602 phan tich moi truong

8/14/2019 602 Phan Tich Moi Truong

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PHN TCH MI TRNG

B mn: K thut mi trngKhoa Qun l cng nghip v Mi trng

Tc Gi: Hong Vn Hngi Hc Nng Nghip HN


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Mc ch mn hc

Cung cp kin thc v:

- Ch th mi trng- Tiu chun nh gi cht lng mi trng- Phng php x l v phn tch cc thng s

cht lng mi trng.- m bo cht lng v kim sot cht lng

trong phn tch mi trng.


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Ti liu tham kho. Hunh Trung Hi - Bi ging Phn tch mi trng -

Vin Khoa hc cng ngh Mi trng Bch khoa. Vin th nhng nng ho. S tay phn tch t, n

c, phn bn v cy trng. Nh xut bn nng nghip,

1998.

Trn T Hiu - Gio trnh Ha phn tch - Trng ihc khoa hc tng hp H Ni - 1992.

Cc TCVN v mi trng.

APHA. Standard Methods for the Examination of Water and

Wastewater. 19th Edition, 1995. Hong Minh Chu, T Vn Mc, T Vng Nghi. C s Ha hc

Phn tch. Nh xut bn Khoa hc v K thut, H Ni, 2002.Trang web: http://www.nea.gov.vn


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Chng I: Ch th mi trng v tiuchun nh gi cht lng mi trng

I.1. Khi nim v ch th mi trng

I.2. Tiu chun cht lng mi trng


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I.1. Khi nim v ch th mi trng

* Ch th (indicator) l g ?

Khi bn b m v b st, s tng thn nhit ca bnchnh l mt ch th.

Mt ch th mi trng cng tng t nh mt thc onhit mi trng.

Nng xy thp ca mt con sng l ch th cho thy mt

lng ln cht hu c c thi vo con sng .

Vy, vic truyn t thng tin chnh l chc nng chnh cacc ch th.


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Ch th mi trng l c s lng ha cht lng mitrng, theo di din bin cht lng mi trng, lp bo co

hin trng mi trng. B Ti nguyn v Mi trng ban hnhb ch th mi trng quc gia p dng trong c nc.

- Theo UNEP: Ch th mi trng (CTMT,Environmental Indicator) l mt o tp hp

mt s s liu v mi trng thnh mt thng tintng hp (Aggregate) v mt kha cnh mi trng ca mt quc gia hoc mt a phng.

-Theo Lut Bo v Mi trng s 52/2005/QH11 ngy 29 thng

11 nm 2005: Ch th mi trng l mt hoc tp

hp thng s v mi trng ch ra c trngca mi trng.

* Khi nim v ch th mi trng

Nhiu ch th mi trng hp li thnh mt b

CTMT ca mt nc, hoc mt vng, mt a ph


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Ch th p lc mi trng: din tch rng b mt trong

nm (ha, % tng din tch ca nm trc) Ch th trng thi mi trng: tng din tch rng

hin c (ha, % tng din tch lnh th)

Ch th p ng ca x hi: Din tch rng trng/nm(ha)

Th d v mt s ch th mi trng lin quan n suy

thoi ti nguyn rng:


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* Chc nng:o Cung cp thng tin cho cc chnh tr gia, cc nh hoch nh

chnh sch: Vn ang tin trin th no?

Cc tin t c so vi mc tiu ra?

Quy hoch v d bo ni chung mi lin h gia pht trin

kinh t v qun l mi trng.

o Hoch nh chnh sch:

t ra cc mc tiu, ch tiu

Theo di vic thc hin chnh sch

Hoch nh, thc thi, nh gi hiu qu ca chnh sch

o Cung cp thng tin cho cng ng

Chuyn ti thng tin, tuyn truyn, nng cao nhn thc v

thay i hnh vi ca cng ng.


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* Qu trnh xy dng ch th mi trng v cc tiu ch

la chn ch th mi trng:

Qu trnh xy dng ch th mi trng:

Theo GS.L Thc Cn: Trong qu trnh xc nh cc

ch th ph hp v kh thi, ly nhu cu ca ngi sdng vi cng v l nh qun l mi trng lmxut pht im, c th cch tip cn di y s gipch:


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Trong lnh vc mi trng ang cp ti, xc nh ccvn v/hoc cc c tnh quan trng nht.

Xc nh mc ch thng tin u tin cn c t ch th.

Xc nh nhng ch th mang tnh chin lc nht (vimt s lng t nht cc ch th c th phc v nhiu nhtcc mc ch thng tin) t c cc mc ch thng tintrn.

Kim tra li tnh sn c ca cc d liu hin ti v xemxt cc kha cnh lin quan n cht lng ch th.

Nu cn, kim tra cc kh nng ci thin tnh sn c ca

d liu: cc kh nng trc mt cng nh trong thi gianngn hn.

La chn cc ch th.


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+ M hnh ng lc - p lc - Hin trng - Tc ng - png (Dynamic - Pressures - State - Impacts Response: m hnhDPSIR) trong xy dng ch th mi trng.

M hnh DPSIR m t mi quan h tng h gia:

- ng lc trc tip hoc gin tip (D - Driving forces ): V d: sgia tng dn s, s pht trin nng nghip, cng nghip, giao thng vnti...

- p lc do con ngi gy ra (P- Pressures): V d: S x thi cc

cht thi gy nhim. Cc ngnh/ tc nhn/ quy trnh ang ngvai tr nh th no?

-Hin trng mi trng (S -State of the Environment ): tnhtrng l, ha, sinh ca mi trng.. Vn ang din bin nh th

no?-Tc ng (I- Impacts) ca s thay i hin trng mi trng: V d:tc ng ln h sinh thi, sc khe con ngi, kinh t, s pht trin...Cc tc ng ang din bin nh th no?

- Phn hi (R- Response) t x hi vi nhng tc ng khng mongmun: V d : Cc ho t n ca x h i nhm bo v mi trn ... tnh


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S m hnh DPSIR:

- Nngnghip

- Cngnghip

- Nng

lng

- H gianh

.

Sn xutv c cusn xut

S dngcng ngh

Tiu dng

Cht thi

S dngti nguynthin nhin

Hin trngsinh hc

- a dngsinh hc

Trng thi tnhin- Thy vn- a hnh- Ti nguyn

Trng thiha hc- Cht lngkhng kh- Cht lngnc- Cht lngt

Chc nngca h sinhthi- Nc bin- Nc tronglc a- Rng

D

Kinh t

Tc ng nmi trng- Cc ch thp ng- Tc ngn cc vn khc

Tc ng nnn kinh t- Chi ph chonhng binphp khcphc- Hu qu vkinh t

Cc cngc kinh t

v m

Chnh schcho tnglnh vc cth

Chnh schv mitrng

Xc nhmc tiu

u tin

chnh sch v k hoch hnh ng

P

Thin nhin v mi trng

S I

R


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Cc tiu ch la chn ch th mi trng: (lin quann vic xem xt mc ch v cht lng ca ch th)

Ph hp v chnh sch: c kim nghim thng qua vic xem xttham kho cc vn bn chnh sch, cc k hoch, lut nh

Tnh sn c ca d liu: vic thu thp cc d liu phc v cho chth cn mang tnh kh thi c v mt chuyn mn cng nh ti chnh.

C th so snh: v d nh so snh gia cc tnh (nh gi bngchm im).

c ti liu ha y v qun l c cht lng: tiu ch nyc nh gi thng qua cng tc ti liu ha i vi ch th cng nhmc cp nht cc ti liu ny.

C c s v mt khi nim cng nh phng php lun. iu nyphi c th hin trong cc m t v phng php lun v cngthc s dng, cc tham kho khoa hc cho phng php lun vcng thc , cc m t ny cn phi a vo phn ti liu ha ca

ch th.


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n gin v d hiu nh c mt nh ngha r rng vthng nht v ch th, trnh by ch th mt cch hp l,

lun lun c s i chiu gia cc ch th vi nhau.

Cho thy tin t c so vi mc tiu ra: ckim nghim thng qua cc thng tin trong cc vn bnchnh sch. Trong trng hp thiu cc mc tiu, c th

s dng mc ngng.

Mc bao ph v khng gian v thi gian: nht qunv khng gian v c tnh n cc tnh ph hp i vi

mt vn mi trng nht nh. Ch th bao ph mtkhong thi gian c th cho thy xu hng theothi gian.

Ph hp vi cp tnh v mang tnh i din cho cc

tnh nhm h tr vic so snh.


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Ch th mi trng khng kh:

Tc ngNng nghip lin kvng nhim

Din bin cc h sinhthi trong th

Ri ro v phi nhim nhim khng kh i visc kho cng ng

ng lcPht trin dn sDin bin GDP hng

nmCc lnh vc c linquan

- Giao thng- Cng nghip- Xy dng- Sinh hot th- Nng lng

p lcNgun thi cc cht nhim: NO2, SO2, bi

(TSP, PM10), CO,VOC

Hin trng mi trngNng cc cht nhim

(NO2, SO2, bi (TSP,PM10), CO, O3,nmVOC) trong mitrng khng kh thS ngy c nng vtqu tr s cho php th i vi NO2, SO2, bi(TSP, PM

10

), CO

p ng:- Hiu sut nng lng: nng lng tiu th so vi pht trin kinh t- Cc chnh sch mi trng t c mc tiu ca quc gia v mi trng (VD: tiu chun, tiu ch nhmiu tit p lc)- Cc chnh sch i vi ngnh (cc gii hn v kim sot s tng trng ca ngnh nhm lm gim hocthay i cc hot ng hay cc p lc m cc hot ng ny gy ra)- S dng nhin liu sch hn- Ngun nng lng sch hn- u t cho BVMT- Din tch cy xanh th- Nhn thc mi trng- Chnh sch xa i, gim ngho c th


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Ch th mi trng nc:

ng lcS gia tng dn s nichung.

Cc lnh vc c lin quan- Nng nghip-Ng nghip-Thy in-Nc sinh hot-Cng nghip-Dch v-Xy dng-H gia nh-Khai thc m-Lm nghip-Giao thng ng thy-nh bt thy sn ncngt

p lcS dng nc cho nngnghip, tiu dng v

cng nghip-Thi cc cht nhimvo sng h-Xy dng p, cng...-Xi mn-Khai thc cc ngunthy sn

Tc ng:Tnh a dng sinh hcH sinh thi: t ngp

nc, rng ngp mn

Ti nguyn thin nhin:thy sn nc ngt, tnng nghip b nhimv mn ha

Con ngi: nhimnc ung, bnh tt do nhim nc, gim thunhp/dinh dng tnh bt thy sn ncngt v hot ng nngnghip, ti nh c, l lt,kh hn.

Hin trng mi trng- Tr lng nc v dngchy-Ngp ng, l lt-Lu chuyn trm tch, lngng bn-Hnh thi sng ngi-Cht lng nc-Cc cht gy bnh-Ph dng, bng pht to-Tnh a dng v hin trng

thm thc vt, ng vt v sinhvt ph du, c.-Xm thc mn nc sng vnc ngm

p ng- Hnh ng gim thiu- Cc chnh sch mi trng t c mc tiu ca quc gia v mi trng (VD: cc tiu chun, cc tiu ch nhmiu tit p lc)-Cc chnh sch i vi ngnh (cc gii hn v kim sot s tng trng ca ngnh nhm lm gim hoc thay i cchot ng hay cc p lc m cc hot ng ny gy ra)- Nhn thc mi trng- Chnh sch xa i, gim ngho c th

- Qun l tng hp cc thy vc


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Ch th mi trng t:

nhim mi trng t c xem l tt c cc hintng lm nhim bn mi trng t bi cc cht nhim: do cc cht thi sinh hot, do cht thi cngnghip, hot ng nng nghip.

Phn loi nhim t theo cc tc nhn gy nhim:

nhim t do tc nhn ha hc: Bao gm phn bnN, P (d lng phn bn trong t), thuc tr su (clohu c, DDT, linan, P hu c), cht thi cng nghipv sinh hot (kim loi nng, kim, axit)

nhim t do tc nhn sinh hc: Trc khun l,thng hn, cc loi k sinh trng (giun, sn,)

nhim t do tc nhn vt l: Nhit (nh hngn tc phn hy cht thi ca sinh vt), cht

phng x (Uran, Thori)


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Tiu chun cht lng mi trng: l gii hn cho php ti a

v liu lng hoc nng ca cc tc nhn gy nhim cho

tng khu vc c th hoc cho tng thnh phn mi trng.

Tiu chun mi trng xung quanhTiu chun thi

Thng s cht lng mi trng: l nhng thng s th

hin nhng c tnh c bn ca mi trng.

Thng qua vic xc nh gi tr ca cc thng s mi trng v

cn c vo tiu chun cht lng mi trng c th nh gi

cht lng mi trng v gim st tnh trng nhim mi

trng.

Mi mi trng c cc thng s cht lng mi trng c

trng ring.

I.2. Tiu chun cht lng mi trng


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V d: Tiu chun cht lng nc:

1. TCVN 5942:1995 - Tiu chun cht lng nc mt

2. TCVN 5944:1995 - Tiu chun cht lng nc ngm

3. TCVN 5945:2005 - Tiu chun nc thi cng

nghip


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- Nguyn tc: Xc nh cc thng s cht lngmi trng (kh, nc, t) m khng lm thayi thnh phn (bn cht) ca mu mi trng

tng ng.V d: - Xc nh SS, TSS: lc mu, sy mu- Xc nh ting n...

- Xc nh dn in ca nc

- Xc nh nhit ca nc, khng kh

II.1. Phng php vt l


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II.2.1. Phng php khi lng

Nguyn tc:

- Kt ta thnh phn cn xc nh di dng hp

cht t tan, khng tan.- Lm sch kt ta: lc, ra,

- Sy, nung kt ta nhit cao n khi lng

khng i.

- Cn sn phm thu c v tnh hm lng

thnh phn cn xc nh.

II.2. Phng php ha hc


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Mt s iu kin quan trng trong qu trnh phntch bng khi lng:

- S kt ta hon ton:

Chn iu kin thch hp kt ta hon toncht cn xc nh (kt ta trong iu kin ti u)

nh nhit , dung mi, kch thc ht kt ta tothnh, lng thuc kt ta, pH ca dung dch, stn ti cht in li l.

- sch ca kt ta:

Kt ta to thnh phi c tinh khit cao, do cn ch n s hp ph v cng kt ca kt ta.


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ng dng trong phn tch mi trng

- V d: phn tch SO42- trong nc

B sung dung dch BaCl2 long t t vo nc cnxc nh SO42- cho thm HCl

un n gn si

ngui khong 12h (hoc em un cch thy 2-3h)

Lc kt ta

Ra sch ion Cl-

Nung kt ta 800 - 9000C n khi lng khng i Cn kt ta

Tnh SO42- theo cng thc ha hc


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Nguyn tc:

- xc nh nng cht A, s dng dung dchcha cht B bit trc nng (dung dchchun). Cho dung dch B tc dng vi dung dch A

theo s phn ng: A + B = C + D. Khi B tcdng va ht vi A th ngng li, khng thm tipdung dch B vo dung dch A na. Da vo

V(ddA), V(ddB) v C(ddB), tnh c C(ddA).- Qu trnh ny gi l qu trnh chun .- Thi im hai cht A v B tc dng ht vi nhau gi l

im tng ng.

II.2.2. Phng php phn tch th tch


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im tng ng xc nh nh nhng tn

hiu c bit c th nhn thy c, v d sthay i mu ca loi cht c thm vo vi

mt lng rt nh gi l cht ch th, hoc s

thay i t ngt ch s my o (in th, dn,).

Cc phng php phn tch th tch: trung

ha, oxi ha - kh, kt ta, to phc.


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Nguyn tc:

- Trong qu trnh chun , [H+] (pH) ca dung dch thayi. im tng ng dung dch c pH xc nh.

Bng cch no xc nh c thi im no trongqu trnh chun pH t n gi tr ny v lc ta

kt thc chun . Mun th c th dng my o pH,

my o in th hoc dng cht ch th axit-baz (muchuyn i theo pH).

(1). Chun theo phng php trung ha (chun axit-baz):


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- Chn cht ch th axit-baz:+ Chun axit mnh bng baz mnh hoc ngc li,

pH im tng ng bng 7, bc nhy pH trongkhong 4 10; do c th dng cht ch th thngdng l Metyl da cam hoc Phenolphtalein xc nhim tng ng.

+ Chun baz yu bng axit mnh, im tngng pH nm trong min axit, bc nhy pH ngnnn cht ch th thng dng l Metyl da cam (v dchun dung dch NH

3

bng HCl).

+ Chun axit yu bng baz mnh, im tngng pH nm trong min baz, bc nhy ngn nncht ch th thng dng l Phenoltalein.


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+ Phng php ny da vo phn ng gia 2 cp oxiha kh: OX1/Kh1 v OX2/Kh2:

n2

OX1

+ n1

Kh2

n2

Kh1

+ n1

OX2

+ Trong qu trnh chun in th oxi ha kh cadung dch thay i v im tng ng in th c mt gi tr xc nh (Et).

gn im tng ng c bc nhy in th.Nu chn c cht ch th m s thay i mu can xy ra ng lc qu trnh chun to ra bcnhy in th th c th xc nh im tng

ng.

(2).Chun theo phng php oxy ha kh:

Nguyn tc:


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+ Cc phn ng oxi ha kh c dng trong

chun phi tha mn cc iu kin sau:

Phn ng xy ra nhanh

Phn ng hon ton v theo mt t lng nht nh, theo

chiu hng xc nh

Khng xy ra phn ng ph

Phi c cch hoc cht ch th thch hp xc nh c

im tng ng.


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- Nhng cht ny ni chung cng l nhng cht oxi ha kh v

ngi ta thng chn nhng cht c E0 (in th oxi ha kh tiu

chun ca cht ch th) nm trong bc nhy in th ca qu trnh

chun .

Cht ch th l cc cht hu c c tnh cht oxi ha kh, c

mu dng oxi ha v dng kh khc nhau, v thay i ph thucvo th oxi ha ca dung dch.

- Cc cht ch th c kh nng cho php nhn ra im cui ca s

chun , nhng s thay i mu khng ph thuc vo th ca

dung dch.V d: Dng dd KMnO4 chun cc cht kh nh Fe2+, H2O2..., sau

im tng ng d mt git dung dch KMnO4 th dd s nhum

mu hng.

Dung dch h tinh bt to vi I2 t do mt hp cht mu xanh...

* Cc cht ch th:


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Phn tch COD:

+ Phng php ny da vo phn ng oxi ha cht hu c bngCr2O72- trong H2SO4 m c, c mt cht xc tc Ag2SO4 (v

HgSO4 to phc vi Cl- ngn nga nh hng ca n).

Cht hu c + H+ + Cr2O72- 2Cr3+ + CO2 + H2O+ Sau chun lng Cr2O72- d bng dung dch mui Mo

(amoni sunfat: (NH4)2Fe(SO4)2.6H2O - FAS), vi cht ch th

Feroin dd chuyn t mu xanh lam sang mu nu nht.

Cr2O72- + 14H+ + 6Fe2+ 2Cr3+ + 7H2O + 6Fe3+

* ng dng trong phn tch mi trng:


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Cc phn ng kt ta phi p ng nhiu yu cu rt

cht ch nh:+ Kt ta khng tan

+ Phn ng to xy ra nhanh, khng c hin tng qubo ha

+ Xc nh c chnh xc im tng ng (khng bnh hng ca hin tng cng kt)

V nguyn tc, xc nh im tng ng ngi tacng tin hnh tng t nh hai phng php trn.

(3). Chun theo phng php kt ta:

M+ + A- MA Nguyn tc: da vo phn ng to kt ta


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+ V d: Phn tch hm lng Cl- trong nc:

Chun Cl- bng dung dch AgNO3 c th dng

K2CrO4 lm cht ch th v sau im tng ng,

Ag+ d s to kt ta gch Ag2CrO4.

Ag+ + Cl- AgCl trng2Ag+ + CrO42- Ag2CrO4 gch

C th Chun Ag+ bng dung dch CNS-, dng chtch th l Fe3+ to phc Fe(CNS)

3mu sau im

tng ng.

Ag+ + CNS- AgCNS trngFe3+ + 3CNS Fe(CNS)3

- ng dng:


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II.2.2. Phng php phn tch bng cng c

Cc cng c phn tch, gii thiu y l nhng thit b

dng tin hnh vic phn tch bng cc phng phpvt l v ha l.

B pht

tn hiu

B cm

bin tnhiu vo

B cm

bin tnhiu

B chuyn

i tn hiu

Thng thng mi b thit b nh th gm 4 phn chnh

nh s sau:


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B cm bin tn hiu vo: chuyn i cc tham s ha hc hocvt l thnh 1 dng tn hiu khc, thng l tn hiu in.

B pht tn hiu:

- Tn hiu pht sinh t chnh i tng cn phn tch

V d s pht bc x mu vng ca Na khi t nng cc mu

c cha nguyn t ny trong quang k ngn la.

- Tn hiu khng pht sinh t mu phn tch nhng khi i qua muphn tch tn hiu b bin i m s bin i c lin quan ncu to cng nh nng cc thnh phn trong mu.

B chuyn i tn hiu: chuyn cc tn hiu in c cibin thnh thng tin c th c c, ghi c t ngiphn tch c th din gii c nhng vn cn tm hiu i vi

mu phn tch.

B cm bin tn hiu: l khi thit b in t thc hin cc thao

tc nh khuych i, lc tn hiu.


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Cc phng php phn tch bng cng c:

- Phng php quang ph pht x nguyn t

- Phng php quang ph hp th nguyn t

- Phng php quang ph hp th in t

- Phng php phn tch theo ph dao ng

- Phng php in th/Phng php in cc ionchn lc

- Phng php phn tch Von Ampe

-Phng php sc k


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II.2.2.1. Phng php quang ph pht x nguyn t

Nguyn tc:

S to thnh ph pht x:

+ trng thi bnh thng, cc electron trong nguyn t chuyn ngxung quanh ht nhn trn nhng orbital vi nhng mc nng lngb nht. Trng thi ny gi l trng thi c bn.

+ Khi nguyn t c cp thm mt ngun nng lng t bn ngoi,cc e chuyn ln mc nng lng cao hn ty thuc vo nnglng hp th c. Nguyn t chuyn sang trng thi kch thch.Trng thi ny khng bn, sau mt thi gian rt ngn (10-7 10-9s)nu cc electron khng b mt nng lng do va chm hay phn ng

ha hc n s tr v trng thi nng lng thp hn (trng thi cbn hay trng thi kch thch vi mc nng lng thp). Nng lngd c gii phng di dng bc x in t (quang ph pht x:E = Ee Ef = h. v = E/h (Ee v Ef: nng lng ca trng thikch thch v nng lng mc thp hn; h: hng s Planck; : tns ca bc x (cm-1), (tc l ca vch quang ph).

T h d h ht t


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+ Khi mt e thc hin mt chuyn dch t mc nng lng cao v

mc nng lng thp hn, bc x pht ra c (hay ) xc nh.+ C rt nhiu kiu dch chuyn nh trn, do s pht x ca

mt nguyn t khi b kch thch khng phi ch to ra mt vch

(mt tia) m l mt s vch c tn s khc nhau ng vi cc E

khc nhau.+ V mi nguyn t c h thng nng lng nguyn t ring nn

ph pht x nguyn t cng c trng cho nguyn t ca

nguyn t .

+ ng dng trong php phn tch nh lng ngi ta chn lymt vch ph c trng nht tc l vch ph xut hin cui cng

khi gim dn nng cht. S thay i cng ca vch ny

s xc nh lng nguyn t cn phn tch.

Tnh a dng ca ph pht x nguyn t:

Cng ca vch quang ph:


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I: cng ca vch ph

A: hng sN0: s nguyn t ca nguyn t trng thi hi c trong 1 cm3

hi nguyn t .K: hng s Bolzman (1,38.10-23J)Ek: th kch thch

T: nhit

/KT.eA.NI kE0=

Cng ca vch quang ph:

+ I ph thuc N0 (tc cng l ph thuc nng C), th kch thch,nhit . S ph thuc I vo C c biu din bi h thcLomakin:

I = a.C.ba, b: l h s ch s ph thuc iu kin kch thch v vch

quang ph cng nh trng thi vt l ca mu nghin cu.

C : l nng ca nguyn t cn xc nh trong mu.


42/102

lgI = lga + blgC, l biu thc c s cho php phn tch quangph nh lng.

lgI

lgC

th mi quan h gia I v Cc dng ng thng

Ngi ta thy rng: Khi tng nng

nguyn t c th xy ra hin tng thp th pht x, tc l nhng nguyn tkhng b kch thch s hp th mt phnnng lng bc x. V vy bt u tmt giai hn nng no (xc nh

i vi mi nguyn t) th quan h gia Iv C s khng l tuyn tnh. Do ,phng php ny ch gn trong mtphm vi nht inh v nng vi tngnguyn t. Nn th s c dng:

lgI

lgC


43/102

l nng ca nguyn t phn tch m khi thu

c vch ph c trng cho nguyn t . S thay i cng vch ph ny s xc nhlng nguyn t cn phn tch.

Xc nh C0: Pha long dn dung dch n nng Cmin = C0 nhiu vch ph mt i do cng b, chcn 1 vch ph gi l vch cng hng.

Nu pha long tip n nng C


44/102

Ngun kch thch: Lm cho mu chuyn thnh hi, nguyn tha mu, kch thch nguyn t chuyn ln trng thi nng lngcao hn.

Ngun kch

thch

Mu H tn

sc

B thu v x l

tn hiu

Thit b quang ph pht x nguyn t:

Detector: ghi quang ph. Trong cc my quang ph ngi tathng dng Detector l t bo quang in v tt nht l dng cc

ng nhn quang (PMT: PhotoMultiplier Tube). Cc ng nhn

quang va c chc nng chuyn i t nh sng thnh dng

in, va c chc nng khuch i tn hiu (c th khuch i 1

triu ln).

H tn sc (b phn tch tia n sc): Thng dng lng knh

hoc cch t nhiu x. B phn ny c chc nng phn ly cc

chm bc x a sc thnh tia n sc.


45/102

Phn tch nh tnh: so snh ph ca mu vicc ph chun, tm cc vch ph cui cng.

Phn tch bng phng php quang ph phtx nguyn t:

Phn tch nh lng: xy dng ng chungia nng v cng vch ph, t xc nhnng ca cht cn phn tch c trong mu. C th

xc nh c hu ht cc nguyn t tr C, O, H, N.

II 2 2 2 Ph h h h th t


46/102

II.2.2.2. Phng php quang ph hp th nguyn t

Nguyn tc:

Di tc dng ca ngun nhit khng cao lm, cc cht ha hi,cc phn t b phn ly thnh nguyn t v a s cc nguyn t

trng thi khng b kch thch (trng thi c bn), ch mt phn

nh nguyn t b kch thch v chng chim khong 10-5- 10-7

phn.

Cc nguyn t ca mt nguyn t trng thi c bn c c tnh

l c kh nng hp th mt cch chn lc cc bc x do chnh

n pht ra, c bit l bc x cng hng. Bi vy nu lm cho

mt cht ha hi v chuyn thnh cc nguyn t trng thi c

bn ri cho tia cng hng ca chnh nguyn t pht ra iqua, th cc nguyn t trng thi c bn s hp th mt phn

nng lng ca bc x cng hng. Kt qu l cng ca

bc x gim i.


47/102


48/102

Phn tch nh tnh: Da trn c s l cc nguynt to ra trong b nguyn t ha mu hp th haykhng hp th tia cng hng pht ra t n cattrng lm bng mt nguyn t no nhn bit

trong mu phn tch c hay khng c nguyn t .Phn tch nh lng:

+ Da vo h thc: lg(I/Io) = A = k.b.C

hay A = lg(I/Io) = K.C+ o hp th A c th xc nh C (nng ), c th

tin hnh tnh C theo hai cch: Xy dng ngchun v phng php thm chun

Phn tch bng phng php quan ph hp thnguyn t


49/102

o Ngn la hay l graphit hay ha hi lnh.o di sng cn chn.

o Thnh phn ca mu, c khi s c mt ca mt ion cth gy kh khn cho s nguyn t ha v do nh

hng n s hp th bc x ca mt nguyn tkhc, v d ion PO4

3- nh hng n s nguyn t ha

ca Mg, Ca

o S ion ha: mt s nguyn t d b kch thch, d bion ha nh Na, K lm gim nhy. khc phc,ngi ta thng thm vo nhng cht d ion ha hnnh Li (gi l cht kh ion ha hay cht m bc x).

Ch c nhiu nh hng khc nhau nn phi tmcc iu kin ti u v:

II 2 2 3 Ph h h h th i t


50/102

II.2.2.3. Phng php quang ph hp th in t

Bc x t ngoi UV bao gm: cc tia c nm

trong vng t 100 nm n 400 nm:

100 200 nm: Vng t ngoi xa: t 100 200 nm, c

nng lng rt ln nhng t dng trong cc phngphp phn tch.

200 400 nm: Vng t ngoi gn, c nng lng thp

c s dng nhiu trong php phn tch.

Vis (Visiable - Vng nhn thy): 400 800 nm c nng

lng thp c s dng nhiu trong php phn tch.

- Gii thiu:

- Nguyn tc:


51/102

S hp th bc x t ngoi v trng thy:

+ Phn t ca cc cht c kh nng hp th mt cch chn

lc cc bc x chiu qua n. Khi hp th nng lng bc

x, trong phn t xy ra cc bc chuyn nng lng ca

in t, bc chuyn nng lng dao ng, bc chuyn

nng lng quay ca ton phn t

ph hp th rt phctp, khng c dng vch sc nhn m l nhng bng ph

tri rng.

+ s hp th in t: s hp th bc x lm bin i nng

lng ca in t.+ Trong phn t, cc e (lp ngoi) c vai tr khc nhau: tham

gia lin kt gi l in t ha tr, khng tham gia lin kt gil cc in t khng chia hay in t c thn.

- Nguyn tc:


52/102

+ Cc e ha tr c th to lin kt hoc ; cc e khng

tham gia lin kt lp v e ngoi k hiu l n. Khi e ha

tr tham gia lin kt s to thnh cc obital phn t: obitallin kt v obital phn lin kt ( v *, v *). Cc e

ny c th cc mc nng lng khc nhau ty thuc

cc obital to thnh; trong obital c nng lng

thp nht cn obital * c mc nng lng cao nht.

+ Trong iu kin thng cc phn t tn ti mc nng

lng thp (trng thi c bn), cc e mc nng lng

thp nht. Khi phn t hp th nng lng s chuyn ttrng thi c bn sang trng thi kch thch, cc e t mc

nng lng thp chuyn ln mc nng lng cao:

**


53/102

+ iu kin xy ra bc chuyn nng lng e lE = h., E l bin thin nng lng ng vi bc

chuyn, l tn s bc x in t. C th xy ra cc

bc chuyn *, - *, n - *, n - *.

+ Khi phn t hp th bc x in t gy ra cc bcchuyn nng lng in t to nn hiu ng ph hp

th.

n

h l t b h th h ( h l t


54/102

nh lut c bn ca s hp th nh sng (nh lut

Lambe Bia):

+ H thc c bn:

Io I

b

C

lg(Io/I) = A = a.b.C = K.C

C t h h i l h i i h th


55/102

+ Cc yu t nh hng n s sai lch i vi h thc

c bn: gia A v C khng cn quan h tuyn tnh.

Cc nguyn nhn chnh l:o nh sng khng n sc: nu dng nh sng c khong rng

th kt qu o s c lch m. Bi vy c kt qu o chnh

xc ngi ta phi tin hnh o vi nh sng c khong cng

hp cng tt, tt nht l n sc, v chn bc sng c hp

th ln nht (max).o nh hng ca nng cht cn xc nh: i vi mi cht gia

A v C ch c quan h tuyn tnh trong mt khong nng xc

nh.

o pH ca dung dch: pH thay i c th lm cn bng to phc thayi, do nng cc phn t hp th nh sng thay i theo.

o S c mt cc cht l: c th nh hng n s hp th nh

sng ca cc cht cn xc nh theo nhiu c ch khc nhau.


56/102

1 23 4

5

a

b

c

1. Ngun chiu sng

2. H tn sc3. Cuvt ng dung dch (mu)

4. Detect (t bo quan in, nhn quang)

5. B ghi o (a. in k, b. my t ghi hay hin s, c. my tnh)

- My trc quang UV-Vis:


57/102

Ngun chiu sng: to ph lin tc, nu o trong vng kh kin th

dng n si t W. Nu cn o trong vng t ngoi th dng n

hiro, teri hay n thy ngn. Ngun chiu sng phi c cng

n nh.

H tn sc: Dng tch tia n sc, b hp th mnh khi qua dung

dch o. Thng dng lng knh hoc tt hn l dng cch t nhiu

x.

Cuvt ng dung dch: Trong cc my hin nay thng dng cuvt

c khong gia 2 thnh trong 1cm ( di b). Nu cn o trong vng

nh sng t ngoi th phi c cuvt l bng thch anh. Detector: chuyn nh sng thnh dng in, thng dng t bo

quang in, tt nht l nhn quang in t. Cc my trc quang hin

i thng c km my tnh iu khin cc qu trnh chn iu

kin o v x l kt qu.


58/102

Xc nh nng theo phng php trc quang:

C s l h thc A = KC Phng php ng chun.

Phng php vi sai: xc nh mt cht c nng l Cx,

th ngi ta ly mt dung dch bit nng C1 m C1 C1). o A2 ca dung dch ny, ly dung dch c nng

C1 so snh. o Ax ca dung dch nng Cx vi dung

dch so snh, nng C1

A2 = abC2 abC1

Ax = abCx abC1

Cx


59/102

II 2 2 4 Phng php phn tch theo ph dao ng


60/102

II.2.2.4. Phng php phn tch theo ph dao ng

Gii thiu:

Bc x hng ngoi c s sng t 13000 n 10 cm-1hoc c trong khong 0,8 n 1000 m.

thun tin ngi ta chia vng ph rng ny thnh:

Vng hng ngoi gn (13000 4000 cm

-1

) Vng hng ngoi gia (4000 400 cm-1)

Vng hng ngoi xa (400 10 cm-1)

N t


61/102

+ Gi s c phn t AB do 2 nguyn t A v B lin kt vi nhau

to thnh. Xem 2 nguyn t A, B l 2 khi cu ni vi nhau bng

mt l xo, A c khi lng m1, B - m2. Khong cch gia 2 nhn

nguyn t A, B l r. khong cch r khng phi khng i m khi A,

B dao ng theo trc AB, khong cch ny s dao ng t gi tr

nh nht rmin n gi tr ln nht rmax quanh gi tr cn bng r0 (l

gi tr c xc sut ln nht ca r); dao ng ny gi l dao ng

lin kt hay dao ng co gin tun hon.

Dao ng ca phn t 2 nguyn t:

Nguyn tc:

A, m1 B, m2

rA Br0 r

A


62/102

+ T d l khi M h K


63/102

+ Tn s dao ng cng ln khi M cng nh v K cng

ln.

+ i vi cc lin kt bi =, hng s lc gp 2, 3 ln linkt n, do tn s dao ng gp 2, 3 ln.

v: l s lng t dao ng, v = 0, 1, 2, 3, mcnng lng dao ng thp nht: v = 0, phn t vn c

nng lng dao ng.

+i vi dao ng iu ha, nng lng dao ng ch c

th nhn mt dy gi tr gin on, theo h thc:

+=

+=

2

1vh

2

1v

M

K

2

hE s


64/102

iu kin hp th bc x hng ngoi:

c bc chuyn nng lng dao ng ch cn nng

lng tng i b, tng ng vi bc x hngngoi, do thng gi ph dao ng l ph hngngoi. Tuy nhin khng phi bt k phn t no cngc kh nng hp th tia hng ngoi cho hiu ng

ph dao ng, m cn c mt s iu kin:o Cc phn t ch hp th bc x hng ngoi chuyn sang trng thi kch thch khi s dao ng lmthay i momen lng cc. Bi vy cc phn t nhN2 (NN), O2 (O=O) khng hp th bc x hng ngoi

v chng c mmen lng cc bng 0, n khng bmmen lng cc lm thay i.

o Cc phn t hp th tia hng ngoi c tn s ng bng


65/102

Cc phn t hp th tia hng ngoi c tn s ng bngtn s dao ng ring ca n. a s cc trng hp phnt nhit thng ng vi mc v = 0. Khi hp th bc

x hng ngoi c tn s chuyn ln mc v = 1 tc lchuyn ln mc c nng lng Ev=1, hiu nng lng (hay

bin thin nng lng): Ev=1 Ev=0=hs(1+1/2)-hs/2 = hs=h. Tn s ny l tn s c bn.iu ni trn cng c ngha l cc phn t hp th tia hngngoi chuyn ln mc nng lng dao ng ng viquy tc ny ng dng cho cc dao ng iu ha. Trongthc t, dao ng ca cc phn t khng phi l dao ng

iu ha cho nn khng tun theo qui tc trn, m michuyn dch gia cc mc nng lng u c th xy ra,tc l c th v = +2, +3, ... v tn s tng ng vi ccbc chuyn xp x 2s, 3s gi l cc m biovertone .

Dao ng ca phn t nhiu nguyn t:


66/102

Dao ng ca phn t nhiu nguyn t:

Trong phn t 2 nguyn t, chuyn ng dao ng cbn duy nht l dao ng co dn mt cch tun hon

(gi l dao ng lin kt hay dao ng ha tr) lm thay

i di lin kt. i vi phn t c nhiu nguyn t,

chuyn ng dao ng rt phc tp. Trong cc phn t

ny ngoi dao ng ha tr cn c cc dao ng bin

dng lm thay i gc lin kt theo cc kiu khc nhau.

minh ha ta xt dao ng ca mt phn t ba nguyn


67/102

+

X X

A

X X

A

X X

A

X X

A

X X

A

X X

A

Dao ng lin ktkhng i xng Dao ng bin dngkiu li ko (trongmt phng)

Dao ng bin ikiu con lc (trongmt phng)

Dao ng bin dng vung gc v hai phamt phng kiu ci qut (ngoi mt phng)

Dao ng bin dng kiu xon (ngoimt phng)

Dao ng lin kti xng

+- +

minh ha ta xt dao ng ca mt phn t ba nguynt: AX2


68/102

+ Tuy nhin c th phn mt chuyn ng dao ng

phc tp thnh mt s hu hn nhng dao ng n

gin hn gi l dao ng c bn hay dao ngchun. Gi s phn t c N nguyn t, mi nguyn t

c xc nh bi 3 phng chuyn ng trong ta

cc (Descartes) tc l c 3N bc t do, trong

3 bc t do m t chuyn ng tnh tin v 3 bc t

do m t chuyn ng quay ca phn t xung quanh

trc. Nh vy ni chung phn t c N nguyn t s

c 3N-6 dao ng c bn (trong c N 1 dao ngha tr, hay dao ng co dn lin kt).

+ Trng hp N nguyn t nm trn mt ng thng


69/102

Trng hp N nguyn t nm trn mt ng thng

th ch c 2 bc t do xc nh trng thi quay ca

phn t, nn s dao ng c bn s l 3N 5. V d

phn t nc (H2O) c 3 nguyn t khng thng hngs c 3x3-6 = 3 dao ng c bn.

+ Tuy nhin trong cc phn t nhiu nguyn t skiu dao ng thc t c th tng hoc gim nhiu so

vi s dao ng c bn do nhiu l do khc nhau, v

d s xut hin cc bi m, t hp m (do cc

dao ng tng tc vi nhau) hoc khng xut hintrn ph do dao ng khng lm thay i momen

lng cc, hoc nhng dao ng c bn c cng tn

s (dao ng suy bin) ...

Ph dao ng v cu to phn t:


70/102

Ph dao ng v cu to phn t:

+ Cc kiu dao ng v tn s dao ng lin quan n

cu trc phn t.V d: T 4000 2500 cm-1: s hp th c trng cho dao

ng co dn ca nguyn t H vi cc nguyn t c khi

lng 19.

V d lin kt C H trong C C H tn s dao ng co

dn lin kt xut hin 3300 cm-1, trong hp cht vng

thm v cha no khong 3000 3100 cm-1. Vng tn s

trung gian 2500 1540 cm-1 thng l vng cha no.

V d: Lin kt c m ph hp th 2500 2000 cm-1,

Lin kt = c m ph hp th 2000 1540 cm-1.

+ T d h t t h t t h


71/102

+ Tn s dao ng ca nhm nguyn t no trong phn t t ph

thuc vo phn cn li c gi l tn s c trng cho nhm v

thng dng pht hin cc nhm chc trong phn t. Tn s c

trng ca nhm t thay i th khng c ngha l max hp th khngi m l max dao ng trong mt vng ph kh hp, v thc ra tn

s c trng cng chu nhiu nh hng khc nh thay i trng

thi (kh, lng), nh hng ca dung mi, tng tc gia cc phn

t

1300-1000C-O-2550S-H

1650C=C3300-2700C-H

1850-1650C=O3500-2900N-H2200CC3650-3250O-H

Tn s cm-1NhmTn s cm-1Nhm

Bng tn s dao ng ha tr ca mt s nhm nguyn t:

My quang ph hng ngoi :


72/102

1

2

2 3

4 5

| | | |

Truynquang

(%)

100

4000 3000 2000 1000 cm-1

0

S sng

Ch thch:

1.Ngun bc x hngngoi

2. Cuvet ng mu

2. Cuvet ng dung dchso snh

3. Quang k n sc

4. Detector

5. Cu trc ghi ph

S ph quang k hng ngoi hai tia sng:

ng dng ca phng php ph dao ng:


73/102

+ Pic 3000 cm-1: Dao ng co dn lin kt C-H trong -CH3.

+ Pic 1430, 1370 cm-1: Dao ng i xng v bt i xng ca CH3.

+ Pic 1724 cm-1: Dao ng ca CO.

+ Pic 1218 cm-1: Dao ng ca t hp nhm C-(C=O)-C

+ =

, cm-1| | | | |

1724

14301370

1218

5000 3000

Ph hngngoi ca

C3H6O

Nhn bit cc cht:

Xc nh tp cht :


74/102

Xc nh tp cht :+ Khi mt cht c ln tp cht, s xut hin thm cc

m ph s lm nhe ph. Khi tp cht hp th mnhmt bc x IR m thnh phn chnh khng hp th

th vic xc nh rt thun li, v d trong mt

hidrocacbon c ln mt lng nh xeton th tn s hp

th 1720 cm-1 chng t iu v hidrocacbon thct khng hp th vng ph ny.

Phn tch nh lng:Vic phn tch nh lng cng da vo h thc Lambert

Beer: A = lg(Io/I) = abC


75/102


76/102

II.2.2.5. Phng php in th

Nguyn tc chung:


77/102

g y g Nguyn tc ca phng php l o in th cn bng ca cc ch th

xc nh nng cn bng ca cht cn phn tch hoc theo dis bin thin nng ca n khi cht tham gia phn ng vi mt

cht khc (phng php chun in th). T nm 1966, phng php phn tch o in th c mt bc tin

ln nh s pht minh ra mt loi in cc mi gi l in cc chnlc ion (sau y s k hiu l CLI) tc l cc in cc phn hi mtcch chn lc i vi cc ion khc nhau.

Khi o in th, ta khng xc nh th cn bng tuyt i ca mtcc ring bit m ch xc nh th ca n so vi th ca mt ccdng lm chun, c th khng thay i nh cc Ag/AgCl hayHg/HgCl2, gi l in cc so snh. Cc m th ca n bin thin theonng (chnh xc l hot ca cht cn o gi l cc ch th).

Nh vy in th o c E = ct ss + jTrong :

ct: th ca in cc ch th; ss: th ca in cc so snh;

j: th khuch tn. ss v j khng i trong qu trnh o.

II.2.2.5.1. Phng php in th/cc loi in cc chn lcion


78/102

ion Gii thiu: in cc mng rn: c th l mng ng th hay d th. Cc mng rn

ng th thng c ch to t cc loi n tinh th, v d n tinhth LaF3, t mui nng chy ng rn, t bt mui nn di p sutcao. in cc mng rn d th: tinh th cc cht c kh nng dn inbng ion c phn b u vo khung to mng thch hp nhpolietilen, PVC, ...

in cc mng rn ng th tuy cho lp li v chnh xc caonhng kh ch to, in cc mng rn d th v mng mng ch tohn.

Mng ch?n l?c Ion

Dung d?ch

trong

C?c so snh trongAg/AgCl

Mng polyme

Ch?t l?ng h?u ctrao ?i ion

C?c Ag/AgCl

a b

Dung dchtrong

Cc so snh trong

Mng chn lc ion

Cht lng hu ctrao i ion

Cc Ag/AgCl

in cc chn lc mng

rn

in cc chn lc mng

lng

in cc mng lng c kh nng trao i ion: l mt mng polime


79/102

mng cha cht trao i ion.

in Cc chn lc mng lng xc nh Ca2+ dung dch trong lCaCl2 nng khng i, trong c in cc so snh trong

Ag/AgCl. Mng xp polime k nc cha ionit lng hu c ca Ca2+,mt pha tip xc vi dung dch trong, pha kia tip xc vi dungdch phn tch.

Nguyn l lm vic ca in cc mng rn: s b tr mch o

C?c so

snh trong

2

Dung d?ch

trong (2)

aj (2)

Mng ClI

M

Dung d?ch

phn tch (1)

aj (1)

C?c so

snh ngoi

1

C?c ClICc CLI

Cc so Dung dch Dung dch Cc so

Khi ni cc CLI vi cc so snh ngoi, sc in ng ca pin:

E = + ( : in th mng + = )


80/102

E = 2 + M 1 (M: in th mng, 2 + M = CLI).

Trong trng hp n gin nht, dung dch ch cha ion j v khngc ion cn tr th

aj(1), aj(2) l hot ion j trong cc dung dch tng ng; aj(2) =

constant v Z l in tch ion nn c th rt gn biu thc trn CLI = f(lnaj(1))

Nu trong dung dch c cc ion cn tr l i, hot l ai, h s chn

lc ca ion j i vi i l Kij th theo cng thc Niconsky, ta c:

Nh vy trong trng hp n gin v php o thc hin 250C ththay tt c cc s hng l hng s vo cng thc trn ta s c:

)2(j

)1(j

Ma

a

lnZF

RT=

++=

i

j

ijij

j

CLIZ

ZaKaln

FZ

RTconst

)1(ja algZ

059,0EE +=

Ea l hng s ca ring tng in cc CLI


81/102

Phn tch nh lng:

Phng php ng chun: T biu thc trn c th xc nh c a

+ Nhng gi tr cn tm l C, a= f.C. Khi xy dng ng chun ta pha ccdung dch c C bit trc nn t a suy ra C tng ng, phi gi hs f (h s hot ) khng i, m:

Ci, Zi l nng v in tch ca cc ion trong dung dch. Do , mun

gi f khng i ta phi gi khng i. Mun vy, ngi ta thm vodung dch in ly c nng tng i ln v khng i (ting Anh vit

tt l TISAB: Total Ionic Strength Adjustment Buffer: dung dch mchnh lc ion). Khi chun b cc dung dch u phi thm dung dch mny nh nhau. T ng chun E C, vi dung dch c nng Cx sau

khi o c Ex ta c th tm c Cx.

1

0,5Zlgf

2

+

= 2

iiZC2

1=v

Phng php thm chun: xc nh nng C ca


82/102

Phng php thm chun: xc nh nng Cx ca

mt ion (dung dch ta c chun b vi lc ion khngi), ly mt th tch Vo, o c E1. Sau thm mt

th tch rt nh v nng Ca bit. o li in th,

c E2. T biu thc quan h nng v in th d

dng tm c Cx.

ng dng:


83/102

Dung d?ch trong

C?c so snh trongAg/AgCl

Mng th?y tinh

Dung dchtrong

Cc so snhtrong (Ag/AgCl)

Mng thy tinh

Cu to in cc thytinh

ng dng:

o pH bng in cc thy tinh:

+ in cc thy tinh l loi in cc chn

lc ion (ion H+) ra i sm nht. Mngchn lc ion H+ l mng thy tinh c cuto theo s hnh sau. S mch ocng tng t mch o in th in ccchon lc ion, ch khc l dung dch trong lmt dung dch m c xc nh. Cng lpcc php tnh nh i vi in cc chnlc ion, cui cng ta s c:

E = const = 0,059 pH (vi pH = - lgaH+).

+ in cc thy tinh l in cc tt nht o pH trong khong pH = 2 10. T pH 11, php o khng chnh xc v nh hngca cc ion Na+, K+

II 2 2 5 2 Phng php phn tch Von Ampe (pp


84/102

II.2.2.5.2. Phng php phn tch Von Ampe (ppcc ph)

Phng php Von Ampe l tn gi chung ca nhm cc

phng php phn tch da vo vic nghin cu ng

cong phn cc biu din quan h gia in th vcng dng khi in phn dung dch nghin cu vi

cc in cc lm vic c bit: mt trong 2 in cc c dintch b mt rt nh v nh hn nhiu ln so vi din tch b mt ca

cc kia. in cc b gi l vi in cc, c th l catt hay ant.Phng php Von Ampe da trn qu trnh in phn vi in

cc git Hg thng c gi l phng php cc ph.

* Nguyn tc chung:

* S phn cc trn in cc git Hg


85/102

+ Xt trng hp ip phn vi vi

in cc l git Hg, ng vai tr

catt v ant l mt lp Hg y

bnh in phn. Sau ny ngi ta

hay dng ant l cc Calomen.

+ Gi E l in th gia 2 cc, A l

th ant, K l th catt, R l in

tr ton mch, I l cng dng,lc :E = A K + IR

+ I thng rt b (10-5 10-7A), R rt

nh nn c th b qua s hng IR.

V in cc ant c b mt rt ln,

mt dng rt nh nn hu nhkhng c phn ng in cc xy ra

ant v A c th coi nh khng

i. Do c th coi nh E = - K =

f(I).

1. Ngun in 2. Bnh in phn

3. Ant 4. Catt

5. in k 6. Bin tr

Git Hg chy ra t mao qun, ng knhtrong khong 0,03 mm, tc chy 3 4

giy/git. in phn bng dng in 1 chiu,

in th t vo 2 cc c th iu chnh nh

bin tr 6.

23

16 -+

* Sng cc ph. C DI


86/102

Ta nghin cu mt trng hp c th, v d in phn dung

dch ZnSO4 10-3M. Tng in th t t theo tc u, ghi

dng tng ng.

+ Tip tc tng in th th xy ra phn ng: Zn2+ + 2e = Zn(Hg) (hn hng Zn).

Nng ca ion kim loi lp st in cc gim, s chnh lch gia CO su trong

dung dch v CM st in cc tng, dn n s khuch tn tng v cng dng

cng tng (on BC). Nhng khi tng in th n mt gi tr no , vn tc khuch

tn bng vn tc kh, lc C0 - CM = 0 v do dng rt nh (~10-5A) nn CO thc t

khng i v th sau d tng in th th dng hu nh khng i Dng ny gi l

dng gii hn v cng ph thuc CO (on CD). ng cong ABCD gi l sng

cc ph.

A B

E1/2V

Sng cc ph.

+ Khi in th cha t n gi tr xy ra phn ng kh ion

H+, ta thy xut hin dng rt b gn nh nm ngang (on AB)

gi l dng d Ir Dng d ny gm dng t Ic v dng

Faraday If, cng khong 10-7A. Dng t sinh ra do b mt

in cc xut hin lp in kp coi nh l mt t in Dng

Faraday do s kh cc vt tp cht, oxy

Vy, dng d Ir = Ic + If.

+ Tuy nhin, thc t dng gii hn gm 2 thnh phn:


87/102

o Dng khuch tn Ikt ph thuc vo vn tc khuch tn, (chnh

lch nng ).

o Dng vn chuyn Ivc do tc dng ca in trng (in tchm ca catt ht in tch dng l ion dng).

+ Cc phng trnh tnh ton sau ny ch p dng cho trng

hp khi khng cn dng vn chuyn Ivc, tc l dng gii hn

Id ch hon ton do hin tng khuch tn (Id = Ikt)

+ loi b dng vn chuyn ngi ta thm vo dung dch

nhng cht in li tr (khng c phn ng in cc) nng

tng i ln nh KCl, Na2SO4, NH4Cl (v cc cht tophc, dung dch m ...) gi l cht nn cc ph; cc ion

K+, Na+ to thnh tng chn in trng tc dng ln

cc ion dng (ion kim loi), nu in cc git lm catt.

C


88/102

+ Nhiu khi sng cc ph b bin dng do xut hin s

tng t ngt dng khuch tn, gi l cc cc i:

cc i xut hin trong mt khong th hp (loi 1), cc

i xut hin v ko di trong mt khong th kh rng(loi 2).

Cc yu t nh hng n dng sng cc ph:

I+ Cc i loi 1: S tng t ngt cad t t kh th t h D


89/102

Ea

b

a: Cc i loi 1b: Cc i loi 2

Cc cc i trn sng cc ph

dng trong mt khong th rt hp. Do

chuyn ng b mt ca git Hg lm

tng cng dng khuch tn.

loi b cc cc i, ngi ta thm 1lng rt nh cc cht hot ng b

mt nh gelatin, aga

+ Cc i loi 2: S tng t ngt ca

dng trong mt khong th rng. Dotrong dung dch nghin cu lun lun

c oxi ho tan m O2 trong mi trng

axit cng nh mi trng kim khi b

kh to ra 2 sng.

trnh sng nhiu ca O2 cn loi b n trc khi ghi sng cc ph.

Mun vy ngi ta cho kh tr sch O2 nh N2, H2, Ar thi qua dung dch

mt thi gian. Trong mi trng kim c th thm mt t tinh th Na2SO3tinh khit vo dung dch.

Phn tch bng phng php cc ph: Ph t h h t h

I


90/102

Phn tch nh tnh: I

EE1/2

Xc nh E1/2 trn

sng cc ph

1/2

E E

I

IIdln

+ Th ng vi chiu cao sng cc

ph l mt i lng khng i,ch ph thuc bn cht cc chtnghin cu v cht nn ccph. Do c th da vo th

na sng (1/2) nhn bit cccht (trong thc t gi tr o cl E1/2 khi so snh vi th in cc

Calomen c khng i).

+ C th tm E1/2 nh hnh trnhay theo phng trnh sng ccph:

= =

I

II

nF

RTEE

d

+= ln2

1(Id: cng dnggii hn )

Phn tch nh lng:


91/102

+ Quan h gia Id v CM (nng ion kim loi) c biu din

bi phng trnh Inkovitch:

Id = 605.n.D1/2.m2/3.t1/6.CM

Trong :

o n: s e tham gia phn ng kh in cc.

o D: h s khuch tn, cm2.s-1

o m: khi lng Hg chy ra t mao qun trong 1 giy (mg.s-1)

o t: thi gian to git Hg (s), CM: nng ion kim loi (mmol/l)

+ Nu duy tr D, m, t khng i th phng trnh trn c dngthu gn: Id = K.CM

+ Da vo h thc ny c th xc nh nng CM theo ng

chun Id CM, hoc theo phng php thm chun.


92/102


93/102

- c trng ca cht tan:


94/102

+ H s phn b:

H s phn b D c xc nh bi i lc ca cht tan i vihai pha. Trong sc k D l t s nng tng ca cht tan trong

pha tnh CS v pha ng CM:D= CS/CM

D cng ln th cht phn b cng nhiu trong pha tnh v dichuyn cng chm.

+ Th tch lu v thi gian lu:o Thi gian lu tr (retention time) l thi gian t khi np cht tan

vo ct sc k n khi xut hin nng cc i detector.

o Th tch lu tng ng VR (retention volume) t l vi tR

VR = tR x Fc (trong Fc l lu tc, ml/pht)

Tc di chuyn ca mt cht c th c c trng bi h sphn b D ca n gia hai pha hoc bi cc i lng v s

lu gi ca cht trn pha tnh (thi gian lu, th tch lu)

o Gi tM l thi gian i qua ct sc k ca cht tan khng b lu, th


95/102

cng l thi gian lu ca pha ng (coi nh thi gian cht). VM gi l

th tch cht cng chnh l th tch pha ng i qua ct.

o Ngi ta cn dng mt tham s khc l t s phn b K, l t s smol cht tan trong pha tnh v pha ng: K= (Cs.Vs)/(Cm.Vm) =

D.(Vs/Vm). Trong phng php sc k ngi ta thng phi chn

iu kin iu chnh sao cho K nh hn khong 20, nu khngthi gian lu qu di khng chp nhn c.

tM

tR

N?ng?

Thi im

np mu

Thi gian lu, pht

Nng

Sc ca mt

cht

- Sc k kh (GC):


96/102

+ GC da trn nguyn tc sau: khi mt hn hp cc cht

bay hi c kh mang (pha ng) vn chuyn qua ct

cha mt cht hp ph rn hoc thng thng hn l

qua mt pha lng hp ph ln mt cht rn (pha tnh),mi thnh phn hi c phn b trong kh mang v

cht rn hoc cht lng.

+ Ty theo thi gian lu, mi thnh phn hi s thot ra

khi ct sc k cc thi gian khc nhau v c xc

nh bi detector thch hp, c th xc nh nh tnh

cng nh nh lng.

Nguyn tc:

+ u im :


97/102

Kh nng phn tch rt cao, ngay c i vi nhng hnhp phc tp;

nhy, chnh xc v tin cy rt cao;

Thi gian phn tch ngn, C th phn tch hng lot.

+ u im :

Thit b GC:


98/102

Thit b GC:

61 3 4 5 7 8 92

1. B cung cp kh mang; 2. B iu chnh p sut;

3. B o lu lng; 4. B np mu;

5. Ct sc k; 6. Bung n nhit;

7. Detector; 8. B khuch i in t;9. B x l tn hiu

+ Ct sc k: C hai ct: ct nhi v ct h hay ct mao qun


99/102

o Ct nhi:

Thng ch to dng ng bng thp khng g, thy tinh. ng knh

1,6 9,5 mm, chiu di khong 3m. Trong sc k kh rn vt liunhi ct thng l Silicagel, polime xp hoc sng phn t nh

Zeolit. Trong sc k kh lng cht nhi ct ng vai tr cht mang

pha lng (pha tnh), cht lng l cht khng bay hi c tm ln

cht mang thnh mt lp mng. Cht lng thng dng l duSilicol, polietilen glycol Cht mang thng l t Diatomit, gch

chu la nghin.

o Ct mao qun:

Thng dng l ct mao qun h, trn thnh ct c mt lp cht

lng mng, u, ng knh trong ca ct nh hn 1mm, chiu

di t 30 90 mm. Ct thng c ch to t kim loi, thy tinh

hoc cht do.

+ Kh mang:


100/102

Trong GC, kh mang l kh dng vn chuyn cc cht kh

nghin cu qua ct sc k, chnh l pha ng. Kh mang phi

l cc kh tr, khng tng tc vi mu, vi pha tnh, vi cc bphn tip xc, phi c tinh khit cao (t nht l 99,995%), phi

chn cho ph hp vi Detector v cc yu cu khc v phn

tch. Ngoi ra phi chn kh mang c gi thnh r v an ton, ty

tng trng hp c th dng N2, H2, He, Ar, O2 v khng kh.

+ Detector:

Ghi cc tn hiu thu c t qu trnh sc k, phn tch tn hiu vbit c cc cht cn phn tch, tch.

Trong GC hin nay ngi ta s dng Detector dn nhit, Detector

ion ha ngn la, Detector hp th electron

* Detector ion ha ngn la (FID: Flame Ionization

D t t ) D th i d i l H


101/102

Detetor): Da vo s thay i dn in ca ngn la H2t trong mt in trng khi c cht hu c cn tch chuyn

qua. Trong ngn la ca ring H2 v khng kh, dn inthp nn dng in o c b. Khi c cc cht c kh nng

ion ha mnh hn t ct sc k ra i vo ngn la, b t

nng, b ion ha, dng in s tng mnh. Detector ny c

nhy cao gp hng trm n hng nghn ln so vi TCD v

phn hi vi hu ht cc cht hu c tr axit fomic,

andehitfomic. C th o c nhng dng in n 10-12A,

pht hin c n 10-9 gam.

* Detector cng kt in t (ECD: Electron CaptureDetector): Da vo i lc khc nhau ca cc cht i vi ccelectron t do, c bit rt thch hp i vi cc hp cht Clo

ha, Alkyl ch c th xc nh c mt s thuc tr su clo

ha n mc picogam (10-12

gam). nhy cao.

Phn tch bng GC:

+ Phn tch nh tnh:T k t h t hi


102/102

+ Phn tch nh tnh:T sc k ta s nhn c cc tn hiung vi tng cu t gi l cc pic sc k. Thi gian lu hay th

tch lu ca pic l c trng nh tnh cho cht cn tch. So snh

thi gian lu (th tch lu) ca mu th vi mu chun ghi cng

iu kin.

+ Phn tch nh lng: Tn hiu thu c Detector t l vinng hoc hm lng cc cu t. Tn hiu y thng l

chiu cao pic, din tch pic. t c hiu qu phn tch ng,

iu cn thit l phi tch cc cu t cn nghin cu mt cch

hon chnh, khng c s xen ph pic ny vi pic khc.

ng dng ca phng php sc k:Phn tch sc k c ng dng tch phn li, phn tch nhiuhp cht khc nhau, v c cng nh hu c, c bit l phn tchcc hp cht hu c

602 phan tich moi truong

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