background of the eluent ions because the eluent is also an electrolyte. In 1980s, [PERSON] et al. [4] used the ion chromatography system without the suppression device for the first time. They also used eluents with very low conductivity. They created a new type of ion chromatography, i.e., the non-suppressed ion chromatography. Both the suppressed and non-suppressed ion chromatography modes can be applied to examine various sample matrices. However, when it comes to anion analyses, the application of the suppressed ion chromatography is much more popular. Although the ion exchange remains a prevailing separation mode in ion chromatography [5; 6], other related methods, such as ion-exclusion (IEC) [7], ion-pairing chromatography (IPC) [8], and reversed phase liquid chromatography (RPLC) [9], can also be employed. A short overview of ion chromatography and related methods (with consideration for separation mechanism, eluents, and detectors) is given in Table 1.  
The obtaining of reliable results in ion chromatography depend on many factors, such as types of eluents and stationary phases, detection modes, and sample preparation methods. The applications of ion-exchangers in the chemical analysis were described by [PERSON] and [PERSON] [10]. The stationary phases used in the ion-exchange chromatography columns can be classified according to their applications and ion-exchange capacities. An overview of stationary phases used for ion chromatography is given by [PERSON] and [PERSON] [11]. Figure 1 shows a list of selected stationary phases used in ion chromatography. Figure 1: Stationary phases used in ion chromatography. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Method** & **Separation** & **Functional** & **Typical Elements** & **Selected Analyses** & **Detection Modes** \\  & **Mechanism** & **Group** & & & \\ \hline \multirow{4}{*}{ \begin{tabular}{c} Anion-exchange \\ chromatography \\ (suppressed and non-suppressed) \\ \end{tabular}  } & \multirow{4}{*}{Ion-exchange} & \multirow{4}{*}{-NRS\({}^{\ast}\)} & Suppressed ion chromatography: & F-, C\({}^{1}\), Br-, C\({}^{1}\), CO-, CO-, CO-, CO-, CO-, HCO-, HCO-, HCO-, HCO-, HCO-, HCO-, HC  
In ion chromatography, organic polymers are often used as stationary phases, because they have much higher stability over an extreme pH range when compared to the silica-based materials. These copolymers can be divided into the surface aminated polystyrene-divinylbenzene (PS/DVB) and surface aminated ethylenovinylbenzene-polystyrene-divinylbenzene (EVB/DVB) copolymers. There are also the methacrylate-based stationary phases with quaternary amine functional groups stable at pH = 1-12, and macroporous polyvinyl resins stable at pH = 0-14 [12]. A special type of a peculiar anion exchanger (called latex-based) was introduced in 1975 [13]. In comparison with organic polymers, silica-based stationary phases have the advantage of higher mechanical stability. However, they can only be used with eluents in the pH range between 2 and 8 [14]. Inorganic and organic anions can be separated on cross-linked polymers modified with cyclic ethers, but the number of applicable crown ethers is limited [15] or cryptand-based phases [16]. Similarly to the anion exchangers, cation exchangers are divided into: polymer-based cation exchangers (PS/DVB, EVB/DVB, polyvinyl, and polymethacrylate copolymers), latex-agglomerated cation exchangers, silica-based, and others (e.g., crown ethers, Al\({}_{2}\)O\({}_{3}\)). Simultaneous separations of alkali- and alkaline earth metals and aliphatic amines are possible with acid cation exchangers with carboxylic groups. Organic polymers are usually applied for cation-exchange chromatography. In some cases, silica-based exchangers [17] as well as cross-linked polymers modified with cyclic ethers [18] are also used. Moreover, zwitterionic ion-exchangers demonstrate unique separation selectivities for simultaneous separations of anions and cations [19]. Recently, monolithic columns have been used in different types of ion chromatography [20; 21].