JOURNAL OF SCIBNCI: OF i INUE Natural Sci., 2014, Vol. 59, No. 4, pp. 45-53 This paper is available online at http://stdb.hnue.edu.vn
NGHIEN CUU PHUONG PHAP XAC DINH HAM LUONG XIANUA VA DANII GIA 6 NHIEM MOT SO N G U 6 N N U O C THAI
Bui Thi ThLr\ Trinh Kim Y c n \ Dao Van Bay- va Dang Xuan Thtl-
^Khoa Moi Infdng. TrUdng Dai hgc Tdi nguyen vd Mdi trudng Hd Ndi ''Khoa Hda hgc, TrUdng Dai hgc Su Pham Hd Noi
Tom tat. Bili hao gidi Ihieu phUdng phap xdc dinh ham lUdng xianua hang phUdng phap do quang vdi sU tau phUc cua xianua vdi thuoc thi^ pyndin - barbilunc. Ket qua khao sal cac dieu kicn idi Uu: A,,-,,^,, = A,^^,; = 580 nin: pll|,-„^u = 6.05; ihe lich cloramin T = 1,0 ml.; the tich thudc ihU tdi Uu = 2.5 inL: thtJi gian tao phUc loi Uu
= 20phiil, Gidi han dinh lupng: LOD =4,75.10-3 mg/L; gidi han phat hien: LOQ
= 0.014 mg/L. Tii nhu'ng dieu kicn toi uu cua phiin Ung tao phiic ap dung de xac dinh hiim lUdng xianua trong mot so mau nifdc Ihiii ma tai cac xUdng ma lliiipc xii Lien Hiep. huyiin Phiic Tho, thanh phd Ha Noi.
Tif khda: Xianua, thuoc ihU pyridin - barbiluric, phUdng phap do quang, phUdng phap danh gia
1. Mdd^u
O nhiem nude dang la mdi quan tam Idn ctia loan can. Tai hdi nghi thudng dinh the gidi ve phcit trien ben viing (Johannesburg, 2002) nUdc difdc xep la tiii nguyen thicn nhien quan trpng thU hai sau tai nguyen con ngUdi. Tai nguyen nUdc dang chiu anh hUdng Idn bdi ini bien ddi khi hau, tdc dd tang dan sd. phat trien manh me cua cac hoal ddng phat trien kinh t e , . , Va tinh trang suy Ihoai, d nhiem nUdc ngay ciing tram trpng Qua trinh dd thi hda. cdng nghiep hda, hien dai hda phat trien cang manh ihi nhu cau ve nUdc ngpt cimg Idn. Vi vay ngudn nUdc ngpl ngiiy cang bi can kiet. O nhiem trd ihiinh hicn tUdng phd bien va ngay cang nghiem trpng tren toan the gidi.
(.) nude la vSn dd d nhiem cac ngudn nUdc da va dang gay lo ngai tai cac thanh phd va khu cdng nghiep. Su bung no dan sd ciing vdi tdc dd dd thi hda. cdng nghiep hda nhanh chdng da tao ra mpl st?c ep Idn tdi mdi trUdng sdng. dac bicl ngudn nUdc sinh hoa! ngay cang trd nen thieu hut va d nhicm Mdi trudng nUdc d nhieu dd thj. khu cdng nghiep va
Njiay nh.in bai. 16/.'i/2(114. Ngay iiluiu dang; 16/6/2()!4.
Tac piii lien tac Biii 'I'hi Thif, dui chi c-mail' hijiihuS4(?'yahoo.coni
Bui Thi ITiU, Trinh Kim Yen. Dao Van Bay va Dang Xuan Thu
lang nghd ngay cang bi d nhidm bdi nude thai, khi thai va chSt thai ran. Trong nUdc thai nhdm nude thai chUa xianua dac biet dUdc quan tam vi doc tinh cua nd. Axit xianhidric va cac muoi xianua tan ciia nd la nhUng chit doc rit manh, chi can lupng chUng 50 mg la cd the gicl ehgt mot ngUdi. Tuy nhien cac mudi kim loai cua axit xianhidric lai cd vai trd rat Idn trong nhidu nganh cdng nghiep. Do doe tinh ciia xianua, ham lUdng xianua trong nude tliai ra mdi trUdng phai rat nho. Theo tieu chuan d Viet Nam, gidi han cho phep ctia xianua trong nUdc mat la 0,005 mg/L ddi vdi nUdc sinh hoat; 0,02 mg/L doi vdi nUdc diing cho ludi tieu. giao thdng thiiy [I, 3].
Vi nhung li do tren chiing tdi da nghien cu'u phUdng phap xac dinh ham lUdng xianua bang phUdng phap trac quang sijt dung thuoc thd pyridin - barbutiric va danh gia d nhidm mdt sd ngudn nUdc thai cd chiJa xianua tren dia ban thanh phd Ha Ndi.
2 . N o i d u n g n g h i e n cufu 2 . 1 . Thijfc n g h i e m
* Dung cii, may mdc
May do pH meter HM - 16S do hang TOA Nhat Biin san xuAt. Can phan tich Moden GP 150 - 3P, Sartorius ctia DUc. dp chinh xac Ji 0,1 mg. May cat nUdc 2 lan ctia hang Bibby do Anh siin xuat. May quang phd UV- Vis Biochrom Libra S60 eua Anh san xuat.
Cac dung cu thiiy tinh diing trong phan tich: pipet cac loai, binh dinh mitc cac loai.
* Hda chdt
- Dung dich xianua chuan 1000 mg/I.; 100 mg/L; 10 mg/I..
- Dung dich CN - phan tich 2 mg/L.
- Dung dich cloramin T 1%: Hoa tan I gam cloramin T, CyHyClNNaO^S.SHaO trong 100 mL nitdc cat va bao quan lanh cho den luc sCi dung.
- Thudc thd axit pyridin-barbituric: Can 15 gam axit barbituric C^H.jX^O:,, cho vao binh dinh mUe 250 mL, sau dd them nudc cat (khoang 100 mL) trang thanh binh va lam udl axil barbituric. Them 75 mL pyridin Cr.Hr.N va \ic ddu. Them licp 15 mL HCl dac, liic trpn cho tdi khi axit brabituric tan hct, dung dich tir miiu trang due chuyen .sang vang nhat rdi Ihcm nUdc cat tdi 250 mL. lac deu. Thuoc thU niiy cd the bao quan trong gan 6 thang neu dUdc giiT trong mdi IrUdng lanh, tdi.
- Chi axelal (CII,!COO>;Pb 0.08 M.
- Cac dung dich axit HCl, bazd NaOIl cd ndng dd khac nhau de dieu chinh pi I.
* Phuong phap xdc dinh xianua
Chung tdi suf dung (hudc thU pyridin - barbutiric dc xac dinh hiim lUdng xianua biing phtfdng phap do quang, dUa tren qua Hinh oxi hda xianua bang cloramin T thimh xianclorua d pH < H (tranh phan Ung thiiy phan). Sau dd, xianclorua ket hdp vdi thudc ihit pyridin-barbiluric cho phuc mau hdng canh sen va cd eUc dai hap thu tai budc sdng 580 nm 15, 7|. Xac dinh gidi han phat hien (LOD) va gidi han dinh lUdng cua phudno nhap (LOQ) [4,8]. • • ^ ^ "^
Nghien citu phuang phdp xdc dinh ham lifOng .xiiuiua vd ddiih gid d nhiem mdt sd ngudn nude thai
2.2. Xac dinh ham lifOng xianua trong cac mau nurdc thai
- Ddi tugng nghien cdu: Doi tUdng nghien cUu la cac mau nUdc thai ma tai cac xUdng ma Ihudc xa Lien Hiep, huyen Phuc Thp, thanh phd Ha Ndi.
- Vi tri lay mau: Mau 1, 2, 3 {Ml, 2, 3): LSy tai vi tri cUa xa nUdc thai ra mdi trUdng cua xUdng ma kim loai; each khu ma khoang 100 m; 800 m tai xa Lien Hiep, huyen Phuc Thp, thanh pho Ha Ndi; Mau 4, 5, 6 (M4, 5, 6): Lay tai vi tri ciia xa nUdc thai ra mdi trudng ciia xi nghiep gia cdng kim loai; each khu gia cdng khoang 300 m; 1500 m tai xa Lien lliep, huyen Phiic Thp, thanh phd Ha Ndi.
- Phuong phdp Idy mdu vd bao qiidn mdu:
Tidn hanh theo cac tieu chuan: TCVN 5992:1995 (ISO 5667-2: 1991): TCVN 6000:1995 (ISO 5667-11: 1992). Ngoiii ra, vi xianua thudc loai chat thai nguy hai (CTNH), can phai lay mau theo hudng d5n tai QCVN 10: 2009/BTNMT.
Lay 6 mau d 3 vi tri xac dinh, tien hanh 2 ddt thi nghiem cho mdi mau. Cac mau nUdc thai dUde lay true tidp tU cac vi tri da chpn, cho vao binh nhua polyclylen dung tich 500 mL vii 1000 mL da dUdc xil li sach bang axit HNO{ va HCl, rUa sach vii trang lai bang chinh nude thai tai vi tri lay mau.
Ciic mau lay vc phdng thi nghiem can dUdc phan lich ngay trong ngiiy, ddi vdi cac mSu chUa the phan lich ngay dUdc biio quan lanh d =:; 5 ^C, nhiim han che sU hoal ddng ciia vi sinh vat.
- Xu' If vd chung col mau: Cac mfiu nUdc lay trtfc tiep Id ngudn thai thUdng bi due.
can lpc de loai bd cac can Id lilng. Lay khoang 1 lit man nUdc thai, ipc tren giay ipc bang xanh ctia Di'fc (loai 390). Cac mau dUdc chung cat theo sd dd d Hinh 1
Hinh I. Sif dd thiet bi chUng cat xianua I. Ik-p dun. 2. liiiih cdr ihiiy itnli (hm nliiel diin^ tirli 500 luL. S. Sinh lii'in.
4 PIK'II tliihitld ihSOi. 5 Bon,!- liim dnna dirli iClliCOOh^l^ df'linn .MKli Uu IICN.
ft. Uinh hiipllunhKiidd NaOII. 7. Boni- uini dun^iluh axil punr + NiiiCO^ dc phcil hen khi IICN
* Tad pluin ihig mdu vd do quang.
Chuan hi 7 binh dinh mUc V = 50 mL, lay viio mdi binh \" = 5 mL dung dich X.
Them lan lUdl viio cac binh 1 mL dung dich cloramin 1 lac ki. dc yen khoang 3 phiii;
47
Bill Thi Thu, Trinh Kim Yen, Diio Van Bay va Dang Xuan Thu
Them tiep vao m6i binh 2,5 mL dung djch thu6c thu: pyridin-barbituric, lac ki. Dinh miic tdi vach va dc yen 15 :- 25 phut cho mau on dinh.; Do quang loat dung djch mau tren may quang pho UV - Vis Biochrom Libra S60 tai bu6c song toi Uu. Dung dich nen chuan bj tuong tu nhung khong co C N " . XOr li thong ke cac ket qua do tim dUdc gia trj nong do CCN- (mg/I.).
2.3. K e t q u a va t h a o l u a n
2.3.1. Xay diing dirbng chuan xac dinh xianua
* Ket qua khao sat sd bo budc sdng cho phan ting tao phutc mdu
Do pho ciia dung dich mau CO nong do xianua 0,1 mg/L tren may quang pho tii ngoai kha kien S60 Biochrom trong khoang budc sfeng tif 400 -: 800 nm, thu dUdc pho d6 CO gia trj A,„,,^ ung v6i budc song Amj^. KSt qua duoc bieu dien tren Hinh 2.
Hinh 2. Pho hdp thu electron cua dung dich mau cd ndng do xianua 0,1 mg/L so vdi nUdc cat trong khoang budc sdng 400 -^ 700 nm (1): Phd hdp tiiu electron ciia dung dich thudc thii pyridin - harhulinc
(2): Phd hdp ihu electron ciia dung dich phiic xianua - thudc thu
Hinh 3. Phd hdp thu ciia dung dich mau cd nong do xianua khac nhau (0,02 mg/L; 0,1 mg/L; 0,2 mg/L) so vdi dung dich nin
trong khoang budc sdng tit 400 -; 700 nm
(I): Phd hdp thu electron ciia phiic mdu giiia xianua 0,02 mg/L vd thudc thii:
(2i: Phd hdp thu electron ciia philc mdu giCla xianua 0.1 mg/L vd thudc thii:
(3): Phd hup Ihu electron ciia phiic mau giiia xianua 0.2 mg/L vd Ihudc thif.
Ji
Nghien cdu phuong phdp xdc dinh hdm lupng xianua vd danh gid d nhiem mot sd ngudn mfdc thai
Ket qua tren Hinh 2 va Hinh 3 cho Ihay: Khi ndng dp C N " tang thi gia tri mat dp quang ciia phiJc mau cung tang len va cac pic cue dai diu 6 ciing gia tri bUdc sdng A^ax = 580 nm. Vi vay chiing tdi chpn gia tri bUdc sdng 580 nm lam bude sdng de khao sat cac dieu kien toi Uu ciia phan ting tao phUc mau.
* Ket qua khao sat diSu kien toi Uu cho phan iing tao phdc mdu
D'lhx chinh pH ctia cac dung dich philc mau trong khoang tif 4,0 -^ 8,5 bang cac the tich dung dich axil HCl, bazd NaOH cd ndng dp khac nhau. Xac dinh chinh xac pH cua cac dung dich bang may do pH. Ket qua khao sat anh hUdng cua pH den phan Ung tao phiJc mau dupc bieu diSn d Hinh 4.
Hinh 4. Khao sat anh hudng cua pH den phan Ung tao phuc mdu hay suphu thuoc A =f(pH)
Nhu vay, trong khoang pH = 5,84 -.- 6,42 la thich hpp nhat cho phan ilng tao philc mau. Chiing tdi chpn gia tri pH = 6,05 la pH toi uu cho cac phan Ung tiep theo.
Khao sat the tich cloramin T anh hUdng den phan ling tao philc mau tU 0.1 den 2,0 mL, ket qua bieu didn tren Hinh 5; the tich thudc thif pyridin - pyrazol dupc khao sal tU 0,5 den 10 mL, kdt qua anh hudng ti le thudc thil bieu dien d Hinh 6.
Hinti S. Sir phu thiiiic tint mat do qnanf; 4 Hinh 6. Sirphij tliiioc iiiti iiiul do ifiia/i^ A vao the licit thuoc thir pyridiii-harbitiiric viio the tich doriimin T
49
Bill Thi Thu, Trinh Kim Yen, Dao Van Bay va Dang Xuan Thu
Nhu vay, trong khoang VT^ = 2,5 -^ 4,5 mL, mat dp quang A Idn nhat va kha on dinh. Trong cac thi nghiem tiep theo, chiing tdi chpn Vrr = 2,5 mL la the tich thudc thil tdi Uu. Trong khoang VcioraminT = 1,0 -^ 1,5 mL, mat dp quang A Idn nhat va kha on dinh nen chiing tdi chpn V^r = 1.0 mL la the tich cloramin T toi Uu.
Khoang thdi gian thich hdp va tot nhat cho phan dng tao phiJc mau giiia xianua va thudc thu' pyridin - barbutiric la tijt 15 -H 40 phut, do la khoang thdi gian toi Uu de do mat dp quang cua philc mau. Trong cac thf nghiem tilp theo, chiing tdi de thdi gian do quang la sau 20 phiit ke tit khi tao philc mau.
* Ket qua xay dUng diibng chuan xdc dinh hdm lUdng xianua
Tien hanh xay dung dUdng chuan xac dinh hiim lUdng xianua d cac dieu kien tdi Uu, chiing tdi thu dUdc ket qua dUdc bieu diln d Hmh 7.
y = 2,5112.s- 0.0179
.^
,^
0 0 0 0 0 2 0 0 4 0.06 0.08 0 . 1 0 0 . 1 3 0 . 1 4 0 160 18 0.20 0.22 xiHnua t..ncentrali„n (ms/l)
Hinh 7. Dudng chuan xdc dinh hdm lUdng xianua
Xii li phuong trinh duSng chuan bang thong ke loiin hoc chiing toi thu duoc phuong trinh dubng chuan co dang: A = 2,5112.Cp.^ + 0,0179. Xii li phuong trinh duflng chuan bang Excel, thu duOc phuong trinh ducfng chuan co dang: A = 2,5112.0^^ + 0,0179; vdi he s6 tuong quan R^ = 0,9985. Xii li phUOng trinh dudng chuan bang phSn mim Origin 8.0 thu duoc phuong trinh du6ng chuan co dang: A = (2,5112 ± 0,0323)C^.^, + (0,0178
± 0,0040); vdi he s6 tuong quan R- = 0,9985.
Nhu vay phuong trinh dudng chuan xiJ li theo ba phuong phap ddu cho ket qua nhil nhau, VI viiy trong cac phep phan tich tiep theo chung toi sil dung phuong trinh dUbng chuan tren de tien hanh phiin tich.
2.3.2. Xac dinh gidi ban phat hien va gi6i ban dinh luong cua phuong phap xac dinh ham luong xianua bang thuoc thuf pyridin - barbutiric
Chuan bj 10 dung djch mau cd nong do bSng nhau tir dung dich xianua 2 mg/L. do gia trj mat do quang A tai budc sdng tdi Uu, chung toi xac dinh gidi ban phat hien va gidi han dinh luong cua phUOng phap, ket qua thu duOc cac gia tri sau:
Nghien cdu phuong phdp xdc dinh hdm lUdng xianua vd ddidi gid d nhiem mot so ngudn nude thdi
Dd lech chuan: S=
E(A,-A)^
= 3,62.10"^; Gia tri trung binh: X ^ 0,01923;
3 3S 3 3 .3 fj2 10"'^
Gidi han phat hien: LOD = ^ ^ ^ ^ = '^^^^^—'-^ ^ 4, 75.10"^ (mg/L);
Gidi han dinh lUpng: LOQ = -lOS
2,5112 0,014 (mg/L) 4,05
Chiing tdi nhan thay 4 < R < 10 thi ndng dp dung dich thut la phii hdp va LOD tinh dUdc la dang tin cay.
2.3.3. Ket q u a xac dinh ham liTdng xianua trong m a u nirdc thai
Chung tdi tien hanh do nhanh de xac dinh pH trong mau nUdc thai ciia xUdng ma kim loai tai xa Lien Hiep, huyen Phiic Thp, thanh phd Ha Ndi, ket qua dUdc trinh bay d Bang 1.
Bdng 1. Ket qua xdc dinh gid tripH cdc mdu nude thdi ciia xudng ma kim loai d Lien Hiep, Phiic Tho, Hd Ndi stt
M a u pH TDdtl
\ Dot 2 1 Ml 8,42 8,46
2 M2 8,39 8,37
3 M3 8,31 8,30
4 M4 8,21 8,29
5 M5 8,19 8,25
6 M6 8,11 8,13 Bang 2 bieu dien ket qua phan tich mau nUdc thai tai cUa xa nUdc thai ra mdi trUdng ciia xUdng ma kim loai va xi nghiep gia cdng kim loai tai xa Lien Hiep, huyen Phuc Thp, thanh phd Hii Noi.
Bang 2. Kit qua xdc dinh hdm lUdng CN~ trong mdu nUdc thdi Hani lUUng
CN- (mg/L) Irong mau
Ml MJ M4 M5 M6
tai Lien Hiep, Phiic Thp
D a t l 0,254 ± 0,006 0,211 ±0,005 0,158 ±0,006 0,267 ± 0,005 0,166 ±0.004 0,074 ± 0,004
So liin vuot QCVN 40:2011/BTNMT
2,54 2,11 1,58 2,67 1,66 0,74
Ha Noi
D(Jt2 0,246 ± 0,004 0,241 ± 0,006 0,072± 0,006 0,250 ±0,004 0.145± 0.007 0,065 ± 0,007
So lan vuut QCVN 40:2011/BTNMT
2,46 2,41 0,72 2,50 1,45 0,65 K6l qua thu dUdc iren Bang 2 chd thay cac mau nUdc thai d^u phat hien dUdc xianua Phan Idn cac mau nUdc thai deu bi d nhiem xianua. Ham lupng xianua trong cac mSu do
Bai Thi Thu, Trinh Kim Yen, Dao Van Bay va Dang Xuan Thu
dUdc a khoang gia tri tii 0,065 dSn 0,276 mg/L. So vdi QCVN 40:2011/BTNMT cd 9/12 mSu nudc bj o nhiem xianua (theo QCVN 40:2011/BTNlVIT miic gidi han cho phep cila ham luong xinua la 0,1 mg/L).
Sau khi lay m l u va ti6n hiinh phan tich nUdc thai tai co sd ma vii xi nghiep kim khi xa Lien Hiep, huyen Phiic Tho, thanh pho Ha Noi. Chung toi nhan thay ham lUOng xianua d diiy deu vUdt qua miic cho phep doi vdi nUdc thai cdng nghiep va nUdc mat. Dae biet nUdc thai tai co sd ma co hiim lUdng xianua vUdt qua miic tdi 2,76 l^n so vdi nUdc thai cong (theo QCVN 40:2011/BTNMT) vii vuot qua mile tdi 13,3 so vdi tieu chuan chit lUdng nudc mat, loai B (QCVN 08: 2008/BTNMT). Toan bd lugng xa thai nay dUOc thai true tiep ra moi truclng mil khong qua xii li se anh hudng nghiem trpng den siic khde ciia ngUdi dan, ciia cac loai vat nudi nhu triiu, bd, v i t . . . . Sau do toan b<5 ngudn nUdc nay se chay viio song gay 6 nhiem mdi trUdng nUdc.
3. Ket luan
Dii khao sat duoc di6u kien tdi Uu cho phan ting tao phiic mau giiia xianua vii thudc thii pyridin-barbituric: pHi^j ^^ = 6,05. The tich thudc thii tdi Uu V^-T- - 2,5 mL. The tich chloramin T tdi Uu Vci„„i,„„ ^ = 1,0 mL Budc sdng hap thu tdi Uu A,;,, „„ -- A„,„ = 580 nm.
Khoang thdi gian cd do ben mau tdt nhat: t^^mu = 15 -^ 40 phiit.
Dii xiiy dung dUdc dudng chuiin xac dinh ham lugng xianua d cac dilu kien tdi Uu da chon. PhUdng trinh dudng chuan: A = (2,5112 ± 0,0323)CJ„ + (0,0179 ± 0,0040);
Sai sd ciia dudng chuiin nam trong gidi han cho phep. Gidi ban phat hien, gidi han dinh lugng phuong phap: LOD = 4 , 7 5 . 1 0 - ' mg/L; LOQ = 0,014 mg/L.
Da sii dung dudng chuan xay dung dUdc de xac dinh ham luong xianua trong cac mau nudc thai ciia co sd ma va xi nghiep kim khi tai xa Lien Hiep, huyen phuc Tho, thanh phd Hii Ndi. Ket qua xac dinh cho thay 9/12 mSu phan tich hiim lugng xianua dlu vugt qua miic cho phep ciia tieu chuan nUdc thai cdng nghiep, loai A ciia QCCN 40: 2011/BTNMT va tieu chuan chat lUdng nUdc mat, loai B (QCVN 08: 2008/BTNMT).
TAI H E U THAM KHAO
[1] Bg Tai nguyen mdi trudng QCVN 08: 2008/BTNMT. Quy chuan ki thuat qudc gia ve chSt lUdng nUdc mat.
[2] Bd Till nguyen mdi trudng QCVN 10: 2009/BTNMT, Quy chuan kl thuat qudc gia ve ngUdng chilt thiii nguy hai.
[3] Bd Tai nguyen mdi trudng QCVN 40: 2009/BTNMT, Quy chuan ki thuat quoc gia ve nude thai cong nghiep,
[4] Doerffel Dozent, 2008. Thdng ke trong Hda hoc phan tich. Nxb DH Quoc gia Ha Ndi.
[5] APHA- AWWA- AEF, 1995. Standard Methods jar Examination of water and U'a.srevi'a/er, 19th Edition.
Jii
Ngiiien cdu phUOng phdp xdc dinh hdm lUOng .xianua vd danh gid d nliiein mdt sd ngudn nude thdi
[6] Bark, L. S and Higson, H. G. 1964. Investigation of Reagents for the Colorimetric Determination of Small Amounts of Cyanide. Talanta, 2:471-479,
[7] Methods for chemical analysis of water and waste, 1983. Method 335.2. Cyanide, total, environmental monitoring systems laboratory (EMSL), Cincinnati, OH.
[8] Vien kiem nghiem an toan ve sinh thUe pham qudc gia, 2010. Thcfin dinh phuong phdp trong phan tich hda hoc vd vi sinh vat. Nxb Khoa hoc va KT thuat
ABSTRACT
Determining and assessing the extent of xyanide pollution in wastewater This paper presents the results of a method used to determine cyanide levels in water using the spectrometric method on a complex of cyanide and a pyridine-barbituric reagent. The results showed that optimal conditions are: Aop, = \ma\ - 580 nm; pH„pi
= 6.05; cloraminT volume = I.O mL; reagent volume - 2.5 mL with optimal time of complete complex reaction = 20 minutes. The cyanide content was found to be LOD = 4,75.10"^ nig/L and LOQ = 0.014 mg/L and therefore the initial conclusion is that this method can be applied to determine the concentration of cyanide in the plating industry's wastewater samples in Lien Hiep Commune, Phuc Tho District, Hanoi.
