phn tchphi ln to thu nhn c tn hiu cao hn tnhiu nhiu ca thit b (thng th tn hiu phn tchphi cao hn 3 ln tn hiu nhiu).phi cao hn 3 ln tn hiu nhiu).

Cng thc tng qut st nh gii hn phn tchX = X + 3 x SD


XLD = Xmu trng + 3 x SDmu trngTrong :

XLD l nng thp nht c th phn tch c Xmu trng l tn hiu ca mu trng SDmu trng l lch chun tn hiu ca mu trng.

Nh vy trong cng thc trn, bin ng ca mu Nh vy trong cng thc trn, bin ng ca mutrng (hoc ni rng hn l tn hiu nhiu) s xcnh nng gii hn phn tch.

Phn ln cc lnh vc khoa hc s dng quy trnh v th m t v nh gi mi lin h gia cc

ng chun: phn tch hi quy

th m t v nh gi mi lin h gia ccthng s.

Trong lnh vc phn tch, chng ta phn ln ch quantm n: ng chun Phn tch hi quy tuyn tnh Phn tch hi quy tuyn tnh

ng chun c s dng xc nh nng ca ca mt cht.

ng chun

ca ca mt cht. Thng thng ngi ta s dng mt lot cc nng

chun xc nh trc, sau s phn tch cc thngs tng ng vi tng nng (v d nh hp th, dn in v.v).

Kt qu l chng ta c th x-y (thng l ngthng) m t mi lin h gia nng v thng s o.thng) m t mi lin h gia nng v thng s o.T ta c th o v xc nh c nng cn tmbng php ni suy t ng chun.

Thng thng nng c th hin trn trc x. Gitr trn trc ny c gi l bin s c lp v c

ng chun

gi nh l khng c sai s. D liu trc y (bin s ph thuc) c th c sai s. Gi nh ny trn thc t khng hon ton ng, v

cng c sai s trong nng chun. Vi nhng thit b hin i ngy nay nhng sai s Vi nhng thit b hin i ngy nay nhng sai s

ny l rt nh.

V d v ng chun

Xc nh nng caffeine trong thc phm. ycaffeine c phn tch bng HPLC s dng UVdetector bc sng 272 nm (phng php phn tch

V d v ng chun

detector bc sng 272 nm (phng php phn tchny s c cp chi tit phn phn tch quanghc).

Phn din tch ca peak ti 272 nm s t l thun vinng ca caffeine.

Trn thc t ng chun khng bao gi hon tonthng v i qua gc ta .

Trn thc t ng chun khng bao gi hon tonthng v i qua gc ta .

V d nh hm lng caffeine ca mu vi din tch4000 s c xc nh c gi tr vo khong 42-43ppm.

Chng ta c th s hi quy tuyn tnh tm ngchun.

Phng trnh ng thng s c dng y = ax + b.

Phn tch hi quy

Phng trnh ng thng s c dng y = ax + b. tm h s gc a v giao tuyn b chng ta c th s

dng cc phng trnh hi quy sau.

( )( )( )

= 2xx

yyxxa ii xayb =

Ngy nay chng ta c th d dng s dng cc phnmm vi tnh xc nh cc h s trn.

( ) xxi

S dng s liu trong v d trn=> a = 90,073 v b = 84,661.

V d phn tch hi quy

Vi din tch peak ca nng cha bit l 4000,

caffeine ppm 43,46890,073

84,6614000a

byx =

=

=

Trong phn ln cc trng hp nh th ny, s dngphng trnh y = ax (i qua gc ta ) cng s chomt kt qu gn tng t.

H s tng quan (r hoc R) cho thy mc cc sliu x-y tng quan vi nhau.

H s tng quan

( )( ) i vi ng chun, trng hp l tng l tt c

cc s liu s nm trn ng thng. Trn thc t iu ny s khng bao gi xy ra v lun

( )( )( ) ( )

=2

i

2

i

ii

yyxx

yyxxr

Trn thc t iu ny s khng bao gi xy ra v luntn ti cc sai s t hp cht chun cho n php o.

Trong v d ng chun caffeine, ta c r=0.99943(thng th ngi ta ly t nht 4 s l).

Minh ha v H s tng quan

Thng thng r nn 0,997. Trong phn tch ngi ta thng dng H s xc nh

H s quyt nh

Trong phn tch ngi ta thng dng H s xc nh(r2) v n gip ta nhn thc tt hn v ng thng drng n khng trc tip lin quan n tng quan.

V d nh trng hp caffeine trn th r2=0.99886.C ngha l ch c 0,114% (1.0000 - 0.99886=0.00114 x 100%=0.114%) khng bin i theo s=0.00114 x 100%=0.114%) khng bin i theo sthay i gia x v y theo mi quan h ng thng.

Sai s trong x dng ng hi quy

Bn cnh vn c nhiu trng hp ng khngtuyn tnh:

Cc trng hp khc

tuyn tnh: c t Chu k pht trin v suy gim ca vi sinh vt

Tuy nhin ngy nay vi cc phn mm chuyn dngchng ta d dng xc nh v phn tch cc d liuphn tch bt k dng no.phn tch bt k dng no.

S dng s cc ch s c ngha th hin nhyv tin cy ca phng php phn tch.

iu kin c ngha ca cc ch s

v tin cy ca phng php phn tch. Ch s cui cng l cha s cn nghi ng, cc ch s

cn li l chc chn. V d nh 64,72 bao gm 4 ch s c ngha, trong c ba ch s chc chn (6, 4 v 7) v ch s 2l khng chc chn m cng c th l 1 hoc 3.l khng chc chn m cng c th l 1 hoc 3.

Theo quy c, cc ch s c tnh l ch s cngha khng ph thuc vo v tr thp phn, ngoi tr

Mt s quy c

ngha khng ph thuc vo v tr thp phn, ngoi trcha s 0. V d 64,72; 6,472; 0,6472 v 647,2 u bao gm 4 ch s

c ngha Ch s 0 ng trc du phy thp phn m trc n

khng cn ch s no khc th khng c ngha.khng cn ch s no khc th khng c ngha. V d 0,6472 ch c 4 ch s c ngha. V d 20,6472 ch c 6 ch s c ngha.

Ch s 0 sau du phy thp phn khng c nghakhi khng c ch s khc ng trc du phy. V d: 0,0072 c 2 ch s c ngha

Mt s quy c

V d: 0,0072 c 2 ch s c ngha 1,0072 c 5 ch s c ngha.

Cc trng hp khc, ch s 0 sau du phy thpphn th lun c ngha. V d 64,720 v 64,700 u c 5 cha s c ngha.

Nhng ch s 0 ng cui th khng c ngha tr Nhng ch s 0 ng cui th khng c ngha trphi c thm vo du phy v mt ch s 0 khc. V d 7000 th ch c 1 ch s c ngha, trong khi 7000,0

th c 5 ch s c ngha.

Trong php nhn v php chia: s ch s c nghaca kt qu c lm trn theo s ch s c ngha

Mt s quy c

thp nht. V d: 36,54 x 238 x 1,1 = 9566.172

= 9600 (v 1.1 ch c 2 ch s c ngha) Trong php cng v php tr: s ch s c ngha ch

tnh t sau du phy thp phn V d: 7,45 + 8,725=16,175

=16,18 (v 7,45 c 2 ch s c ngha pha sau duphy thp phn)

43,5ppm caffeine c pha long 50 ln bng ngong th tch

Cn trng khi s dng nguyn tc lm trn

= 43,5g/ml x 50 = 2175g/ml= 2000 g/ml (v 50 ch c 1 ch s c ngha)

Lu sai s ca ng ong th tch ( 0,05ml)= 43,5g/ml x 50,0 = 2175g/ml= 2180g/ml (50,0 c 3 ch s c ngha)= 2180g/ml (50,0 c 3 ch s c ngha)

i khi chng ta phi kim tra cc s liu nghi nghoc sai s th nhm lm tng chnh xc khi thycc s liu ny qu cch bit vi cc s liu khctrong cng iu kin o.

Lai tr cc s liu

trong cng iu kin o.

Trong : X1 l s liu nghi ng X2 l s liu gn vi X1 nht W l khong dao ng ca d liu (X X )

WXXQ 21 =

W l khong dao ng ca d liu (Xmax Xmin) Kt qu cho thy Qtnh > Qbng th ta loi b X1 Gi tr Qbng ph thuc vo xc sut tin cy (thng

chn 95%) v s lng mu.

Cc gi tr tiu chun ca chun Q

(Ngun: Analytical Chemistry, Vol. 63, No. 2, January 15, 1991)

V d nh trong o hm lng m ca hamburger vi4 s liu thu c l 64,53; 64,45; 64,78 v 55,31.

Ga tr 55,31 l ng nghi ng v ta c th tnh Q cho

V d v Lai tr cc s liu

Ga tr 55,31 l ng nghi ng v ta c th tnh Q chogi tr ny.

Tra bng xc sut tin cy 95% vi s mu n=4 ta c

0,9755,3164,7855,3164,45Q =

=

Tra bng xc sut tin cy 95% vi s mu n=4 ta cQbng = 0,829.

Kt qu cho thy Qtnh > Qbng nn ta c th loi bgi tr 55,31%.

Kin thc ton hc c bn p dng trong nh gi ktqu phn tch th nghim: gi tr trung bnh, lchchun, h s dao ng khi nh gi cc mu c

Tng kt ni dung cn nm

chun, h s dao ng khi nh gi cc mu cphn tch lp li.

nh gi ng chun : hi quy tuyn tnh, h stng quan

Cc hng dn trnh by cc s liu nhm th hintnh chuyn bit v tinh cy ca php phn tch:tnh chuyn bit v tinh cy ca php phn tch:ch s c ngha, lm trn s v s dng php th Q loi b s liu th sai lch.

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