Simple flow-injection system for the simultaneous determination of nitrite and nitrate in water samples

Transcription

1 Tlnt 64 (4) Simpl low-injtion systm or t simultnous trmintion o nitrit n nitrt in wtr smpls Rojn Burkm, Mitsuko Osim, Kt Grupn, Soji Motomizu, Dprtmnt o Cmistry, Fulty o Sin, Cin Mi Univrsity, Cin Mi, Tiln Dprtmnt o Cmistry, Fulty o Sin, Okym Univrsity, Tsusim-nk, Okym 7-85, Jpn Riv 29 Frury 4; pt 24 Mr 4 Avill onlin 24 Jun 4 Astrt A novl sptropotomtri rtion systm ws vlop or t trmintion o nitrit s wll s nitrt in wtr smpls, n ws ppli to low-injtion nlysis (FIA). T sptropotomtri low-injtion systm oupl wit oppris mium rutor olumn ws propos. T ttion ws s on t nitrostion rtion twn nitrit ion n ploroluinol (1,3,5-triyroxynzn), ommrilly vill pnoli ompoun. Smpl injt into rrir strm ws split into two strms t t Y-sp onntor. On o t strms mr irtly n rt wit t rnt strm: nitrit ion in t smpls ws tt. T otr strm ws pss trou t oppris mium rutor olumn, wr t rution o nitrt to nitrit ourr, n t smpl zon ws tn mix wit t rnt strm n pss trou t ttor: t sum o nitrt n nitrit ws tt. T optimis onitions llow linr lirtion rn o.3. NO 2 -N ml 1 n. 1. NO 3 -N ml 1. T ttion limits or nitrit n nitrt, in s tr tims t stnr vition o msur lnks r 2.9 n NO 2 -N ml 1 n 2.3 n NO 3 -N ml 1, rsptivly. Up to smpls n nlyz pr our wit rltiv stnr vition o lss tn 1.5%. T propos mto oul ppli sussully to t simultnous trmintion o nitrit n nitrt in wtr smpls. 4 Elsvir B.V. All rits rsrv. Kywors: Flow-injtion nlysis; Ploroluinol; Nitrit; Nitrt; Simultnous trmintion 1. Introution T trmintion o nitrit n nitrt is o nrl importn us o tir rmul impt on umn lt. T toxiity o nitrit is primrily u to t t tt it n rt wit sonry or trtiry mins prsnt in umn oy to orm nitrosmins, wi r known to rinons, n nitrit n rt wit iron(iii) o moloin to prou mtmoloinmi iss. Morovr, nitrit n us s n importnt initor or t orni pollution o wtr, sin it oul orm urin t iortion o nitronous orni mttr. Nitrt n ntr t nvironmnt s rsult o lin rom t soils ontinin nitronous rtilisr. Elvt onntrtions o nitrt Ppr prsnt t t 12t Intrntionl Conrn on Flow-injtion Anlysis, Vnzul, 7 13 Dmr 3. Corrsponin utor. Tl.: E-mil rss: motomizu@.okym-u..jp (S. Motomizu). in wtr sours l to potntil risk to umn lt us nitrt is lso ru to nitrit in nvironmnt. Numrous nlytil tniqus v n propos or t trmintion o nitrit n nitrt. Simultnous trmintion o ot ions is usully omplis y svrl mtos su s ion romtorpy [1,2], s romtorpy mss sptromtry [3] n pillry ltroporsis [4,5]. Howvr, tir instrumnttion is xpnsiv, ns t sprtion stp n is not suitl or tir us or nlysis o lr numr o smpls. A low-injtion nlysis (FIA) is tror prrly us or t simultnous trmintion o nitrit n nitrt tr tir onvrsion into msurl spis. Svrl rtions n ttion mtos v n vlop [6 12]. Som o tos r tim-onsumin, n tin or lrtion o t ttion rtion, somtim solvnt xtrtion is nssry or nlyt sprtion n prours r rtr omplit. Motomizu t l. vlop simpl ttion rtion or nitrit ion: t rtion ws s on t nitrostion o N,N-is(2-yroxypropyl)nilin in ii mium t 39-91/$ s ront mttr 4 Elsvir B.V. All rits rsrv. oi:.16/j.tlnt

2 126 R. Burkm t l. / Tlnt 64 (4) C [13,14]. Durin t nitrostion rtion unr tin t 8 C, t r-olour intrmit pprs n sows t sorption t nm o t sorption mximum, wi is rully rs: t inl prout o t nitrostion rtion is 4-nitroso-N,N-is(2-yroxypropyl)nilin (λ mx = nm). Tror, t rtion ws vourly ppli to FIA or t trmintion o nitrit n nitrt. A wily us mto or t simultnous trmintion o nitrit n nitrt is s on t rution o nitrt to nitrit n susqunt sptropotomtri trmintion vi t izotiztion rtion o sulnilmi n t sussiv ouplin rtion wit N-(1-nptyl)tylnimin (NED) [15,16]. Howvr, tr r som prolms or t izotiztion-ouplin rtion, su s t toxiity o t rnts us n t nssity o rt r ontrollin t iity or stp o nlysis. A vrity o ruin nts v n invstit to ilitt t onvrsion o nitrt to nitrit inluin zin [17], yrzin [18,19], mlmt mium [] n oppris mium [21 23]. Poto-inu rution o nitrit to nitrt ws lso ppli to t onvrsion o nitrt to nitrit [24]: t onvrsion iiny ws 7 84%. Nitrt is ru to nitrit mostly y usin oppris - mium olumn, wi is ssntilly prrr wn usin low-injtion systm. In tis work, FIA systm ws vlop or t simultnous trmintion o nitrit n nitrt. T ttion prinipl is s on t sinl-stp nitrostion o ommrilly vill pnoli ompoun. T proution o nitroso ompoun orm y t rtion o nitrous i wit pnoli spis is sily prorm unr mort onitions n l to t rsult in t inorportion o nitroso untionl roup onto romti rin o t pnoli ompoun. Ploroluinol, ontinin tr yroxyl roups, n rt quikly wit nitrit ion in ii mium, s sown in Fi. 1. Nitrt ws ru to nitrit y usin t oppris mium rutor olumn. Nitrit n nitrt n trmin simultnously y t propos FIA systm. 2. Exprimntl 2.1. Cmils n rnts All o t rnts us wr nlytil rnt r. Wtr purii wit Milli-Q systm (Elix 3/Milli-Q El- HNO2 (room tmp.) HO ploroluinol HO N O (λ mx = 312 nm) N(CH 2 CHCH 3 ) 2 + N(CH 2 CHCH 3 ) 2 N(CH 2 CHCH 3 ) 2 HNO 2 8 C - H + N,N-is(2-yroxypropyl)nilin H N O NO (λ mx = nm) [14] (λ mx = nm) CO CO HO sliyli i 2,6-iyroxynzoi i rsorinol Fi. 1. Sm o nitrostion rtion.

3 R. Burkm t l. / Tlnt 64 (4) mnt, Nion Millipor) ws us trouout t xprimnts. Stok stnr solutions o NO 2 -N ml 1 n NO 3 -N ml 1 wr prpr y issolvin soium nitrit n soium nitrt in wtr, rsptivly. Workin stnr solutions wr rsly prpr y ilutin t stok stnr solutions to t sir onntrtions wit wtr. A rrir solution ws prpr orin to Hiui n Motomizu [25] y issolvin 1. mmonium lori n.35 EDTA (isoium slt, iyrt) in wtr, t ph ws just to 8.2 wit N n t solution ws ilut to ml wit wtr Apprtus Sptropotomtri msurmnts wr otin usin UV-PC UV-Vis rorin sptropotomtr (Simzu, Jpn). T FI systm us is smtilly pit in Fi. 2. T mniol ws quipp wit oul plunr pump (FI-7L SNK, Jpn), six-port injtion vlv, oppris mium rutor olumn (2 mm i.. 15 m) [25], sptropotomtr (UV-8, Toso, Jpn) n sinl rorin FIA monitor/t prossin pprtus (F.I.A. Instrumnts, Jpn). T rrir n t rnt solutions wr pump vi t oul plunr pumpin systm n t stnrs or smpls wr injt into t NH 4 Cl/EDTA rrir strm y usin t six-port injtion vlv. T injt smpl ws split into two strms t t Y-sp onntor. On o t strms mr irtly n rt wit t rnt strm; NO 2 in t smpls ws tt (irst pk). T otr strm ws pss trou t oppris mium rutor olumn, wr t rution o NO 3 to NO 2 ourr. T smpl zon ws pss trou t ly oil to otin sprt pk n tn mix wit t rnt strm n pss trou t ttor; t sum o NO 3 n NO 2 ws tt (son pk). Tus, t NO 3 onntrtion ws trmin y t irn. 3. Rsults n isussion 3.1. Sltion o t rnt suitl or rpi nitrostion rtion Svrl kins o rnts or t nitrostion wit nitrit ion wr xmin wit rspt to rpi n rprouil rtion in mort xprimntl onitions. T rnts xmin r sown in Fi. 1. As rport in t prvious stuis [13,14], t inl prout o N,N-is(2-yroxypropyl)nilin wit NO 2 is lss snsitiv tn ploroluinol. Otr pnol n nptol rivtivs v smll mounts o nitroso ompouns n wr lss snsitiv tn ploroluinol. O ts rnts, ploroluinol oul rt wit NO 2 to orm its nitroso ompoun vry quikly. As rsult, ploroluinol ws slt s t ttion rnt. Unr t milr onitions mploy or t rtion totr wit lss ritil in ph ontrol, t rnts n t prout, ll involv lss toxiity omprin to tos oun y usin t ommonly us rnt, N-(1-nptyl)tylnimin (NED), wi provis vnts in prtil nlysis Asorption sptr Fi. 3 sows t sorption sptr o ploroluinol in.3 mol l 1 HCl, or n tr t rtion wit nitrit n nitrt ions. As n sn, t sorption inrs rtly in t prsn o nitrit. T mximum sorption ws otin t 312 nm. On t otr n, tis rnt os not rt wit nitrt ion. Tror, nitrt ws trmin tr its rution to nitrit y t oppris mium olumn Optimistion o t low-injtion systm In orr to otin wll sprtion twn two pks, orrsponin to NO 2 n NO 2 plus NO 3, t lnt o t ly oil ws optimis. T rsults otin sow tt oo sprtion twn two pks ws m y usin t ly oil lnt o m. C R P V RC DC MC D W FIA monitor Fi. 2. Flow-injtion systm us or t simultnous trmintion o nitrit n nitrt: C, rrir solution; R, rnt solution; P, oul plunr miro pump; V, six-port injtion vlv; RC, rutor olumn; DC, ly oil; MC, mixin oil; D, ttor; W, wst.

4 1262 R. Burkm t l. / Tlnt 64 (4) Asorn (A.U.) , Tl 1 Slt onitions or t simultnous trmintion o nitrit n nitrt y t propos FI systm Crrir.5 mol l 1 NH 4 Cl mol l 1 EDTA (ph 8.2) Rnt solution mol l 1 ploroluinol +.4 mol l 1 HCl Rutor olumn Coppris mium olumn (2 mm i.. 15 m) Dly oil lnt (m) Mixin oil lnt (m) Injtion volum ( l) Totl low rt (ml min 1 ) 1. (.75 ml min 1 ) Dttion (nm) 312 ( mm pt lnt). 6 wvlnt (nm) Fi. 3. T sorption sptr o ploroluinol n its rivtiv wit nitrit n nitrt: () 5. mmol l 1 ploroluinol; () +.3 mol l 1 HCl; () + 1. ml 1 NO 3 ; () +. ml 1 NO 2 ; () +. ml 1 NO 2 ; () +. ml 1 NO 2 ; () +.75 ml 1 NO 2 ; () + 1. ml 1 NO 2. T low rt o t rrir n t rnt solutions ws vry importnt wit rspt o t rution iiny wit t oppris mium rutor olumn, t rsin tim nssry or t nitrostion rtion n t sprtion o two pks. T t o totl low rt o t oul plunr pump ws xmin ovr t rn o ml min 1. T rsults r sown in Fi. 4() n (). T snsitivity o nitrit n nitrt n vry littl y vryin t low rt in t rn stui. By usin t oppris mium rutor olumn o 15 m, t rution rt is vry st nou or t onntrtion rn o. 1. NO 3 -N ml 1. Morovr, t nitrostion rtion twn nitrit ion n ploroluinol is vry st. T lnt o rtion oil ws lso xmin. Lonr rtion oils v lonr rsin tim, wrs too lon rtion oil oul l to ron pk n poor rprouiility. Tror, t rtion oil lnt o m ws slt or tis work Optimistion o rnt onntrtion Aorin to t nitrostion rtion, t ormtion o nitroso rivtiv oul tkn pl in n ii mium. Tror, t t o onntrtions o HCl ws stui in t rn o.1 1. mol l 1. Fi. 4() n () sows t t o HCl onntrtions on t snsitivity o nitrit n nitrt trmintions, rsptivly. T pk it, otin y usin t FIA systm in Fi. 2, slitly inrs wit inrsin t onntrtions o HCl. Howvr, ir nois lvl ws otin y usin i onntrtions o HCl. Tror,.4 mol l 1 HCl in t rnt solution ws osn or tis xprimnt. T t o t onntrtion o rnt, ploroluinol, ws stui in t rn o 1 mmol l 1, s sown in Fi. 4() n (). T snsitivity, pk it, inrs wit inrsin t rnt onntrtion n r t onstnt t 5 mmol l 1. Tror, t onntrtion o ploroluinol o 7.5 mmol l 1 ws opt Anlytil rtristis Unr t slt xprimntl onitions summris in Tl 1, t nlytil rtristis o t propos mto wr vlut y xminin linr rn, prision, ttion limit n smplin rquny. T rsults r summris in Tl 2. T ttion limit in s t onntrtion o nlyt ivin sinls quivlnt to tr tims o t stnr vition o t lnk sinl. In orr to vlut t prision o t mto, 11 injtions o t stnr solutions ontinin.15 n.4 NO 3 -N ml 1 wr prorm. T R.S.Ds. lss tn 1.5% wr otin. T low sinls orrsponin to t nitrit n nitrt solutions t t onntrtion rn o.3. NO 2 -N ml 1 n. 1. NO 3 -N ml 1, rsptivly, r sown in Fi Et o orin ions T inlun o ommon ions normlly oun in wtr smpls ws xmin unr t slt onitions. For tis stuy, t tim, orin ion o known onntrtion ws to solution ontinin ix onntrtions o mol l 1 nitrit or.15 NO 2 -N ml 1 n mol l 1 nitrt or. NO 3 -N ml 1. Si- Tl 2 Anlytil rtristis o t FI systm or t simultnous trmintion o nitrit n nitrt Prmtrs Nitrit Nitrt Linr rns.3. NO 2 -N/ml 1 Limit o ttion (3σ) 2.9 n NO 2 -N/ml 1 Prision (n = 11, R.S.D.%) 1.5 (.15 NO 2 -N/ml 1 ) Smpl trouput ( 1 ). 1. NO 3 -N/ml n NO 3 -N/ml 1 1. (.4 NO 3 -N/ml 1 )

5 R. Burkm t l. / Tlnt 64 (4) (1) 6 (2) pk it (mv) pk it (mv) pk it (mv) (3) (5) low rt (ml/min) HCl (mol/l) ploroluinol (mmol/l) pk it (mv) pk it (mv) pk it (mv) low rt (ml/min) (4) (6) HCl (mol/l) ploroluinol (mmol/l) i j i j i j Fi. 4. Et o som xprimntl prmtrs on t trmintion o nitrit n nitrt y t propos mto: (1) t o low rt on t nitrit trmintion; (2) t o low rt on t nitrt trmintion; (3) t o HCl onntrtion on t nitrit trmintion; (4) t o HCl onntrtion on t nitrt trmintion; (5) t o rnt onntrtion on t nitrit trmintion; (6) t o rnt onntrtion on t nitrt trmintion. Conntrtion o nitrit: (). NO 2 -N ml 1 ; (). NO 2 -N ml 1 ; ().15 NO 2 -N ml 1 ; ().7 NO 2 -N ml 1 ; ().3 NO 2 -N ml 1 ; onntrtion o nitrt: () 1. NO 3 -N ml; ().6 NO 3 -N ml 1 ; (). NO 3 -N ml 1 ; (i). NO 3 -N ml 1 ; (j). NO 3 -N ml 1. nls wr osrv n t rovris wr lult y omprin t sinls wit tos otin usin t stnr solution witout orin ion. T tolrn limit ws in s t mximum onntrtion o orin ion usin Asorn.1 A.U. NO2 - NO2 - + NO3 - Tim 55 min Fi. 5. Flow sinls or nitrit n nitrt stnr solutions: () lnk; ().3 NO 2 -N ml 1 +. NO 3 -N ml 1 ; ().7 NO 2 -N ml 1 +. NO 3 -N ml 1 ; ().15 NO 2 -N ml 1 +. NO 3 -N ml 1 ; ().25 NO 2 -N ml NO 3 -N ml 1 ; (). NO 2 -N ml NO 3 -N ml 1. vition o lss tn ±5%. T rsults r summris in Tl 3. It n sn rom Tl 3 tt t ions normlly prsntin in ommon wtr smpls o not intrr wit t trmintion o nitrit n nitrt in t propos prour Applition to smpls In orr to invstit t ppliility o t propos mto to t nlysis o rl smpls, som nturl wtr smpl su s tp wtrs, rivr wtrs n som lolly vill minrl rinkin wtrs wr nlys or nitrit n nitrt. T wtr smpls wr ollt n nlys witin 24 witout ny prsrvtion. Bor injtin t smpls into t FIA systm, t wtr smpls wr iltr trou.45 m mmrn iltr tt to t smpl injtion syrin. Tl 4 sows t nlytil rsults o nitrit n nitrt in wtr smpls, s wll s t rsults o t rovry tst t irnt nitrit n nitrt onntrtion lvls. Quntittiv rovris wr otin. Tl 5 sows t omprison o t propos mto wit t stnr mto [16]. T vlution y t-tst t 95%

6 1264 R. Burkm t l. / Tlnt 64 (4) Tl 3 Tolrn limit o orin ions in t simultnous trmintion o nitrit n nitrt Ion A s Tolrn onntrtion (mol l 1 ), o orin ion to t trmintion o Nitrit Nitrt Cl NCl F NF SO 2 4 N 2 SO CO 3 N 2 CO PO 3 4 KH 2 PO N + NCl K + KCl NH + 4 NH 4 Cl C 2+ CCl M 2+ MSO Mximum onntrtion stui. Tolrn limit inition ivn in t txt. A solution ontinin nitrit o mol l 1 (or.15 NO 2 -N ml 1 ). Nitrt o mol l 1 (or. NO 3 -N ml 1 ). onin lvl inits tt t rsults otin y t propos mto r wll wit tos otin y t stnr mto. It soul noti tt nitrit ws not tt in t smpl. In nrl, rivr wtr smpls in Jpn, wi r not ontmint wit inustril n omsti wsts, ontin nitrit n nitrt t onntrtions o 6 n 5 mol l 1, rsptivly. Nitrit possily n oxiis to nitrt y oxyn, sunlit n som miro ornisms. For tp wtrs, lorin is, n tror, ni- Tl 5 Rsults o nitrit n nitrt trmintions usin t propos n t stnr mtos Smpl Nitrit oun ( NO 2 -N ml 1 ) Propos mto Stnr mto [16] Nitrt oun ( NO 3 -N ml 1 ) Propos mto Stnr mto [16] A1 n.. n.. n.. n.. A2 n.. n A3 n.. n B n.. n A: minrl rinkin wtr; B: tp wtr; n..: not tt. trit nnot prsnt. Also, rinkin wtrs r pr-trt or ottlin. For t nlysis o s wtr, urtr optimistion n t pr-trtmnt stp my nssry. 4. Conlusion A FI simultnous trmintion o nitrit n nitrt usin nw rnt, ploroluinol is propos. T FI prour is quit simpl, rpi n os not n rul ph n tmprtur ontrols. T mto is rprouil n ovrs n nlytilly vlul ttion rn wi is suitl or nturl wtr smpls. T oppris mium rutor olumn is utomtilly rnrt y t rrir solution ontinin NH 4 Cl/EDTA n it n ontinuously us or rltivly lon prio. Applition to som ln wtr smpls ws monstrt. Tl 4 Dtrmintion o nitrit n nitrt in irnt wtr smpls usin t propos mto Smpl Nitrit Nitrt A ( ml 1 ) Foun ( ml 1 ) Rovry (%) Foun in smpl ( ml 1 ) A ( ml 1 ) Foun ( ml 1 ) Rovry (%) A1 n A2 n B B2 n C1 n C2 n C3 n A: tp wtr; B: rivr wtr; C: minrl rinkin wtr; n..: not tt. Foun in smpl ( ml 1 )

7 R. Burkm t l. / Tlnt 64 (4) Aknowlmnts T Ministry o Univrsity Airs, Tiln, n t Postrut Eution n Rsr Prorm in Cmistry (PERCH) r rtully knowl or t solrsip to R. Burkm. Rrns [1] B.S. Yu, P. Cn, L.H. Ni, S.Z. Yo, Anl. Si. 17 (1) 495. [2] C.D. Stliks, C.N. Koniri, C.G. Nnos, J. Cromtor. A 2 (3) 237. [3] S. K, K. Kuo, N. Ik, J. Anl. Toxiol. 26 (2) 3. [4] F. Kiii, T. Koji, T. Sori, I.W. Sin, Y. Mstk, H. Kunisi, J. Cromtor. A 838 (1999) 3. [5] K. Fukusi, T. Miyo, N. Isio, H. Nisio, K. Sito, S. Tk, S. Wki, Eltroporsis 23 (2) [6] X.F. Yu, Z.Q. Zn, H.T. Yn, Tlnt 62 (4) 97. [7] Y. Kn, M. Tr, Anl. Si. 19 (3) 695. [8] L. Monsr, S. Sok, G.M. Grnwy, I. S, R.F. Ulow, Tlnt 57 (2) 511. [9] P. Mikusk, Z. Vr, Anl. Cim. At 495 (3) 225. [] N. Ht, M. Kwsim, I. Ksr, S. Tui, Anl. Si. 19 (3) 239. [11] S. Motomizu, H. Miks, K. Toi, Tlnt 33 (1986) 729. [12] R. Kowki, S. Nkno, T. Kwsim, Tlnt 48 (1999) 3. [13] S.C. Rui, S. Motomizu, K. Toi, Bunski Kku 36 (1981) 7. [14] S. Motomizu, S.C. Rui, M. Osim, K. Toi, Anlyst 112 (1987) [15] B.E. Sltzmn, Anl. Cm. 26 (1954) [16] L.S. Clsri, A.E. Grnr, A.D. Eton, Stnr Mto or t Exmintion o Wtr n Wstwtr, t., APHA AWWA WEH (1998), Amrin Puli Hlt Assoition, pp [17] T.J. Cow, M.S. Jonston, Anl. Cim. At 27 (1962) 441. [18] M.T. Oms, A. Cr, V. Cr, Anl. Cim. At 315 (1995) 321. [19] L.J. Kmpk, S.A. Hnn, J.M. Con, Wtr Rs. 1 (1967) 4. [] A.W. Morris, J.P. Rily, Anl. Cim. At 29 (1963) 272. [21] F. Nyl, Tlnt 23 (1976) 349. [22] A. Kzmz, A.A. Ensi, Anl. Cim. At 442 (1) 319. [23] P.H. Ptsul, G.M. Grnwy, S.J. Hswll, Anl. Cim. At 428 (1) 155. [24] S. Motomizu, M. Sn, Anl. Cim. At 8 (1995) 6. [25] K. Hiui, S. Motomizu, Anl. Si. 15 (1999) 1.