3.1. Cn v xc nh khi lng

Xac nh khoi lng la bc thng xuyen trong quy trnh phan tch. Can la thiet b phong th nghiem cần thiết trong hau het cac phep phan tch. Tuy nhien, phep can lai la nguon pho bien gay sai so kho phat hien.

Quy trnh mo ta di ay ap dung trc tiep tren cac can ien t.

Quy trnh xac nh khoi lng co the chia thanh ba bc c ban: Chuan b can, kiem tra can va can xac nh khoi lng.

3.1.1.      Chuan b can

Bc ban au la chon, trang b cac dung cu th nghiem thch hp, nh cac o ng vat can (giay can, pheu can), bnh cha, kep gap, pipet, tha co kch c phu hp

S dung o ng co kch c khong vt qua tai trong cua can va phai am bao sach, kho.

Chuan b cac mau can va cac hoa chat can thiet, neu co yeu cau, pha cac dung dch, thuoc th.

Mau can co the yeu cau nghien mn hoac say kho. Mot vai mau can phai c lam nong hoac bao quan trong thiet b lam lanh. Trc khi can, mau can phai am bao c can bang nhiet vi nhiet o cua can. e tranh s ngng tu hi am, cac mau can lam lanh phai c e ti nhiet o phong trc khi m nap bnh dng.

3.1.2.      Kiem tra can

Can phai c kiem tra trc khi tien hanh can e loai cac sai so co the xay ra.Ngi s dung can can kiem tra moi trng can, hieu chuan can va kiem tra o khong am bao o cua can.

Moi trng can

Can phai c at v tr thch hp co mc rung ong u thap, khong co luong kh va co nguon ien on nh.

Can va khu vc lam viec chung quanh phai c gi gon gang va sach se. Nen dung ban chai long mn lam sach a can trc khi can.

Khi can c di chuyen en ni khac, can phai e can on nh ti nhiet o cua moi trng mi va phai hieu chuan lai can.

Hieu chuan can

M nguon va e can on nh trong t nhat 1 gi trc khi tien hanh hieu chuan (cac can vi phan tch can e on nh 24 gi e at s can bang).

Cac can phan tch ien t co he thong noi chuan da tren tai trong xac nh.

S hieu chuan c tien hanh trong ieu kien nhiet o phong.

o khong am bao o cua can

Cach giam o troi

o troi la mot trong nhng sai so thng gap va cung la yeu to co the lam giam hoac loai bo de dang nhat.

Kiem tra can phan tch va moi trng phong th nghiem e loai bo cac nguyen nhan sau ay co the gay sai so:

Ca buong can m.

Nhiet o cua can va mau can khong ong nhat.

Mau can tang hoac giam khoi lng.

Can mi c di chuyen nhng cha c e can bang vi moi trng hoac cha c hieu chuan lai.

Co cac luong gio trong phong th nghiem.

Nhiet o trong phong th nghiem thay oi.

Can khong at that thang bang.

Cac hoat ong trong phong th nghiem gay rung ong.

Anh hng cua cac bo phan c hoc xay ra trong suot qua trnh can.

Hien tng tre c hoc

Hien tng tre cua can la do s cang qua mc cac lo xo, chu yeu gay bi viec can qua tai hoac bi anh ri vat nao o len a can.

Quy trnh am bao chat lng cho s o o troi cua can

o troi cua can trong mot khoang thi gian, c giam sat bang viec kiem tra khoi lng vat can chuan tren c s a ang ky. Viec kiem tra nay nen thc hien sau khi can a c hieu chuan nhiet o phong th nghiem, trc khi can mau au tien trong ngay hoac sau mot s co co the lam sai lech can (mat nguon ien, di chuyen can en v tr khac...)

Vat can chuan phai co khoi lng hang nh va khong vt qua mc trong tai cua can. Moi can nen c cung cap mot vat can chuan, ng trong hop bao ve va at canh can.

Can thc hien nhng quy trnh sau ay e lam giam cac sai so can va kha nang sai so do o troi.

am bao noi nguon ien cho can, kiem tra bot nc thang bang cua can.

Hieu chuan can phan tch hoac can vi phan tch.

Ngi au tien s dung can moi ngay nen can vat can chuan, ghi chep khoi lng nay vao so theo doi e so sanh vi cac lan can trc. Neu s chenh lech ln hn gii han cho phep cho can phan tch va can vi phan tch, phai bao cao e sa cha.

(Cac vat can chuan phai c bao quan, tranh s tiep xuc vi nhng chat gay o nhiem trong khong kh, co the lam sach bang mot mieng vai gac c lam am bang mot lng nho dung moi thch hp nh ether ethylic).

Can phan tch

Chon mot vat can chuan co khoi lng phu hp e kiem tra can phan tch. Neu co the, cai at can e oc ti so thap phan th 5. Can theo hng dan cua nha san xuat.

Dung kep gap vat can chuan at can than len ia can, tranh e ri vai xuong a can. at vat can vao chnh gia a can e loai tr o lech goc. Neu khong co s troi, khoi lng cua vat can chuan se hang nh.

nh ky can mot vat can co nh se phat hien c o troi cua can (neu co). Viec kiem tra o troi c thc hien bang cach can nhng v tr nhay nhat. Mc dao ong khoi lng thu c khong c vt qua 0,2 mg. V du: Vi vat can 20 g, neu gia tr trung bnh oc c la 19,9984 g, khoi lng dao ong t 19,9982 en 19,9986 g la chap nhan c.V vay phai oc ket qua nhieu lan trc khi thiet lap dung sai.

Can vi phan tch

Tien trnh nh hng dan cho can phan tch nhng dung mot vat can chuan thch hp cho loai can nay.

V du: Co the dung vat can chuan 100 mg cho can co mc trong tai la 150 mg hoac co the dung vat can chuan 10 mg cho mot can sieu vi phan tch co mc trong tai la 15 mg.

(Ngi s dung can phai biet trong tai toi a cua can e chon vat can chuan thch hp).

Can bieu th khoi lng bang miligam. Ghi chep khoi lng ngay sau khi ket qua oc on nh mot vai giay. S bien thien khoi lng phai trong gii han phu hp vi gii han ky thuat cua nha san xuat nhng khong c ln hn 0,1% lng mau can.

V du: Neu thng can cac mau 10 mg, s bien thien khoi lng cua vat can chuan khong the vt qua 0,01 mg.

3.1.3. Can xac nh khoi lng mau

Trong bc cuoi nay, chon phan thap phan cua ket qua can c theo yeu cau cua quy trnh phan tch. Phan ln cac phep phan tch trong dc pham s dung mot lng nho mau th, nen yeu cau gia tr oc tren can cai at ti so thap phan th nam e at o ung can thiet.

So thap phan th t thch hp hn vi cac khoi lng mau can gan bang gam.

Khong can mau qua lau e tranh nhng thay oi gay ra bi s tng tac vi nc trong khong kh va kh carbonic.

Gii han trong tai

Chon can phu hp vi khoi lng phai can va o ung can thiet. Moi can co mot gii han trong tai, khong nen vt qua. Moi nha san xuat can a xac nh trong tai toi a cua can va gii han nay thay oi vi tng loai can. Ngi s dung nen biet gii han trong tai e tranh lam hong can.

Vat cha mau can

Nhng vat cha mau can thong thng la lo can, thuyen can (pheu can), giay can, bnh non Vat cha mau thch hp phu thuoc vao khoi lng va trang thai mau can (long, ran. bot). Phai chon vat cha mau thch hp cho tng mau can. Khoi lng vat cha cong khoi lng mau can can phai khong vt qua trong tai toi a cua can. Kch c, hnh dang cua vat cha phai ph hợp vi a can va khong gian buong can e khong anh hng en cac thao tac can. Quan trong la vat cha mau phai sach va kho.

Can s dung gang tay, kep gap va cac dung cu e lay cac vat cha v mo hoi t tay co the anh hng ti khoi lng can.

Thuyen can thng c s dung nhieu nhat v no va la vat cha va la pheu giup chuyen de dang mau can vao bnh. Thuyen can co nhieu c khac nhau, nen chon c phu hp cho tng trng hp.

Giay can thng s dung e can chat ran. Giay can c cam bang tay, phai can than e tranh lam ri, o mau can.

Cac phng phap can

Nhng phng phap sau ay thng c s dung va cho ket qua phan tch tot.

Phng phap 1

Can tr b: at vat cha rong len chnh gia a can va nhan phm can tr b e khoi lng cua vat cha khong hien th na (gia tr 0). Cho mau can vao vat cha va ghi nhan khoi lng mau can. Chuyen lng mau can vao bnh nh mc roi can lai vat cha ban au. (Chu y khong thay oi s cai at can tr b cua can gia 2 lan can nay). Khoi lng oc c lan can th 2 chnh la lng mau th khong chuyen het vao bnh nh mc (con dnh lai tren vat cha mau can) va c tr vao khoi lng mau can oc c lan can th nhat e xac nh khoi lng mau th a c chuyen vao bnh.

Phng phap 2

Can khong tr b: Cho mau th vao vat cha va at len chnh gia a can. Ghi nhan khoi lng can va chuyen mau th vao bnh nh mc, can lai vat cha ban au. Khoi lng oc c lan can th 2 la tong khoi lng cua vat cha mau va lng mau can khong c chuyen het vao bnh (con dnh lai tren vat cha mau can). Hieu cua khoi lng can ban au va khoi lng can lan 2 la khoi lng mau th a chuyen vao bnh nh mc.

Phng phap 3

Phng phap nay c xem nh la phng phap chuyen toan lng. Mau can c cho vao vat cha a can b, xac nh khoi lng mau can bi s chenh lech gia khoi lng can oc c va khoi lng can b. Toan bo lng mau th c chuyen het vao bnh bang cach dung mot dung moi e hoa tan mau va trang vat cha mau.

Quy trnh x ly mau can an toan

Ngi tien hanh can can oc ky cac thong bao ve mau th, cac tai lieu an toan ve hoa chat, nguyen vat lieu trc khi can.

Nhng nguyen lieu, hoa chat nguy hiem (chat oc, chat an mon, chat de chay, chat no, chat gay d ng, chat phong xa) phai at ni rieng biet, kn, co he thong loc kh thch hp.

S dung khau trang che mui va mieng e ngan nga viec ht cac bui hoa chat. Can dung gang tay e tranh s tiep xuc vi da va cung e ngan nga hi am, mo hoi bam tren vat cha khi can mau. Trong suot qua trnh can, ngi tien hanh can phai tiep xuc vi cac chat lieu nguyen chat nong o cao, do o phai luon luon quan tam en bien phap bao am an toan.

Quy trnh can c thc hien tren nhieu loai mau th khac nhau nh chat ran, bot mn, chat long (nht hoac khong nht, bay hi hoac khong bay hi)

Moi loai mau th yeu cau nhng thao tac rieng biet.

Can chat ran

Chat ran co 2 dang: Nhng khoi ln co hay khong co bot tren be mat, dang bot mn hay nhng tinh the nho.

Khi can chat ran can dung giay can e bao ve can. Mau chat ran phai lay bang kep gap, khong lay bang tay.

Khi can chat ran la khoi ln co bot tren be mat, dung giay can e bao ve can. Khi can nhng khoi chat ran khong co bot tren be mat, tr, co the at trc tiep len a can (v du: vien bao).

Mau chat ran phai lay bang kep gap khong lay bang tay.

Hien tng tch ien:

Dang bot mn co xu hng tch ien, lam cac tieu phan bay xung quanh. Hien tng nay phai c loai bo trc khi can. Co the dung thiet b chong tch ien e lam giam en mc toi thieu van e nay.

Hien tng tch ien phu thuoc vao o am tng oi cua phong th nghiem. Trong ieu kien nao o, co the s tch ien c tao ra bi loai quan ao ma ngi thao tac can ang mac. ien tch nay gay nhng sai so ln ve khoi lng trong qua trnh can.

Quy trnh can:

at vat cha len a can, ong ca buong can va can theo ch dan Cac phng phap can. Can than them mau can dang bot bang mot tha xuc vao vat cha cho ti khi at lng mong muon. Thao tac can than e tranh ri vai ra ngoai. ong ca buong can va ghi khoi lng mau can ngay khi can on nh.

S ri vai:

Neu chat ran b ri vai ra ngoai, lay vat cha ra, loai bo hoan toan cac chat lieu ri o tren can, lam sach ben trong, ben ngoai buong can, ban can, tranh e ngi sau tiep xuc vi cac chat lieu ri vai.

(Chu y: khong bao gi cho tr lai lo cha goc cac mau can d ma phai vt bo mot cach phu hp)

Can chat long

Chat long co the bay hi hoac khong bay hi va nht hoac khong nht. Moi loai co nhng chu y rieng biet.

Can theo hng dan Cac phng phap can, chu y them cac phan sau:

Chat long luon luon c can vao mot bnh, lo co nap ay e tranh s bay hi. Tot nhat chat long nen c cho vao bnh can ti mc d oan, ben ngoai can e tranh o tran tren can.

(Chu y: chat long o tran trong buong can co the gay nhng h hong nghiem trong cho can va kho lau chui sach).

Chat long khong nht co the c lay bang mot pipet Pasteur co gan mot qua bop cao su nho nh ong nho giot. Chat long c rot vao bnh, ay nap va at len can.

Mot lng nho chat long nht co the c lay bang cach cham mot ua thuy tinh ti be mat chat long roi can than cham que nay ti thanh bnh can mau e mot t chat long c chuyen qua.

Can cac chat lieu an mon

Nhieu hoa chat co tnh an mon, nh cac muoi. Cac chat lieu co tnh an mon khong nen e ri o tren a can hoac ben trong buong can. Can than khi can cac chat lieu nay.

 

3.1.4. Ket luan

Thc hien chat che theo cac quy trnh ch dan tren, nhan vien phong th nghiem co the loai bo nhieu sai so trong qua trnh tien hanh can.

Can phai co can bo ky thuat co chuyen mon bao tr va hieu chuan nh ky. Phai dung cac qua can chuan a c noi chuan vi he thong chuan quoc gia.