7.1 Xc nh ch s ACETYL

 

Ch s acetyl l s miligam kali hydroxyd cn thit trung ho acid acetic c gii phng sau khi thy phn 1 gam ch phm acetyl ho.

Cch xc nh

a) Xc nh ch s x phng ho ca ch phm theo Ph lc 7.7.

b) Acetyl ho ch phm theo phng php sau: Ly 10 g ch phm cho vo bnh Kjeldahl dung tch 200 ml, thm 20 ml anhydrid acetic (TT). Lp ng sinh hn ngc dng ngun lm lnh l khng kh. t bnh trn tm li ph cht chu nhit c khot mt l trn ng knh 4 cm . un si nh trong 2 gi bng ngn la nh c chiu cao khng qu 25 mm v c iu chnh la khng chm vo y bnh. ngui, rt vo mt cc to cha sn 600 ml nc, thm 0,2 g bt (TT) v un si 30 pht. Lm ngui, chuyn sang bnh gn v gn b lp di. Ra ch phm acetyl ho t nht 3 ln, mi ln vi 50 ml dung dch natri clorid bo ho (TT) m, cho n khi nc ra khng cn phn ng acid vi giy qu. Cui cng, lc vi 20 ml nc m v loi tht kit nc. Rt ch phm acetyl ho vo mt bt s nh, thm 1 g natri sulfat khan (TT), khuy k ri lc qua giy lc kh gp np.

c) Xc nh ch s x phng ho ca ch phm acetyl ho theo Ph lc 7.7.

d) Tnh ch s acetyl ca ch phm theo cng thc sau:

 

(b - a) 1335

Ch s acetyl =

1335 - a

 

a: Ch s x phng ho ca ch phm cha acetyl ho.

b: Ch s x phng ho ca ch phm acetyl ho.

 

7.2 Xc nh ch s ACID

 

Ch s acid l s miligam kali hydroxyd cn thit trung ho cc acid t do cha trong 1 gam ch phm.

Cch xc nh

Nu khng c ch dn khc trong chuyn lun ring, cn chnh xc khong 10g ch phm, thm 50 ml hn hp ng th tch ethanol 96% (TT) v ether (TT) c trung ho trc vi dung dch kali hydroxyd 0,1 N (C), dng 0,5 ml dung dch phenolphtalein(CT1) lm ch th. Lc ch phm tan hon ton. Nu ch phm kh tan, c th un hi lu trn cch thy. Chun bng dung dch kali hydroxyd 0,1 N (C), lc lin tc cho n khi xut hin mu hng bn vng trong 15 giy.

Tnh ch s acid ca ch phm theo cng thc sau:

 

5,610 a

Ch s acid =

P

a: S ml dung dch kali hydroxyd 0,1 N (C) dng.

P: Lng ch phm em th (g).

 

7.3 Xc nh ch s ESTEr

 

Ch s ester l s miligam kali hydroxyd cn thit x phng ho cc ester c trong 1 gam ch phm.

Cch xc nh

a) Xc nh ch s x phng ho ca ch phm theo Ph lc 7.7.

a) Xc nh ch s acid ca ch phm theo Ph lc 7.2.

Tnh ch s ester bng cch ly ch s x phng ho tr i ch s acid ca ch phm.

7.4 Xc nh ch s hydroxyl

 

Ch s hydroxyl l s miligam kali hydroxyd cn thit trung ho acid t hp do acyl ho 1 gam ch phm.

Cch xc nh

S dng phng php A, tr khi c ch dn khc trong chuyn lun ring.

Phng php A

Nu khng c ch dn khc trong chuyn lun ring, cn chnh xc mt lng ch phm (theo ch dn trong bng 7.4) cho vo bnh acetyl ho dung tch 150 ml c lp ng sinh hn ngc dng ngun lm lnh l khng kh, thm lng thuc th pyridin - anhydrid acetic (TT) tng ng. un si 1 gi trong cch thy, iu chnh mc nc cao hn mc cht lng trong bnh khong 2,5 cm. Ly bnh cng ng sinh hn ra khi ni cch thu, ngui, dng 5 ml nc ra ng sinh hn. Nu hn hp b c, thm pyridin (TT) va lm trong. Ghi li s ml pyridin (TT) thm. Lc v un li trong cch thy 10 pht na, ri ly ra, ngui. Ra ng sinh hn v thnh bnh vi 5 ml ethanol 96% (TT) trung ho trc vi dung dch phenolphtalein (CT1). Chun bng dung dch kali hydroxyd 0,5 N trong ethanol (C), dng 0,2 ml dung dch phenolphtalein (CT1). Song song tin hnh mt mu trng.

Tnh ch s hydroxyl ca ch phm theo cng thc sau:

 

(b - a) 28,05

Ch s hydroxyl = + ch s acid

P

 

a: S ml dung dch kali hydroxyl 0,5 N trong ethanol (C) dng trong mu th.

b: S ml dung dch kali hydroxyl 0,5 N trong ethanol (C) dng trong mu trng.

P: Lng ch phm em th (g).

Bng 7.4:

Ch s hydroxyl

Lng ch phm cn ly (g)

Lng thuc th

pyridin - anhydrid acetic (ml)

10 - 100

2,0

5,0

100 - 150

1,5

5,0

150 - 200

1,0

5,0

200 - 250

0,75

5,0

250 - 300

0,60 hay 1,20

5,0 hay 10,0

300 - 350

1,0

10,0

350 - 700

0,75

15,0

700 - 950

0,5

15,0

 

Phng php B

Cho lng ch phm ch dn vo bnh nn nt mi hon ton kh dung tch 5 ml, thm 2 ml thuc th anhydrid propionic (TT). y nt v lc nh nhng cho n khi ch phm tan hon ton. yn trong 2 gi. Nu khng c ch dn khc, m np, cho c bnh vo mt bnh nn rng ming dung tch 500 ml, c cha sn 25,0 ml dung dch anilin trong cyclohexan (TT) v 30 ml acid acetic bng (TT). Lc trn, yn 5 pht v chun bng dung dch acid percloric 0,1 N (C) cho n mu xanh ngc, dng 0,05 ml dung dch tm tinh th (CT) lm ch th. Song song tin hnh mt mu trng.

Tnh ch s hydroxyl ca ch phm theo cng thc sau:

(a - b) 5,610

Ch s hydroxyl =

P

 

a: S ml dung dch acid percloric 0,1 N (C) dng trong mu th.

b: S ml dung dch acid percloric 0,1 N (C) dng trong mu trng.

P: Lng ch phm em th (g).

Xc nh hm lng (%) nc trong ch phm (A) theo Ph lc 10.3. Tnh ch s hydroxyl hiu chnh theo cng thc sau:

Ch s hydroxyl hiu chnh = Ch s hydroxyl - 31,1 A

 

7.5 Xc nh ch s IOD

 

Ch s iod l s gam halogen, tnh theo iod, kt hp vi 100 g ch phm trong nhng iu kin qui nh.

Cch xc nh

S dng phng php iod bromid, tr khi c ch dn khc trong chuyn lun ring.

 

Phng php iod bromid

Nu khng c ch dn khc trong chuyn lun ring, ly lng ch phm theo ch dn trong bng 7.5 th.

Bng 7.5:

Ch s iod

Lng ch phm cn ly (g)

Di 20

1,0

20 - 60

0,25 n 0,5

60 - 100

0,15 - 0,25

Trn 100

0,10 - 0,15

 

Cn lng ch phm ch dn, cho vo bnh nn nt mi c lm kh hoc c trng bng acid acetic bng (TT), nu khng ch dn khc, ho tan trong 15

ml cloroform (TT) . Thm t t 25,0 ml dung dch iod bromid (TT), y nt, nu khng ch dn khc, yn trong ch ti 30 pht, thnh thong lc. Thm 10 ml dung dch kali iodid 10% (TT) v 100 ml nc ct. Chun bng dung dch natri thiosulfat 0,1 N (C), lc mnh cho n khi dung dch c mu vng nht, thm 5 ml dung dch h tinh bt (CT) v tip tc chun chm cho n khi dung dch mt mu. Song song tin hnh mt mu trng.

Tnh ch s iod ca ch phm theo cng thc sau:

1,269 (b a)

Ch s iod =

P

 

a: S ml dung dch natri thiosulfat 0,1 N (C) dng trong mu th.

b: S ml dung dch natri thiosulfat 0,1 N (C) dng trong mu trng.

P: Lng ch phm em th (g).

Phng php iod monoclorid

Nu chuyn lun quy nh dng bnh nh lng iod, tr khi c ch dn khc, dng loi bnh dung tch 250 ml v p ng cc tiu chun quc gia.

Ho tan lng ch phm ch dn vi 10 ml dicloromethan (TT) trong mt bnh nh lng iod kh. Thm 20 ml dung dch iod monoclorid (TT). y nt c lm t vi dung dch kali iodid 10% (TT), yn 30 pht trong ch ti nhit 15 - 25oC. Nh 15 ml dung dch kali iodid 10% (TT) ln ming bnh v cn thn m nt. Ra nt, ming v thnh bnh vi 100 ml nc, lc u. Chun bng dung dch natri thiosulfat 0,1 N (C), lc mnh cho n khi dung dch c mu vng nht, thm 5 ml dung dch h tinh bt (CT) v tip tc chun chm cho n khi dung dch mt mu. Song song tin hnh mt mu trng.

Tnh ch s iod ca ch phm theo cng thc sau:

1,269 (b a)

Ch s iod =

P

 

a: S ml dung dch natri thiosulfat 0,1 N (C) dng trong mu th.

b: S ml dung dch natri thiosulfat 0,1 N (C) dng trong mu trng.

P: Lng ch phm em th (g).

C th tnh lng ch phm em th (g) bng cch ly 20 chia cho ch s iod l thuyt cao nht ca ch phm. Nu mu th tiu th qu na lng thuc th iod monoclorid cho vo, phi lm li th nghim vi lng ch phm nh hn.

7.6 Xc nh ch s PEROXYD

 

Ch s peroxyd l s mili ng lng gam oxygen hot tnh biu th lng peroxyd cha trong 1000 g ch phm khi c xc nh theo cc phng php di y.

Cch xc nh

S dng phng php A, khi chuyn lun ring khng qui nh phng php th.

Phng php A

Cn 5,00 g ch phm cho vo bnh nn nt mi dung tch 250 ml, thm 30 ml hn hp gm 3 th tch acid acetic bng (TT) v 2 th tch cloroform (TT), lc cho tan v thm 0,5 ml dung dch kali iodid bo ho (TT). Lc ng 1 pht, thm 30 ml nc. Chun chm bng dung dch natri thiosulfat 0,01N (C), lin tc lc mnh, cho n khi mu vng gn nh bin mt. Thm 0,5 ml dung dch h tinh bt (CT) v tip tc chun , lc mnh, n khi dung dch mt mu.

Song song tin hnh mt mu trng. Lng dung dch natri thiosulfat 0,01N (C) dng trong mu trng khng c vt qu 0,1 ml.

Ch s peroxyd ca ch phm c tnh theo cng thc sau:

(a b) 10

Ch s peroxyd =

P

 

a: S ml dung dch natri thiosulfat 0,01N (C) dng trong mu th.

b: S ml dung dch natri thiosulfat 0,01N (C) dng trong mu trng.

P: Lng ch phm em th (g).

Phng php B

Tin hnh th trong iu kin trnh nh sng.

Cn chnh xc mt lng ch phm (theo ch dn trong bng 7.6) cho vo bnh nn nt mi dung tch 250 ml, thm 50 ml hn hp gm 3 th tch acid acetic bng (TT) v 2 th tch trimethylpentan (TT). y nt, lc cho tan v thm 0,5 ml dung dch kali iodid bo ho (TT). y nt, yn 59 61 giy, lc mnh, ri thm 30ml nc. Chun chm bng dung dch natri thiosulfat 0,01N (C), lin tc lc mnh, cho n khi c mu vng gn nh bin mt. Thm 0,5 ml dung dch h tinh bt (CT) v tip tc chun , lin tc lc mnh, nht l gn im kt thc gii phng ht iod ra khi lp dung mi. Thm tng git dung dch natri thiosulfat 0,01N (C) cho n khi mt mu lam.

 

Bng 7.6

Ch s peroxyd

Lng ch phm cn ly (g)

0 - 12

2,00 5,00

12 - 20

1,20 2,00

20 - 30

0,80 - 1,20

30 - 50

0,50 - 0,80

50 - 90

0,30 0,50

 

Ty thuc vo lng dung dch natri thiosulfat 0,01N (C) s dng, nu cn c th thay th bng dung dch natri thiosulfat 0,1N (C).

Ghi ch: i vi ch s peroxyd 70, khi chun n dung dch c mu vng nht, ch 15 30 giy mi thm dung dch h tinh bt (CT), do trimethylpentan c xu hng ni ln b mt lp nc v y l thi gian cn thit trn dung mi vi dung dch nh lng, ng thi gii phng ht iod. Nn dng dung dch natri thiosulfat 0,1N (C) khi ch s peroxyd ln hn 150. C th cho lng nh dung dch cht nh ho cn bng a nc/a du cao (nh polysorbat 60) 0,5 1,0% (kl/kl) vo hn hp phn ng lm chm s tch pha v y nhanh thi gian gii phng iod.

Song song tin hnh mt mu trng. Nu lng dung dch natri thiosulfat dng trong mu trng vt qu 0,1 ml, tin hnh th nghim li.

Ch s peroxyd ca ch phm c tnh theo cng thc sau:

(a b) 1000 x c

Ch s peroxyd =

P

 

a: S ml dung dch natri thiosulfat dng trong mu th.

b: S ml dung dch natri thiosulfat dng trong mu trng.

c: Nng ng lng gam ca dung dch natri thiosulfat.

P: Lng ch phm em th (g).

7.7 XC nh CH S X PHNG HO

 

Ch s x phng ho l s mili gam kali hydroxyd cn thit trung ho cc acid t do v x phng ho cc este cha trong 1 g cht th.

Cch xc nh

Nu khng c ch dn khc trong chuyn lun ring, ly lng ch phm theo ch dn trong bng 7.7 th.

 

Bng 7.7

Ch s x phng ho

Lng ch phm cn ly (g)

3 - 10

12,0 15,0

10 - 40

8,0 12,0

40 - 60

5,0 8,0

60 - 100

3,0 5,0

100 - 200

2,5 3,0

200 - 300

1,0 2,0

300 - 400

0,5 1,0

 

Cn chnh xc lng ch phm ch dn cho vo bnh nn nt mi dung tch 250 ml. Thm 25,0 ml dung dch kali hydroxyd 0,5 N trong ethanol (C) v vi vin bi thu tinh. Lp ng sinh hn ngc v, tr khi c ch dn khc, un si 30 pht trn cch thu, thnh thong lc. Thm l ml dung dch phenolphtalein (CT1) v chun ngay (khi dung dch cn ang nng) bng dung dch acid hydrocloric 0,5 N (C). Song song tin hnh mt mu trng.

Ch s x phng ho ca ch phm c tnh theo cng thc sau:

 

28,05 (b - a)

Ch s x phng ho =

P

a: S ml dung dch kali hydroxyl 0,5 N trong ethanol (C) dng trong mu trng.

b: S ml dung dch kali hydroxyl 0,5 N trong ethanol (C) dng trong mu th.

P: Lng ch phm em th (g).

 

 

7.8 Xc nh cht khng b x phng ho

 

Cht khng b x phng ho, c tnh bng t l phn trm (kl/kl), l phn khng bay hi 100 - 105 oC thu c khi chit ch phm c x phng ho vi mt dung mi hu c.

Cch xc nh

Dng phng php 1, tr khi c ch dn khc trong chuyn lun ring.

Phng php 1

Cn chnh xc khong 2,0 - 2,5 g ch phm cho vo bnh dung tch 250 ml, thm 25 ml dung dch kali hydroxyd 0,5 N trong ethanol v un si 1 gi di sinh hn ngc trong cch thy, thnh thong lc. Chuyn dung dch sang bnh gn, trng ra bnh vi 50 ml nc v khi dung dch cn ang m, chit bng cch lc mnh 3 ln, mi ln vi 50 ml ether khng c peroxyd (TT), dng 50 ml ether u trng ra bnh. Tp trung dch chit ether vo mt bnh gn khc cha sn 20 ml nc. Nu dch chit ether c cha cc tiu phn rn l lng, lc qua giy lc loi khng c cht bo, ri ra giy lc bng ether khng c peroxyd (TT). Lc nh bnh gn trong vi pht, yn cho tch lp v loi b lp nc. Ra dch chit ether bng cch lc mnh 2 ln, mi ln vi 20 ml nc v sau 3 ln, mi ln vi 20 ml dung dch kali hydroxyd 0,5 N (TT), lc mnh v ra vi 20 ml nc sau mi ln x l. Cui cng ra nhiu ln, mi ln vi 20 ml nc, cho n khi nc ra khng cn phn ng kim vi dung dch phenolphtalein (CT1). Chuyn dch chit ether vo mt bnh cn b v trng bnh gn bng ether khng c peroxyd (TT). Ct bay hi ether, ri thm 3 ml aceton (TT). Dng lung khng kh nh nhng ui ht dung mi ra khi bnh c ngm ngp trong nc ang si, nghing v quay trn. Sy bnh n khi lng khng i nhit khng qu 80 oC.

Ho tan cn trong bnh vi 10 ml ethanol 96% (TT) mi un si v c trung ho vi dung dch phenolphtalein (CT1). Chun bng dung dch natri hydroxyd 0,1 N trong ethanol (C) vi ch th l dung dch phenolphtalein (CT1).

Nu lng dung dch natri hydroxyd 0,1 N trong ethanol (C) tiu th khng qu 0,1 ml, khi lng cn cn c l lng cht khng b x phng ho. Tnh t l phn trm cht khng b x phng ho c trong ch phm.

Nu lng dung dch natri hydroxyd 0,1 N trong ethanol (C) tiu th qu 0,1 ml, phi lm li th nghim.

Phng php 2

Cn chnh xc lng ch phm theo ch dn (P g) cho vo mt bnh dung tch 250 ml, thm 50 ml dung dch kali hydroxyd 2 M trong ethanol (TT) v un 1 gi di sinh hn ngc trn cch thy, thnh thong lc. Lm ngui ti nhit di 25 oC v chuyn dung dch sang mt bnh gn, trng ra vi 100 ml nc, ri chit cn thn 3 ln, mi ln vi 100 ml ether khng c peroxyd (TT). Tp trung dch chit ether vo mt bnh gn khc cha sn 40 ml nc, lc nh vi pht, yn cho tch lp v loi b lp nc. Ra dch chit ether 2 ln, mi ln vi 40 ml nc v sau 3 ln, mi ln vi 40 ml dung dch kali hydroxyd 3% (TT), ra vi 40 ml nc sau mi ln x l. Cui cng ra nhiu ln, mi ln vi 40 ml nc, cho n khi nc ra khng cn phn ng kim vi dung dch phenolphtalein (CT1). Chuyn dung dch ether vo bnh cn b, ra bnh gn vi ether khng c peroxyd (TT). Ct cn thn cho bay hi ht ether, thm 6 ml aceton (TT) vo cn. Dng lung kh nh nhng ui ht dung mi ra khi bnh v sy kh cn n khi lng khng i nhit 100oC 105 oC. ngui bnh trong bnh ht m v cn xc nh khi lng cn (A g). Tnh t l phn trm cht khng b x phng ho trong ch phm theo cng thc 100 A/P.

Ho tan cn trong 20 ml ethanol 96% (TT) c trung ho trc vi dung dch phenolphtalein (TT) v chun bng dung dch natri hydroxyd 0,1 N trong ethanol (C). Nu lng dung dch natri hydroxyd 0,1 N trong ethanol (C) tiu th qu 0,2 ml, cn cn khng c coi l cht khng b x phng ho v phi lm li th nghim.

7.9 XC NH LU HUNH DIOXYD

p dng phng php 1, tr khi c ch dn khc.

Phng php 1

Dng c

Bnh cu dung tch 1000 1500 ml c lp vi sinh hn ngc. u trn ca sinh hn ni lin tip vi hai ng hp th, mi ng cha 10 ml dung dch hydrogen peroxyd 20 th tch (TT) mi c trung ha vi dung dch natri hydroxyd 0,1 N (C), dng dung dch xanh bromophenol (CT) lm ch th. Bnh c lp mt vi sc kh vi u gn chm y bnh.

Cch tin hnh

Cho 500 ml nc v 20 ml acid hydrocloric (TT) vo bnh. Sc lung kh nit hay carbon dioxyd i qua dung dch natri carbonat 10% (TT), un t t dung dch trong bnh cho n si. Duy tr lung kh sc, dung dch si trong khong 10 pht, lm ngui bng cch nhng bnh t t vo nc. M np, cho nhanh lng ch phm cn (50 100 g) vo bnh, un nh v si trong 45 pht. Tho hai ng hp th trc khi ngng sc kh. Gp dung dch trong hai ng hp th v chun bng dung dch natri hydroxyd 0,1 N (C).

1 ml dung dch natri hydroxyd 0,1 N (C) tng ng vi 3,203 mg SO2.

Lp li php th trn, nhng khng c ch phm. Dung dch trong ng hp th vn phi trung tnh.

Phng php 2

Cho 150 ml nc vo bnh A (Hnh 7.10) v sc kh carbon dioxyd 15 pht qua ton b h thng vi tc 100 ml/pht. Ly 10 ml dung dch hydrogen peroxyd long (TT), thm 0,15 ml dung dch xanh bromophenol trong ethanol (CT). Thm dung dch natri hydroxyd 0,1N (C) cho n khi xut hin mu tm xanh (khng vt qu im tng ng) v chuyn dung dch thu c vo ng nghim D.

Duy tr lung kh sc carbon dioxyd, tho bnh gn B ra v dng 100 ml nc chuyn khong 25,0 g ch phm vo bnh A. Qua bnh gn, cho 80 ml dung dch acid hydrocloric 10% (TT) vo bnh A v un si l gi. M kha bnh gn, ngng sc kh, dng un nng v nc sinh hn. Dng mt t nc chuyn dung dch trong ng nghim D sang bnh nn ming rng dung tch 200 ml. un 15 pht trn cch thy v ngui. Thm 0,1 ml dung dch xanh bromophenol trong ethanol (CT) v chun bng dung dch natri hydroxyd 0,l N (C) cho n khi chuyn mu t vng sang xanh tm.

Song song tin hnh mt mu trng.

Hm lng lu hunh dioxyd (phn triu) c tnh theo cng thc sau:

 

n

32030 (V1 V2)

m

Trong :

V1: S ml dung dch natri hydroxyd 0,1 N (C) dng trong mu th.

V2: S ml dung dch natri hydroxyd 0,1 N (C) dng trong mu trng.

n: Nng ng lng gam ca natri hydroxyd 0,1 N (C).

m: Lng ch phm em th (g).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Hnh 7.10: Dng c xc nh lu hunh dioxyd.

 

7.10 xC NH cc cht oxy ho

Cch xc nh

Nu khng c ch dn khc trong chuyn lun ring, cn chnh xc khong 4,0 g ch phm cho vo bnh nn nt mi dung tch 125 ml, thm 50,0 ml nc. y nt v lc 5 pht. Chuyn sang ng nt mi dung tch 50 ml v ly tm. Ly 25,0 ml dung dch trong trn cho vo bnh nn nt mi dung tch 125 ml, thm 1ml acid acetic bng (TT) v 0,5 1,0 g kali iodid (TT). y nt, lc nh v yn 25 30 pht trong ch ti. Thm 1 ml dung dch h tinh bt (TT) v nh lng bng dung dch natri thiosulfat 0,002N (C) cho n khi dung dch mt mu. Song song tin hnh mt mu trng.

1 ml dung dch natri thiosulfat 0,002N (C) tng ng vi 34 mg cht oxy ho, tnh theo H2O2.

Hm lng cht oxy ho, tnh theo H2O2, khng c qu 0,002% (kl/kl), tr khi c ch dn khc trong chuyn lun ring.

 

7.11 XC NH carbon hu c ton phn trong nc dng CHO ngnh dc

Lng carbon hu c ton phn (TOC) c trong nc dng cho ngnh dc c xc nh bng mt php nh lng gin tip cc cht hu c. Vic nh lng TOC cng c th c dng kim sot qu trnh thc hin cc cng on khc nhau trong sn xut thuc.

C nhiu phng php xc nh TOC. Bi vy, thay v a ra mt k thut c th, chuyn lun chung ny ch m t cc quy trnh c s dng nh gi phng php chn v x l kt qu trong cc php th gii hn. Mt dung dch chun c phn tch sau nhng khong thi gian thch hp, tu thuc vo tn sut o. Dung dch chun ny c pha t mt cht d b oxy ho (nh ng trng) c nng c iu chnh thit b pht hin c v tng ng vi gii hn TOC cn o. thch hp ca h thng c xc nh bng vic phn tch dung dch mt cht kh b oxy ho hn (nh 1,4-benzoquinon).

Ni chung, cc kiu thit b dng xc nh TOC trong nc dng cho ngnh dc u hot ng theo nguyn l oxy ho hon ton cc phn t cht hu c trong mu nc th thnh carbon dioxyd, sau nh lng carbon dioxyd to thnh v dng kt qu thu c tnh hm lng carbon trong nc.

Thit b s dng phi phn bit c carbon hu c v carbon v c (thng tn ti dng carbonat). Kh nng phn tch phi hiu qu bng cch xc nh lng carbon v c ri tnh lng carbon hu c bng cch tr n khi hm lng carbon ton phn. Cng c th loi sch carbon v c khi mu th trc khi oxy ho. Trong trng hp ny c th c nhng phn t carbon hu c cng b loi theo, tuy nhin, nhng cht hu c tn ti rt t trong nc dng cho ngnh dc.

Thit b

S dng loi thit b c hiu chnh gn trn dy chuyn hoc t ring r. Thm nh thch hp ca h thng sau nhng khong thi gian thch hp nh m t di y. Thit b phi c gii hn pht hin 0,05 mg carbon/l.

Nc TOC

S dng nc tinh khit cao t cc tiu chun sau:

in dn sut: Khng qu 1,0 mS.cm 1 25 0C.

TOC: Khng qu 0,1 mg/l.

Tu thuc vo loi thit b s dng, hm lng kim loi nng v ng c th phi c khng ch. Cn tun theo cc hng dn ca nh sn xut thit b.

Chun b thu tinh

S dng thu tinh c ra sch cn thn bng phng php thch hp loi b cc cht hu c. Cui cng, dng nc TOC trng li.

Dung dch chun

Ho tan ng trng, c sy kh 3 gi 105 0C, trong nc TOC thu c dung dch cha 1,19 mg ng trng/l (0,50 mg carbon/l).

 

Dung dch th

Thc hin tt c cc bin php cn thit trnh nhim. Ly y nc cn th vo mt bnh kn. Kim tra nc cng nhanh cng tt gim thiu nhim do cha v nt y ca n.

Dung dch kim tra thch hp ca h thng

Ho tan 1,4-benzoquinon trong nc TOC thu c dung dch c nng 0,75 mg 1,4-benzoquinon/l (0,50 mg carbon/l).

Kim sot nc TOC

S dng nc TOC thu c vo cng thi im ly pha ch dung dch chun v dung dch kim tra thch hp ca h thng.

Cc dung dch kim tra

Ngoi vic kim sot nc TOC, chun b cc dung dch trng thch hp hay cc dung dch cn thit khc hiu chnh ng nn theo hng dn ca nh sn xut thit b. Tin hnh th cc mu trng thch hp chnh thit b v khng.

thch hp ca h thng

Tin hnh th v ghi li p ng ca cc dung dch sau: nc TOC (RN), dung dch chun (RC) v dung dch kim tra thch hp ca h thng (RTH). Tnh t l phn trm hiu qu p ng theo cng thc sau:

RTH RN

RE = x 100

RC - RN

H thng c coi l thch hp nu RE nm trong khong 85,0 115,0%.

Cch tin hnh

Tin hnh kim tra mu nc th v ghi li p ng (RT). Mu nc th c coi l t yu cu khi RT RC RN.

 

C th p dng phng php ny khi s dng thit b t trong dy chuyn c hiu chnh ng mc v c thch hp h thng chp nhn c. V tr t thit b phi c la chn m bo cc p ng l i din cho nc c s dng.