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TCVN T I U C H U N q u c g i a
TCVN 3707:1990
Sot xt ln 1
thu sn phng php xc nh
hm lng nit amin-amoniac
Aquatic products
Method for the determination of amino-ammonia nitrogen
content
H ni 2008
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Tcvn 3707:1990
2
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Tcvn 3707:1990
3
Li ni u
TCVN 3707:1990 thay th TCVN 3707:1981;
TCVN 3707:1990 do Vin nghin cu Hi sn bin son, B Thu
sn ngh, Tng cc Tiu chun o lng Cht lng trnh
duyt, U ban Khoa hc v K thut Nh nc (nay l B Khoa
hc v Cng ngh) ban hnh;
Tiu chun ny c chuyn i nm 2008 t Tiu chun
Vit Nam cng s hiu thnh Tiu chun Quc gia theo quy nh
ti khon 1 iu 69 ca Lut Tiu chun v Quy chun k thut v
im a khon 1 iu 6 Ngh nh s 127/2007/N-CP ngy
1/8/2007 ca Chnh ph quy nh chi tit thi hnh mt s iu ca
Lut Tiu chun v Quy chun k thut.
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Tcvn 3707:1990
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Tcvn 3707:1990
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T I u c h u n q u c g i a tcvn 3707:1990
Sot xt ln 1
Thu sn Phng php xc nh hm lng nit amin-amoniac
Aquatic products Method for the determination of amino-ammonia
nitrogen content
Tiu chun ny quy nh phng php xc nh hm lng nit amin-amoniac i vi
cc nguyn liu,
bn thnh phm v sn phm thu sn.
1 Ly mu
Ly mu v chun b mu th theo TCVN 5276:1990.
2 Nguyn tc chung
Cho foocmon tc dng vi nhm amin (ca axit amin, peptit) v vi mui
amon c trong mu th.
Chun nhm COOH c gii phng ra trong phn ng bng dung dch natri
hydroxyt 0,1 N cho
n khi dung dch t pH = 9,2. Da vo lng kim tiu tn khi chun tnh hm
lng nit amin-
amoniac.
3 Dng c v ho cht
- Bnh nh mc dung tch 100 ml; 250 ml; 1000 ml;
- Bnh nn, nt mi, dung tch 100 ml; 250 ml;
- Cc thu tinh, dung tch 100 ml; 250 ml;
- Buret 25 ml;
- Pipet 1 ml; 10 ml; 25 ml;
- Phu thu tinh;
- Cn phn tch, chnh xc 0,001 g;
- a thu tinh;
- Giy lc
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Tcvn 3707:1990
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- Axit clohydric (HCl), dung dch 0,1 N;
- Natri hydroxyt (NaOH), dung dch 0,1 N;
- Bromothimol xanh, dung dch 0,05 % trong etanol 60 %;
- Phenolphtalein, dung dch 0,5 % trong etanol 60 %.
- Thimolphtalein, dung dch 1 % trong etanol 60 %;
- Foocmon tinh khit, dung dch trung tnh 30 %, chun b nh sau:
50 th tch dung dch foocmon 30 % ho tan vi mt th tch dung dch
thimolphtalein 1 %, thm dung
dch natri hydroxyt 0,1 N cho n khi dung dch va c mu xanh
nht.
- Ch th hn hp: trn ln 5 th tch dung dch dung dch bromothimol
xanh 0,05 % vi 4 th tch dung dch
phenolphtalein 0,5 %.
- Natri hydrophosphat, dung dch M/15 (A): cn chnh xc 2,59 g
Na2HPO4.12H2O (hoc 1,1876 g
Na2HPO4.2H20) ho tan trong bnh nh mc dung tch 100 ml, thm nc ct
n vch mc.
- Kali dihydrophosphat, dung dch M/15 (B): cn chnh xc 0,707 g
KH2PO4, ho tan trong bnh nh mc
dung tch 100 ml, thm nc ct n vch nh mc;
- Dung dch m pH = 7,0: ho ln 61,2 ml dung dch (A) v 38,8 ml dung
dch (B);
- Dung dch mu tiu chun pH = 7,0: cho vo bnh nn dung tch 100 ml:
20 ml dung dch m pH = 7,0
v 0,1 ml dung dch ch th hn hp, dung dch c mu xanh l m;
- Dung dch m pH = 9,2: cn chnh xc 1,9018 g natri tetraborat
(Na2B4O7.10K2O) ho tan trong bnh
nh mc dung tch 100 ml, thm nc ct n vch mc;
- Dung dch mu tiu chun pH = 9,2: cho vo bnh nn dung tch 100 ml:
20 ml dung dch m pH = 9,2,
1 ml dung dch ch th hn hp. Dung dch c mu tm.
4 Tin hnh th
Cn chnh xc 10 g n 15 g mu th vo cc thu tinh dung tch 100 ml. Dng
nc ct ho tan mu v
chuyn ton b (c nc trng cc) vo bnh nh mc dung tch 250 ml, thm nc
ct n khong
200 ml. Sau , lc 1 min, yn 5 min, lp li 3 ln. Thm nc ct n vch
mc, lc u sau lc.
Dng pipet ly chnh xc 200 ml dch lc vo bnh nng dung tch 250 ml,
thm 1 ml dung dch ch th
hn hp, trung ho dch lc cho n khi dung dch c mu ging dung dch mu
tiu chun pH = 7,0.
Sau dng buret cho thm 20 ml dung dch foocmon trung tnh 30 % vo
ri y nt bnh li, lc u,
yn 5 min.
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Tcvn 3707:1990
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Chun bng dung dch natri hydroxyt 0,1 N cho n khi dung dch c mu
ging dung dch mu tiu
chun pH = 9,2.
Tin hnh xc nh mu trng vi tt c lng ho cht v cc bc th nghim nh
trn, thay dch
mu th bng 20 ml nc ct.
5 Tnh kt qu
Hm lng nit amin-amoniac (X10) tnh bng phn trm, theo cng thc:
m
VVX
=
20
1002500014,0( )2110
trong :
V1 l th tch dung dch natri hydroxyt 0,1 N tiu tn khi chun mu th,
tnh bng ml;
V2 l th tch dung dch natri hydroxyt 0,1 N tiu tn khi chun mu
trng, tnh bng ml;
m l khi lng mu th, tnh bng gam;
0,0014 l s nit tng ng vi 1 ml dung dch NaOH 0,1 N;
250 l th tch ton b dch lc, tnh bng ml;
20 l th tch dch lc xc nh, tnh bng ml
100 l h s tnh ra phn trm.
Ch thch
i vi nc mm, mu th c pha long 20 ln, ly 20 ml dch pha long xc
nh.
Hm lng nit amin-amoniac (X10) c tnh bng g/l theo cng thc:
))
2121
10 (4,120
1000200014,0(VV
VVX
= =
trong :
20 l pha long ca nc mm;
20 l th tch dch pha long xc nh, tnh bng ml;
1000 l h s tnh ra g/l.
Cc k hiu khc nh ghi trn.
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