Article. Manoochehr Bahmaei,*,a Hossein Ali Mashayekhi b and Faezeh Khalilian c. Introduction

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1 Article A J. Brz. Chem. Soc., Vol. 26, No. 7, , Printed in Brzil Sociedde Brsileir de Químic $ Appliction of Ultrsound-Assisted Emulsifiction Microextrction Bsed on Applying Low Density Orgnic Solvents to the Extrction nd Determintion of Mononitrotoluenes in Wter Smples Mnoochehr Bhmei,*, Hossein Ali Mshyekhi b nd Fezeh Khlilin c Fculty of Chemistry, North Tehrn Brnch, Islmic Azd University, Tehrn, Irn b Deprtment of Chemistry, Tonekbon Brnch, Islmic Azd University, Tonekbon, Irn c Deprtment of Chemistry, College of Bsic Science, Ydegr -e- Imm Khomeini (RAH) Brnch, Islmic Azd University, Tehrn, Irn In this study, simple nd efficient ultrsound-ssisted emulsifiction microextrction (USAEME) bsed on pplying low density orgnic solvents combined with gs chromtogrphy flme ioniztion detector (GC-FID) ws developed for the preconcentrtion nd determintion of mononitrotoluenes (MNTs) in wter smples. In this method, the fine droplets of toluene were formed nd dispersed in the smple with the help of ultrsonic wves which ccelerted the formtion of the fine cloudy solution without using disperser solvents. Severl fctors influencing the extrction efficiency such s the nture nd volume of orgnic solvent, extrction temperture, ionic strength nd centrifugtion time were investigted nd optimized. Using optimum extrction conditions, dynmic liner rnges of µg L -1, nd limit of detections (LOD) of 0.3 µg L -1 were obtined for o-nitrotoluene, m-nitrotoluene nd p-nitrotoluene. Finlly, the method ws successfully pplied to the extrction nd determintion of MNTs in the wter smples in the rnge of microgrms per liter with reltive stndrd devitions (RSD) < 12%. Keywords: ultrsound-ssisted emulsifiction microextrction, mononitrotoluenes, wter smples, gs chromtogrphy Introduction Isomers of mononitrotoluenes (MNTs) re widely presented in the qutic environmentl due to their vst spred of uses in severl industril nd chemicl mnufcturing pplictions. In toluene nitrtion, three isomers re produced in rtio of bout 58.8%, o-nitrotoluene, 36.8% p-nitrotoluene, nd 4.4% m-nitrotoluene. MNTs re used in the synthesis of intermedites for production of dyes, rubber chemicls, drugs, resin modifiers, opticl brighteners, suntn lotions, nd photogrphic developing gents. 1 Nitrotoluenes re highly toxic compounds in low concentrtions. Moreover, the romtic mines formed by biodegrdtion re suspected to be crcinogenic. The tolernce limits of m-nitrotoluene, o-nitrotoluene nd p-nitrotoluene in wter smples re below of 2 microgrm per liter. Consequently, there is incresing interest in *e-mil: bhmni.mnouchehr@yhoo.com the determintion of concentrtions of MNTs t low levels in vrious mtrices. 2,3 The most common wys to extrct MNTs re liquid-liquid extrction (LLE), 4 solid-phse extrction (SPE), 2 solid-phse microextrction, 5 single drop microextrction (SDME) 6 nd hedspce solvent microextrction (HSME). 7 LLE needs lrge mounts of toxic solvents nd is time-consuming procedure. SPE is lso time-consuming method in which solvent evportion step is required in order to pre-concentrte the nlytes before finl nlysis. 8 SPME hs been developed to extrct MNT. 5 However, it is expensive, nd the fiber used is frgile nd hs limited life time. Further, smple crry-over in this method cn be problemtic. 9 SDME hs been developed s solvent-reduction smple preprtion procedure, nd since smll mount of solvent is used, there is miniml exposure to toxic orgnic solvent. However, it is time-consuming method in which equilibrium could not be ttined fter long time. 10 Recently, Rezee et l., 11 hve introduced more effective solvent microextrction

2 1476 Appliction of Ultrsound-Assisted Emulsifiction Microextrction J. Brz. Chem. Soc. technique with high extrction recovery termed dispersive liquid-liquid microextrction (DLLME). In DLLME, the pproprite mixture of extrction solvent nd disperser solvent is rpidly injected by syringe into queous smples contining nlytes. Thereby, cloudy solution forms. In fct, the cloudy stte results from the formtion of fine droplets of extrction solvent dispersed in the smple solution. This cloudy solution is centrifuged nd the fine droplets re sedimented t the bottom of conicl test tube. The determintion of nlytes in the sedimented phse cn be performed by instrumentl nlysis. However, consumption of disperser solvent in DLLME hve led to some disdvntges such s decresing of prtition coefficients of nlyte into the extrcting solvent nd incresing of the cost, s well s, environmentl pollution, plus the vriety of solvents tht cn be used in this method is limited Ultrsound-ssisted emulsifiction microextrction (USAEME) procedure combines micro extrction system nd ultrsonic rdition in one step. In the USAEME technique, the ppliction of ultrsonic rdition fcilittes the emulsifiction phenomenon nd ccelertes the mss trnsfer process between two immiscible phses. This leds to n increment in the extrction efficiency in minimum mount of time. 16 In fct, this preconcentrtion technique hs been developed by Regueiro et l., 17 who successfully pplied it to determine synthetic musk frgrnces, phthlte esters nd lindne in queous smples. Sleh et l. 18 pplied low-density orgnic solvent using home-designed centrifuge glss vils for determintion of polycyclic romtic hydrocrbons (PAHs) in wter smples nd Sobhi et l. 19 pplied DLLME for the determintion of MNT in wter smples. This work evlutes the suitbility of USAEME for the extrction nd determintion of MNTs in wter smples. The fctor ffecting the microextrction efficiency ws investigted in detil nd the optiml conditions were then estblished. The results indicted tht the method could be successfully pplied to determine MNTs in different wter smples. Experimentl Chemicls nd regents The studied MNTs including o-mnt, m-mnt nd p-mnt were purchsed from Merck (Germny). The stock stndrd solutions (500 mg L -1 ) were prepred in methnol. All of the stndrd solutions were kept in the refrigertor t 4 ºC. Working solutions of stndrds t suitble concentrtion were prepred every dy from the stock solution. Toluene, 1-octnol, 1-undecnol, 1-dodecnol nd NCl were obtined from Merck. The wter used ws purified on Youngling ultr pure wter purifiction system Aqu Mx TM from Ultr (Dongn-gu, Kore). Apprtus A 40 khz nd kw ultrsonic wter bth with temperture control (Tecno-Gz SpA, Prm, Itly) ws pplied to emulsify the orgnic solvent. 125 µl Hmilton syringes (Bonduz, Switzerlnd) were used to inject the orgnic solvent into the smples. Twenty milliliters home designed centrifuge glss vils were used for extrction nd collection procedure (Figure 1). A 10.0 µl of Hmilton gs-tight syringe ws pplied for the collection of floted orgnic solvent nd injection into the gs chromtogrph (GC). A GC (Agilent GC-7890, Snt Clr, USA) equipped with split/splitless injector system nd flme ioniztion detector ws used for seprtion nd determintion of trget nlytes. Ultr pure helium gs (99.999%, Air products, Millennium Gte, UK) ws pssed through moleculr sieve nd oxygen trp (Crs, Louisville, USA) nd ws used s crrier gs with flow rte of 2 ml min -1. The injection port ws held t 250 ºC nd operted in the splitless mode for 1 min nd then split vlve ws opened nd split rtio of 1:5 ws pplied. Seprtion ws crried out on DB5, 25 m 0.32 mm i.d. nd 0.25 mm film thickness from J&W Scientific cpillry column. The oven temperture ws kept t 100 ºC for 1 min nd then incresed to 140 ºC t the rte of 10 ºC min -1 nd then incresed to 250 ºC t the rte of 40 ºC min -1, nd ws held for 3 min. The flme ioniztion detector (FID) temperture ws mintined t 270 ºC. Hydrogen ws generted by hydrogen genertor (OPGU 2200S, Shimdzu) for FID t flow rte of 40 ml min -1. The flow of ir (99.999%, Air products) for FID ws 400 ml min -1. USAEME procedure Smple ws plced in home-designed centrifuge glss vil (length: 11 cm nd dimeter: 1.5 cm) (Figure 1). Then, 14.0 µl of toluene ws injected into solution nd smple ws sonicted for 30 s t 25 ºC in n ultrsonic bth (Figure 1b). As result, oil-in-wter emulsions of toluene in wter were formed. After centrifuging t 3500 rpm for 5 min, the orgnic solvent droplet ws floted on the surfce of the queous solution due to low density below wter. After seprtion of the two phses, few microliters of doubly distilled wter were dded into the vil through the glss tube fixed on the side of the vil (length: 3 cm nd dimeter: 0.5 cm) (Figure 1c). The floted orgnic solvent ws rised into the cpillry tube ttched to the top of the

Vol. 26, No. 7, 2015 Bhmei et l. 1477 vil nd collected by gs-tight syringe (Figure 1d). Two microliters of collected orgnic solvent ws injected into GC-FID instrument. Tble 1.

3 Vol. 26, No. 7, 2015 Bhmei et l vil nd collected by gs-tight syringe (Figure 1d). Two microliters of collected orgnic solvent ws injected into GC-FID instrument. Tble 1. Extrction efficiency (%) of different extrction solvents evluted for the extrction of the trget nlytes Compound Extrction efficiency / % 1-Octnol 1-Undecnol Toluene 1-Dodecnol o-mnt m-mnt p-mnt Extrction conditions: extrction solvent volumes: 20.0 µl (1-octnol), 10.0 µl (1-undecnol), 14.0 µl (toluene), 12.0 µl (1-dodecnol); concentrtion of nlytes: 100 µg L -1. Effect of centrifugtion time Figure 1. Schemtic representtion of the proposed method () smple solution in the home-designed emulsifiction glss vil without slt ddition; (b) simultneous injection nd dispersion of 14.0 µl toluene into smple; (c) ddition of few µl of doubly distilled wter into the vil nd (d) collection of toluene trnsferred into the cpillry tube t the top of the vil (bout 6 µl). Results nd Discussion In the proposed method, n ultrsound-ssisted emulsifiction microextrction (USAEME) bsed on pplying low density orgnic solvents s new smple preprtion technique ws used for the extrction of MNTs from wter smples. The influences of vrious prmeters such s the kind nd the volume of the extrction solvent, ionic strength, extrction temperture nd centrifugtion time on the extrction efficiency were studied nd then the optimum conditions were selected. Selection of extrction solvent The selection of suitble extrction solvent is criticl for the USAEME process. In the USAEME, the extrction solvent should hve following chrcteristics: (i) lower density thn tht of wter, (ii) low solubility in wter, (iii) the bility to extrct interest nlytes. Bsed on these requirements, four orgnic solvent cndidtes, including toluene, 1-octnol, 1-undecnol nd 1-dodecnol were investigted. The results (Tble 1) reveled tht the extrction recovery obtined for the nlytes using toluene were higher thn those with the other solvents. Therefore, toluene ws selected s the extrction solvent for the study. Centrifugtion is essentil to seprte extrction solvent from queous solution in USAEME, becuse centrifugtion time my ffect the volume of floted phse. The effect of the centrifugtion time on the extrction efficiency ws exmined from 2 to 20 min t 3500 rpm. Theoreticlly, longer centrifuging time would result in more orgnic drops nd higher enrichment fctors of the trget compounds becuse fst seprtion of solvent extrction from the queous solutions would be difficult. Extrction solvent drops were very smll when the centrifuging time ws too short, nd excessing centrifuging time resulted in het genertion, dissolving of prt of the extrction solvent nd losing sensitivity. Therefore, it is necessry to find suitble centrifuging time. In the presented work, t higher centrifugtion times (> 15 min), the volume of collected solvent ws decresed. Therefore, considering the extrction efficiency, 10 min ws selected s the optimum centrifugl time. Effect of volume of extrction solvent The effect of the volume of the extrcting solvent on the proposed method of MNTs ws lso investigted t five levels in the rnge of µl. Volumes smller thn 10 µl were dissolved in queous bulk. The minimum collectble volume of orgnic solvent in the designed system ws 2 µl (12 µl of emulsified toluene). Preconcentrtion fctor (PF) ws clculted using the eqution 1: C C collected PF = (1) initil In the eqution 1, C collected re the concentrtions of the nlytes in the collected orgnic phse nd C initil the initil concentrtions of the nlytes in the smple solution. Figure 2 shows the preconcentrtion fctor of the nlytes versus different volumes of toluene. As shown in Figure 2,

4 1478 Appliction of Ultrsound-Assisted Emulsifiction Microextrction J. Brz. Chem. Soc. the concentrtion of the nlytes in the orgnic phse decresed by incresing of the volume of the orgnic phse due to the dilution effect. Results showed tht mximum preconcentrtion fctor ws chieved by using 12 µl of toluene for the extrction procedure. But, due to the difficulty of the collection of 2 µl of the floted toluene tht produced poorer precision, the volume of 14 µl ws chosen s the optimum volume of the orgnic solvent. Preconcentrtion fctor Slt ddition o-mnt m-mnt p-mnt Volume of extrction solvent / µl Figure 2. Effect of extrcting solvent volume on the preconcentrtion fctor. Conditions: smple solution: 10 ml of 100 µg L -1 of the nlytes; solution temperture: 25 ± 3 ºC; dispersion time: 30 s; centrifugtion time: 10 min. The influence of ionic strength ws evluted t 0-8% (m/v) of NCl levels while other prmeters were kept constnt. The experimentl results showed tht slt ddition hd no significnt effect on the extrction efficiency of the nlytes. This is possibly becuse of two opposite effects of ddition of slt. One is to increse the volume of the collected orgnic phse nd decrese the dispersion efficiency, which reduces the extrction efficiency; nother is the slting-out effect, which increses the extrction efficiency. It is mentioned tht by incresing the slt concentrtion, the volume of the collected orgnic phse increses, becuse of the decrese of solubility of the extrction solvent in the presence of slt. Therefore, ll the following experiments were crried out without dding slt. Effect of emulsifiction-extrction temperture Temperture ffects orgnic solvent solubility in wter s well s the emulsifiction phenomenon. Thus, this ffects the mss-trnsfer process nd the extrction efficiency. To determine the influence of the extrction temperture, extrction producers were done in different tempertures such s 20, 25, 35, 40 nd 50 ºC. The results re shown in Figure 3. It ws observed tht the highest extrction efficiency ws obtined t the rnge of ºC, but in higher temperture (35-50 ºC), extrction recoveries decrese. This event is possible becuse of the decrese in distribution coefficient (K D ) in higher temperture. Hence, 25 C ws used for further experiments. Extrction recovery / % Influence of extrction time nd ultrsound time The extrction time is defined s the intervl time strted fter dispersion nd ended just before centrifugtion. The results show tht extrction time hs no significnt effect on the extrction efficiency of the nlytes. It ws reveled tht the contct surfce between extrcting solvent nd queous smple ws infinitely lrger nd equilibrium stte ws chieved during few second. Therefore, in further experiments the centrifugtion ws crried out just fter dispersion process. The effect of ultrsound time on the extrction efficiency ws exmined in the rnge of s. The results (Figure 4) show tht in the less thn 30 s, extrction efficiency is low, becuse of the ultrsound Extrction recovery / % o-mnt m-mnt p-mnt Temperture / ºC Figure 3. Effect of extrction temperture on the extrction efficiency. Conditions: smple solution: 10 ml of 100 µg L -1 of the nlytes; volume of orgnic phse: 14.0 µl; dispersion time: 30 s; centrifugtion time: 10 min o-mnt m-mnt p-mnt Ultrsound time / s Figure 4. Effect of ultrsound time on the extrction efficiency. Conditions: smple solution: 10 ml of 100 µg L -1 of the nlytes; volume of orgnic phse: 14.0 µl; solution temperture: 25 ± 3 ºC; dispersion time: 0, 15, 30, 60, 90, 150 nd 180 s; centrifugtion time: 10 min.

5 Vol. 26, No. 7, 2015 Bhmei et l Tble 2. Quntittive results of USAEME nd GC-FID method for MNTs compounds Anlyte Liner rnge / LOD / LOQ / b PF c ER / % d R 2e o-mnt m-mnt p-mnt LOD: limit of detection for S/N = 3; b LOQ: limit of quntifiction for S/N = 10; c preconcentrtion fctor t the concentrtion nlytes of 100 µg L -1 ; d extrction recovery; e coefficient of determintion. time is not enough for dispersion phenomenon nd fter 30 s the extrction efficiency do not chnged significntly, becuse of equilibrium stte ws chieved few second. Therefore, 30 s ws selected s the optimum vlue for further experiments. Method performnce Anlyticl performnce To evlute the prcticl pplicbility of the USAEME method, nlyticl qulity prmeters (i.e., linerity, repetbility, limit of detection (LOD) nd limit of quntifiction (LOQ)) were investigted. The performnce of the method under the optimum conditions is shown in Tble 2. The liner dynmic rnges were from 0.5 to 500 µg L -1 for o-mnt, p-mnt nd m-mnt in wter smples. Good LODs (0.3 µg L -1 ) were obtined, bsed on S/N = 3 nd lso, LOQs 1.0 µg L -1 were obtined, bsed on S/N = 10. The preconcentrtion fctors (PF) were in the rnges of 1066 to 1132 in wter smples. The reltive stndrd devition (RSD%) for extrction nd determintion of the nlytes were obtined t three different concentrtion levels nd the results ws shown in Tble 3. Tble 4 compres proposed method with other extrction methods for the determintion of the trget nlytes in wter smples. The comprison of extrction time of the proposed method with solid-phse microextrction (SPME) 5 nd single drop microextrction (SDME) 6 for the extrction of the trget nlytes indictes tht this novel method hs very short equilibrium time compring to the mentioned methods nd the extrction time needed Tble 3. Reltive stndrd devition for MNTs compounds t three different concentrtion levels by using the proposed method Anlyte Reltive stndrd devition (RSD%), n = µg L µg L µg L -1 o-mnt m-mnt p-mnt for the proposed method is few seconds. Quntittive results of proposed method re better thn SPME nd SDME without using sensitive detector such s mss spectrometer (MS). Quntittive results of the proposed method re comprble with homogeneous liquid-liquid extrction (HLLE) 20 method nd better thn of dispersive liquid-liquid microextrction (DLLME) method. 19 The RSD of the proposed method re better thn of DLLME nd HLLE methods. Also, consumption of disperser nd homogeneous solvents in DLLME nd HLLE hve led to some disdvntges such s decresing of prtition coefficients of the nlytes into the extrcting solvent nd incresing of the cost s well s environmentl pollution, plus the vriety of solvents tht cn be used in this method is limited. Finlly, it cn be concluded tht, the brod liner dynmic rnge combined with the low detection limit suggests high potentil for monitoring MNTs in wter smples by pplying the USAEME-GC-FID method. Anlysis of rel smples In order to test the pplicbility of the proposed method, four different wter smples (tp, well, river nd se wter) Tble 4. Comprison of the proposed method with other extrction methods for the determintion of MNTs compounds in wter smples Method RSD / % Dynmic liner rnge / Limit of detection / Extrction time / min DLLME-GC-FID < < 3 19 SPME-GC-MS < SDME-GC-MS < HLLE-GC-FID < < 3 20 Reference USAEME-GC-FID < A few seconds This work

6 1480 Appliction of Ultrsound-Assisted Emulsifiction Microextrction J. Brz. Chem. Soc. Tble 5. Determintion of MNTs compounds in tp, well, river nd se wter nd reltive recovery of MNTs compounds in them Smple Concentrtion of o, m nd p MNTs / ± SD, n = 3 Added o, m nd p-mnts / Found o, m nd p-mnts / ± SD, n = 3 Reltive recovery / % o m p o m p o m p o m p Tp wter nd e nd e nd e ± ± ± ± ± ± ± ± ± Well wter b nd e nd e nd e ± ± ± ± ± ± ± ± ± River wter c nd e nd e nd e ± ± ± ± ± ± ± ± ± Se wter d n.d e n.d e n.d e ± ± ± ± ± ± ± ± ± Wter ws tken from Tonekbon Brnch, Islmic Azd University (Tonekbon, Irn); b wter ws collected from well in Tonekbon (Tonekbon, Irn); c smple ws collected from Lngrud River (Giln, Irn); d smple ws collected from the Cspin Se (Sri, Irn); e not detected. were extrcted nd nlyzed. The results re recorded in Tble 5. All the wter smples were spiked with MNTs stndrd solution t three different concentrtion levels (2.0, 5.0 nd 10.0 µg L -1 concentrtion levels) to ssess the mtrix effects. The obtined reltive recoveries were between 82.5 nd 99% (Tble 5). The results show tht mtrix hs negligible effect on USAEME of MNTs. Figure S1 shows GC-FID chromtogrms of river wter prior (Figure S1) nd fter (Figure S1b) spiking with MNTs t 2.0 µg L -1 level. Conclusions In the present study, USAEME combined with GC FID ws pplied to determine MNTs t trce levels concentrtions in wter smples. The present USAEME technique reduced smple extrction time nd orgnic solvent consumption. Under the optimized conditions, good recovery, linerity nd reproducibility were obtined. The proposed method ws simple, rpid nd chep nd possessed gret potentil in the nlysis of MNTs in rel wter smples nd cn be used to monitor MNTs in rel wter smples. Supplementry Informtion Supplementry dt (USAEME-GC-FID chromtogrm of MNTs) re vilble free of chrge t s PDF file. Acknowledgements Finncil support by North Tehrn Brnch, Islmic Azd University (Tehrn, Irn) for the support during the period of this reserch is grtefully cknowledged. References 1. Groggins, P. H.; Unite Process in Orgnic Synthesis, 5 th ed.; McGrw Hill: New York, Wlsh, M. E.; Rney, T. A.; Determintion of Nitroromtic, Nitrmine, nd Nitrte Ester Explosives in Wter using SPE nd GC/ECD; Comprison with HPLC, Specil Report 98-2, United Sttes Army Cold Regions Reserch nd Engineering lbortory: Hnover, United Sttes Environmentl Protection Agency (USEPA), Drinking Wter Stndrds nd Helth Advisories, EPA 822- B , United Sttes Environmentl Protection Agency: Wshington, United Sttes Environmentl Protection Agency (USEPA), SW-846, Method 8330; Nitroromtics & Nitrmines by High Performnce Liquid Chromtogrphy (HPLC), United Sttes Environmentl Protection Agency: Wshington, Psillkis, E.; Klogerkis, N.; J. Chromtogr. A 2001, 938, Psillkis, E.; Klogerkis, N.; J. Chromtogr. A 2001, 907, Ebrhimzdeh, H.; Ymini, Y.; Kmrei, F.; Khlili-Znjni, M.; Tlnt 2007, 72, Drrch, M. R.; Chutjin, A.; Plett, G. A.; Environ. Sci. Technol. 1998, 32, Helen, P.; Locit, I. K.; Trends Anl. Chem. 1999, 18, 272.

7 Vol. 26, No. 7, 2015 Bhmei et l Ahmdi, F.; Assdi, Y.; Milni Hosseini, S. M. R.; Rezee, M.; J. Chromtogr. A 2006, 1101, Rezee, M.; Assdi, Y.; Milni Hosseini, M. R.; Aghee, E.; Ahmdi, F.; Berijni, S.; J. Chromtogr. A 2006, 1116, Rezee, M.; Ymini, Y.; Frji, M.; J. Chromtogr. A 2010, 1217, Rezee, M.; Ymini, Y.; Shriti, S.; Esrfili, A.; Shmsipur, M.; J. Chromtogr A 2009, 1216, Mshyekhi, H. A.; Abroomnd-Azr, P.; Sber-Tehrni, M.; Wqif, S. H.; Chromtogrphi 2010, 71, Mshyekhi, H. A.; Abroomnd-Azr, P.; Sber-Tehrni, M.; Wqif, S. H.; Int. J. Environ. Anl. Chem. 2011, 91, Cstro, M. D. L.; Priego-Cpote, F.; Tlnt 2007, 72, Regueiro, J.; Llomprt, M.; Grci-Jres, C.; Grci Montegudo, J. C.; Cel, R.; J. Chromtogr. A 2008, 1190, Sleh, A.; Ymini, Y.; Frji, M.; Rezee, M.; Ghmbrin, M.; J. Chromtogr. A 2009, 1216, Sobhi, H. R.; Kshtiry, A.; Frhni, H.; Jvheri, M.; Gnjli, M. R.; J. Hzrd. Mt. 2010, 175, Ebrhimzdeh, H.; Ymini, Y.; Kmrei, F.; Shriti, S.; Anl. Chim. Act 2007, 594, 93. Submitted: Februry 19, 2015 Published online: My 8, 2015

Determination of Anions in Acid Rain by Ion Chromatography

Determination of Anions in Acid Rain by Ion Chromatography Appliction Updte 16 Determintion of Anions in Acid Rin by Ion Chromtogrphy INTRODUCTION The increse in cidity of wet nd dry tmospheric depositions hs been ttributed to the increse of SO 2 nd NO 2 emissions