Xác định lượng vết asen bằng phương pháp điện hoá hoà tan

mo

'ujG

KI KIEU VA GbU T X T

trg
1. MO
2

±;AU

TO]^"G ^LAl^'

TAI

LISU

2 . 0 / Sd li:Ldc c a c pbifdng p b a p x a c dinbi lu'dng v e t e s e n
2 . 1 / T i n b c h a t d i e n hoa cua a s e n
2 . 2 / Cac phu'dng p b a p

5
12

d i e n boa boa t a n x a c d i n h

asen

2 . 5 . 1 - Pbitdng p b a p d i e n boa b o a t a n a n o t

1?

2 . ^ . 2 - Pbufdng p b a p d i e n hoa boa t a n c a t o t

19

2 . 3 / Cac van de n g b i e n ciiu t r o n g l u a n an nay '

20

3
3-0 /

GAG PHtfdNG

PHAP

I^IGHIEK CUb \fl. i^lJu 'ixl^l:^ TIiUG JNGlxlSk

Cac phu'dng p b a p d i n b bijfdng n g b i e n cu'u

3 - C . l - Phu'dng p b a p cu'c pbo

23

3 . 0 . 2 - Phiidng p b a p von-ampe vong

25

3-i /

Cae p h u d n g p b a p d i e n boa boa

tan

3 . 1 . 0 - Ban c h a t pb\j:dng p b a p

'

26

5 . 1 . 1 - Nb5ng v a n de l i e n quan d e n g i a i t t o a n lam g i a u

28

3 - 1 . 2 - ATn-Sng v a n de l i e n q u a n clen g i a i d o a n b o a t a n

31

3 . 2 / Dieu k i e n tbirc nghiem
3.2.1 - May.thiet bi

•

'
..

•
36

3.2.2 - Dien ciic

36

3-2.3 - Hoa chat va dung dieb

38


3.2.4 - Ky tbuat ghi

^0

3.2.5 - l^ay mau va ehuan bi

^1

3.2.6 - Xi ly so lieu tbrfc ngbiem

41

4

4.0 /

iOi^T 'CQD^ VA bAiM LlJAl'i

Cac d i e n cite so s a n b

4 . 0 . 1 - iJien cifc e a l o m e n va b a e e k o r u a

•
•
4 . 0 . 2 - B i e n ci:fc c b i s u n f a t
.
*

.

^
5^

4.0.3 - Pbam vi sxl dung cac dien cue so sanb

57

4.1 / Tinb chat dien boa cua asen

59

4.2 /Xac dinh asen bSng pbu:dng pbap dien boa boa tan anot
4.2.1 - Cac tin bieu boa tan anot cua dong
4.2.2 - Hoa tan anot he Cu-As

67
72

4.2.3 - Hoa tan anot be

Cu-Au

73

4.2.4 - Hoa tan anot be

Cu-As-Au

75

4.2.5 - £'ieu kien xac dinb asen tbeo be

Gu-As-Au

bS.ng pbtfdng pbap dien the tbdi gian hoa tan anot

76

4.3 / Xac dinb asen bang pbifdng pbap dien hoa boa tan catot
4.3.1 - Xac dinb asen tbeo he Gu-As bSng pb^idng pbap
von-ampe boa tan catot

81

4.3.2 - Xac dinh asen tbeo be I-Gu-As bSng pb\:fdng pbap
von-ampe boa tan catot , dung dien ciic tbuy
ngan tinb
4.3.3 - Xac dinb asen theo he I-Cu-As

85
bling phudng pbap

dien the tbdi gian boa tan catot , dung
ci/e mang t b u y n g a n

dien
95


4.4 / Xac dinb asen bSng pbi:fdng pbap von-ampe boa tan
xoay cbieu boa tan bae bai

.

100

4.5 / So sanb cac pbiidng pbap di ngbien cu'u .
Ban ve cd ebe

5

101

AP DbNG THUG T^

5.1 / Xac dinb triic tien luldng vet asen trong cac mau
tbT^c te

110

5.1.1 - Pban tich boa chat tinh kbiet

113

5-1.2 - Pban tieb nufde

115

5.1.3 - Pban tieb cac doi tu:dng sinb b9e

116

5.2 / Xac dinb bam l-\X6nQ: asen sau khi cat dudi dang AsH^
6

idlT LUAN

119
120

TAI LiSb

THAIV.

—0 1984

ivb.AO

123


E.T HI^U VA CHU^ TAT

: dien tieb dien cUc
•

^As ' ^Cu

•

-

, CTT : nong do i o n e s e n
xig

, dong , t b u y n g a n t r o n g

dung d i c h

nong do dang oxi boa trong dung dicb

'Ox

nong do kim loai trong tbuy nga n
D

h| so khueeh tan cua dang oxi hoa trong dung dicb
he so kbuecb tan cua kim loai trong tbuy ngan

©THT

dien the tbdi gian boa tan

( phudng pbap )

E

the dieu ci;c ; bien gidi tin cay

E^

the oxi boa kbit tieu ehuan

^1/2

the ti2& song cua song cu:c pbo ;'
the itng vdi nUa tbdi gian cbuyen

Ed

the dien pban

E

the dinh

Epa '
, Epk
,
E

the dinh anot

va

catot

•

' •

bien gidi tin cay bieu dien tbeo 6.6n vi tijfdng doi
tbuy ngan ; dien ciic tbuy ngan tinb ( dang tree )

HgTT

dien ci/c mang tbuy ngan tren dia than tbuy tinb

I

dong boa tan trong pbiidng pbap ±)THT

i

5 ik

dong boa tan anot va catot trong phu^dng pbap BTHT

a '
P
Kb

dang khu' cua chat boat don^: dien

Ox

dang oxi boa cua chat boat dong dien

Q

dien lu'dng , tij:dng ditdng vdi ludng kim loai da bi

dong dinb

ket tua tren dien ciic

s

; do nbay ve dong dien cua may ghi

SCE

: dien eiic ealomen bao boa ( dung dicb KCl )

SPbE

: dien cu'c cbi sunfat

T

: nbiet do dung dicb

: dien cu'c than mem

Tm

a

.

TT

: dien ciic dia than tbuy tinh

VAHT

: von-am.pe boa tan ( pbitdng pbap )

( quay )

T

1

: dong dien trung binh trong pb;:rdng pbap cu'c phS

i^

: dong kbuecb tan gidi ban trung binh
: bing so toe do cua pban u'ng dien hoa d dien the
tieu ehuan

: cbieu day cua mang tbuy ngan

1

*

m

: toe do ehay cua tbuy ngan trong mao quan cua dien
eiie giot tbuy ngan

n

so electron tham gia phan ling d dien cu:e ;
so Ian tbi nghiem doc lap

r

ban kinh gi9t tbuy ngan

s

\ sal

giay

so binh pbiidng trung. binh

bay

do lech ehuan
.

sv

•

: so vdi
t
: tbdi gian
t^

; cbu ky giot tbuy ngan

: tbdi gian dien pban

V

: toe do quet the
X

: gia tri trung binii cong cua n Ian thi ngbiem
: he so cbuyen cua phan u'ng dien cue

cT

: cbieu day Idp kbuecb tan

Z

: tbdi gian cbuyen
1 pp^
1 ppm

1.10'^ %
1.10 -4 ol

1 nm

1.1C~^ m

1 ng

l.lC •9

1

1.10

(Jig

=

•o

0 -


1
J

Md

BAU

^ n g ed the dong vat va thuc vat c6 asen . Vdi lUdng

rat nbo , asen c6 tac dung kieb tbieb qua trirJri song . NbUng
neu vUdt qua mot gdi ban nao do , no trd tharih chat doc .HgUdi
bi ngo doe asen kinh nien se roi loan bo may tieu hoa , cac
niem mac bi hoai va eo the tu: vong . -Asen ehiem -10
a

•

i

khoi

•

lUdng vo qua dat , cbu yeu ton tai dUdi dang sunTua nbu: reanga
( As^S. ) , oepimen ( As^S^ ) va mim Ian Ion vdi quang kim
loai kbae . Khi Ifehai tbac qu|ng , pbai cbu y den asen . Asen
dude sU dung trong y hoc ,^tbuoe da , san xuat tbuy tinln , v
vat lieu ban dan v.v. . Trong nong ngbiep , dan xuat cua asen
lam thuoe trU sau cbo cay trong . Trong boa hoc pban tich ,
asen la thanb pban quan trong cua nhieu tbuoc tbu; huu ed quy
nbu : asenazo , berilon IV , sunfaxazen , thoron I v.v. .
San ludng asen cua the gidi tu bin nSm 1940 la

46.000 T / 57 /•

Asen va cae ebe pbam cua no d^^X^c san xuat hang nam' , bSng
nbieu con dUdng kbae nbau , bi thai dan ra song , ho , bien .
Xac dinb ludng vet cac nguyen to , trong do c6 asen , la
mot trong nbung van de tbdi sU cua boa hoe pban tich nude

ta

nb§m phuc vu nbieu cbUdng trinh phat trien kinh te , kboa hoc
ky tbuat va bao ve moi trudng . Be laioi viec nay , ehung ta
thudng dung pbUdng pbap tr§c quang , pban tich quang pbo pbat
xa I^oSc hap tbu nguyen tu! . Phudng pbap dien boa boa tan

da

bat dau phat buy tac dung d mot so phong thi nghiem , nbung
nhin ehung , no chUa dii6c pho bien rong rai .
Tren the gidi , dien boa boa tan da tr5 tbanlj mot phudng
pbap pban tieb vet quan trong trong khoang
diem
CO

noi
the

bat
so

cua
sanb

phudng
d\l6o

pbap

vdi

do

nsj

la
nbay

20

n^m nay . tfu

do

nbay
cua

rat cao ^
pbudn^

pbUdng pbap kieb

boat ndtron / 3914,35^^,55 / ina trang bi

va ky tbuat lam viec lai kha ddn gian . I'o eo the tbUe bien
ngay ca tren cac m.ay cue pbo thong tl!iudng da eo tai nbieu
pbong tbi ngbiem thuoe cac bo . Bing phudng pbap dien hoa boa
tan , ngudi ta da xac dinh

dude nbieu nguyen to trong nbieu

doi tUdng f 3»14,53 7 • Tuy nbien
nguyen to , trong do eo

asen

, viec xac dinh

mot so

, can pbai ngbien euu Jhem .

Hien nay , viec xac dinb asen thUdng dude tbue bien bllng
pbUdng pbap tr4c quang dung bae-diaylditbioeacbamat / 1,18,
44, 47 7 - Bo la pbUdng pbap tieu ehuan cua nbieu nude va
nbieu tS chuc quoc te / 18,24,25,47 / . Bo nbay -5-10"''^mo 1/1.
TbUc te ngbien cUu va Ung dung

trong nUde mUdi nSm qua

ehung to la , b^ng phudng pbap dien boa boa tan , cbu yeu la
von-ampe boa tan , ehung ta da xac dinb dude nbieu nguyen to
d vung nong do
kbae

10"- lC"\ol/l , tru asen va vai nguyen

. Neu ngbien euu thanb cong mot phudng pbap xac

to

dinh

asen c6 do nbay , do ebon loc vao ed nbu cac phudng pbap xac
dinb Gu,Pb,Cd,Zn ( cac nguyen to sd trudng cua

dien boa boa

tan ) thi ta de dang tboa man nbieu nbu eau thue te cua dat
nudc , trong do c6 nbu eau cua cong tac bao ve^moi trudng .
3di vay , ehung toi ebon de tai ngbien eUu la

:

Xac dinb lUdng vet asen
bSng cae pbUdng pbap dien boa boa tan
Asen c6 kboi ludng nguyen tu la
tbu tu

74,92 d.v.6. , mang.so

: 33 trong bang tuan bo^n Mendeleep . m

V A , cbu ky 4 , n5.m gilia

Ge

va

trung gian giua a kim va kim loai

thuoe nb6m

oe . Asen eo tinh chat
. l^-'o c6 nhieu tinh chat

dien boa d^c biet , pban ung dien cue kbong tbuan nghich .Do


.'

\

do , viec xac dinb asen bSng phudng pbap dien boa boa tan
kbong giong nhu viec xac dinb

Cu,Pb,Gd,Zn . Sau khi khao

sat nhieu he , dSe biet la eac be bae ba CU-AS-AU va I-Gu-As,
a

'

a

a

a

a

'

ehung toi ebon ra mot pbUdng pbap xac dinh ludng vet asen dap
ung dude cac yeu eau da neu a I^o da dude dung de xac dinh
ham ludng asen trong mot so mau tbue te .
Trong qua trinb ngbien cUu , ehung toi con

phat bien

mot so van de eo y nghia cbung trong linh vUe pban tich dien
boa boa tan .

00 -


2

T6i^ G

^b M

TAI

LI^U

2.0 / 2£l_l2£^lL-gA^....^^^^^^ ^^^^ ^^^ ^^^-^ l^»

Nbung thong tin quan trong ve cae pbUdng pbap bien dai
xac dinh ludng vet eac nguyen to , trong do eo asen , de
dang tim tbay trong eac tai lieu cua Korenman I.M. / 15 /,
BAoracbevxki lu. V. / ^0 / va Koch 0. .^. / 44 / . Sau

phudng

pbap trie quang eo y nghia nbat trong viec xac dinb lUdng vet
asen da dude mo ta ty my
va

trong cbuyen khao cua Bavko A. K.

Pilipenko A. T. / 1 7 .

Asen CO the dudc xac dinh 3 dang xanb cua pbuc di da
axit asenomolipdic vdi chat kbu la bidrazinsuniat

boae SnCl^

f 1 7 ' Tinh chat phUc nay tUdng tu tinh chat pbuc di da cua •

Ge , Si, dS.c biet rat giong phUc di da cua P . Trong eac doi
tUdng tu nbien va ky tbuat , ham ludng photpho

thudng Idn

bdn asen vai ebiie den vai tram Ian . Bdi vay,phudng pbap nay
trong tbue te pbai di kem vdi mot pbUdng pbap taeh kbae ,
thudng la chiet hoSc cat . Gong viec nay cbiem nbieu tbdi gian
va can

dung moi bUu cd nbu GHClv , CCl^ v.v.

PbUdng pbap xac dinb ludng vet asen dung tbuoc tbu bacdietylditbiocaebamat la pbUdng pbap tot , dude cong nban
phudng pbap tieu ehuan cua

la

ISO , SEV , Lien xo , hy { 18,

24,25,47 7 v^-v- • luan 'kxi sU dung phudng pbap nay

lam pby:dng

pbap doi ehung .
NgUdi ta dung kem kim loai khu

asen trong moi trUdng

axit thanb asin ( AsH^ ) roi bap tbu no bIng dung dieb bacdietylditbiocacbamat pha trong piridin . Pban Ung xay ra nhu

sau :
AsH^ ^ 6 (C^H-)2NCSSAg —>

6 Ag -s- 3 (G2,:H^)^NGSSH ^
7 (G2H^)^NGSS 7^As

Kbi AsH-z trUde khi vao dung dich hap fhu dude dan qua Idp
3
giay ( bo§c bong ) tam cbi axetat de lam sach vet H^S .Gudng
do mau cua dung dicb hap tbu ty le vdi nong do asen . Bo
nbay -5.10"'^ mol/1 - Bung dicb thuoe tbu eo mui h^e va

rat

doc - No de bi pban buy dudi tac dung cua anb sang va nbiet
do,gay kbo khan cbo viec bao quan .
Co tbf xac dinb asen bSng pbUdg_pbap so mau vet tren
giay 7 1 7 • ^ ^ay ^ asen dude khU bing kem kim loai trong
moi trudng axit thanb asin . Khi nay di qua giay tam
axetat de lam sacb

vet

H^S roi den giay tarn HgBr^

cbi
boae

HgCl^ . Ham ludng asen dUdc danb gia qua viec stb sanb cudng

do mau cua giay tam muoi tbuy ngan Ung vdi mau phan tich va
mau doi cbieu - Cong viec nay lam bing m§t thudng , sai so
cbu quan Idn . Koch 0- G. £ ^^ J kbong xep pbUdng pbap
vao hang cac pbUdng pbap dirib ludng asen . Tuy theo

nay

ludng

asen bi hap tbu tren giay , cae hdp chat c6 mau kbae nbau
se d^i6Q. tao thanb [ \ 7 '- H(HgBr)^As - mau vang , (HgBr)-,;As •
mau nau , Hg^As^ - mau d^ii . Hien nay cac pbong tbi nghiem
trong nude sU. dung bai loai tbiet bi . Gbung kbae nbau cbu
yeu d each d|t giay tam muoi tbuy ngan . PbUdng pbap nay
kbong du do nbay de xac dinh asen trong toe va mau vi bam
ludng asen trong cae doi titdng nay qua nbo va ludng mau can
pban tieb qua Idn , kbong eo dieu kien cung cap . Kbi

pban

tieb nude , pbai dung bang lit va qua giai doan boc bdi rat
au


/

Cac pbUdng pbap kbae it c6 y nghia trong tbiie tien
nude ta . Chang ban phudng pbap dung di thiol va butylrodamin
bi

P va Si can trd .
PbUdng_nba£_auan2_pbo_ba2_tbu_ngu2|n_tU
Binh luat Kiecsop la ed s3 cua pbUdng pbap nay - Tbeo

do , moi nguyen tU se bap tbu bUc xa c6 do dai song ehinh
bing do dai song cua bUe xa ma no phat ra kbi d trang thai
kieb tbich . Cudng do bap tbu ty le vdi nong do nguyen

tu

can xac dinb . Be tbUc hien pbUdng pbap nay , ve nguyen tac ,
ta pbai c6 moi den rieng cbo moi nguyen to can xac dinb . Ca
tot cua den nay dudc ebe tao bing ehinh nguyen to can xac d
dinb . NgUdi ta dUa mot nguyen to nao do den trang thai nguyen
tu bing nbieu each , pho bien nbat la dung

ngon lUa .

Phudng pbap quang pbo hap tbu nguyen tu eo do ebon loc cao,
toe do pban tich nbanh nen dUdc sU dung rong rai d cac nude
ti'en

tien . Vdi ngon lUa axetylen - kbong kbi

va den ca-

tot asen cbo vacb 189,042 nm ,c6 the pbat bien dUdc nong do
asen trong dung dicb thap den 1.10" % , tuc -lCu^^;;r2C7 •
S nUde ta , cbi vai pbong tbi ngbiem

dau nganh va mot

so trUdng dai hoc Idn mdi thUc bien dvl^c phudng pbap nay vi
tbiet bi rat dit . Hdn nua , viec s ^ du bo den kbong pbai
de , ma tuoi tbo cua moi den lai eo ban .
'

.

a

a

?^!i^-S_E^ap_quang_pbo_£h8t_xa_nguyen_tu
Nguyen tu kbi dUdc dUa len trang thai kieb tbieb

tfhi

pbat xa . DUa vao viec ngbien cUu pho vacb cua bUc xa , ta
CO the dinh tinh va dinh ludng mot nguyen to nao do . Tuy
tbeo tinb chat nguyen to can xac dinb , doi tudng phan tieb


8

, eau tao tbiet bi ma n,gudi ta dung cac nguon kieb tbieb
kbae nbau : ngon lUa ( 2.000 - 3-000 ^K ) , bo quang (4.0006.000 "^K ) , tia dien ( 10.000 - ^0.000 ''K ) , laser (7-0008.000 ^K ) . Koch 0. G. / 4 4 7 cbo biet , lUdng asen thap.
nbit. CO the pbat hien

khi dung nguon ho quang li 1 (ug -Tbeo

Indicbenko L. N. 7 10 7 ,c6 the pbat bien dUdc 0;i^03 % As
trong khoang vat nbd vacb

23^,984 ma , eUdng do manh nbat.

Hien nay 5 nUde ta,cae may quang pbo eo nguon laser rat
hiem . Vdi eac may quang pbS pbat xa thong tbUdng

dung nguon

bo quang tbi do nbay kbong tboa man de pban tich nbieu doi
tUdng tbue te ma 5 do ham lUdng asen cbi vao khoang 1 ppm 1 ppb
PbUdng 2i^a£_kich__hoat_ndtron
PbUdng pbap kieb boat ndtron la mot trong eac phudng
pbap pban tich pbong xa . 8 pbUdng pbap nay , ngUdi ta bien
cae nguyen t6 can xac dinh tbanli cac
tao

dong vi pbong xa nban

nbd eac pban Ung bat nban kbi cbieu mau ngbien cUu bBng

cac bat • electron , ndtron , proton , hat nban

heli v.v.

CO nSng ludng cao va tiep sau do , do do pbong xa cua ehung .
Phudng 'pbap nay eo do nbay rat cao ( 0,01 ppm - 0,1 ppb
/" 15,20,44 7 • KHi cbieu mau bing dong ndtron 10

, gidi ban dUdi cua sU xac dinb asen la

)

n-em'^^.s"

2 ng /" 44 7 • i^9 -^

nbay nay tboa man nbu eau xac dinh asen trong bau bet cac doi
tudng . Vdi pbUdng pbap kieb boat ndtron , Vasen da cbo biet
•

bam ludng asen trong mot it toe eon sot lai cua Napoleong
Idn bdn trong toe ngUdi binh thudng 13 Ian . Tu do dan
mot each bieu kbae ve nguyen nban

den

lam cbo vi cUu boang de


kia chet mot each dot ngot .
Huon phan tieb bing pbUdng pbap kieb boat ndtron ,
can CO nbung tbiet bi rat pbUc tap , dit tien . Ngoii ra
•

,

nbung cong trinb pbong , ebong nhiem xa cung kha ton kem .
Bdi vay , cbi nbung ed sd dau nganh cua nba nUdc mdi xay

di^ng dude pbUdng pbap nay .

NgUdi ta biet rat nbieu nen cue pho asen /17,^0 ]

.Tuy

nbien , do do Idn cua dong tu dien va phan ung dien cue cua
asen kbong tbuan ngbich , pbUdng pbap cUc pho c6 dien kbong
the xac dinb nguyen to nay d nong do dUdi lO'-^mol/l . Nam
1981 , Le LUdng ( Vien boa hoc cong ngbiep , Tong cue

boa

chat ) da dung cUc pho song vuong xac dinh asen ; do nbay
chUa vUdt qua 1.10"-^ mol/1 . Sd di nhu: vay vi may cUc pbo
song vuong OH-104 chi nbay doi vdi cac nguyen to eo pban
Ung dien cUc tbuan ngbich . Cac may cUe pbo tast , cue pbo
xung cbo do nbay xac dinb cao bdn , song do ebUa eo

thiet

bi nay nen cbUa tbu nghiem dUdc .
Nam 1983 , Le v^n Bi-oh ( luan an tot ngbiep dei I'.oc
Tong hdp Ha noi ) da xac dinb du:de asen thap den 1.10"
mol/1 dUa vao song xue tac bidro trong nen LiCl 0,llu -sFe (III) 5,8.1C~\ol/l

( pH = 3,2 ) . Bo nbay nl-y cbUa

tboa man yeu eau thUe te .
•

PbUdng_£ba£_di|n lioa_boa_tan
Vdi cac may cUc pho c^ dien , ta eo the tbUe bien d\i6c,
•

pbUdng pbap dien boa boa tan . Co the xem day la mot

•

.

bien

the cua phudng pbap cUe pho . Bdi v|y , pbUdng pbap nay


10

eon dude goi la pbUdng pbap cue pbo eo lam giau , cue pbo
n^Ude ( Inverse Polarogrspby ) hay von-ampe n^\i6c

( Inverse

Voltammetry ) . Tbeo Koch 0. G. 7 44 7 , pbUdng pbap

dien

boa boa tan c6 the xac dinb nhieu nguyen to d nong do thap
den 1 ng/ml . NbU vay , ve m§t do nbay , pbUdng pbap nay so
sanb dUde vdi pbUdng pbap kieb boat ndtron va bdn ban

pbUdng pbap kbae da trinb

bay d tren . Nhieu tac gia nUdc

ngoai da dung pbUdng pbap dien hoa boa tan
de xac dinb asen . Ho da

cac

ngbien cUu van

dat d-\l6Q, mot sd ket qua

dang

kbieb le , song cung eon nhieu van de pbai ban crude kbi ap
dung vao boan canb cu the nUdc ta bien nay .
Trong nbung nam ebong My cu:u nUde , vdi nhUng bai bao
le te trong cac tap cbi tbieu so , ehung toi biet the gidi
bit dau phat trien phudng pbap pban tieb dien boa mdi nay.
Bdi vay , dau nSm 1973 i i^gsy sau kbi hiep dinb Pari ky
ket , tu gia ndi sd tan trS ve Ha noi , ehung toi da lam
nbung viec can tbiet de xay dUng pbUdng pbap nay . Bai bao
dau tien trong nude tbuoc linh vuc nay viet ve viec xac
dinb bae trong cbi tinb kbiet /^ 62 7 • ^"^1 may ^'^^ P^o OH102 va

dien cue Pt tu ebe , Tr^n Huu Hoan va con^^ sU da
.

•

a

'

xac dinb dude bam lUdng Ag thap den

a

•—'

.

n.lO"^ o ma kbong qua

eac giai doan taeb boSe lam giau . Gong trinh nay da dUdc
pbuc vu viec ngbien euu nang cao chat ludng acqai chi va
viec tinh ebe chi bing phudng pbap nong ehay vung . Trai
qua nam thing , phUdng pbap pban tich dien boa boa tan

da

dudc xay dung "s va pbat trien d mot so cd sd nbu : Bo mon
pban tich cua Kboa boa Trudng dai hoc T^ng hdp Ha noi ,
Phong phan tieb cua Vien boa Vien kboa hoc Viet nam ,Pbong
pban tich cua Vien boa boc cong ngbiep Tong cue boa chat .


11
o

0

o

Tu nbung dieu trinb bay tren , ta thay , cae phudng
pbap quang , bao gom : trSe quang , quang pho hap tbu nt^njen
tu , quang pbo pbat xa nguyen tU
xac dinh asen d lUdng nbo bdn

deu kbong du do nbay de

100 ng hoSe 0,1 ppm . Luon sU

dung dude cac phudng pbap do pbai lay ludng mau Idn va qua
giai doan lam giau rat pbUc tap . Hdn nua , van de cung
, nbap

cap

tbiet bi vat tU can tbiet cbo mot so pbUdng pbap von

dUde Ua ebuong tren the gidi ( nbu quang pho bap tbu nguyen
tu ) gap kbo khan,khien cbo

ehung kbo ap dung rong rai d

nude ta . Phudng pbap kieb boat ndtron dat do nbay ly tudng
, CO the tboa man dude moi yeu eau thUc te ve viec xac dinh
asen . Song ehung toi kbong du trinb do va tbiet bi de tbue
hien phudng pbap nay . Va lai , luan an eo mue dieb tim

mot pbUdng pbap xac dinb asen du nbay va de dang
cac cd sd de mong dap ung

pbo cap den

d\i(ic rxhieu yeu eau da dang trong

n\X6c . Trong cac phUdng pbap con lai thi pbUdng pbap
boa boa tan eo by vong hdn ca . Chung toi ebon phudng

dien
pbap

nay vi ngoai nbung uu diem cua no da ke tren , trude bet
cbung toi CO phudng tien vi da tich luy dude it nhieu kinh
ngbiem •
Muon ngbien euu tot , trUde tien ta can biet cac thong
tin da eo ve tinb chat dien boa cua asen vi tinh binh xac
dinb asen tren the gidi bing phudng pbap da ebon .

>fH

0
;so

'J* '«tfr-.^;K^>a:3»"-"-


12

2 . 1 / Tinb chat dien hoa cua asen
Tinb chat dien boa cd ban cua asen ( tren dien cUc giot
tbuy ngan )

da trinh bay trong cac tai lieu / 17,20,34,45 7-

NbUng thong tin nay eo the soi sang pban nao ed ebe cua cae
pbUdng pbap dien boa boa tan xac dinb asen va giup ta

dinb

budng ngbien cUu tiep theo .
/

2.1.1 - Asen boa tri

V

NgUdi ta tbay vai song nbo cua asen (V) trong HCl 6M
boae 8M vi mot song kbU kep trong

HCl 11,5 M , cbieu cao

cua no giam theo nong do axit va mat ban trong HCl 9 ^ /48 7Nbung , nhin cbung , asen (V) kbong bi khu tren dien cue gi,t
tbuy ngan

/ 17,^5 7 •

Trong tu nbien , asen c6 the ton tai d dang boa tri (V),
do do muon xac dinb no pbai cbuyen ve boa tri (III) nhd phan

Ung boa hoc .
2.1.2 - Asen boa tri

III

• Tinh chat dien boa cua asen (III) , trfen dien eUc giot
tbuy ngan , trong moi trudng HCl da d\l(5c ngbien cUu ky nbat
va cung tbu d\X6c nbieu thong tin mau tbuati nbat . TRong moi
trudng nay , asen ton tai d nbieu dang kbae nbau . Theo
Arnold f3^

7 GO tac gia cbo rang , trong HCl , asen (III)

CO the ton tai d cae dang sau : AsCl^ , As(OH)Gl-, ,As(0H).-Cl,
As(OH)^^ , H^AsO^ , kbong c6 anion phUc eloroasen . Trong
HCl 12 M , dang Uu tien li AsGl-. , trong HCl 9 K. li AsCl,. va
va
3
As(0H)Cl2 , con trong HCl 5M , c6 tat ca 3 dang ke tren . c6
"o
tac gia lai cbo ring , trong HCl 4M c6 cac anion pbuc cloro
vi du AsCl^ . Tai lieu sac ky trao dgi ion / 20 7 cbo tbay


13

trong HCl tU 0 den 12 mol/1 he so pban bo cua asen tren eationit Dowex-50 be bdn 1 . Bieu do congbia la , asen neu ton
tfi d dang ion dUdng dien tbi cung cbi vdi ty le rat nbo .
Tren anionit Bov/ex-1 , he so pban bo cua asen be bdn 1 kbi
nong c?o Eei be bdn 4mol/l , vi Idn bdn 10 khi nong do HCl Idn

hdn 8 mol/1 . Bieu do c6 nghia la , khi nong do HCl Idn hdn
4 mol/1 , trong dung dicb eo anion pbuc eloroasen va ty

le

pbuc anion cbiem Uu the kbi nong do HCl Idn hdn 8 mol/1 . Ket
hdp bai tii lieu sic ky trao doi ion tren , ta suy ra ring ,
trong dung dicbHGl

tu 0 den 4 mol/1 , asen ton tai cbu yeu

3 dang hdp chat trung tinb .Tim bieu dang ton tai cua asen
trong dung dieb HCl eo Idi cbo viec thao luan ket qua ngbien
eUu sau nay .
Tbeo Kriukova T. A. / 17 7 , i^ot; so tac gia thay , tron^
moi trudng HCl , asen (III) cbo 4 song cue pbo , dang vi the
cua ehung tbay doi tbeo nong do axit .Song tbu nbat Ung vdi
sU tao thinb asen nguyen to ( elemental arsenic ) , song tbu
bai va tbu ba Ung vdi sU khu cua H^AsO^, va AsjO- , con song
tbu tu Ung vdi sU khu cua asen nguyen to den

ASH- . Vi sii

phue tap cua pb6 nen eac tac gia nay cbo ring moi trudng

HCl

kbong tbieb hdp cbo mue dieb pban tieb .
Koltboff I. h. 7 ^3 7 cbo biet , mot so tac gia kbae
thay , Trong HCl IM chUa 0,01 % gelatin , asen (III) cbo mot

song pbuc tap bit dau t'u" -0,4 V ( sv. SCE ) va dong g^idi ban
dUdng nbu dat d\t6c d -0,8 V den -0,9 V ung vdi sU khu du

6

electron thanb asin ( ASH^ ) . Tuy nbien ho ban kboan la ,sau
dong gidi ban do eon eo mot song kbae.nen ngbi ngd ehinh ~-ia
tbuyet cua minb


14

Tbeo Milner G.'V.C. / 48 7

i Kaxirkova cbo rang , trong

HCl BI , asen(III) cbi cbo 2 song 3 vung -0,3 va -0,6 V ( sv.
SCE ) , song thU nbat kbong dinb lUdng va eo the ung vdi sU t
tao tbinb asen nguyen to eon song tbu bai Ung vdi sU khu asen
nguyen to tdi asin , cbieu cao song niy ty levdi nong do asen
trong dung dieb . Cung theo IVIilner G.V;/.C. , ileites thay asen
(III) ebo bai song trong dung dieb HCl . Song tbU nbat eo
E-, yp » - 0,428 V ( sv. SCE ) , cbieu cao cua no ty le vdi nong
do asen trong khoang 1,8.10"^ - 9*10

mol/1 . Kbi nong do asen

tang , cbieu cao song nay kbong bien doi nUa . Tac gia do giai

tbieb la , asen nguyen to d\L6o sinb ra da tao thanb mang ( film)

vi bi hap phu tren be mat dien cue giot tbuy' ngan . Song thU
bai chi bieu bien tot kbi nong do asen (III) tang den 5«10"''^
'

. Khi nong do asen cao bdn , song nay eo cue dai kep ky

di . Khi dung xanbmetylen de ebong cUc dai , Leites tbay ring^
bing so dong kbuecb tan ( i^- C" .m"^*^. t" ""^^^ ) cua song tbu
bai gap doi bing so nay cua song thU ribat . Ngbien cUu sau sic
hdn , tac gia niy cbo ring , trong HCl lii. , asen bi khu thanb
bai bude , moi bude tbu 3 electron . Neu nbunn ket luan ed
ban cua

Meites phu bdp thUc te , tbi ta c6 the xac dinh asen

bing pbUdng pbap dien boa boa tan dUa vao sU dien pban lam
giau

no d dang boa tri

(0) .

Qua trinb khu asen (III) tren dien cue giot tbuy ngan
rat pbuc tap . Nbieu cd ebe c6 ging giai tbich qua trinh niy
da dudc neu ra . Boi vdi song tbu nbat , cd ebe sau day c6 le
tbich Yi^-g bdn cs,
As(OH)J
As(OH)Cl

^

f ':>^ /
Gl" -^

^

As (I) ^

e

:

'

e -SilMk^
_cham_^

e

. ^^^^>

•As(0H)Gl

^

OH"

^^ ^^^

^

^^^-. ^

As

^^^


15
Tbeo cd ebe nay , ion CI
mot eau noi giUa

trong Idp kep boat dong nbu

dien cue lam viec va ion asen (III) . Loai

cd ebe eau iori kieu nay thudng gap trong eac phan ung

oxi

boa kbu - Song thU bai chUa giai tbieb d\i(5c tboa dang . Cd
che tren ngoii viec ehung to qua trinb khu tren dien eUc giot
tbuy ngan cua asen rat phiie tap , con noi len ring qua trinh
do khong tbuan nghich . NbU the , phudng pbap eUc pbS song
vuong xac dinh asen ( xem mac 2.0 ) kbong tbich hdp . Luon
dung phudng pbap nay , pbai tim dUdc nen sao sho asen phan
Ung dien o^c du tbuan ngbich .
Su kbu asen (III) trong cae moi trudng kbae cung dudc
ngbien cUu f 17,^5,^8 7 . Trong H^SO^ 0,5 Ivi chUa o,01 ^i ge'latin , asen cbo bai song . Cbieu cao song thU nbat ty le
vdi nong do asen (III) . Cac song nay xuat hien d the am

bdn trong moi trUdng
V

HCl vdi the nu?a song Ian ludt la -0,7

vi -1,0 V ( sv. SCE ) . IsTbu vay , muon lam giau asen

trong moi trudng

HpSO^

pbai dien pban d the am hdn

trong

moi trudng HGl , do do nbieu kim loai bi dien pban theo nen
do ebon loc se kem hdn . Trong HNO^ IM , asen cung cbo bai
song vdi the ntfa song tudng tu
trUdng rudu

trong H ,S0_^ . Trong moi tr

-f axit sunfurie , asen cung cbo eac song ro

vdi the HL^a song Ian ludt la -0,6 V , -0,88 V va -1,15 V .
Asen (III) kbong bi khu trong moi trUdng kiem , trung tinb
boSe kiem tatrat . Trong moi trUdng kiem manh , asen (III)
cung bi oxi boa den asen (V) . Nbu vay , ta tbay moi trudng
kiem va trung tinb -kbong Idi cbo phudng pbap xac dinb dUa
vao each lam giau asen S dang boa tri

(C). .

Su kbu asen (III) trong dung dieb KI cung dude xem xet
r '5^ 7 ' Trong KI 0,1 M

ehUa chat ebong cue dai , asen cbo


16

bai song ro kbi nong do cua no thap h(5n 8.10"

mol/1 . Trong

KI 0,1 M ( pHaa 2,0 " ^,4 ) , cbieu cao song ty le vdi

nong

do asen (III) cbo den I.IO"'^ mol/1 . Neu nong do asen Idn
bdn , quan be tren kbong eon nUa . Cbieu cao song dat gia
tri

gidi ban

kbi nong do asen vudt qua

4.10"'^mo 1/1 .Nbd

tinb toan ly tbuyet , ngUdi ta tbay , d day eo bien tudng

bap phu ding nbiet Trong eac moi trUdng eo chat tao pbUc manh nbu pirogalol
, axit oxalic , axit tatric , EBTA
song cua asen dicb ve phia am
moi trudng ay

-t KCN

v.v. , the nife.

boae mat bSn . Bdi vay , eac

cung kbong tbieb bdp vdi phudng pbap dien

boa boa tan xac dinb asen .

Tu nbung dieu da trinb bay , ta rut ra may nban xet
nbu sau

:

1 ) M S I trudng
cbo viec xac dinh
2 )

HCl eo le la moi trudng tbieb hdp hdn ca
asen bing phudng pbip dien boa boa tan .

Trong dung dicb KI , asen c6 bap phu ding nbiet .

3 ) Muon xac dinb asen (V) , pbai kbu no den boa tri (III)

bing eac pban Ung boa hoc tbieb bdp .


17

2.2 / Cac pbUdng pbap dien boa boa tan xac dinb asen
Tbeo eac thong tin ve tinh chat dien boa cua asen da
trinb bay d mue tr-ude , ta thay ring , cae phudng pbap dien
boa boa tan xac dinh asen deu dUa tren kha nang dien pban
lam giau asen d dang

As (0) . Nbung tai lieu xac dinh asen

da eng bo d nudc ngoai eo the chia lam bai nbom nhu sau :
2.2.1 - PHUdng_£ba£_dien_hoa_boa_tan_anot
Cac pbUdng pbap dien hoa boa tan anot deu dua tren kha
nang oxi boa dien hoa As (0) da tao tbqnb trong giai doan
lam giau den

As(III) ..

Cic moi trudng HGIO^ 7 ^2 7 , H^SO^ £ 5^ 7 , K^SO^

^

HNO^ £ IS J CO the dung lam moi trudng dien pban . Tuy nbien,
HGl 1 Iv! la moi trudng dudc sU dung nbieu hdn ca /" 11,12,13,
21,32,42,54 7 .
Bo nbay xac d^inh phu tbuoc nbieu vao loai dien cue lam
viec d-i/dc sU dung , Vdi dien cUe Pt , dung moi trudnfe HCl Uvl

, Truebina L.P. / 32 7

c6 the xac dinh dude nong do asen

thap den 2.10'^^ mol/1 , eon Gustaf,; P. £^2

7 da dat tdi

do nbay 2.10 ^ mol/1 . Bien cue vang dxt6o sU dung nbieu nbat
/ 11,12,13,21,42,46,54 7 va cung dat do nbay cao nbat / 12,
13,42,46 7 • Ching ban , kbi dung dien cue vang , trong moi
trudng HGl lii^ , Kaplin A.A.
mol/1 , con

/ 12 7 dat dudc do nbay 6.10"^

Gustaf F. ^ 42 7 cong bo pbat hien dUdc 0,02

ng/ml , tuc "3.10*"^^ mol/1 . Kaplin n.k.
xac dinb Asen rat nhieu ngay ca kbi
Idn bdn

£ On(11) 7

: £ ks{lll)

1 : 2 . Trong eac doi tUdng tu nbien va ky tbuat

\-\16n^ Cu thudng Idn bdn
cue

thay Cu cin trd sU

ludng As . Nbu vay , neu dung dien

vang pbai ket bdp vdi mot qua trinb tach tbich hdp

l,H_Ml^^

7


18

Kbi dung dien cue Pt va Au , Gustaf E. / 42 7 i^ban thay cbung
de bap phu oxi , gay trd ngai ebo sU xac dinb . Ngoai ra , e
cac dien cUc nay c6 do ben cd hoc kem nen kbo sU dung . Bien
cue graphit kbong

nbay / 11, 32 / - Cbing ban , vdi dien cue

do , khao sat d moi trUdng HGIM vi H^SO^ 0,5 M , Trushina L.
P. 7" 32 7 kbong the xac dinh asen 3 nong do be bdn 1.10" mol/1 .
Tuy nbien , neu van dung dien cUc graphit mi cbo asen

cung

dudc lim giau vdi dong trong giai doan dien pban tbi trong giai
doan boa tan ngUdi ta tbu dude tin bieu pban tich c6 cUdng do
manh bdn ro ret / 11,16,^3 7 • Roizenblat E. M. £ 2.7 7

^|^

tbay , ngay ca lUdng vet Cu (II) trong nude cat cung lam tang
boa tan anot cua asen - Fnieu tac gia cbo ring £ 16,

dong dinb

23,27 7 kbi Ou va As cung bi dien pban 3 dang boa tri ( 0 ) ,
tren be mat dien cue da tao thanb hdp chat gian kim loai
•

a

a

.

•-•-

—'

bae
a

a

bai Cu-As eo boat tinh dien boa manh . Khi dung dien eUc graphit ket hdp vdi be bae bai Cu-As , Krapivkina T. A. £ 16 7
va Neiman E. Ya. 7 25 7 c6 the xac dinh asen d nong do 10" 10"-^ mil/l .
Thong tbUdng , pbUdng pbap'xung vi pban boa tan nbay bdn

pbUdng pbap von-ampe boa tan khoang 100 Ian . Tuy nbien , doi
vdi asen , pbUdng pbap xung vi pban boa tan kbong the hien uu
viet ve mat do nbay so vdi phudng pbap kia 7" ^2 7" •
Be tang do ebon loc , doi kbi ngUdi ta eon su dung ky
tbuat doi itfoi trUdng . Muon lam viec nay , dau tien nguyen to

can xac dinh dxL6Q, lim giau 3 moi trudng tbich hdp , sau do dudc
boa tan d mot moi trudng cb9n lo^ kbae - Vdi ky tbuat nay ,
Toropova V. P. £ 31 7 da xac dinb asen trong hon hdp vdi 10 Ian
Cu(II) , 100 lin Bi(III) , Sb(III) , Sn(II) ya Pb(II) . T^e gii
nay sU dung moi trudng

dien phan la HCl 5 - 8 M , moi trudng

boa tan li KOH IM vi dien cUe tbuy ngan tinh . Tuy njrjien , do


19
nbay cua phudng pbap kbong dat tdi 1.10

mol/1 .

Kbi doc cae tai lieu pban tieb asen bing cac pbUdng pbap
dien boa hoi tan anot

, ta eo mot so suy ngbi xung quanh van

de dung dien cue so' sanb

va do nbay rat cao mi nbieu tac gia

da cong bo . Tran HUu Hoan / 63,64 7 da nban thay cae dien cue
ealomen va bae elorua loai tbUdng mai c6 the dUa vao dung dieb
do mot ludng vet Hg(II) boae Ag(I) - Trong cae moi trudng axit
vo cd , tin bieu boa tan anot cua tbuy ngan , bae , asen gan
nbu trung nbau nen de gay nbami Ian . Ii.ac dau , ngudi ta dinb
kha nbieu giay mo ta

viec xac dinh seen

mot cbu tbich nio ve viec dung
neu , Gustaf F.

asen , song kbong eo

dien eUc so sar±i . NbU tren da

cong bo phat bien dudc As 0,02 ng/ml , song

cbi dUa ra pb6 von-ampe boa tan cua dung dicb 1 (ug/ml , tUc
50.000 Ian Idn bdn . Mae dau vay , tin bieu nay cung cbi li mot
dinb kbong dep , tu , cbieu rong nua dinh do dUde tdi -140 mV .

2.2.2 - 5iJl?^5S_Eiii2_Sil^ ^22_-^2§_5§2-_2552!^
Cac phudng pbap dien boa boa tan catot dUa tren kha nang
khu dien boa

As(0) thanb asin ( AsH^ )

Nam 1980 , Brainina Kb. Z. / 4,29 / dung dien eUc mang tbuy

ngan tren graphit xac dinh d\i6c nong do asen thap den 1.10"^mol/l
bing pbUdng pbap von-ampe boa tan catot . Tac gia nay sU

dung

dung dicb nen nbu sau : HCl 1,5 M ^ 2 M

Esi^O^).^

-s- KI 0,4 M

-s-

3,5 .10" - 5 95-10" M . Phudng pbap nay eo do ebon loc tot ,
nbieu nguyen to , trong do eo cac kim loai kiem , kiem tbo •, ^'e
(II) , Co

, S O " , Cl~ Ya PO^" kbong can tr3 . Tuy nbien , Cu(Ii;

can trd ; ngay ca khi nong do Gu(II) gap 10 Ian As(III) , tin
bieu pban tich

cung bien mat . Tac gia c6 dUa ra vai Ung dung

tbUe te , nbung kfeong cbu y den kha nang mat asen lue xu ly mau


20

bing hon bdp HpSO^

•!• HF

nbd sU dung dong vi As^

/ 29 7 - Theo Bolezal ^.£77

»

, tu lau , ngudi ta biet eo den 45 %

asen bi mat khi dung hon hdp axit do .
Belova T. Ya. /" 2 7 sU dung be bae ba I-Gu-As dau tien
vao nam 1975 • lac gia niy dung dien cUc tbuy ngan tinb xac d
dinb asen trong nen
3 nbiet do

HCl 3M

-s- KI 0,015 M

^

CuSO^ 5.10"^ M ,

80 - 180 ^ C . Neu tinb den do ben cua KI vi tbuy

ngan kim loai

trong moi trUdng axit manb , nbiet do cao , ta

tbay pbUdng pbap niy rat kbo thUe hien . Vdi phudng pbap vonampe boa tan catot dong

xoay cbieu , h9 xac dinli dudc asen d

vung nong do 1.10 ' mol/1 . Phan ung xac dinb asen nay d\i6Q,
gia tbiet li theo cd che xue tac .
2.3 / Cac van de ngbien eUu trong luan an nay
Tu phan tong quan tren , ta rut ra dUdc nhSng nban xet
tong quat nhU sau :
1) Ngudi ta CO ging tang do nbay bing each dung cae dien cue
che tao tii kim loai qui nbu Au , Pt boae su dung cae bdp chat
gian kim loai Cu-As kbi dung dien cue graphit , tbuy ngan tinb
2) Moi trudng dien pban thudng dung la HCl HI ( boa tan anot )
boae HCl 1 -- 3 M ( boa tan catot ) . Co le HGl li chat dien ly
tbieb bdp nbat cbo viec xac dinh asen bing cac phudng pbap
dien boa boa tan . Nban xet nay phu bdp vdi dieu da rut ra tu
tinb chat dien boa cua asen , neu 3 mue 2-1
.

'

a

3) Trong cae doi tudng tu nbien va ky tbuat ,feemludng vet
Cu tbUdng Idn bdn ludng vet As . Cae dien cue lam bing kim 1
loai qui cbo do nbay cao song bi Cu gay tr3 ngai

. Bdi vay ,

trong sU dung tbue te pbai qua mot giai doan taeh pbuc tap .
Kbi dung he

Cu-As , ngudi ta pbai them mot ludng muoi Gu(II)

vao dung dieb do , do do tren tbue te , Gu (II) trong mau


21

kbong can tr3 , nen kbong can taeh trude .
4) CbUa CO mot phudng pbap dien boa boa tan xac dinh asen boan
ehinh , du 6n dinb va tin tu3ng di giai quyet cac yeu eau tbue
te 3 nude ta vi con nhieu van de ton tai trong each dung dien
ci^c so sanb , each xU ly mau tbue te Qung nbung kfeo khan ve
dieu kien thUe nghiem

va thiet bi -

5) Phudng pbap dien the tbdi gian hoa tan ehUa dudc sU dung
de xac dinb lUdng vet asen .
• ^

Tu nbung dieu da trinb bay , ehung'toi thay c6 nl^iem vu
pbai xem xet lai lei mot so pbUdng pbap da c6 , cai tien cbung
boae ngbien euu phudng pbap mdi nbim dat tdi mue tieu cua luan
an la tim dudc mot phUdng pbap xac dinh lUdng vet asen nbay den
10"

mol/1 va eb9n loc ( cbu yeu la doi vdi Gu ) dong tbdi pbai

CO du dieu kien ap dung rong rai 3

trong nude . Muon lam dUdc

dieu do , can di sau xem xet cac be chUa Gu(II) . Ta xac dinb
asen theo cae be niy se eo bai dieu Idi ehinh : mot la , tan
duns: boat tinb dien boa manb cua eac hdp chat gian kim loai CuAs

de tang do nbay ,; bai la , kbong bi Gu

trong mau can tr3.

He_Cu-As : Wciom Krapivkina T. A. , Neiman E. Ya.

dung dien

ci/c graphit ngbien euu he Cu-As bang phUdng pbap von-ampe boa
tan anot . Kha nang xae dinb asen tbeo budng boa tan catot he
nay , kbong eo I~ , chUa ai biet . Bdi vay , cbung toi xem xet
lai he nay bing cac pbUdng pbap boa tan anot va ca catot. Bien
^
cue lam viec la dien cue tbuy ngan boae ran , tuy\ tung
trudng

bdp cu the .
He Cu-As-Au : tfu diem n6i bat ve do nbay cua dien cue Au va
bieu qua tang do nbay doi vdi dien cue graphit kbi dung be CuAs

lam cbung toi ngbi den kha nang xac dinb asen tbeo he bae

ba Cu-As-Au vdi cae loai dien cue than . He nay chUa dudc tac