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t I u c h u n v I t n a m

TCVN 6634 : 2000ISo 8245 : 1999

cht l ng n c h ng dn xc nhcacbon hu c tng s (TOC) v cacbon

hu c ho tan (DOC)Water quality Guidelines for the determination of

total organic carbon (TOC) and dissolved organic carbon (DOC)

H ni -2000

tcvn

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Li ni u

TCVN 6634 : 2000 hon ton t ng ng vi ISO 8245 : 1999.

TCVN 6634 : 2000 do Ban K thut Tiu chun TCVN/TC 147Cht l ng n c bin son, Tng cc Tiu chun o l ng Chtl ng ngh, B Khoa hc, Cng ngh v Mi tr ng ban hnh.

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t i u c h u n v i t n a m TCVN 6634 : 2000

Cht l ng n c H ng dn xc nh cacbon hu c tng s (TOC) v cacbon hu c ho tan (DOC)

Water quality Guidelines for the determination of total organic carbon (TOC) and

dissolved organic carbon (DOC)

1 Phm vi p dng

Tiu chun ny h ng dn xc nh cacbon tng s (TC), cacbon v c tng s (TIC) v cacbon huc tng s (TOC) trong n c ung, n c ngm, n c mt, n c bin v n c thi. N cng nh nghacc thut ng, qui nh nhng cn tr thuc th v cc x l tr c mu n c.

Ph ng php m t trong tiu chun ny p dng cho cc mu n c c hm l ng cacbon hu c t 0,3mg/l n 1000 mg/l. Nng thp hn ch p dng cho cc tr ng hp ring, th d nh n c ung,v c o bng my c nhy cao. Nhng nng cao hn c th xc nh c sau khi pha longthch hp.

Tiu chun ny khng bn n tnh cht ph thuc cng c. Nhng cht hu c nh benzen, toluen,cyclohexan v cloroform cng c th c xc nh bng ph ng php ny.

Xyanua, xyanat v cc ht cacbon (m hng) khi chng tn ti trong mu cng c xc nh vi

cacbon hu c.

2 Tiu chun trch dn

TCVN 5993: 1995 (ISO 5667-3 : 1994) Cht l ng n c Ly mu H ng dn bo qun mu.

3 Thut ng v nh ngha

Trong tiu chun ny nhng thut ng v nh ngha sau y c dng.

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3.1 Cacbon tng s

TC

Tng cacbon v c v hu c trong n c, k c cacbon nguyn t.

3.2 Cacbon v c tng s

TIC

Tng cacbon tn ti trong n c d i dng cacbon nguyn t, cacbon dioxyt tng s, cacbon monoxyt,cyanua, cyanat v thiocyanat.

Ch thch My TOC th ng o TIC nh l CO2 c ngun gc t hydrocacbonat v cacbonat.

3.3 Cacbon hu c tng s TOC

Tng cacbon lin kt hu c tn ti trong n c, k c dng tan v khng tan, gm c cyanat, cacbonnguyn t v thiocyanat.

3.4 Cacbon hu c ho tanDOC

Tng cacbon lin kt hu c tn ti trong n c, i qua mng lc c l 0,45 m, gm c cyanat v

thiocyanat.

3.5 Cacbon hu c bay hiVOC

Cacbon hu c thi c.

PCO

Cacbon hu c tn ti trong n c, chng c th thi c d i cc iu kin ca ph ng php ny.

3.6 Cacbon hu c khng bay hi

NVOC

Cacbon hu c khng thi c.

NPDC

Cacbon hu c tn ti trong n c, chng khng th thi c d i nhng iu kin ca ph ng php ny.

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4 Nguyn tc

Cacbon hu c trong n c c oxy ho n cacbon dioxyt bng t chy, bng cch thm cht oxyho thch hp, bng tia cc tm hoc tia nng l ng cao khc.

S dng tia cc tm vi mt mnh oxy l cht oxy ho c hn ch cho n c t nhim, cha nng TOC thp.

Ch thch Tr ng hp c hurnic, gi tr TOC thp c th xc nh c khi dng tia cc tm.

Cacbon dioxyt to ra bng oxy ho c th xc nh trc tip hoc sau khi kh, th d n metan (CH4).

Vic xc nh CO2 c th dng nhiu cch, th d nh quang ph hng ngoi, chun (trong mitr ng khng n c), dn nhit, dn in, in l ng, dng sensor nhy CO 2 v ngn la ion ho (dng

sau khi CO2 b kh n metan...). Ngoi cacbon hu c, mu n c cn cha cacbon dioxyt hoc ccion ca axit cacbonic. xc nh TOC, c bn l cacbon v c ny phi c loi i bng cch dngkh nit khng CO2 hoc cacbon hu c sc vo dung dch axit ca mu. C th xc nh cacbon tngs (TC) v cacbon v c tng s (TIC) ri tnh hm l ng cacbon hu c (TOC) bng cch ly TC tr TIC. Ph ng php ny rt tt khi cacbon v c tng s nh hn TOC. Cc hp cht hu c thi cnh benzen, toluen, cyclohexan v clorofom c th c loi i mt phn. Khi c cc cht ny, TOC c xc nh ring hoc dng ph ng php hiu s (TC - TIC = TOC). Khi dng ph ng php hiu s gi tr TOC cn cao hn TIC hoc t nht l bng.

5 Thuc th

Ch s dng thuc th tinh khit phn tch.

Trong tiu chun ny ch cc ho cht v kh c dng vi a s cc ph ng php TOC mi c s dng. Thuc th c dng theo ch dn ca hng sn xut v nu cn th phi x l tr c.

5.1 N c pha long

N

c dng pha long hoc pha cc dung dch chun cn c TOC thp c th b qua so viTOC thp nht khi xc nh (xem bng 1).

Chn ph ng php x l tr c mu n c dng pha long ph thuc vo khong nng ca munh ch bng 1.

Ch thch o nng TOC < 0,5 mg/l nn chun b n c pha mu trng v dung dch ngaytr c phn tch (xem bng 1).

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Bng 1 c tnh n c pha long

TOC ca mu

mg/l

TOC cc i chp nhn c ca n c pha long

mg/l

N c pha long:ph ng php x l

< 10 0,1 *)

0,3

X l t ngoi

Lm c

10 n 100 0,5 Ct hai ln vi KMnO4/K2Cr2O7

> 100 1 Ch ng ct

*) Ch vi n c siu sch.

5.2 Dung dch gc kali hydrophtalat, (C hc) = 1000 mg/l

Ho tan 2,125 g kali hydrrophtalat (C8H5KO4 ) ( sy 105oC n 120oC trong vng 1 h) trong bnhnh mc 1000 ml bng n c (5.1) v inh mc n vch.

Dung dch ny bn khong 2 thng nu y kn v trong t lnh.

5.3 Dung dch tiu chun kali hydrophtalat, (C hu c) = 100 mg/l

Dng pipet ht 100 ml dung dch gc kali hydrophtalat (5.2) cho vo bnh nh mc 1000 ml, thm n cn vch. Dung dch ny bn khong 1 tun l nu y kn v trong t lnh.

5.4 Dung dch tiu chun xc nh cacbon v c, (C v c) = 1000 mg/l

Ho tan 4,415 g NO2CO3 [ sy 1 h (285 5)oC] trong bnh nh mc trong khong 500 ml n c (5.1).

Thm 3,500 g NaHCO3 ( lm kh 2 h trn silicagel), v nh mc bng n c (5.1).

Dung dch ny bn khong 2 tun l nhit phng.

5.5 Dung dch tiu chun

kim tra c tnh k thut vn hnh ca h thng.

Ch thch 1 Trong mt php th lin phng th nghim, ng phtalocyanin c dng cho mc chny. Dung dch th ng phtalocyanin, (C hu c = 100 mg/l) c th c pha nh sau:

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Ho tan 1,256 g ng phtalocyanin tetrasunfonic (mui tetranatri) (C32H12CuN8O12S4Na4) trong bnh nh mc

1000 ml, thm n c n vch mc.

Dung dch bn khong 2 tun l.

Cnh bo : Thuc th ny c.

Ch thch 2 Cc cht chun bn khc c th thay 5.2, 5.4 v 5.5.

5.6 Axit khng bay hi, ui CO2, nh H3PO4 0,5 mol/l hoc nu cn c th c hn.

5.7 Kh, nh khng kh, nit, oxy, khng cha CO2 v cc tp cht hu c.

Dng kh khc ph hp vi my theo h ng dn ca hng sn xut.

6 Thit b, dng c

6.1 My xc nh cacbon hu c.

6.2 My trn, th d my khuy t c kh nng trn u cht, my siu m hoc my khuy tc cao.

7 Ly mu v mu

7.1 Ly mu

Xem thm TCVN 5993: 1995 (ISO 5667-3).

Cn ly mu i din (c bit khi c cht khng tan) v khng mu nhim bn bi cc hp chthu c.

Ly mu vo bnh thu tinh hay polyetylen, ly y bnh, v nu nghi c vi khun hot ng th axit hon pH 2 [th d bng H3PO4 (5.6)]. Trong mt s tr ng hp c th mt CO2 khi axit ho mu. Nu c

cht hu c bay hi, cn tin hnh o ngay trong vng 8 h sau khi ly mu m khng cn axit ho.Mu c th l u gi trong t lnh nhit 2oC n 5oC c 7 ngy. Nu gi mu 15oC n 20oCth c th c nhiu tun.

7.2 Chun b mu n c

Nu mu khng ng th v khng th ly mu i din ngay khi lc rt k th dng my thch hp (6.2) trn mu.

Tnh ng th ca mu c th kim tra bng cch phn tch phn trn v phn d i bnh mu ring r.

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Nu ch xc nh cht hu c ho tan (TOC) th lc mu qua mng lc c c l 0,45m ra bngn c nng ui ton b cht hu c bm dnh. Tuy vy cn thn trng trong xc nh hm l ngcacbon hu c trong n c lc.

8 Cch tin hnh

8.1 Chun ho

Cc ph ng php so snh (th d hng ngoi) cn chun ho. Tr ng hp cc ph ng php tuyt inh ph ng php trung ho hoc in l ng, chun ho dng kim tra ph ng php phn tch.

Chun ho my theo h ng dn ca hng sn xut.

Xy dng ng chun da trn phn tch dung dch tiu chun kali hydrophtalat. Th d khongnng 10 mg/l n 100 mg/l th chun b t nht 5 dung dch chun t dung dch gc kali hydrophtalat(5.2) nh sau:

a) chun b dung dch hiu chun, dng pipet ht vo cc bnh nh mc 100 ml : 0 ml (trng) ml, 2 ml, 3 ml, 5 ml v 10 ml dung dch gc kali hydrophtalat (5.2) ri thm n c (5.1) n vch;

b) phn tch cc dung dch v mu trng (bnh khng thm kali hydrophtalat) theo s ch dn cahng sn xut;

c) xy dng ng chun nng TOC tnh bng miligam cacbon trn lit - n v tn hiu trn my

( I ).

Gi tr nghch o ca dc ng chun l h s chun ho f, tnh bng mg C/l.

xc nh gi tr TIC cn phi xy dng ng chun t cc dung dch chun pha t cc dung dch 5.4.

xc nh gi tr TOC t hiu s TC TIC cn phi xy dng ng chun bng cc dung dch chunpha t cc dung dch 5.3 v 5.4.

8.2 Ph ng php kim tra

Phn tch cc dung dch th (5.2, 5.3, 5.4 hoc 5.5) vi mi lot mu kim tr tnh ng n ca cckt qu thu c bng ph ng php.

Nu lch tm thy cao hn tiu chun cht l ng trong phng th nghim th phi nghin cu nguynnhn gy sai s :

my hot ng sai (th d trong s oxy ho hoc s pht hin, sai trong nhit hoc kh, d r);

thay i nng dung dch th;

h thng o b nhim bn.

Th ng xuyn kim tra ton b h thng o ph hp vi h ng dn ca hng sn xut.

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Cc kim tra ny tin hnh thm cng vi kim tra my c h ng dn bi hng sn xut.

8.3 Xc nh

Xc nh TOC ca mu theo s h ng dn ca hng sn xut. Khi xc nh TOC trc tip cn tr c htui cacbon v c bng axit ha dung dch n pH d i 2. Cn thn trnh cc cht hu c d bayhi bc mt.

Nng TOC phi nm trong ng chun. iu c th t c bng cch pha long mu.

Tr c khi xc nh mi l mu (th d c 10 mu) tin hnh kim tra theo ngh ca hng sn xuthoc theo qui nh ca phng th nghim.

Sau khi axit ho, cho 1 dng kh tr khng cha CO2 v tp cht hu c qua h thng (th d 5 min) ui CO2.

9 Biu th kt qu

9 1 Tnh ton

Ph thuc vo loi my c dng m tn hiu thu c l khc nhau, t nng TOC hoc DOCtrong mu c tnh ton. Khi o gin on, cc gi tr ny c th l, th d chiu cao pic, din tch pichoc th tch thuc th tiu tn. Thng th ng, din tch pic hay c dng. Chiu cao pic ch cdng khi chng t l vi nng . Khi o TOC hoc DOC gn lin tc, nng CO2 sinh ra do t cccht hu c c ghi li trn b ghi. Khong cch gia ng ghi c v ng zero t l vi nng TOC.

Nng c xc nh da vo ng chun (8.1).

Nng TOC hoc DOC, miligam cacbon trn lit, tnh theo cng thc:

I x f x V ______________________

V p

trong I l tn hiu trn my;

f l h s chun ho tnh bng miligam cacbon trn lit, xc nh theo 8.1;

V l th tch ca mu n c pha long tnh bng mililit;

V p l th tch mu ch a pha long.

Kt qu c biu din vi hai hoc ba s c ngha dng theo sai s ngu nhin ( chnh xc) ca

php o.

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Th d : (TOC) = 0,76 mg/l hoc

(TOC) = 530 mg/l hoc (TOC) = 6,32 . 103 mg/l

9.2 chnh xc

Thng tin v ti lp v ti lp khi th lin phng th nghim cho trong ph lc A.

10 Bo co kt qu

Bo co kt qu cn c cc thng tin sau:

a) trch dn tiu chun ny;

b) chi tit nhn dng mu th;c) chi tit v l u gi mu tr c khi phn tch bao gm c thi gian t khi ly mu n khi phn tch;

d) x l mu tr c (thi gian lng, lc);

e) nng TOC v DOC trong mu, miligam cacbon trn lit;

f) chi tit v mi sai khc so vi cch lm c qui nh trong tiu chun ny v mi tnh hung cth nh h ng n kt qu.

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Ph lc A

(tham kho)

Kt qu th lin phng th nghim xc nh TOC

Bng A.1Mu Gi tr TOC Tm thy ti lp lp li S S kt Kt qu

thcTOCmg/l

trungbnhtngmg/l

% lchchun

mg/l

H s lch

%

lchchunmg/l

H s lch

%

phngth

nghim

quphn

tch saukhi loi

b

b loib

1 2,3 2,99 129,9 0,687 23 0,19 6,3 55 259 132 18,5 19,2 103,9 1,23 6,4 0,38 2 56 260 9

3 120 139 115,9 12,4 8,9 2,8 2 54 236 16

4 307 13,9 4,5 3,8 1,2 54 244 20

Mu 1 : ng phtalocyenin tetrasunfonic, mui tetranatri.

Mu 2 : Hn hp kali hydrophtalat v ng phtalocyanin tetrasunfonic, mui tetanatri.

Mu 3 : Hn hp kali hydrocacbonat, kali hydrophtalat v ng phtalocyanin tetrasunfonic, muitetranatri

Mu 4 : N c thi cng nghip, mu tht, c lc.Ch thch 1 L do tm thy l 130% mu 1 (mu vi nng TOC thp) l do sai s h thng

(khng xem xt hoc xem xt phn no nng TOC ca mu trng).

Ch thch 2 tm thy tng mu 3 c th do nng TIC cao. Tr ng hp t ng t cho bi hngsn xut my l do th tch axit v thi gian ui l khng .

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Ph lc B

(tham kho)

Xc nh TOC cc mu cha cht rn

B.1 Nhng iu kin ph thm

c tnh ca my o TOC cn phi tch hp o cc ht rn c kch th c 100 m (qui c).

Ch thch 1 Trong th lin phng th nghim (xem bng B.1) cc mu cha ht rn c kch th c ti 100m c o.

Ch thch 2 Kt qu xc nh TOC trong cc mu cha ht rn th ng khng lp li, ngay khi trn u.Mu c th c lc v xc nh ring TOC trong n c lc v cn.

H thng dng oxy ho bng tia cc tm l khng thch hp xc nh microxelulo [xem B.4, bngB.1, mu 1b)].

B.2 Th huyn ph

Th huyn ph kim tra s ng th v tm thy ca cc cht rn t tan.

chun b huyn ph ta dng 225 mg xelulo (C6H10O5)r (kch th c ht t 20 m n 100m, nng cacbon trong huyn ph l 100 mg/l) cho vo bnh nh mc 1000 ml, tm t bng n c. Thmn c n vch mc v khuy bng my t cho huyn ph ng th. Khng nn dng siu m v n lmgim kch th c ht. Hn hp bn trong khong 2 tun l khi trong t lnh, nh ng cn khuy mikhi dng. C th dng loi huyn ph thch hp khc, th d n c thi ca nh my giy.

B.3 Th s ng th v tm thy ca cc cht t tan (kim tra ht rn)

Vi mi ht mu cha cht rn, s ng th v tm thy ca cc cht to huyn ph (kh nng phntch ht rn ca my) cn c kim tra bng th huyn ph (B.2). Ly mu trong khi khuy. Nu dngly mu t ng th cn khuy lin tc khi phn tch. Gi tr trung bnh khi phn tch ba ln s gia 90mg/l v 110 mg/l, h s lch lp li s nh hn 10%.

Ch thch 1 Trong php th ny kch th c ht l quan trng.

Ch thch 2 ng th ho ti u v d nh dng my khuy dao ng.

B.4 Hiu qu

Xem bng B.1.

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Bng B.1 Kt qu th lin phng th nghim xc nh TOC

Gi tr TOC ti lp lp li S S kt Kt quMu thc

TOCmg/l

trungbnhtngmg/l

Tm thy

%

lchchun

mg/l

H s lch

%

lchchun

mg/l

H s lch

%

phngth

nghim

qu saukhi loi

b

loi b

1 a 20 16,65 83,2 7,5 45,1 2 12,0 32 149 0

1 b 20 0,53 2,7 0,4 75,0 0,15 27,3 15 56 10

Mu 1 a : Vi tinh th xelulo ( c xc nh bng t chy).

Mu 1 b : Vi tinh th xelulo (oxy ho bng t ngoi).

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Ti liu tham kho

[1] DURR.. , W, v MERZ, W. nh gi TOC - Th lin phng th nghim ISO v tho lun kt qu,Vom Wasser, 55, 1980, tr 287 - 294.

[2] Cc ph ng php xc nh n c v cc cht lin quan. Xc nh cacbon hu c tng s, yucu oxy tng s. Her Majesty s Stationery Office, London, 1995.

[3] ISO /TR 13530 Cht l ng n c H ng dn kim tra cht l ng phn tch n c.

_____________________