luận văn Thạc sỹ Khoa học Xác định crom trong mẫu sinh học bằng phương pháp phổ hấp thụ nguyên tử không ngọn lửa

Header Page of 16 I HC QUC GIA H NI TRNG I HC KHOA HC T NHIấN CAO TH MAI HNG TI: XC NH CROM TRONG MU SINH HC BNG PHNG PHP PH HP TH NGUYấN T KHễNG NGN LA Chuyờn ngnh: Húa phõn tớch Mó s: 60 44 29 TểM TT LUN VN THC S KHOA HC H Ni - 2011 Footer Page of 16 Header Page of 16 BNG CC CH VIT TT AAS Atomic absorption spectrophotometry ( Phng phỏp quang ph hp th nguyờn t) AbsCr Absorbance of chromium ( hp th quang ca crom) BG Background signal (blank signal) ( Tớn hiu ng nn ) CV Coefficient variation (H s bin ng) ER Relative error ( Sai s tng i) F - AAS Flame atomic absorption spectrophotometry ( Phng phỏp quang ph hp th nguyờn t k thut ngn la ) F - AES Flame atomic emission spectrophotometry ( Phng phỏp quang ph phỏt x nguyờn t k thut ngn la) GF - AAS Graphite furnace atomic absorption spectrophotometry ( Phng phỏp quang ph hp th nguyờn t k thut khụng ngn la) ETA-AAS Electro Thermal Atomizers Atomic Absorption Spectrocopy (Phng phỏp quang ph hp th nguyờn t k thut khụng ngn la) IAEA-CRM International Atomic Energy Agency-Certified Reference Materials (Mu chun) HPLC High Performance Liquid Chromatography ( Phng phỏp sc ký lng hiu nng cao) HCL Hollow cathode lamp ( ốn catot rng ) Footer Page of 16 Header Page of 16 HMDE Hanging mercury drop electrode ( in cc git thy ngõn treo) ICP - MS Inductively coupled plasma mass spectrometry ( Phng phỏp ph plasma cao tn cm ng ) LOD Limit of detection (Gii hn phỏt hin ) LOQ Limit of quantitortion ( Gii hn nh lng ) ppb part per billion ( Phn t ) ppm part per million ( Phn triu) RSD Relative standard deviation ( lch chun tng i) SS Sum of square ( Tng cỏc bỡnh phng) UV - Vis Ultraviolet - Visible spectrophotometry (Phng phỏp quang ph t ngoi - kh kin ) Footer Page of 16 Header Page of 16 DANH MC BNG Bng 1.1- Hm lng Cd, Cr, Pb t trng rau Bng 3.1 - Kho sỏt chn vch o ph ca Crom Bng 3.2 - Kho sỏt chn cng dũng ốn HCL Bng 3.3 - Kho sỏt rng khe o Bng 3.4 - Kho sỏt nhit tro hoỏ mu Bng 3.5 - Kho sỏt nhit nguyờn t hoỏ mu Bng 3.6 - Kho sỏt nh hng ca nng axit HNO3 Bng 3.7 - Kho sỏt nh hng ca nng axit HCl Bng 3.8 - Kho sỏt nh hng ca nng axit H2SO4 Bng 3.9 - Kho sỏt nh hng ca nng axit CH3COOH Bng 3.10 - Kho sỏt nh hng ca cỏc cht ci bin húa hc Bng 3.11 - Kho sỏt nng ca (NH4)H2PO4 Bng 3.12 - Kho sỏt thnh phn cỏc nguyờn t cú rau Bng 3.13- Kho sỏt nh hng ca cỏc kim loi kim th Bng 3.14 - Kho sỏt nh hng ca cỏc cation kim loi húa tr III Bng 3.15 - Kho sỏt nh hng ca cỏc cation kim loi nng húa tr II Bng 3.16 - Kho sỏt nh hng ca tng cỏc cation kim loi Bng 3.17 - Kho sỏt nh hng ca cỏc anion Bng 3.18 - Kho sỏt nh hng ca tng cỏc cation v anion Bng 3.19 - Gii hn hm lng cỏc cation v anion Bng 3.20 - Kt qu kho sỏt khong tuyn tớnh ca Crom Bng 3.21 - Kt qu sai s v lp li ca phộp o Bng 3.22- Kt qu phõn tớch bng phng phỏp ng chun Bng 3.23 - Kt qu phõn tớch bng phng phỏp thờm chun Footer Page of 16 Header Page of 16 Bng 3.24 - Kt qu so sỏnh gia phng phỏp ng chun v thờm chun Bng 3.25 - Kt qu so sỏnh gia phng phỏp GF-AAS v ICP-MS Bng 3.26 - Hiu sut thu hi Cr lng thờm chun Bng 3.27 - Hiu sut thu hi Cr theo mu chun Bng 3.28 - Kt qu phõn tớch ca hai mu rau bng phng phỏp ng chun Footer Page of 16 Header Page of 16 DANH MC HèNH Hỡnh 2.1 - H thng mỏy quang ph hp th nguyờn t Model AA 6800 Hỡnh 2.2 - B phn nguyờn t hoỏ cha cuvet graphit Hỡnh 2.3 - B phn ly mu t ng ASC - 6100 Hỡnh 3.4 - th kho sỏt nhit nguyờn t húa ca crom Hỡnh 3.5 - Kho sỏt khong tuyn tớnh ca crom Hỡnh 3.6 - ng chun ca crom Hỡnh 3.7 - th thờm chun xỏc nh crom mu rau ci bp ci non Hỡnh 3.8 - th thờm chun xỏc nh crom mu rau ci cỳc Hỡnh 3.9 - th thờm chun xỏc nh crom mu rau cn Footer Page of 16 Header Page of 16 M U Xó hi ngy mt phỏt trin, nhu cu ca ngi ngy cng cao S tng trng mnh ca nn kinh t ó a nhu cu ca ngi t mong mun n no, mc lờn n ngon, mc p Vỡ th nhu cu v thc phm sch, m bo sc khe ó tr thnh nhu cu thit yu, cp bỏch v c xó hi quan tõm hng u nc ta, s bựng n dõn s cựng vi tc ụ th hoỏ, cụng nghip hoỏ nhanh chúng ó to mt sc ộp ln ti mụi trng sng Vit Nam Vn v sinh an ton thc phm i vi nụng sn nht l rau xanh ang c c xó hi quan tõm Rau xanh l ngun thc phm cn thit v quan trng khụng th thiu c mi ba n hng ngy, l ngun cung cp vitamin, khoỏng cht, vi lng, cht x, cho c th ngi khụng th thay th c Ngoi ra, rau cũn c dựng nh mt loi thuc cha cỏc bnh thụng thng: nc rau mỏ giỳp gii nhit, rau ngi cu giỳp an thai, rau dip cỏ dựng h st, rau mung giỳp cm mỏu Tuy nhiờn, hin nhiu khu vc trng rau ang cú nguy c b ụ nhim cht thi ca cỏc nh mỏy, xớ nghip cựng vi vic s dng phõn bún mt cỏch thiu khoa hc dn n mt s loi rau cú th b nhim cỏc kim loi nng, cú nh hng n sc kho ngi Cỏc nguyờn t thuc nhúm kim loi nng nh Cr, Pb, Cd gõy c hi i vi c th ngi tu thuc vo hm lng ca chỳng Mt s khỏc nh Cu, Fe, Zn l nhng nguyờn t vi lng cn thit cho c th ngi Tuy nhiờn hm lng ca chỳng vt quỏ ngng cho phộp chỳng bt u gõy c Thi gian gn õy, rau sch ang l núng bng c nhiu c quan mụi trng v Xó hi quan tõm: Theo bỏo Lao ng s 288 Ngy 12/12/2008 thỡ Trung bỡnh 33km2 mi cú im bỏn rau an ton Theo Chi cc Bo v thc vt H Ni, n thi im ny, sn lng rau an ton ca ton thnh ph hng nm ch ỏp ng c gn 14% nhu cu rau xanh ca ngi dõn th ụ Nh th, vic iu tra, ỏnh giỏ cht lng rau sch tr nờn vụ cựng cp thit Mt cỏc ch tiờu dựng ỏnh giỏ an ton ca thc phm núi chung v rau sch núi riờng l ch tiờu v hm lng cỏc kim loi nng Nhm mc ớch phc v sc khe ngi v bo v mụi trng, nhm úng gúp cho chng trỡnh nh nc v nghiờn cu v iu tra iu kin dinh dng ca ngi Vit nam, bn lun ny chỳng tụi nghiờn cu vic s dng phng phỏp ph hp th nguyờn t khụng ngn la (GF-AAS) phõn tớch (xỏc nh) lng vt crom mu sinh hc Footer Page of 16 Header Page of 16 Chng - TNG QUAN 1.1 Gii thiu chung v nguyờn t Crom.[18] Crom l mt nguyờn t thuc phõn nhúm VIB, chu k bng h thng tun hon, cú cu hỡnh lp electron ngoi cựng: 3d5 4s1 Crom c ký hiu l Cr, s th t nguyờn t l 24, nguyờn t lng Crom l 51,996 vC, Crom cú s oxi hoỏ c trng nht l +3 v kộm c trng hn l +6 Ngoi ra, hp cht Crom cũn cú cỏc s oxi hoỏ: +1; +2; +4; +5 Tr lng thiờn nhiờn ca Crom l 6.10-3 % tng s nguyờn t v trỏi t, ngha l tng i ph bin Khoỏng vt chớnh ca Crom l st cromit Fe(CrO2)2 Crom c s dng luyn kim, m in hoc nhum mu, thuc da Cỏc hp cht cromat thng thờm vo nc mn c ch s n mũn kim loi Trong nc t nhiờn, Cr3+ tn ti dng Cr(OH)2+, Cr (OH) , cũn Cr(IV) tn ti dng CrO 24 , v Cr2 O 72 Ngi ta cho rng Cr3+ to phc bn vi cỏc amin v nú c bỏm vo cỏc khoỏng sột Crom c coi l khụng cn thit cho cõy trng nhng li l nguyờn t cn thit cho ng vt Crom kim loi c iu ch bng cỏc phng phỏp nhit nhụm, dựng bt nhụm kh Crom(III) oxit Cr2O3 + 2Al = 2Cr + Al2O3 Crom thu c cha 97,99% Cr v cht st 1.2.Tớnh cht ca Cr [ 9] 1.2.1 Tớnh cht vt lý: V mt lý hc, crom th hin rừ rt tớnh cht kim loi Nú l kim loi mu trng bc cú ỏnh kim, dn in v nhit tt Crom tinh khit d ch hoỏ c hc nhng ln cht thỡ tr nờn cng v giũn Vỡ vy, kim loi Crom k thut rt cng Vic a crom vo thộp lm tng cng, bn nhit, bn n mũn, v bn hoỏ cht ca cỏc loi thộp c bit Thộp dng c cha 3% ữ 4% Cr, thộp khụng r cha 18% ữ 25% Cr Mt s hng s vt lý quan trng ca Cr: Nhit núng chy (Tnc): 1890oC Footer Page of 16 Header Page of 16 Nhit sụi (Ts): 3390oC Th in cc (Eo): -0,91V õm in theo paoling: 1,6 Bỏn kớnh nguyờn t : 1,27 Ao Nng lng iụn hoỏ : 6,77 eV 1.2.2 Tớnh cht hoỏ hc: Crom l cht kh ging nh Al, trờn b mt c bao ph mng oxit mng, bn vi khụng khớ Crom khụng phn ng trc tip vi H2, iu kin thng khụng phn ng vi O2 nhng t chỏy khụng khớ to thnh Cr2O3 4Cr(rn) + 3O2 = 2Cr2O3 H = - 1141 KJ/mol Tuy nhiờn nhit cao, Crom phn ng vi nhúm Halogen Th in cc tiờu chun ca Crom E oCr / Cr = - 0,91 (V) Crụm kh c H+ cỏc dung dch HCl, H2SO4 loóng, núng gii phúng H2 Cr + 2H+ = Cr2+ + H2 Crom b th ng axit HNO3 v H2SO4 c ngui Crom khụng tỏc dng vi nc cú lp oxit bo v Crom tan c dung dch kim Cr + NaOH + H2O = NaCrO2 + 3/2 H2 Crom tỏc dng vi mui ca nhng kim loi cú th tiờu chun cao hn to thnh mui Cr(II) Cr + Cu2+ = Cr2+ + Cu 1.2.3 Cỏc hp cht ca Crom 1.2.3.1 Hp cht Cr(II) Cỏc hp cht ca Cr(II) u cú tớnh kh nh CrO 1000oC b khớ H2 kh thnh crom kim loi Cũn Crom(II) hiroxit th hin tớnh kh mnh hn 2Cr(OH)2 + O2 (kk) = 2Cr(OH)3 V d b oxi hoỏ thnh Cr (III) Vớ d: Footer Page of 16 Header Page 10 of 16 4CrCl2 + 4HCl + O2 = 4CrCl3 + 2H2O Mui Cr(II) ớt b thu phõn E Cr / Cr = - 0,41 (V), cỏc mui tan c nc cho iụn hirat hoỏ [Cr(H2O)6]2+ cú mu xanh lam 1.2.3.2 Hp cht Cr(III) Cỏc hp cht ca Cr(III) bn hn hp cht ca Cr(II) v cú nhiu ng dng thc t a Cr(III) oxit: L hp cht bn nht ca crom, nú núng chy 2265oC v sụi 3027oC Cr2O3 tr v mt hoỏ hc, nht l sau ó nung núng, nú khụng tan nc, dung dch axit v dung dch kim Tớnh lng tớnh ca Cr2O3 ch th hin nu chy vi kim hay Kali hirụ sunfat Cr2O3 + 2KOH = 2KCrO2 + H2O Cr2O3 + 6KHSO4 = Cr2(SO4)3 + 3K2SO4 + 3H2O b Cr(III) hiroxit: Cr(OH)3 cú tớnh cht ging vi nhụm hirụxit, nú l kt ta nhy, mu lc nht, khụng tan nc v l cht lng tớnh Khi mi iu ch Cr(III) hiroxit tan d dng axit v dung dch kim Cr(OH)3 + 3H3O+ = [Cr(H2O)6]3+ Cr(OH)3 + OH + nH2O = Cr (OH) (H O) Tt c nhng ion ny c gi chung l hiroxo Cromit, nú luụn kộm bn, un núng dung dch ó phõn hu to thnh kt ta Cr(OH)3 S d nh vy l vỡ Cr(OH)3 cú tớnh axit yu hn Al(OH)3 Cr(III) hirụxit tan khụng ỏng k dung dch NH3 nhng tan d dng amoniac lng to thnh phc hecxanano Cr(OH)3 + 6NH3 = [Cr(NH3)6](OH)3 c Mui Crom(III): Ngi ta ó bit c nhiu mui Crom(III) nhng mui ny c vi ngi Nhiu mui Crom(II) cng cú cu to v tớnh cht ging vi mui nhụm(III) Bi vỡ cỏc ion Footer Page 10 of 16 AbsCr Header Page 56 of 16 0.7 0.6 Parameter Value Error -A 0.0732 0.01982 B 0.05092 0.00265 0.5 0.4 R SD N P 0.9993 0.02369 0.00269 0.3 0.2 0.1 C (ppb) Cr 0.0 10 12 14 AbsCr Hỡnh 3.8 - th thờm chun xỏc nh crom mu rau ci cỳc 0.8 0.7 Parameter Value Error A 0.2009 0.01912 B 0.05035 0.00255 0.6 0.5 0.4 R SD N P -0.99744 0.02285 0.00256 0.3 0.2 0.1 CCr(ppb) 0.0 10 12 14 Hỡnh 3.9 - th thờm chun xỏc nh crom mu rau cn Kt qu phõn tớch c ch bng 3.23 Bng 3.23 - Kt qu phõn tớch bng phng phỏp thờm chun STT Mu Hm lng (g/kg) CV(%) Lỏ bp ci non 300,2 10,6 2,5 Rau ci cỳc 185,7 3,5 6,3 Rau cn 516,3 26,2 7,8 Footer Page 56 of 16 55 Header Page 57 of 16 3.6.3 So sỏnh phng phỏp ng chun v phng phỏp thờm chun S dng phn mm Minitab 14.0 so sỏnh hai phng phỏp ng chun v phng phỏp thờm chun i vi tng mu phõn tớch cho kt qu nh sau: Mu rau bp ci non Phng phỏp N ng chun Thờm chun Giỏ tr trung bỡnh lch chun sai chun 295,0 4,44 2,0 300,2 3,53 1,6 (GTTB) S sai khỏc : GTTB (1) - GTTB (2) c lng cho s sai khỏc : -5,2 Khong tin cy 95% cho s sai khỏc: (-3,3 ; 8,4) Chun student (chun t) kim tra s sai khỏc, giỏ tr t = -1,01; tr s P = 0,3; n= Ta cú P = 0,3 > 0,05 Do ú, hai giỏ tr trung bỡnh khỏc khụng cú ý ngha thng kờ (bng 3.24) Bng 3.24 - Kt qu so sỏnh gia phng phỏp ng chun v thờm chun STT Mu Hm lng ( g/kg) ng chun Thờm chun P Lỏ bp ci non 295,0 6,7 286,2 10,6 0,3 Rau ci cỳc 175,0 2,8 185,7 3,5 0,1 Rau cn 501,3 20,9 516,3 26,2 0,5 Kt lun Khỏc khụng cú ngha Khỏc khụng cú ngha Khỏc khụng cú ngha Nhn xột: i vi ba mu phõn tớch, hai giỏ tr trung bỡnh u khụng khỏc Vy hai phng phỏp ng chun v phng phỏp thờm chun khỏc khụng cú ngha thng kờ, ngha l phng phỏp u cho kt qu chp nhn c 3.6.4 So sỏnh phng phỏp GF - AAS v phng phỏp ICP-MS S dng phn mm Minitab 14.0 so sỏnh hai phng phỏp GF-AAS v phng phỏp ICP-MS i vi tng mu phõn tớch cho kt qu nh sau: Footer Page 57 of 16 56 Header Page 58 of 16 Mu rau bp ci non : chun t so sỏnh cp gia GF-AAS v ICP-MS Phng phỏp N GF-AAS ICP-MS S sai khỏc Giỏ tr trung bỡnh lch chun sai chun 295,0 3,3 1,5 302,5 4,5 2,0 -7,5 10,8 3,0 (GTTB) S sai khỏc : GTTB(1) - GTTB(2) c lng cho s sai khỏc : -7,0 Khong tin cy 95% cho s sai khỏc : (-7,8 ; 3,7) Chun student (chun t) kim tra s sai khỏc, giỏ tr t = -0,8; tr s P = 0,4; n=8 Ta cú P = 0,4 > 0,05 Do ú, hai phng phỏp GF-AAS v ICP-MS khỏc khụng ý ngha thng kờ (bng 3.25) Bng 3.25 - Kt qu so sỏnh gia phng phỏp GF-AAS v ICP-MS Hm lng (g/kg) STT Mu P GF-AAS ICP-MS 295,0 6,7 302,5 10,3 0,4 456,3 10,3 432,0 8,9 0,5 Rau cn 501,3 20,9 522,6 14,7 0,6 Rau ci xoong 695,0 25,6 673,2 16,8 0,8 Rau ng 413,8 7,5 421,5 9,7 0,9 Lỏ bp ci non Lỏ bp ci xanh Kt lun Khỏc khụng cú ngha Khỏc khụng cú ngha Khỏc khụng cú ngha Khỏc khụng cú ngha Khỏc khụng cú ngha Nhn xột: i vi nm mu phõn tớch, hai giỏ tr trung bỡnh u khụng khỏc Vy hai phng phỏp GF-AAS v ICP-MS khỏc khụng cú ý ngha thng kờ iu ny xỏc nhn quy trỡnh phõn tớch ó nờu l hp lý 3.6.5 ỏnh giỏ hiu sut thu hi bng phng phỏp thờm chun Kt qu phõn tớch thu c ph thuc vo nhiu yu t nh phng phỏp x lý mu, cỏc iu kin xỏc nh, k thut thc hin, thit b Do ú, ỏnh giỏ hiu sut thu hi ca Footer Page 58 of 16 57 Header Page 59 of 16 quỏ trỡnh nh lng mu, chỳng tụi chn mu rau bp ci phn lỏ non tin hnh lm mu thờm Tin hnh phỏ mu rau bp ci non v thờm lng chớnh xỏc dung dch chun Cr vi lng nh sau: 1,00ml dung dch cỏc nng 25,00ppb; 50,00ppb; 100,00ppb Sau ú nh mc 25ml, o ph vi nhng iu kin ó kho sỏt c Xỏc nh hm lng ca Cr mu rau bp ci non (Cn) v cỏc mu thờm bng ng chun (Cdc) Tớnh hiu sut thu hi theo cụng thc: %H C dc C n 100 Ct Hiu sut thu hi lng thờm chun c ch bng 3.26 Bng 3.26 - Hiu sut thu hi Cr lng thờm chun o ph GF-AAS CCr (g/kg) %H Mu rau bp ci v mu thờm chun Mu thc Mu thờm (1,00ppb) Mu thờm (2,00ppb) Mu thờm (4,00ppb) 0,29 0,41 0,54 0,82 - 97% 99% 106% Nhn xột: T cỏc kt qu ca hiu sut thu hi tớnh trờn ng chun u ln hn 97% Do ú, phng phỏp GF-AAS phự hp xỏc nh lng vt Cr cỏc mu rau xanh 3.6.6 ỏnh giỏ hiu sut thu hi dựng mu chun Bờn cnh vic ỏnh giỏ hiu sut thu hi thụng qua phng phỏp thờm chun, chỳng tụi dựng mu chun IAEA-CRM 359 cú nn mu tng t mu nghiờn cu (lỏ bp ci) v cú thnh phn mu xỏc nh ỏnh giỏ hiu sut thu hi ca quỏ trỡnh x lý v phõn tớch mu Mu c x lý lũ vi súng, sau ú tin hnh o ph theo cỏc iu kin ó chn mc 3.4 Kt qu c ch bng sau: Footer Page 59 of 16 58 Header Page 60 of 16 Bng 3.27 - Hiu sut thu hi Cr theo mu chun Mu Nng tỡm c Nng theo Hiu sut thu (g/kg) chng nhn (g/kg) hi(%) 1262,5 25 1300 97,12 2,2 IAEA-CRM 359 Nhn xột: T kt qu ca hiu sut thu hi Cr bng mu chun tớnh trờn ng chun ln hn 95%, kt qu ny tng t tớnh theo hiu sut thu hi Cr lng thờm chun Do ú, phng phỏp GF-AAS phự hp xỏc nh lng vt Cr cỏc mu rau xanh 3.6.7 So sỏnh kt qu mu rau ( vựng cú tỏc ng gõy ụ nhim) v mu rau sch (mua ca hng rau sch ): Mu phõn tớch c x lý lũ vi súng Tin hnh o ph theo cỏc iu kin ó chn mc Kt qu c ch bng 3.28 Kt qu ny l kt qu trung bỡnh ca mu lp, mi mu o ln Bng 3.28 - Kt qu phõn tớch ca hai mu rau bng phng phỏp ng chun STT Hm lng(g/kg) Mu Mu rau vựng cú tỏc Mu rau sch ng gõy ụ nhim Rau mung (phn gi) 312,5 2,5 218,8 3,2 Rau mung (phn non) 260,0 5,6 80,1 4,6 Nhn xột : Ta thy kt qu phõn tớch ca mu rau vựng cú tỏc ng gõy ụ nhim cao hn mu rau sch Tuy nhiờn, hm lng Cr ca cỏc mu ny khụng vt quỏ gii hn cho phộp ca t chc y t (WHO) cho crom thc phm l 1300 g/kg [48] Footer Page 60 of 16 59 Header Page 61 of 16 3.6.8 Kt qu phõn tớch T nhng kt qu phõn tớch bng phng phỏp GF-AAS s dng k thut ng chun, k thut thờm chun v cú tham kho cỏc kt qu thu c bng phng phỏp ICPMS, chỳng tụi thu c hm lng Cr cỏc mu rau : Lỏ bp ci non: 295 6,7(g/kg) Lỏ bp ci xanh: 456,3 10,3(g/kg) Rau cn: 501,3 20,9(g/kg) Rau ci xoong: 695,0 25,6(g/kg) Rau ng: 413,8 7,5(g/kg) Rau ci cỳc (phn non): 175,0 2,8(g/kg) Rau ci cỳc (phn gi:Thõn v R): 276,3 3,1(g/kg) Rau mung (phn non): 260,0 5,6(g/kg) Rau mung (phn gi): 312,5 2,5 (g/kg) Nhn xột : Hm lng Cr cỏc mu rau u nh hn gii hn cho phộp l 1300g/kg [48] KT LUN Footer Page 61 of 16 60 Header Page 62 of 16 Trờn c s cỏc kt qu thc nghim ó nghiờn cu xỏc nh crom mu sinh hc núi chung v mu rau núi riờng bng k thut phõn tớch GF- AAS, chỳng tụi ó thu c kt qu sau: 1.Cỏc iu kin xỏc nh crom bng phng phỏp GF-AAS: Cỏc thụng s ca thit b quang ph: Vch ph hp th : 357,9nm; Cng dũng ốn : 10mA rng khe o : 0,5nm; Tc dũng khớ Ar : 0,1 lớt/phỳt Cỏc thụng s ca lũ graphit: Nhit sy mu: - Bc 1: 1500C 20 giõy, nhit tng tuyn tớnh theo thi gian; - Bc 2: 2500C 10 giõy, nhit tng tuyn tớnh theo thi gian; Nhit tro húa: 8000C 20 giõy, tc 2000C/s; Nhit nguyờn t húa: 26000C giõy, tc 20000C/s; Nhit lm sch cuvet: 27000C giõy Mụi trng cho mu : HNO3 2%; Cht ci bin húa hc : (NH4)H2PO4 0,01%; Lng mu a vo lũ graphit : 20l Khong tuyn tớnh Cr: 2,0ppb - 12ppb Gii hn phỏt hin Cr: 0,3ppb Gii hn nh lng Cr: 0,9ppb Chn c iu kin phự hp x lý mu rau lũ vi súng Hiu sut thu hi ca quỏ trỡnh x lý mu ln hn 95% Da trờn cỏc kt qu thc nghim, ó tin hnh phõn tớch mt s mu thc cho kt qu nh sau : Rau bp ci non : Rau bp ci xanh : 295 6,7(g/kg) 456,3 10,3(g/kg) Rau cn : 501,3 20,9(g/kg) Rau ci xoong : 695,0 25,6(g/kg) Rau ng : Footer Page 62 of 16 413,8 7,5(g/kg) 61 Header Page 63 of 16 Rau ci cỳc : 175,0 2,8(g/kg) R rau ci cỳc : 276,3 3,1(g/kg) Rau mung phn non : 260,0 5,6(g/kg) Rau mung phn gi : 312,5 2,5(g/kg) Vi quy trỡnh phõn tớch ó ra, chỳng tụi nhn thy phng phỏp ph hp th nguyờn t khụng ngn la (GF-AAS) l mt k thut phự hp xỏc nh hm lng vt kim loi Cr cỏc mu rau dựng lm thc phm Kt qu thu c ỏng tin cy v sai s nm gii hn cho phộp (sai s nh hn 15%) TI LIU THAM KHO Ting vit Lờ Lan Anh, Lờ Trng Giang, Vit Anh v V c Li (1998), Phõn tớch kim loi nng Cr, Cd, Pb lng thc, thc phm bng phng phỏp von - Footer Page 63 of 16 62 Header Page 64 of 16 ampe hũa tan trờn in cc mng thy ngõn, Tp phõn tớch Húa, Lý v Sinh Hc, 3, s 2 Lờ Lan Anh, V c Li, Trnh Anh c, Nguyn Th Hng Giang, Nguyn Th Minh Li (2010), Nghiờn cu phõn tớch dng Cr, Cd, Pb t trng trt, Tp phõn tớch Húa, Lý v Sinh hc, 15, s 3 Dng Th Tỳ Anh, Trnh Xuõn Gin, Tng Th Thanh Thy (2010), Nghiờn cu xỏc nh mt s dng tn ti ca crụm nc bng phng phỏp von - ampe hũa tan, Tp phõn tớch Húa, Lý v Sinh hc, 15, s 4,tr 25-29 Nguyn Vn Can (1962), Phũng bnh húa cht, Nh xut bn Y hc Trnh Vn Dõn (2001), Khúa Lun tt nghip, Trng i hc Khoa hc T Nhiờn i hc Quc gia H Ni Lờ Th Khỏnh D (2007), Khúa Lun tt nghip, Trng i hc Khoa hc T nhiờn - i hc Quc gia H Ni Nguyn Th Hng Hnh (2006), Khúa lun tt nghip, Trng i hc Khoa hc T nhiờn - i hc Quc gia H Ni Phan Diu Hng (2001), Khúa lun tt nghip, Trng i hc Khoa hc T nhiờn i hc Quc gia H Ni Nguyn Th Thanh Hoa (2005), Lun thc s khoa hc, Trng i hc Khoa hc T nhiờn - i hc Quc gia H Ni 10 Trn T Hiu, T Vng Nghi, Nguyn Vn Ri v Nguyn Xuõn Trung (2007), Húa hc phõn tớch - phn 2: cỏc phng phỏp phõn tớch cụng c, nh xut bn Khoa hc v K thut 11 Phm Th 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lun tt nghip, Trng i hc Khoa hc T Nhiờn - i hc Quc gia H Ni 21 Lờ Ngc Tỳ (2006), c t v an ton thc phm, nh xut bn Khoa hc v K thut 22 Thnh Trinh Thc, Nguyn Xuõn Lóng, Bựi Mai Hng, Nguyn on Huy v Nguyn Nh Tựng (2007), ng dng phng phỏp cc ph xỏc nh mt s kim loi nng mt s loi thc phm v t trng, B Cụng nghip - V Khoa hc Cụng ngh, thụng tin khoa hc Cụng ngh, www.ips.gov.vn 23 T Th Tho (2006), Bi ging chuyờn thng kờ húa phõn tớch (statistics for Analytical chemistry), Trng i hc Khoa hc T nhiờn - i hc Quc gia H Ni 24 Nguyn Vn Ri v T Th Tho (2003), Thc húa hc phõn tớch - phn I: Phõn tớch nh lng húa hc, Trng i hc Khoa hc T Nhiờn - i hc Quc Gia H Ni Ting Anh 25 Alan H Stern, Natalie C.G Freeman, Patricia Pleban, Robert R Boesch, Thomas Wainman, Timothy Howell, Saul I Shupack, Branden B Johnson, Paul Footer Page 65 of 16 64 Header Page 66 of 16 J Lioy (1992), Residential exposure to chromium wasteurine biological monitoring in conjunction with environmental exposure monitoring, Environmental 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in basic foods of the Spanish diet: seafood, cereals, vegetables, olive oils and dairy products, The Science of The Total Environment, Volume 278, Issues 1-3, Pages 183-189 32 Elene P Nardi, Fỏbio S Evangelista, Luciano Tormen, Tatiana D SaintPierre, Adilson J Curtius, Samuel S de Souza, Fernando Barbosa Jr (2009), The use of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of toxic and essential elements in different types of food samples, Food Chemistry, Volume 112, Issue 3, Pages 727-732 33 F Hesford, Marianne Bỹhre (1978), Determination of chromium sesquioxide in faeces by a spectrophotometric method, Clinica Chimica Acta, Volume 82, Issue 3, Pages 225-22 34 Filik H, Dogutan M, A pak R(2003), Speciation analysis of chromium by separation on a 5-palmitoyl oxine-functionnalized XDA-2 resin and Footer Page 66 of 16 65 Header Page 67 of 16 spectrophotometic determination with diphenyl carbazide Anal.Biona.chem, 376(6); p.928-33 35 Francesco Cubadda, Silvana 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Sciences and Nutrition, Pages 1301-1307 56 S DIlio, F Petrucci, M DAmato, M Di Gregorio, O Senofonte, N Violante (2008), Method validation for determination of arsenic, cadmium, chromium and lead in milk by means of dynamic reaction cell inductively coupled plasma mass spectrometry, Analytica Chimica Acta, Volume 624, Issue 1, Pages 59-67 57 U Tinggi, C Reilly, C Patterson(1997), Determination of manganese and chromium in foods by atomic absorption spectrometry after wet digestion, Food Chemistry Volume 60, Issue 1, Pages 123-128 58 Vincent Dufailly, Laurent Noởl, Thierry Guộrin (2006), Determination of chromium, iron and selenium in foodstuffs of animal origin by collision cell technology, inductively coupled plasma mass spectrometry (ICP-MS), after closed vessel microwave digestion, Analytica Chimica Acta, Volume 565, Issue 2, Pages 214-221 Footer Page 69 of 16 68 Header Page 70 of 16 59 Y Martớnez-Bravo, A F Roig-Navarro, F J Lúpez, F Hernỏndez (2001), Multielemental determination of arsenic, selenium and chromium(VI) species in water by high-performance liquid chromatographyinductively coupled plasma mass spectrometry , Journal of Chromatography A, Volume 926, Issue 2, Pages 265-274 60 Yoanna Shaofen Wang and Kong Hwa Chiu (2004), Simulttaneous Extraction of Cr(III) and Cr(VI) with Dithiocarbamate ReagentFollowed by HPLC separation for chromium speciation, Anlaytical Sciences, Vol.20, p 841-846 61 Wei Wei Zhu, Nian Bing Li, Hong Qun Luo ( 2007), Simultaneous determination of chromium(III) and cadmium(II) by differential pulse anodic stripping voltammetry on a stannum film electrode, Talanta, Volume 72, Issue 5, Pages 1733-1737 62 Wu Y, Hu B, Peng T, Jiang Z (2001), In-situ separation of chromium(III) and chromium(VI) and sequential ETV-ICP-AES determination using acetylacetone and PTFE as chemical modifiers Frisennius J Anal Chem, 307(7):904-8 Footer Page 70 of 16 69 ... hợp phổ hấp thụ nguyên tử (AAS) lửa lò graphit phương pháp Von - Ampe xác định crom Phương pháp phổ hấp thụ nguyên tử xác định crom tổng phương pháp von - ampe có khả phân biệt Cr(tổng) Cr(VI) Phương. .. tạo phổ hấp thụ nguyên tử Đo phổ xác định nguyên tố cần phân tích Trong phương pháp phân tích quang phổ hấp thụ nguyên tử trình chuyển hóa chất cần xác định thành nguyên tử (quá trình nguyên tử. .. vạch phổ phát xạ đặc trưng nguyên tố đó, chúng hấp thụ lượng tia sáng sinh phổ hấp thụ nguyên tử Trên sở xuất phổ hấp thụ nguyên tử, thấy phổ hấp thụ nguyên tử sinh nguyên tử tồn trạng thái khí tự