HA PHN TCH THC PHMTh.S. 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 DY
1. I CNG HA PHN TCH P DNG CHO PHN TCH THC PHM 2. CHUN AXT - BA Z
3. CHUN KT TA 4. CHUN OXY HA KH 5. CHUN PHC CHT 6. PHNG PHP O MAU
7. PHNG PHP PHN TCH QUANG PHO - K thut my hp thu nguyn t AAS - K
thut my quang ph pht x Plasma - ICP 8. L THUYT K THUT SC K - K THUT
SC K KH - GC - K THUT SC K LNG CAO P HPLC
PHAN 1
I/ I CNG HA PHN TCH
1/ NH NGHA TH NO L HA PHN TCH 2/ NH NGHA TH NO L HA PHN TCH THC
PHM
3/ PHAN TCH NH TNH4/ 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/
CCH 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 chuyn 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 ang nghin 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
2. TH NO L PHN TCH HA THC PHMThc 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.
Phn tch ha hc thc phm ( Analytical chemistry of Food) : nhm xc nh
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 gi 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 LNG
3. PHAN TCH NH TNH
3.1.Phan tch nh tnh : Nhm xc nh s hin din ca cc cu t ( ion,
nguyn t hay nhm nguyn t ) trong mu phn tch ( thc phm, mu nc , t ) v
ng thi nh gi s b hm lng ca chng :a lng, vi lng, vt nh vo cc thit b
phn tch v cc phn ng ho hc c trng ln mu, kt ta i vi nguyn t cn xc nh
3.2. PHAN TCH NH LNG
Xc nh chnh xc hm lng ca nhng cu t trong mu. c th hin bng nhng gi
tr sau: %, mg/kg,mg/L (ppm), g/kg, g/L (ppb), ng/kg, ng/L (
ppt)
cc phng php phn tch thch hp v x l s liu phn tch4. Chn
Khi chn phng php s dng cho phn tch thc phm ph thuc vo cc yu cu
sau : S lng, ch tiu yu cu phn tch thit b hin c ti phng th nghim t c
nhng cn nhc khi s dng quy trnh phn tch. - Quy trnh phn tch phi tho
mn cc iu kin sau:
- chnh xc, ng , lp li tt - Quy trnh phn tch c tnh chn lc cao ph
hp vi yu cu cn phn tch - Thi gian phn tch nhanh v c kh nng phn tch
ng thi nhiu nguyn t - Thit b s dng cho phn tch c nhy cao, cc tiu
pht hin nh - Gi thnh phn tch khng cao - Thit b d s dng, d bo tr
- u tin s dng cc phng php phn tch c cng nhn bi cc t chc quc t
sau: ISO : International Organisation for standardusation) AOAC :
Association of Oficial Analytical Chemists , published in the AOAC
book BSI : British Standards Institution TCVN : Tiu chun Vit Nam
FAO : Food and Agriculture OrganisationT chc lng thc-nng nghip ca
Lin Hip Quc
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, vitamin, khng sinh trong nc, at, thuy
san, thc pham
5. NH GI PHNG PHP PHN TCH- chnh xc Precision Biu th qua cc kt qu
phn tch do 01 ngi thc hin hoc do mt s ngi khc thc hin trong cng mt
phng th nghim v s dng cng mt phng php phn tch trn cng mt thit b phn
tch. - lp li Reproducibility Biu th qua cc kt qu phn tch ging nhau
trn mt mu c chia ra lm nhiu ln phn tch do 01 ngi thc hin cng mt quy
trnh phn tch v trn cng mt thit b phn tch. Mt mu lm nhiu ln c lap
nhau khc vi mt mu o nhiu ln.
- 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). lech chuan bang phng phap
thong ke, tnh c nguon sai so ngau nhien va sai so he thong
o khong am bao cua phep o la phai tnh c o
Sai s ngu nhin (sai s khng xc nh) Sai s gy n lp li ca kt qu, sai
s ngu nhin lun c trong qu trnh thc hin phn tch nh cn, o my gim sai
s ngu nhin bng cch tng s ln phn tch ( n= 5, 7,8..)
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 ..., hoc phng php s dng c khuyt im nh cch c, chuyn
i mu khng r Sai s h thng gy nh hng n ng ca php phn tch. Gim thiu
sai s nay bng cch hiu chun thng xuyn cc thit b s dng
Sai so he thong ( sai s xc nh)
PHNG PHAP TNH X LY THONG KE 1/ Tnh gia tr trung bnh cua cac phep
o Xtb = xi
n2/ o lech chuan = ( Xi Xtb )2
n-1 3/ Tnh o bien ong cua ham lng ( RSD) RSD = x100 Xtb Khoan
tin cay (CI) - Confidence interval CI = Xtb tp x
H s bin thin hay ch s phn tn= . 100 Xtb RSD 10% cc Xi t phn tn -
tt RSD
10% < RSD < 20% cc Xi c th s dng c RSD > 20% cc Xi qu
phn tn khng nn s dng
Trnh by kt qu KQ =
HLtb tp .
n
CHAP NHAN KET QUA
1/ 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 %
- Cc tiu pht hin ca u d thit b: LOD limit of detection LOD l hm
lng ti thiu c pht hin bi thit b s dng phn tch. LOD khng ging nhau i
vi tng cht v thit b phn tch. Nguyn tc: LOD ca mi loi u d c xc nh
bng cch so snh trn cng mt thang o- chiu cao tn hiu - S (signal) ca
cht cn phn tch vi chiu cao ca ng nn (n) noise
Thc hin mu trng o chiu cao ca ng nn (n) - Thc hin o mu c nng thp
nht (Cmin ) o chiu cao ca tn hiu (S) sao cho 10 > T = S 3 n
LOD = 3Cmin LOD = Cmin TLOD c th biu din theo nng hoc theo trng
lng
LOQ : Gii hn nh lng ( limit of Quantitation) LOQ l gii hn ti
thiu nh lng ca phng php phn tch. Nguyn tc: LOQ ca mi phng php v mi
cht cn xc nh l khc nhau. Cch tnh LOQ : - Cho vo mu c trng lng hoc
th tch m0 xc nh, cu t cn phn tch bit trc Cmin LOQ = 3Cmim . F T F :
h s pha long hoc lm giu mu
- mu khng lm giu Vi = Uo LOQ = LOD - mu c lm giu ( ui bt dung
mi, hoc c cn bt) Vi
