Pure silica gel as cation−exchange stationary phase in ion chromatography for mono− and divalent cations

Ion chromatography (IC) developed by Small et al . [1] is widely recognized as a simple, powerful and convenient analytical technique for the determination of various low−molecular−weight ionic compounds [2, 3]. Firstly, IC with conductimetric detection (IC−CD) was mainly applied for the determination of inorganic anions. This is because a lightly sulfonated styrene−divinylbenzene co−polymer (S−DVB) resin was used as the cation−exchange stationary phase in IC−CD for cations and, as a consequence, the simultaneous separation of common mono− and divalent cations (Li+, Na+, NH4+, K+, Mg2+, and Ca2+) could not be achieved easily on this type resin column with acidic solution as the eluent [1−3]. Kolla et al . [4], and Kondratjonok and Schwedt [5] applied carboxylated silica gel (polybutadiene−maleic acid on silica gel), as the cation−exchange stationary phase in IC−CD for these mono− and divalent cations [4, 5]. The greatest advantage of the use of this type resin in IC−CD is that the simultaneous separation and highly sensitive conductimetric detection for these mono− and divalent cations can be achieved easily with acidic solution as the eluent. Now, IC−CD with carboxylated silica column or carboxylated S− DVB resin column is widely utilized for the determination of these mono− and divalent cations in various real sample waters. Silica gel is physically stable, unreactive towards organic solvents and its particle size, pore size, pore volume, and surface area Focusing Review