Recent Development and Applications of Ion Chromatography

Home , Ion chromatography

Send Orders for Reprints to [email protected] 90 Current Chromatography, 2014, 1, 90-99 Recent Development and Applications of Ion Chromatography

Rajmund Michalski*

Institute of Environmental Engineering of Polish Academy of Sciences, Skodowska-Curie Street 34, 41-819 Zabrze, Poland

Abstract: Ion chromatography was first introduced in 1975. Since then, it has been applied in most areas of the analytical chemistry. It is an effective technique used to analyze various inorganic and organic ions present in samples with different matrices. Importantly, ion chromatography has almost completely replaced the classical methods of ion determination. Its main advantages include: short analysis time; analysis of small volume samples; high sensitivity and selectivity; simultaneous separation and determination of different ions or ions of the same element at different oxidation states. As a result, it is routinely used to investigate ionic compounds in water, air and soil samples. The most important objectives of the ion chromatography improvement are to develop new stationary phases and enhance the peak capacity with complex eluent profiles. It is also essential to devise new methods of sample preparation and implementation of the hyphenated methods. In order to establish lower permissible limits for more and more ionic contaminants, researchers will need methods that are more accurate. For that reason, ion chromatography will continue to develop and become an even more valuable tool in the future. The following paper briefly describes the history, principles, development and applications of ion chromatography.

Keywords: Anions, bromate, capillary electrophoresis, cations, columns, detectors, eluents, history and development, ion chromatography standards, ion chromatography, metalloids, metals, sample matrix, sample preparation, species analysis, wastewater, water.

INTRODUCTION analyses of lanthanides. It posed a particularly challenging problem because they have closely related properties. As a Chromatography was discovered as a separation method result, ion-exchange methods for the separation of individual in 1903. Mikhail Semyonovich Tswett, a Russian botanist lanthanides were elaborated. They made use of the cation- who worked at the University of Warsaw (Poland), separated exchange resins and elution with complexing agents, such as vegetable dyes. He used the phenomenon of adsorption in a citric acid and ammonium citrate. As the Manhattan Project column filled with different substances, including calcium was confidential, none of this work was published until after carbonate [1]. In order to describe this method with Greek the war. words meaning color and writing, he coined the new term – chromatography. Initially, many scientists ignored the Tswett’s In the 1950s, chromatographic methods were successfully method. Nevertheless, its tremendous significance is recog- applied in chemical analytics. Unfortunately, their applica- nized at present, more than 100 years after its discovery. tions were mainly limited to the determination of organic Chromatographic methods are commonly applied in both compounds. In the late 1950s, a group of employees at the preparative and analytical scales. Importantly, gas chroma- Dow Chemical Research Laboratory (Midland, USA) ac- tography (GC) and thin layer chromatography (TLC) devel- knowledged the benefits of chromatographic methods. They oped faster than liquid chromatography (LC) as they could worked on their application for the inorganic analysis. Un- be more easily handled in technological terms. fortunately, the initial results did not turn out as effective as foreseen. The ion-exchange column was first used for the anion analysis by Bahrdt in 1927 [2]. He determined sulfates in Finally, the breakthrough was made at the beginning of the natural waters. The versatility of selected resins used in the 1970s, when a few publications referring to the use of IEC ion-exchange technology was soon recognized by many aca- for the separation and determination of inorganic cations and demic and industrial chemists. It resulted in the elaboration anions were published [4]. The key events in the development of new and unique applications of the ion-exchange technique. of ion chromatography (IC) are summarized in (Table 1). The work on the Manhattan Project during the World IC is a type of high performance liquid chromatography War II was an important stage in the development of ion- (HPLC) and is based on the ion-exchange mechanisms. The exchange chromatography (IEC) [3]. The project required major differences between the classical IEC and modern IC are listed in (Table 2).

*Address correspondence to this author at the Institute of Environmental PRINCIPLES OF ION CHROMATOGRAPHY Engineering of Polish Academy of Sciences, Skodowska-Curie Street 34, 41-819 Zabrze, Poland; Tel: + 48 32 271 64 81; At present, two main IC types are in use, i.e. suppressed E-mail: [email protected] and non-suppressed ones. In IC with suppressed conductivity

Table 1. Evolution of IC. the signal-to-noise ratio of the detection signal. In non- suppressed IC, the separation column is directly connected to the conductivity detector. The background signal is reduced Year Event to a manageable level with an ion-exchange separation column of low- exchange capacity that lowers the eluent con- Discovery of chromatography as a method of separation 1903 centration required for separation. The eluent ion selected for made by Mikhail Tswett separation must have a large and bulky structure, which low- 1938-1945 Works related to the Manhattan Project ers the equivalent conductance and facilitates the detection of the sample ions [7]. Both suppressed and non-suppressed Publication of the fundamental study by Small H., 1975 modes are applied to examine various sample matrices [8]. et al. [5] However, when it comes to anion analyses, the application of the suppressed IC is much more popular. Presentation of the first ion chromatograph at the meet- 1975 ing of the American Chemical Society in Chicago Ion exchange remains the primary separation mode used in IC today [9, 10]. Nonetheless, the apparatus used for the 1980 Introduction of IC without suppression separation of the ionic species also includes ion-exclusion Introduction of an ion chromatograph in which all parts (IEC) [11], ion-pairing chromatography (IPC) [12] and re- 1981 in contact with the eluent were made from non-metallic versed phase liquid chromatography (RPLC) [13]. materials The separation mechanism in IEC is governed by the First computer program to operate ion chromatographs Donnan exclusion, steric exclusion and sorption processes. It 1984 Introduction of micromembrane suppressors also depends on the type of separator column defined by the hydrogen bonding. The Donnan effect phenomenon results Recognition of IC as a reference method for the from the influence that the presence of charged molecules 1984 determination of ions in water and wastewater by the upon one side of a semipermeable membrane has on the dis- U.S. EPA and ASTM tribution of small, permeable ions across the membrane. At Automatic generator eluent equilibrium, small counterions are more concentrated on the 1997 Implementing the idea of "Just Add Water " macromolecule side of the membrane whereas small ions of the same charge as the molecules are less concentrated there. Introduction of IC standards for the determination of ions At the same time, concentrations of small ions of the oppo- Since in water, wastewater and air by the ISO and other orga- 1992 site charge are equal on the side of the membrane with no nizations macromolecules. A high-capacity and totally sulfonated cation-exchange material based on poly(styrene-co- New types of suppressors, sample preparation methods, divinylbenzene) is employed as the stationary phase. At present miniaturization of instruments, new stationary phases, hyphenated methods [6] Adsorption is the dominating separation mechanism in ion-pair chromatography. The stationary phase consists of a Table 2. IEC vs. IC. neutral porous divinylbenzene resin of low polarity and high specific surface area. Alternatively, chemically bonded octa- decyl silica phases, with lower polarity, can be used. In addi- Ion-exchange Chromatography Ion Chromatography tion to an organic modifier, an ion-pair reagent is added to the eluent, depending on the chemical character of analytes. Strong eluents (0.1-10 M) Weak eluents (0.1-10 mM) The addition of the ion-pair reagent modulates the retention of ionic analytes [14]. Simultaneous determination of Determination of single ions several ions The ion-exchange stationary phases with low ion- exchange capacities allowed the researchers to devise mod- High-capacity ion-exchangers Low-capacity ion-exchangers ern IC techniques. As a result, it was possible to use mobile No suppressor Suppressor (in suppressed IC) phases that contained concentrations of electrolyte counterions in the eluent that were one to two orders of magnitude Slow and non-repeatable analyses Fast and repeatable analyses lower. This, in turn, resulted in the compensation of the con- Classical detection method ductivity signal and removal of the ions from the column Conductivity detection (depending on analytes) effluent in suppressors.

Limits of detection, mg/L Limits of detection, g/L The suppressor was the key in the IC evolution. In the suppressor, the eluent conductance is lowered or suppressed, detection, an eluent with a suitable electrolyte passes through and the conductance of the sample ions is increased, which a special high-performance ion-exchange resin to a device leads to a large increase in the signal-to-noise ratio of the detection signal. The first suppressor was an ion-exchange called a suppressor. From there it travels to a conductivity + - detector. Analyte ions are separated on the ion-exchange column in the H or OH form. High-capacity ion-exchanger materials were used to provide the largest possible reservoir column and the separated sample ions (together with the + - eluent) move to the suppressor. In the suppressor, the con- of H or OH ions and to enable the suppressor to be used for ductance of the eluent is lowered while the conductance of as long as possible. Packed-columns had many disadvan- the eluted analytes is increased. It leads to a large increase in tages. These included the prerequisite for the offline regen-

92 Current Chromatography, 2014, Vol. 1, No. 2 Rajmund Michalski

Fig. (1). Flow chart of suppressor use for anion determination. eration and band-broadening occurring in the suppressor, silica-based column packings used in the classical HPLC, which resulted in the loss of the chromatographic efficiency. organic polymers are employed as the predominant support Moreover, some solute ions, which could be protonated eas- materials in IC. They show much higher stability in the ex- ily, showed variable retention in the suppressor column due treme pH conditions. While silica-based HPLC columns can to the ion-exclusion effects. only be used in the pH range of 2 - 8, ion exchangers based The next generation of suppressors, such as hollow fi- on organic polymers are also stable in the alkaline pH re- gion. Weiss and Jensen [17] give the review of stationary bers, was constructed from a polymeric ion-exchange mate- phases used for IC. rial. The eluent passed through the lumen of fiber, while a suitable regenerant solution passed over the exterior of the Small et al. [5] first introduced a special type of pellicu- fiber, usually in the countercurrent direction. The main lar anion exchangers in their introductory paper on IC in drawback of fiber suppressors was the small internal diame- 1975. Dionex Company further developed these stationary ter of the fiber. Consequently, the surface area of the fiber phases, called latex-based anion exchangers. The latex-based was low, which led to the low ion exchange and resulted in anion exchangers comprised a surface-sulfonated polysty- the low suppression capacity. These problems were over- rene/divinylbenzene substrate (particle diameters: 5 m - 25 come with the micromembrane suppressor, in which the fi- m) and fully aminated high-capacity porous polymer beads ber was replaced with flat sheets of membrane. The advan- made of polyvinylbenzene chloride or polymethacrylate (la- tages of micromembrane suppressor included: minimal band- tex particles). The latter had much smaller diameters and broadening effects; continuous regeneration; high-dynamic were agglomerated to the surface with the electrostatic and suppression capacity; suitability for gradient elution; and Van der Walls interactions. In the classical IEC, columns resistance to many organic solvents. Haddad et al. [15] de- were filled with anion- or cation-exchange resins whose par- scribe the development and use of suppression devices for ticle sizes varied between 75 m and 250 m. After the the conductometric detection of inorganic ions in IC. Cur- sample was applied to the top of the column, it migrated rently, there is a wide selection of suppression devices avail- down the column driven by the gravitational force, and be- able for IC. However, the continuously regenerated high- came more or less separated. Individual fractions of the capacity micromembrane and packed-column suppressors eluant were collected with a fractional collector, and subse- have become the most successful in the commercial terms quently analyzed in the separate work-step. Due to the high [16]. The flow chart of the suppressor use for anion determi- ion-exchange capacity of the columns, high electrolyte con- nation is shown in (Fig. 1). centrations were necessary to ensure the elution of sample In recent years, various stationary phases (of different se- ions from the column. In many cases, several liters of eluent had to be used. Importantly, these columns were easily over- lectivities and capacities) have been developed for both an- loaded by high sample concentrations. ion- and cation-exchange chromatography. The stationary phases do not only differ in the type of the support material, At the beginning, particles larger than 40 m were util- but also in their pore sizes and ion-exchange capacities. The ized for column materials. They generated only between 120 stationary phases used in IC mainly consist of polystyrene, and 300 theoretical plates of efficiency in relation to the col- ethylvinylbenzene, or methacrylate resins copolymerized umn dimension. In the first commercial column used for IC with divinylbenzene and modified with ion-exchange (Dionex AS-1), the particle size was reduced to 25 m and groups. Furthermore, polyvinyl, silica- based and other mate- efficiencies increased to 700 theoretical plates. The modern rials are used. Anion exchangers contain alkanol or alkyl high-capacity columns have efficiencies of over 8000 plates quaternary amine functional groups. Their selectivity varia- and particle size < 3 m. The following general trends in the tion is obtained through modifying the structures of the ion- development of new stationary phases for IC can be identi- exchange sites. Weak anion exchangers may include tertiary fied: new stationary phases, matrices and bonding chemis- amino groups, such as diethylamino ethyl (DEAE) and sec- tries; improvement in the column efficiency; the tendency ondary or even primary amines. Cation exchangers contain toward the reduction in the diameter of a separation column; sulfonic, carboxylic, carboxylic-phosphonic, and carboxylic- and new chemistry of the bonded functional groups/layers phosphonic-crown ether functional groups. In contrast to [18]. Recent Development and Applications of Ion Chromatography Current Chromatography, 2014, Vol. 1, No. 2 93

Zwitterionic ion exchangers are one of the new solutions The selectivity can be modulated through the choice of in the development of stationary phases for various IC the stationary phase and eluent composition, but the eluent modes. The combination of positively and negatively must meet the requirements of the detection system. Al- charged sites in a single particle, or within the functional though the conductivity detector is still the most popular groups of a single molecule attached to the surface of an solution, other types of detection modes (e.g. amperometric absorbent, provides unique opportunities to vary the separa- and potentiometric modes, UV/Vis, chemiluminescence, tion selectivity [19]. This results in reduced shrinking and fluorescence, atomic absorption spectrometry, atomic emis- swelling and improves the mechanical stability of zwitteri- sion spectrometry, inductively coupled plasma-optical emis- onic ion exchangers, in comparison to the traditional ones. sion spectrometry, inductively coupled plasma-mass spec- Moreover, such ion exchangers demonstrate unique separa- trometry, mass spectrometry) can be applied for different tion selectivities and often enable the simultaneous separa- analytes [27]. A survey of the detection methods is given in tion of anions and cations with a single column. Recently, (Table 3). there has been a growing interest in using porous monolithic Although the optimization of the appropriate separation stationary phases for high-performance separation of inor- conditions (column, eluent, detection) is crucial to obtain ganic and organic ions [20]. When compared to the particle reliable results, the sample preparation phase is the major bed columns, monolithic columns are characterized by a error source and the most labor-intensive stage of the analy- single piece of porous cross-linked polymer or porous silica. sis [28]. Sample pretreatment is necessary when the analyti- Monoliths are made in different forms, such as porous rods, cal method cannot provide appropriate separation and quanti- generated in thin capillaries, thin membranes or disks [21]. fication due to the interferences from sample matrix compo- Monoliths help to decrease the pressure drop requirements nents. Sample matrix effects can include changes of reten- and, hence, allow using longer columns. The greatest interest tion times, poor reproducibility and irregular baseline. The in monoliths can be observed in preparative and analytical majority of water samples collected for IC analysis require chromatography, where high throughput (short and fast col- little or no sample pretreatment. Drinking water samples umns) and/or high-efficiency (long columns) separations are usually require no pretreatment other than filtration through required. Monolithic columns are applied in low- and me- a 0.45-m filter to remove particulates. Most wastewater dium- pressure IC, ultrafast IC, capillary chromatography, often requires only dilution and filtration to bring the ana- flow gradients, double-gradient ion chromatography and lyzed analytes into the working range of the method. Many multicolumn/multidimensional ion chromatography [22]. environmental samples (e.g., sea water, wastewater, brines) Carbonate and bicarbonate eluents have been used as the contain high concentrations of chloride, sulfate, and sodium mainstay of anion-exchange IC for many years. However, ions [29]. The matrix removal of these ions is based on their hydroxide seems the ideal eluent as it forms water that has precipitation with suitable counterions. The most commonly virtually zero conductance after suppression. Therefore, it used counterions are Ag+, Ba2+ and H+ for the matrix elimi- provides the perfect conductivity baseline. Unfortunately, the nation of chloride, sulfate and general cations, respectively. hydroxide eluent is difficult to use as it readily absorbs car- The most important sample preparation methods for IC bon dioxide and forms the carbonate. The eluent type for analyses, qualified according to the sample form, are [30, cation-exchange chromatography depends on the applied 31]: detection method [23]. The most popular eluents for cation analysis are low-concentration mineral acids such as HCl, 1). Liquid samples - filtration, dilution, pH adjustment, standard addition, derivatization, liquid-liquid extrac- HNO3 and H2SO4. The eluents can also contain organic modifiers (e.g., ethylenediamine, 2,3-diaminopropionic tion, solid-phase extraction, distillation, micro-diffusion, acid). The organic modifiers in the mobile phase have sig- membrane separation. nificant influence on the retention time and resolution. The 2). Solid samples - drying, homogenization, dissolution, selection of the appropriate separation conditions (stationary extraction/leaching, digestion, ashing, combustion. phase type, eluent concentration and flow rate, suppression and detection mode) depends on many factors [24]. Some 3). Gaseous samples - absorption in liquids, adsorption on manufacturers of the IC instruments offer help in the optimi- solid phases, membrane sampling, chemical conversion. zation of separation processes, in the form of computer soft- The IC analysis of solid and gaseous samples requires the ware. Such software is helpful in selecting the optimum mo- transfer of either the whole sample or the analyte ions into bile phase composition and separation conditions. It also the aqueous phase. This is carried out in different ways, de- supports the selection of the eluent pH, concentration, and pending on the solubility of the analyzed substance and the ionic strength to obtain the optimum conditions for data ionic content to be determined. Generally, the conventional separation of analytes [25, 26]. As corrosive eluents (e.g. IC methods for solid samples are: diluted acids and bases) are often used in IC, all parts of the 1). Fusion methods (alkaline with NaOH, KOH, Na CO , chromatographic system exposed to liquids should be made 2 3 K2CO3; acidification with KHSO4, K2S2O7; fluorination, of inert and metal-free materials. The conventional HPLC chlorination and sulfurization). systems with tubings and pump heads made of stainless steel are eventually corroded with aggressive eluents. Consider- 2). Combustion methods (burning the sample in air/oxygen; able contamination problems are the effect, because metal oxygen bomb; calorimeter bomb; combustion in a stream ions exhibit high affinity towards the stationary phase of ion of oxygen; combustion in an oxyhydrogen flame). exchangers, which leads to a significant loss of the 3). Wet chemical digestions (open acid digestion with re- separation efficiency. flux; pressure digestion; UV pyrolysis).

94 Current Chromatography, 2014, Vol. 1, No. 2 Rajmund Michalski

Table 3. Detection methods used in IC.

Detection Mode Principle Typical Applications

Conductivity Electrical conductivity Anions and cations with pKa or pKb < 7

Oxidation or reduction on Ag-/Pt-/Au- Amperometry Anions and cations with pK or pK > 7 /glassy carbon- and carbon paste electrodes a b

UV-active anions and cations, transition metals after reaction with UV/Vis detection with or without UV/Vis light absorption PAR, aluminum after reaction with Tiron, lanthanides after reaction post-column derivatization with Arsenazo I, polyvalent anions after reaction with iron(III)

Fluorescence in combination with Excitation and emission Ammonium, amino acids, and primary amines post-column derivatization

Refractive index Change in refractive index Anions and cations at higher concentrations

Inductively coupled plasma-optical Hyphenated techniques (e.g. IC-ICP-OES, ICP-MS) for selected emission spectrometry; inductively Atomic emission metal/metalloid ions coupled plasma-mass spectrometry

Mass spectrometry (MS) Electrospray ionization Hyphenated techniques for structural research

The quantitation of inorganic ions in sludge, leachates ume; different detection modes; simultaneous determination and similar solid waste with IC is practically similar to the of anions and cations, or inorganic and organic ions; species soil sample analysis. Such samples are typically leached un- analysis; use of cheap, safe, and environmentally-friendly der aqueous conditions, then filtered and pretreated with the chemicals. The determination of inorganic anions is the most solid-phase extraction before injection, if necessary. Sludge important IC application. The primary reason for such a and solid waste samples can be prepared for the IC analysis situation is the lack of alternative methods for anion analysis. with combustion methods [32]. It is not the case for cation analysis as there are many readily When it comes to gaseous samples, measurements can be available instrumental techniques. However, IC has an ad- made directly with the extracts from filters, bulk collectors, vantage over spectroscopic techniques for cation analysis particle collectors, solution bubblers, or diffusion tubes. The when it comes to metal/metalloid ions and ammonia deter- measurements can also follow concentration on solid car- mination [35-37]. Chromatograms of inorganic anions in tridges or guard columns. Usually, the sample is first passed river water and inorganic cations in industrial wastewater are through the cartridge material and then extracted into solu- shown in (Figs. 2 and 3), respectively. tions for analysis. Ammonia can be converted into the am- IC can be used to analyze inorganic ions in natural water monium cation; sulfur dioxide into the more stable sulfate brines, which include seawater, subsurface brines, geother- anion; and nitrogen dioxide to nitrite and nitrate ions. In ad- mal brines and high-salinity groundwater [38]. From the dition, organic anions (including carboxylic acids and amines) environmental point of view, determining cyanide in various can be determined [33]. Many IC sample preparation tech- samples is crucial because of its large-scale industrial uses niques can be also performed with online instrumentation and extreme toxicity [39]. Polyphosphates are widely used in (easily automated), which is less time-consuming than the industrial water treatment applications as they possess se- application of the offline techniques [34]. questering and dispersing properties. Chelating agents, such as nitriltriacetate acid (NTA) and ethylenediaminetetraacetic APPLICATIONS OF ION CHROMATOGRAPHY acid (EDTA), can also be determined quickly with the same The majority of analytical parameters could not be meas- approach used for polyphosphonates [40]. The analysis of ured automatically. Consequently, it was necessary to de- total nitrogen [41], phosphorous [42], sulfur [43] and their velop and validate new methods to extend the scope of the corresponding oxidized anions (e.g. nitrites, nitrates, phos- measurements. IC, introduced in 1975, was the alternative phates, sulfates) is vital to the assessment of soil conditions able to replace most wet chemical methods used in water and and fertility. Notably, nearly all inorganic species important wastewater analyses. IC is an effective technique, especially for agriculture occur in the ionic form. The control of land- for laboratories which need to determine numerous anions fills, particularly hazardous waste landfills, is becoming in- and cations in several thousand samples but do not have the creasingly important. For the environmental control pur- throughput to justify the purchase of large automatic analyz- poses, leachates from hazardous waste landfills and leach- ers (usually based on the colorimetric procedures). IC elimi- ability test samples have to be analyzed regularly [44]. nates the necessity for using hazardous reagents that are often essential to wet chemical methods. The main areas of IC application are analyses of atmospheric particulates, aerosols, acid rain, sulfur dioxide flue IC offers several advantages over conventional methods gas and car exhaust [45]. The coupling of the annular de- for ion determination, i.e. short analysis time; sensitivity at nuder sampling techniques with IC provides a valuable solu- the g/L level; high selectivity in samples with complex ma- tion to the measurement of atmospheric pollutants as it al- trices; simple water sample pre-treatment; small sample vol- lows the differentiation between the gaseous and particulate

Recent Development and Applications of Ion Chromatography Current Chromatography, 2014, Vol. 1, No. 2 95

Chloride Sulfate Conductivity, μS μS Conductivity,

Nitrate Fluoride

0 0 2,00 4,00 6,00 8,00 10,00 Retention time [min] Fig. (2). Inorganic anions in river water. Separation conditions: Analytical column - Dionex Ion Pac AS9-SC (250 x 4 mm) Eluent - 3.5 mM Na2CO3 + 0.5 mM NaHCO3 Eluent flow rate - 1.4 ml/min Sample volume - 25 l Detection - Suppressed conductivity

Sodium

Calcium

Conductivity, μS μS Conductivity, Potasium Ammonium Magnesium

0 2,00 4,00 6,00 8,00

Retention time [min] Fig. (3). Inorganic cations in industrial wastewater. Separation conditions: Analytical column - Dionex Ion Pac CS12 (250 x 4 mm) Eluent - 20 mM HCl Eluent flow rate - 1.2 ml/min Sample volume - 25 l Detection - Suppressed conductivity phases [46]. Heavy and transition metals, normally present in cations. IC is most often used in the cation analysis for the atmospheric particulates, can be separated and detected with determination of alkali metals, alkaline earth metals and IC with a post-column reaction and spectrophotometric de- ammonia. The key advantage of this method is the ability to tection [47]. determine ammonia in complex samples that contain both inorganic cations and organic amines. The review of the cur- Taking into consideration analytical conditions and rent state and progress of IC as an analytical tool for metal equipment necessary to determine inorganic and organic analysis in environmental samples is described by Shaw and cations (separation column, eluent, detection mode), analytes Haddad [49]. determined with IC methods can be divided into four groups [48]: alkali and alkaline earth metals, and ammonium; heavy IC separation of metal ions with anion exchangers re- and transition metals; lanthanides and actinides; and organic quires their presence as negatively charged complexes. It can 96 Current Chromatography, 2014, Vol. 1, No. 2 Rajmund Michalski be achieved either offline or online. Complexes must be sta- 2). Indirect methods (UV/Vis detection after post-column ble enough to avoid decomposition during separation, or a derivatization). ligand must be added to the eluent. That is why metal com- 3). Hyphenated techniques (ICP-MS and MS detection). plexes are formed before the chromatographic separation in Obviously, methods used for bromate, chlorite and chlo- the offline method. In the online method, complexation is rate analyses have both advantages and disadvantages [62]. performed in the chromatographic column through the addi- The direct methods are based on the selective separation of tion of the proper ligand to the eluent. Among many ligands - BrO3 ions in the presence of other anions in the sample. used for simultaneous IC separation of metals, the most They are detected in the conductivity detector after suppres- common additives are oxalic acid, pyridine-2,6-dicarboxylic sion. These methods are relatively simple and inexpensive acid (PDCA) and ethylenediaminetetraacetic acid (EDTA). but their main disadvantage is the improper resolution of Non-suppressed and suppressed conductivity detection - - BrO3 and Cl ions, whose concentrations in real samples modes are suitable for the detection of alkali and alkaline differ significantly. Considering these drawbacks, methods earth metals. On the other hand, only non-suppressed con- based on post-column derivatization and UV/Vis detection ductivity detection can be used for other metal ions as these provide an effective alternative [63]. The use of UV/Vis de- metals would mostly be transferred into insoluble hydroxides tection with a variety of post-column reagents allows < 1- by the suppressor reaction. Consequently, spectrometric de- g/L detection limits for bromates [64]. Much lower detec- tection after suitable post- or pre-column derivatization is tion limits are obtained with hyphenated techniques, such as usually carried out [50]. Determining various oxidation IC coupled with mass spectrometry detection [65, 66]. The states of elements is also important. Until recently, analytical selection of the most convenient and suitable methods for the methods allowed analysts to determine only the total analyte determination of specific oxyhalides depends on many fac- content. It soon turned out that such analytical data was in- tors, such as the expected concentration of analyte, sample sufficient. Biochemical and toxicological studies show that matrix, limit of determination obtainable by the method used the chemical form of a specific element or the oxidation state and its availability [67, 68]. In addition to the environmental in which that element is introduced into the environment are applications, IC is now routinely used for the analysis of as important as its quantity for living organisms [51]. IC ionic compounds in power plant chemistry [69], semiconductor industry [70], household products [71], detergents plays an important role in hyphenated techniques used for [72], pharmaceuticals [73], biochemistry [74], agriculture species analysis as an effective and reliable separation [75] and food and beverage quality control [76]. Although IC method [52, 53]. is routinely applied to determine inorganic anions and 1). The main IC applications in speciation analysis can be cations, it is becoming more and more popular in the analy- divided into three areas: sis of organic ions. Applications include the determination of - - + organic acids in food [77], precipitations [78] and industrial 2). Determination of nitrogen (e.g., NO2 , NO3 , NH4 ) and - 2- 2- 2- - samples [79]. Hyphenated techniques can also be used for sulfur (e.g., S2 , SO3 , SO4 , S2O3 , SCN ) ions. such analyses [80, 81]. 3). Determination of inorganic water disinfection by- - - - Ion chromatography also concerns amino acids and other products (e.g., BrO3 , ClO2 , ClO3 ) [54] and other halide - - physiological amines. Separation is usually performed on ions (e.g., ClO4 , IO3 ). strong cation exchangers with the amino acid in the proto- 4). Determination of metal (e.g., Cr(III)/Cr(VI), nated form with complex pH, buffer composition and, some- Fe(II)/Fe(III)) and metalloid (e.g., As(III)/As(V), times, temperature gradient. Ion exchange is traditionally Sb(III)/Sb(V); Tl(I)/Tl(III)) ions [55]. used for the isolation, purification and separation of peptides, proteins, nucleotides and other biopolymers [82]. IC is also Water treatment with disinfection processes is thought to th employed in the rapid analysis of carbohydrates in complex have been the major public health achievement of the 20 samples for the biofuel, food and beverage industries [83]. century. Ozonation emerged as one of the most promising alternatives to chlorination. In the early 1980s, it became IC is an established and well-developed technique for the obvious that the application of ozonation for drinking water analysis of anions and cations. Many organizations, such as treatment resulted not only in the formation of oxygenated the International Organization for Standardization (ISO), the compounds but also in bromide-containing water. Moreover, United States Environmental Protection Agency (U.S. EPA), brominated organic compounds and bromates were formed the American Society for Testing and Materials (ASTM) and the Association of Official Analytical Chemists (AOAC), [56, 57]. Recently, bromates have been recognized as the base their standards and regulatory analysis methods upon it most important inorganic oxyhalide by-product. Therefore, [84]. IC-based ISO standards are listed in (Table 4). Besides their concentrations in drinking water have to be controlled the procedures recommended by ISO and U.S. EPA, there [58]. Furthermore, chlorites and chlorates are the subjects of exist many methods developed by chromatography equip- the advanced research [59]. The problem of bromates also ment manufacturers. concerns bottled water. It undergoes numerous treatment processes, such as filtration, deionization, reverse osmosis or Capillary electrophoresis (CE) seemed a promising sub- ozonation, to ensure its quality [60]. The methods concerning stitute for IC over 25 years ago due to its higher speed of the determination of the inorganic disinfection by-products separation. The comparison of IC and CE shows that they with IC can be generally divided into [61]: should be considered as being complementary rather than competitive [85-87]. Although the CE methods are widely 1). Direct methods (suppressed conductivity detection). applicable (e.g. for anions [88] and metal ions [89, 90]),

Recent Development and Applications of Ion Chromatography Current Chromatography, 2014, Vol. 1, No. 2 97

Table 4. ISO standards based on IC.

Number Date of Publication Name

Water Quality - Determination of dissolved fluoride, chloride, nitrite, orthophosphate, bromide, nitrate and 10304-1 1992 sulfate ions using liquid chromatography of ions. Part 1: Method for water with low contamination. Air quality - Stationary source emission - Manual method of determination of HCl. 1911-1 1995 Part 1: Sampling and pretreatment of gaseous samples Part 2: Gaseous compounds absorption. Part 3: Absorption solutions analysis and calculation. Water Quality - Determination of dissolved anions with liquid chromatography of ions. 10304-2 1997 Part 2: Determination of bromide, chloride, nitrate, nitrite, orthophosphate and sulfate in wastewater. Water Quality - Determination of dissolved anions with liquid chromatography of ions. 10304-3 1997 Part 3: Determination of chromate, iodide, sulfite, thiocyanate and thiosulfate. Water Quality - Determination of dissolved anions with liquid chromatography of ions. 10304-4 1998 Part 4: Determination of chlorate, chloride and chlorite in water with low contamination. Water Quality - Determination of dissolved Li+, Na+, NH +, K+, Mn2+, Ca2+, Mg2+, Sr2+ and Ba2+ using ion 14911 1998 4 chromatography method. Stationary source emissions - Determination of mass concentration of sulfur dioxide - Ion chromatography 11632 1998 method. 15061 2001 Water Quality - Determination of dissolved bromate. Method by liquid chromatography of ions. Determination of chelating agents with ion chromatography method. 13368-1 2001 Part 1: EDTA, HEDTA and DTPA. Determination of chelating agents by using ion chromatography method. 13368-2 2001 Part 2: EDDHA and EDDHMA. Characterization of waste and soil - Determination of hexavalent chromium in solid material with alkaline 15192 2001 digestion and ion chromatography with spectrophotometric detection. Water Quality - determination of dissolved bromide, chloride, fluoride, nitrate, nitrite, phosphate and 10304-1 2007 sulfate - method with liquid chromatography of ions. 264125 2010 Ambient air quality — Guide for the measurement of anions and cations in PM 2.5 Water quality - Determination of dissolved bromate - Method using liquid chromatography of ions and 11206 2011 post-column reaction (PCR). there are still no international standards for the CE methods. CONCLUSION The advantages and limitations of both procedures are given Since its introduction in 1975, ion chromatography has in (Table 5). been used in most areas of the analytical chemistry. It is a Table 5. Advantages and limitations of IC and electrophore- versatile and powerful technique for the analysis of many sis methods. ions present in the environment, food and other matrices. The most important IC advantages are: broad range of applications; well-developed hardware; many detection options; IC good accuracy and precision; high selectivity and separation efficiency; good tolerance to sample matrices; and low cost Advantages Limitations of consumables. It is widely accepted as the standard refer- • ence methodology for various analytes in different sample Wide range of applications matrices. The most important challenges related to the IC • Different detection modes • Limited speed of analysis development and applications include: developing new sam- • Repeatability • Higher cost compared to CE ple preparation methods; improving the speed and selectivity • Standards methods of the analyte separation; lowering limits of detection and quantification; extending the scope of applications of meth- Electrophoresis Methods ods and analytical techniques; developing new standard methods; extending the scope of the analysis for new groups Advantages Limitations of substances; and miniaturization. • Speed of analysis • High separation efficiency • Instability CONFLICT OF INTEREST • Good tolerance to high pH • Poor traceability and repeatability The authors confirm that this article content has no con- • Low running costs flict of interest.

98 Current Chromatography, 2014, Vol. 1, No. 2 Rajmund Michalski

ACKNOWLEDGEMENTS Part II Suppressed anion chromatography using carbonate eluents. J. Chromatogr. A, 1999, 850, 29-41. Declared none. [27] Michalski, R. In Encyclopedia of Chromatography, Jack Cazes, Ed.: Taylor & Francis, CRC Press, New York, 2010, Vol. 1, 576- REFERENCES 580. [28] Smith, R. Before the injection - modern methods of sample prepa- [1] Tswett, M.S. Physikalisch-chemische studien uber das chlorophyll. ration for separation techniques (Review). J. Chromatogr. A, 2003, Die adsorptionen. Ber. Deut. Bot. Gese., 1906, 24, 316-332. 1000, 3-27. [2] Bahrdt, A. Bestimmung von Sulfat in Wasser. Fres. Zeit. Anal. [29] Michalski, R. In Encyclopedia of Chromatography, Jack Cazes, Chem., 1927, 70, 109-117. Ed.: Taylor & Francis, CRC Press, New York, 2010, Vol. 1, 802- [3] Lucy, C.A. Evolution of ion-exchange: from Moses to the Manhat- 808. tan Project to modern times. J. Chromatogr. A, 2003, 1000, 711-724. [30] Michalski, R. In Encyclopedia of Chromatography, Jack Cazes, [4] Small, H.; Bowman, B. Ion chromatography: a historical Ed.: Taylor & Francis, CRC Press, New York, 2010, Vol. 3, 2106- perspective. Amer. Lab., 1998, 10, 1-8. 2110. [5] Small, H.; Stevens, T.S.; Bauman, W.C. Novel ion exchange chro- [31] Haddad, P.R.; Doble, P.; Macka, M. Developments in sample matographic method using conductometric detection. Anal. Chem., preparation and separation techniques for the determination of in- 1975, 47, 1801-1886. organic ions by ion chromatography and capillary electrophoresis. [6] Fritz, J.S.; Gjerde, D.T. Ion chromatography, Willey VCH, 4th J. Chromatogr. A, 1999, 856, 145-177. edition, Verlag, Weinheim, 2009. [32] Miyake, Y.; Kato, M.; Urano, K. A method for measuring semi- [7] Gjerde, D.T.; Fritz, J.S. Schmuckler, G. Anion chromatography and non-volatile organic halogens by combustion ion chromatogra- with low-conductivity eluents. J. Chromatogr. A, 1979, 186, 509-519. phy. J. Chromatogr. A, 2007, 1139, 63-69. [8] Small, H. Ion chromatography, New York: Plenum Press, 1989. [33] Dabek-Zlotorzynska, E.; McGrath, M. Determination of low- [9] Gjerde, D.T.; Fritz, J. Ion Chromatography. Weinheim: Wiley- molecular-weight carboxylic acids in the ambient air and vehicle VCH, 2000. emissions: A Review. Fres. J. Anal. Chem., 2000, 367, 507-518. [10] Jackson, P.; Haddad, P.R. Ion chromatography: principles and [34] Saubert, A.; Frenzel, W.; Schafer, H.; Bogenschutz, G.; Schafer, J. applications. Amsterdam: Elsevier, 1990. Sample preparation techniques for ion chromatography. Metrohm, [11] Fritz, J.S. Principles and applications of ion-exclusion chromatogra- Herisau, Switzerland, 2004. phy. J. Chromatogr. A, 1991, 546, 111-118. [35] Michalski, R. Application of ion chromatography for the determi- [12] Cecchi, T. Ion-Pair Chromatography and Related Techniques, CRC nation of inorganic cations. Crit. Rev. Anal. Chem., 2009, 39, 230- Press/Taylor & Francis, New York, 2010. 250. [13] Gennaro, M.C.; Angelino, S. Separation and determination of inor- [36] Michalski, R.; Jablonska, M.; Szopa, S.; yko, A. Application of ganic anions by reversed-phase high-performance liquid chromatogra- ion chromatography with ICP-MS or MS detection to the phy (Review). J. Chromatogr. A, 1997, 789, 181-194. determination of selected halides and metal/metalloids species. [14] Cecchi, T. Ion pairing chromatography. Crit. Rev. Anal. Chem., Crit. Rev. Anal. Chem., 2011, 41, 133-150. 2008, 38, 161-213. [37] Jackson, P.E. In Encyclopedia of Analytical Chemistry. Wiley, [15] Haddad, P.R.; Jackson, P.E.; Shaw, M.J. Developments in suppres- Chichester, U.K, 2000, 2779-2801. sor technology for inorganic ion analysis by ion chromatography [38] Hodge, E.M.; Martinez, M.; Deborah, P.S. Determination of inor- using conductivity detection. J. Chromatogr. A, 2003, 1000, 725- ganic cations in brine solutions by ion chromatography. J. Chroma- 742. togr. A, 2000, 84, 223-227. [16] Liu, Y.; Srinivasan, K.; Pohl, C.; Avdalovic, N. Recent develop- [39] Otu, E.O.; Byerley, J.J.; Robinson, C.W. Ion chromatography of ments in electrolytic devices for ion chromatography. J. Biochem. cyanide and metal cyanide complexes: A Review. Inter. J. Environ. Biophys. Meth., 2004, 60, 205-232. Anal. Chem., 1996, 63, 81-90. [17] Weiss, J.; Jensen, D. Modern stationary phases for ion chromatog- [40] Ruiz-Calero, V.; Galceran, M.T. Ion chromatographic separations raphy. Anal. Bioanal. Chem., 2003, 375, 81-98. of phosphorus species: A Review. Talanta, 2005, 66, 376-410. [18] Haddad, P.R.; Nesterenko, N.; Buchberger, W. Recent develop- [41] Michalski, R.; Kurzyca, I. Determination of nitrogen species (ni- ments and emerging directions in ion chromatography. J. Chroma- trate, nitrite and ammonia ions) in environmental samples by ion togr. A, 2008, 1184, 456-473. chromatography (Review). Pol. J. Environ. Stud., 2006, 15, 5-18. [19] Nesterenko, P.N.; Haddad, P.R. Zwitterionic ion-exchangers in [42] Ruiz-Calero, V.; Galceran, M. T. Ion chromatographic separations liquid chromatography. Anal. Sci., 2000, 16, 565-575. of phosphorus species: a Review. Talanta, 2005, 66, 376-410. [20] Paull, B.; Nesterenko, P.N. New possibilities in ion chromatogra- [43] O’Reilly, J.W.; Dicinoski, G.W.; Shaw, M.J.; Haddad, P.R. Chro- phy using porous monolithic stationary-phase media. Trend. Anal. matographic and electrophoretic separation of inorganic sulfur and Chem., 2005, 24, 295-303. sulfur-oxygen species. Anal. Chim. Acta, 2001, 432, 165-192. [21] Wu, R.; Hu, L.; Wang, F.; Ye, M.; Zou, H. Recent development of [44] Gade, B. Ion chromatographic investigations of leachates from a monolithic stationary phases with emphasis on microscale chroma- hazardous-waste landfill. J. Chromatogr. A, 1993, 640, 227-230. tographic separation. J. Chromatogr. A, 2008, 1184, 369-392. [45] Mulik, J.D.; Sawicki, E. Ion chromatography. Environ. Sci. Technol., [22] Unger, K.K.; Skudas, R.; Schulte, M.M. Particle packed columns 1979, 13, 804-809. and monolithic columns in high-performance liquid chromatogra- [46] Perrino, C.; Concetta, M.; Sciano, T.; Allegrini, I. Use of ion chro- phy - comparison and critical appraisal. J. Chromatogr. A, 2008, matography for monitoring atmospheric pollution in background 1184, 393-415. networks. J. Chromatogr. A, 1999, 846, 269-275. [23] Gjerde, D.T. Eluent selection for determination of cations in ion [47] Caselli, B.M.; Gennaro, G.; Ielpo, P.; Traini, A. Analysis of heavy chromatography. J. Chromatogr. A, 1988, 439, 49-61. metals in atmospheric particulate by ion chromatography. J. Chro- [24] Michalski, R.; yko, A.; Kurzyca, I. Matrix influences on the de- matogr. A, 2000, 888, 145-150. termination of common ions by using ion chromatography. Part 1 - [48] Michalski, R. In: Encyclopedia of Chromatography, Jack Cazes, Determination of inorganic anions. J. Chromatogr. Sci., 2012, 6, Ed.: Taylor & Francis, CRC Press, New York , 2010, Vol. 2, 1201- 31-43. 1205. [25] Madden, J. E.; Haddad, P. R. Critical comparison of retention models [49] Shaw, M.J.; Haddad, P.R. The determination of trace metal pollut- for optimization of the separation of anions in ion chromatography. ants in environmental matrices using ion chromatography. Environ. Part I - Non-suppressed anion chromatography using phthalate eluents Inter., 2004, 30, 403-431. and three different stationary phases. J. Chromatogr. A, 1989, 829, 65- [50] Santoyo, E.; Santoyo-Gutierrez, S.; Verma, S.P. Trace analysis of 80. heavy metals in groundwater samples by ion chromatography with [26] Madden, J. E.; Haddad, P. R. Critical comparison of retention models post-column reaction and ultraviolet-visible detection. J. Chroma- for optimization of the separation of anions in ion chromatography. togr. A, 2000, 884, 229-241.

Recent Development and Applications of Ion Chromatography Current Chromatography, 2014, Vol. 1, No. 2 99

[51] Kot, A.; Namiesnik, J. The role of speciation in analytical chemis- [71] Murawski, D. Ion chromatographic for the analysis of household try. Trend. Anal. Chem., 2000, 19, 69-79. consumer products. J. Chromatogr. A, 1991, 546, 351-368. [52] Ellis, L.A.; Roberts, D.J. Chromatographic and hyphenated meth- [72] Buldini, P.L.; Sharma, J.L. Determination of total phosphorus in ods for elemental speciation analysis in environmental media. J. soaps/detergents by ion chromatography. J. Chromatogr. A, 1993, 654, Chromatogr. A, 1997, 774, 3-19. 129-134. [53] Michalski, R.; Jaboska, M.; Szopa, S. In: Speciation studies in [73] Cassidy, S.A.; Demarest, Ch.W.; Wright, P.B.; Zimmerman, J.B. soil, sediment and environmental samples, Sezgin Bakirdere Ed.: Development and application of a universal method for quantitation Taylor & Francis, CRC Press, New York, 2013. of anionic constituencies in active pharmaceutical ingredients dur- [54] Michalski, R. Inorganic oxyhalide by-products in drinking water ing early development using suppressed conductivity ion chroma- and ion chromatographic determination methods (Review). Pol. J. tography. J. Pharm. Biomed. Anal., 2004, 34, 255-264. Environ. Stud., 2005, 14, 257-268. [74] Salas-Auvert, R.; Colmenarez, J.; Ledo, H.; Colina, M.; Gutierrez, E.; [55] Das, A. K.; Guardia, M.; Cervera, M. L. Literature survey of on- Bravo, A.; Soto, L.; Azuero, S. Determination of anions in human and line elemental speciation in aqueous solutions (Review). Talanta, animal tear fluid and blood serum by ion chromatography. J. 2001, 55, 1-28. Chromatogr. A, 1995, 706, 183-189. [56] Richardson, S.D.; Plewa, M. J.; Wagner, E. D.; Schoeny, R.; De [75] Goyal, S.S. Applications of column liquid chromatography in Marini, D. M. Occurrence, genotoxicity, and carcinogenicity of inorganic analysis in agricultural research. J. Chromatogr. A, 1997, regulated and emerging disinfection by-products in drinking wa- 789, 519-527. ter: A review and roadmap for research. Mutat. Res., 2007, 636, [76] Buldini, P.L.; Cavalli, S.; Trifirò, A. State-of-the-art ion chroma- 178-242. tographic determination of inorganic ions in food. J. Chromatogr. [57] Sadiqa, R.; Rodriguez, M. J. Disinfection by-products (DBPs) in A, 1997, 789, 529-548. drinking water and predictive models for their occurrence: a Re- [77] Michalski, R. In Encyclopedia of Chromatography, Jack Cazes, view. Sci. Tot. Environ. 2004, 321, 21-46. Ed.: Taylor & Francis, CRC Press, New York, 2010, Vol. 2, 909- [58] Michalski, R.; In Encyclopedia of Chromatography, Jack Cazes, 912. Ed.: Taylor & Francis, CRC Press, New York, 2010, Vol. 2, 1212- [78] Cheam, V. Determination of organic and inorganic acids in 1217. precipitation samples. J. Chromatogr. A, 1989, 482, 381-392. [59] Michalski, R.; Mathews, B. Occurrence of chlorite, chlorate and [79] Jian, A.Ch.; Preston, B.P.; Zimmerman, M.J. Analysis of organic bromate in disinfected swimming pool water. Pol. J. Environ. Stud., acids in industrial samples. Comparison of capillary electrophoresis 2007, 16, 237-241. and ion chromatography. J. Chromatogr. A., 1997, 781, 205-213. [60] Matsis, V.M.; Nikolaou, E.C. Determination of inorganic oxyhalide [80] Ahrer, W.; Buchenberger, W. Analysis of low-molecular-mass disinfection by-products in bottled water by EPA Method 326.0 for inorganic and organic anions by ion-chromatography - atmospheric trace bromate analysis. Desalination, 2008, 224, 231-239. pressure ionization mass spectrometry. J. Chromatogr. A, 1999, 854, [61] Michalski, R.; yko, A. Bromate determination. State of the art. 257-287. Crit. Rev. Anal. Chem., 2013, 43, 100-122. [81] Bauer, K.-H.; Knepper, T.P.; Maes, A.; Schatz, V.; Voihsel, M. [62] Michalski, R. Analyzing inorganic disinfection by-products by ion Analysis of polar organic micropollutants in water with ion chro- chromatography. LC GC Europe, May, 2011, 18-23. matography-electrospray mass spectrometry. J. Chromatogr. A, [63] Michalski, R.; yko, A. Determination of bromate in water samples 1999, 837, 117-128. using post column derivatization method with triiodide. J. Environ. [82] Weiss, J.; Handbook of ion chromatography, Wiley-VCH, 2004. Sci. Health Part A, 2010, 45, 1275-1280. [83] Mato, I.; Suarez-Luque, S.; Huidobro, J.F. A review of the analyti- [64] Echigo, S.; Minear, R.A.; Yamada, H.; Jackson, P.E. Comparison cal methods to determine organic acids in grape juices and wines. of three post column reaction methods for the analysis of bromate Food Res. Int., 2005, 38, 1175- 1188. and nitrite in drinking water. J. Chromatogr. A, 2001, 920, 205- [84] Michalski, R. Ion chromatography as a reference method for the 211. determination of inorganic ions in water and wastewater. Crit. Rev. [65] Montes-Bayon, M.; De Nicola, K.; Caruso, J. A. Liquid chromatog- Anal. Chem., 2006, 36, 107-127. raphy - inductively coupled plasma mass spectrometry (Review). J. [85] Haddad, P.R. Comparison of ion chromatography and capillary Chromatogr. A, 2003, 1000, 457-476. electrophoresis for the determination of inorganic anions. J. Chro- [66] Michalski, R. Application of IC-MS and IC-ICP-MS in environ- matogr. A, 1997, 770, 281-290. mental research, Current Trends in Mass Spectrometry. LC-GC [86] Dabek-Zlotorzynska, E.; Dlouhy, J. F.; Houle, N.; Piechowski, M.; North America Suppl. S, October 2012, 32-36. Ritchie, S. Comparison of capillary zone electrophoresis with ion [67] Zwiener, C.H.; Richardson, S.D. Analysis of disinfection by- chromatography and standard photometric methods for the deter- products in drinking water by LC-MS and related MS techniques. mination of inorganic anions in atmospheric aerosols. J. Chroma- Trend. Anal. Chem., 2005, 24, 613-621. togr. A, 1995, 706, 469-478. [68] Thompson, K.C.; Guinamant, J.L.; Ingrand, V.; Elwaer, A.R.; [87] Pacakova, V.; Coufal, P.; Stulik, K.; Gas, B. The importance of McLeod, D.C.; Schmitz, F.; Swaef, G.; Queauviller, P. Interlabora- capillary electrophoresis, capillary electrochromatography, and ion tory trial to determine the analytical state-of the-art of bromate de- chromatography in separations of inorganic ions. Electrophore- termination in drinking water. J. Environ. Monit., 2000, 2, 416-422. sis, 2003, 24, 1883-1891. [69] Toofan, M.; Stillian, J.R.; Pohl, Ch.A.; Jackson, P.E. [88] Li, J.; Ding, W.; Fritz, J.S. Separation of anions by ion

Preconcentration determination of inorganic anions and organic chromatography capillary electrophoresis. J. Chromatogr. A, acids in power plant waters Separation optimization through 2000, 879, 245-257. control of column capacity and selectivity. J. Chromatogr. A, 1997, [89] Dabek-Zlotorzynska, E.; Lai, E.P.C.; Timerbaev, A.R. Capillary 761, 163-168. electrophoresis: the state-of-the-art. In metal speciation studies. [70] Ehmann, T.; Mantler, C.; Jensen, D.; Neufang, R. Monitoring the Anal. Chim. Acta, 1998, 359, 1-26. quality of ultra-pure water in the semiconductor industry by online [90] Ali, I.; Aboul-Enein, H.Y. Speciation of metal ions by capillary ion chromatography. Microchim. Acta, 2006, 154, 15-20. electrophoresis, Crit. Rev. Anal. Chem., 2002, 32, 337-350.

Received: March 05, 2013 Revised: August 28, 2013 Accepted: September 03, 2013