III. PHAN THAO LUAN KET QUA NGHIEN CUTJ
HI PHAN THAO LUAN KET QUA NGHIEN CUtT
3.1. PhUdng phap phan tich.
3.1.L Pbiidng phap SKLM.
Hien n a y nhieu nU6c van cho phep diing phUdng phap SKLM de xac dinh ton lUdng HCBVTV trong moi trUdng [86]. Ngay ca cac tai heu va sach cua TCYTTG cung cho phep diing phUdng phap SKLM de xac dinh ton lUdng HCBVTV trong moi trUcing [100,107]. Cac tac gia deu thong n h a t de nghi : bat buoc phai xac dinh do t h u hoi trong khi xac dinh ton lUdng HCBVTV trong moi trUdng. Do t h u hoi toi thieu phai tren 70% . ThUc te cho thay, ton lUdng HCBVTV trong moi trudng d mot so nU6c dang phat trien r a t cao [5,15,23,116]. Do do dung phUdng p h a p SKLM de xac dinh ton lUdng HCBVTV trong moi trudng ciing la dieu hdp ly. (I) nhiing nUdc phat trien, ton lUdng HCBVTV trong moi trudng d miic nanogam va picrogam. Do do ngUdi ta dung phUdng phap GC/ECD, GC/FPD, GC/MSD de xac dinh [79,80,85,87,88,91]. C) nUdc ta, nhieu tac gia da diing phUdng phap SKLM de xac dinh ton lUdng HCTS trong moi trUdng . P h a m Kim Ciic, H a H u y Khoi da xac dinh ton lUdng DDT trong mot so' loai thiic an [8] va trong siia me [9]. Tran Tii Am, Nguyen Van Tuyen [1], N g u y i n Van Ban [2] xac dinh mot so' HCTS cd clo va cd photpho. N g u y i n Ngoc Kha xac dinh ton lUdng Lindan va DDT trong mot so san p h a m nong nghiep [25]. Nguyen Diic Tam va Nguyen Van Thi xac dinh cac HCTS nhom cd-photpho b^ng phUdng phap SKLM [44]. K J . M e l k s h a m va P.A. Hargreaves [100], B.W. Simpson [85] cung xac
dinh h a m lUdng diazinon trong b^p cai va Bi58 trong ca chua hkng
phUdng phap SKLM.
Tren cd sd do, chiing toi dung phUdng phap SKLM de xac dinh ton lUdng HCBVTV trong moi trUdng d Mien Trung . NhUng trong qua trinh dung phUdng phap SKLM de xac dinh ton lUdng HCBVTV trong moi trudng chiing toi gap mot so trd ngai :
- Khong phai liic nao ciing co san cac boa chat tinh khiet, sieu tinh khiet nhU trong tai lieu da ghi de chiet tach va tinh che mAu.
- Cac qui trinh chiet tach, tinh che ciia cac tac gia neu ra doi khi chi phii hdp vdi dieu kien ciia ho va khong phai liic nao cac qui trinh do ciing toi itu vdi moi phdng thi nghiem.
- Nhieu loai HCTS mdi ra ddi chUa dUdc cac tac gia xay dUng phUong phap p h a n tich hoac neu c6 ciing clii tren nguyen tac chung .
Do do bat buoc chiing toi phai lap dUng phUdng phap phan tich de dap iing yeu cau ciia cong tac dieu tra nghien ciiu. Viec phan tich ton lUdng HCBVTV trong moi trUdng bao gom 3 budc chinh : chiet tach chat ra khdi man, loai cac chat can trd kem theo (tinh che mau) va dinh lUdng chat can nghien ciiu [20, 87,95]. Vi vay toan bo qui trinh phan tich ciia chiing toi deu dUa tren 3 budc nay.
-^ Ve qui trinh chiet tach m^u : Cac nha phan tich deu biet r^ng, ket qua dinh lUdng HCTS co chinh xac hay khdng, phu thuoc rat nhieu vao qua trinh chiet tach, tinh che mau.
- Qui trinh chiet tach HCTS trong mAu rau qiia va nUdc kha on dinh va tUdng ddi n h a n h chdng. Ket qua dUdc trinh bay d bang 2,3,4.
('hiing tdi thitc hien chiet H("TS trong m^u rau ([ua va mkn nUdc 3 lan
vdi dung mdi va cho hieu suat thu hdi cao (tit 82-97% ddi vdi rau qua va 76% ddi vdi nUdc) [32]. Liic dau chiing tdi chiet tach HCTS trong mAu r a u qua va m a u nUdc chi cd 2 lan vdi dung moi, nhUng cho ket qua thap (70%). Do dd chiing tdi tang qua trinh chiet lap lai 3 lan va dUdc do thu hdi tUdng ddi cao (79-95%) nhU bang 7. Cac tac gia nhu Greve P.A, Grevenstuk W.B.F [86] va Krijgsman W va Van de kamp C.G. [88] cung chiet HCTS trong cac mau r a u qua 3 lan.
- Cac tai lieu chi de cap den van de xac dinh DDT trong md, trong san p h a m siia. Chiing tdi dUa tren cd sd phan tich DDT trong san p h a m siia (te xay dUng quy trinh chiet DDT trong sUa me. Theo tai lieu chiet 50 ml siia vdi ete dau hoa [86], liic dau chiing tdi chiet 50 g siia me vdi ete dau boa nhUng ket qua thu hdi thap (70%) sau dd
chiing tdi t a n g iMOng siia len 250g va chiet vdi ete dau boa, ket qua
thu hdi cao hon ban, dat yeu cau cua phan tich vet (85-88%). Dieu nay phii hdp vdi nguyen t^c : khi h a m lUdng chat can nghien cUu cang nhd thi lUdng m a u lay cang phai Idn de dam bao ty le bao h u t nbd.
- Chiing tdi chiet HCTS nhdm cd-clo trong dat vdi soxlet mat 8 gid, chiet HCTS nhdm cd photpho trong pheu chiet m a t 1 gid nhU bang 3 . Trong khi dd P h a m Thi Phong chiet fenvalerat trong dat mat 4 gid[32]. Cd the la fenvalerat de tach ra khdi dat hdn cac HCTS cd clo. Nhieu tac gia khac n b u Nguyen Diic Hue, Nguyen Dinh Trieu chiet cd clo trong dat m a t 5-6 gid [20]
Qui trinh phan tich HCTS trong dat, nitdc, thUc p h a m dUdc neu nhieu nhUng quy trinh phan tich HCTS trong khdng khi it dUdc de
cap. (yhiing tdi da ap dung nguyen tkc lay m a u bui va khi dung trong
2.1.2.1.6. Sau dd dUa vao nguyen tac chung chiet tach HCTS trong mdi trudng ap dung cho viec chiet tach HCTS trong kbdng khi. y-HCH
trong khdng khi dxUjc hap thu cjua giay loc thuy tinb hkng dung cu lay mkn klii filter. Sau dd ducic hoa tan bAng 50 ml ete dau boa rdi
dUdc lam sach tren s^c ki cot. Wofatox dUcJc hap thu vao 20 ml etilengiicol trong dung cu lay mau khi Impinger. Tdc df) hiit khdng khi 2 l/phiit, the tich khdng khi can lay tit 50 - 1001. Sau dd wofatox dUcic chiet b^ng 100 ml chclometan. PhUdng phap nay cho do thu hdi cao, dat yeu cau ciia phan tich vet (90 - 93%). Ket qua nghien citu nay phii hdp vdi ket qua nghien ciiu ciia Tran Quang Toan [53] nhitng dp thu hdi ciia Tran Q u a n g Toan cao hdn ciia cluing tdi (97 - 100%).
- Klii chiet DDT tit m a u gao chiing tdi dimg dung mdi ete dau
hoa chiet soxlet m a t 8 gid. Qua trinh chiet DDT trong gao hkng ete
dau hoa (tUdc tien h a n h t h u a n tiei7,dd thu hdi la 88%. '•• Ve qui trinh lam sach (tinh die) mau.
Mot trong cac k h a u quan trong de tinh die dich chiet H(^TS tii cac m a n la tach loai b^ng sac ky hap phu tren cot.
Tuy titng trUdng hcip cu the ma chiing tdi dimg cac cot s^c ki hap phu khac n h a u de lam sach dich cliiet.
- Dimg cot nhdm oxit t r u n g tinh, 60 Merck, da dUdc giam boat 10% nUdc de tach p h a n doan p,p'-DDT, y-HC^H, wofatox trong hon hdp,
p,p'-DDT dUdc tach ra d p b a n doan 1,2,3,4 (dung mdi rUa giai n- hexan). HCH tach ra d phan doan 6,7,8 (dung mdi rUa giai diclometan: n4iexan, 1:5 theo the tich). Wofatox dUdc tach ra d phan (toan 8,9,10,11 (dung mdi riia giai 30% diclometan-n-hexan) (bang 4).
- Khi tinh che dich chiet HCTS trong khdng khi va trong nUdc chiing tdi diing s^c ki cot gdm 2 g Na2S04 khan va 4 gam nhdm oxit trung tinh 60, Merck, da ducic giam boat 10% nUdc
* - Khi t i n h che dich chiet HCTS tit cac m a u dat, r a u qua, lUdng thuc, md, siia me va y - HCH dang bot, DDT dang bot chiing tdi dimg cot s^c ki gom: 2 gam Na2S04 khan, 4 gam nhdm oxit trung tinh, 60 Merck, da dUdc giam boat 10% nUdc, 1 g than boat tinh - xelit 545 (3:1). N a 2 S 0 4 k h a n gop phan loai bd nUdc ciia dich chiet neu cd. Nhdm oxit de loai bd cac chat gay nhieu va loai bd cac chat dau md [47]. Hdn hdp t h a n hoat tinh - xelit (3:1) co tac dung loai m a u ciia dich chiet [86]. Dich tinh che tii 2 loai sac ki cot nay r a t sach, t h u a n tien cho qua trinh chay SKLM va SKK.
- Do k h a u chiet tach va tinh che dich chiet ky va can t h a n nen ket qua t h u hoi ciia chiing tdi dat yeu cau phan tich vet, ket qua nhU bang 7. Vi vay, ton lUdng HCTS trong phUdng phap phan tich SKLM va phUdng phap GC/ECD gan tUdng dUdng, the Men d bang 35 va 44.
* Xac dinh monitor bang phUdng phap SKLM : Xuat phat tU
thUc te la ndng dan trong r a u thich dung monitor de phun cho r a u ,
(monitor da bi cam s\i dung vi nd cd doc tinh cao) [90, 138].
DUa tren nhiing nguyen t^c phan tich HCTS cd phot pho hkng
phUdng p h a p SKLM [44, 47], chiing tdi da xay dUng phUdng phap SKLM xac dinh monitor. Chiing tdi da chon chat hap phu la silicagel G, Merck (ban mdng dUdc che s i n cua Phap); dung mdi ddng la etylaxetat. Thudc hien m a u la bromphenol xanh va gia tri Rf thUc
da xac dinh dUdc monitor trong 360 m^u rau qua. Chiing tdi cung da hudng dAn cho 10 t r u n g t a m VSPD d mien Trung ciing ap dung.
''^'' Lap dung phitdng phap xac dinh warfarin trong phan rdm.
Dua vao phudng phap dinh tinh dicumarin trong Duoc chen Viet Nam tap I [74], chiing tdi lap dUng phUdng phap dinh lucing warfarin (cumachn) trong p h a n rdm. Sau khi ngluen citu phd hap thu ciia san pham mau, a n h hudng cua lUcing thudc thit deii phan iing mau, anh hUdng ciia pH, khao sat thdi gian ben mau, khoang tuyen tinh cua warfarin, chiing tdi dUa ra qui trinh phan tich warfarin trong phan
rdm. PhUdng p h a p xac dinh warfarin trong phan rdm vdi do thu hdi
93,4% dat yeu cau ciia phep phan tich vi htdng. Ky t h u a t ddn gian, it ton kem, da dem lai hieu qua cao trong xet nghiem chan doan chch. Giai phap nay eta gop phan n h a n h chdng dap tat vu dich xuat huyet da d Ilia tudi nhd hon 5 tudi, n h a t la 1-2 t h a n g tudi do dimg pban rdm cd chua warfarin.
31.2. Phiidng phap GC/ECD va GC/FPD
PhUdng phcip SKLM chi xac dinh HCTS d miic nuligam va microgam. Do (to chiing tdi diing pliUdng phap GC/ECD va GC/FPD de xac dinh mot sd HCTS trong cac ddi tUdng. Chiing tdi xac dinh mtmitor va wofatox sau khi phun (sau 1 ngay, sau 2 ngay, sau 3 ngay, sau 5
ngay) hkng GC/FPD. Tdn lUdng HCTS trong moi trUdng sau bao lut dUdc p h a n tich hkng phUdng phap SKLM va GC/ECD. Ket qua da chiing td rAng hkng phU(mg phap GC/ECD da phat hien (tUdc HCTS d
miic nanogam, trong klii dd SKLM hoan toan khdng phat hien dUdc
[bang 35]. NhUiig neu tdn lUdng HCTS trong cac mkn cd miligam, ket
m a u dat d nhiem HCTS sau bao lut dUdc dUa den trudng Dai hoc Tono- hdp Bremen, Cong boa Lien bang Ditc phan tich tren may GC/MSD.
Ton lUdng HCTS trong 5 mku dat dUcic phan tich b^ng phUdng phap SKLM ciing gan gidng phan tich hkng pliUdng phap GC/MSD (bang 44, phu luc). Dieu dd k h a n g dinh ket qua phan tich hkng phUdng phap
SKLM ciia chiing tdi dat yeu cau phan tich vet va dang tin cay. Trong phan tich lUdng vet, thiet bi phan tich hien dai giiip cho qua trinh phan tich dUdc n h a n h chdng va tien Idi. Cac thiet bi hien dai nhU GC/ECD, GC/FPD, GC/MSD cho phep xac dinh HCTS cd nanogam va picrogam. N h u n g de cd ket qua phan tich vdi do tin cay cao (do thu hdi cao), ngoai thiet bi liien dai ra, phai chiet tach va tinh che mau that can than. Hai k h a u nay da dUcic chiing tdi ngliien ciiu ky. Vi vay chiing tdi da iing dung cac phUong phap tren de xac dinh HCBVTV trong 728 m a u r a u qua, thUc pham, 144 mau khdng khi, 423 mau dat, 120 m i u nudc (tii 1985 - 1993). Tit 1990 den nay, cluing tdi nhan dUcic nhieu tai h e u phantich HCBVTV trong mdi trUdng [ 86, 100, 143, 144, 145, 146, 147, 148]. Cluing tdi ciing dUdc cung cap nhieu loai boa chat quy hiem, tinh kliiet va sieu tinh khiet dung cho s^c ky nhU : AI2O3 trung tinh 60 Merck, diclometan, etylaxetat, ete dau boa, than boat tinh-xelit 545 ... Cluing tdi ciing dUdc cung cap cac dung cu chiet tach,
lam sach, cac t a m skc ky dUdc die san cua Phap, Nhat, Ha Lan..., boa
chat tinh khiet, thiet bi hien dai (GC/ECD cua trUdng Dai hoc Tong hcip Ha Noi, GC/PFD cua trung tam kiem dinh thudc BVTV quoc gia Ha Ndi),GC/MSD cua trudng Dai hoc tong hcip Bremen - Cong boa lien bang Diic, da lam tang do chinh xac cho ket qua nghien ciiu cua chiing
• tdi. D<) t h u hdi khi phan tich HCTS trong cac mau dat, nu(k', khdng
khi, r a u qua ... dat tu 76-95% v(^i phUdng phap SKLM , 82-95% vdi
phitdng phap GC/ECD va GC/FPD, tit 95-102% vdi phudng phap
GC/MSD. Ket (}ua nay hoan toan thoa man vdi yeu cau phan tich
lUdng vet [79, 801. Cac tai lieu deu cho biet : sU mat mat la khdng the tranh khdi. Su m a t m a t do : mot phan chat bi gilt lai tren cot, mot phan chat bi bay hdi klii cat loai dung mdi [91] hoac do sU chuyen chat [87] tit binb nay sang binh kia [87, 100]. Tuy nhien van cd nhieu tac gia xac dinh ton lUc^ng HCTS trong mdi trudng vdi do thu hdi rat cao 94-97% n h u P h a m Tlii Phong [32], 95-100% nhU Tran Quang Toan [53]). Dieu nay cang khich le chiing tdi khi nghien ciiu, phan tich tdn lUdng cua HCTS trong mdi trUdng. Chiing tdi tin r a n g trong th(ii gian tdi, chiing tdi se nghien ciiu va ap dung cac qui trinh pban tich tdi Uu cua cac tac gia trong va ngoai nUdc de cd do thu hdi cao h(to nUa.