Raaidah Saari-Nordhaus

Determination of haloacetic acids by ion chromatography

Two ion chromatography methods for the determination of haloacetic acids are described in this paper. The first method is based on anion-exchange separation with suppressed electrical conductivity detection. The second method is based on anion-exclusion separation with UV detection. Both methods are simple and fast. The detection limits for the haloacetic acids are in the μg/l range. Applications of these methods for the determination of haloacetic acids in some real world samples are shown.

Simultaneous analysis of anions and cations by single-column ion chromatography

Abstract A new technique for the simultaneous analysis of anions and cations is described. The technique involves the use of the existing single column ion chromatography equipment with the addition of a switching valve. An anion and a cation column are used as the separator column. Three eluents are developed to allow simultaneous separation of anions and monovalent cations or anions and divalent cations. A simultaneous analysis of anions such as fluoride, chloride, nitrite, bromide, nitrate, phosphate, sulfate, and cations such as sodium, ammonium, potassium, rubidium, magnesium, calcium, and barium can be accomplished in approximately 20 to 30 min depending on the number of ions present in the sample. The detection limits for most ions are less than 500 μ/l.

Dual-column techniques for the simultaneous analysis of anions and cations

Abstract A dual-column technique for the simultaneous analysis of anions and cations is described. The technique involves the use of the conventional ion chromatography equipment with the addition of a switching valve. Two columns (an anion and a cation column) are used as the separator columns. By using an eluent that contains both anion and cation driving ions, the simultaneous separation of anions and cations can be accomplished with one injection, one pump, and one detector. Two eluents are developed for the simultaneous analysis of anions, monovalent cations and divalent cations. The detection limits for most ions are below 400 μg/l.

Ion chromatographic separation of transition metals on a polybutadiene maleic acid-coated stationary phase

Abstract Transition metals are traditionally analyzed by cation-exchange or ion-pair chromatography. Divalent metal ions are separated on sulfonic acid cation stationary phase using various eluents along with conductivity detection. An alternative method is reversed-phase ion-pair chromatography coupled with conductivity detection. This method of detection is not very sensitive for transition metals. For better separation sensitivity, UVue5f8Vis detection along with pre- or post-column derivatization with an absorbing ligand is the most common method applied. This method is messy and complicated. This paper describes the separation of transition metals on a polybutadiene maleic acid stationary phase. This cation-exchange stationary phase has been successfully applied for the simultaneous separation of mono- and divalent cations. Several cations including group I and group II cations along with transition metals can be analyzed using complexing acid eluents. Detection limits the effect of different eluent concentrations are discussed.

Membrane-based solid-phase extraction as a sample clean-up technique for anion analysis by capillary electrophoresis

The use of membrane-based solid-phase extraction disks as a sample clean-up technique for anion analysis by capillary electrophoresis is discussed. The polytetrafluoroethylene membrane is impregnated with high-purity polystyrene-divinylbenzene sulfonated cation-exchange resin beads. Three different chemistries are used to remove various interfering components from the sample. The applications of this technique for the analysis of various anions in difficult samples are demonstrated.

Simultaneous separation of alkali and alkaline-earth cations on polybutadiene-maleic acid-coated stationary phase by mineral acid eluents

The simultaneous separation of alkali and alkaline-earth cations on polybutadiene-maleic acid-coated silica columns can be achieved with mineral acid eluents. Simple ion-exchange retention mechanisms and the high selectivity of eluent hydronium ions towards the carboxylate group are the basis for the separation. Use of mineral acid eluents allows using this column in both single column and suppressor-based IC systems. Both types of ion chromatography systems provide detection limits in the low-ng/ml range with excellent linearity.

Universal stationary phase for the separation of anions on suppressor-based and single-column ion chromatographic systems

Abstract A stationary phase composed of a hydroxyethyl methacrylate-based macroporous copolymer with quaternary amine functional groups for the separation of anions was evaluated. The material is rigid, stable and compatible with a wide variety of eluents including p-hydroxybenzoic acid, phthalic acid, borate-gluconate, and carbonate-hydrogencarbonate. The column packed with this anion exchange may be used with single-column ion chromatography in addition to suppressor-based ion chromatography. The hydrophilic nature of the methacrylate copolymer provides improved peak shapes for polarizable anions and eliminates system peaks typically encountered with poly(styrene-divinylbenzene) ion exchangers. The column performance with a wide variety of eluents is demonstrated with applications using the both single-column and suppressor-based ion chromatography systems.

Elimination of matrix interferences in ion chromatography by the use of solid-phase extraction disks

The use of solid-phase extraction disks as a sample clean-up device is described. The disks contain a membrane composed of resin beads permanently enmeshed in a polytetrafluoroethylene membrane, housed in a medical-grade polypropylene housing. The resin within the membrane is functionalized to retain specific types of components from the sample. Several chemistries are developed to remove various interfering components. The recovery of the ions after sample treatment is examined.

Analysis of commercial explosives by single-column ion chromatography

Abstract Commercial explosives utilize inorganic salts as an inexpensive and effective oxidizing agent. Important performance criteria of commercial explosives are gathered from the analysis of these salts in the formulation. An optimum ratio of inorganic salts to fuel oil needs to be maintained to produce complete combustion and maximum energy. This information is quickly and accurately provided by an ion chromatographic method described here. The anion analysis is performed on an hydroxyethylmethacrylate-based macroporous copolymer-based anion-exchange column, which provides good peak shapes for nitrate. Analyzing both monovalent and divalent cations in a single chromatographic step is made possible by new cation-exchangers. The dual-column method for the simultaneous determination of anions and cations was applied to the analysis of nitrate, ammonium, hexamethylenetetramine, calcium and magnesium in a single chromatographic analysis of less than 35 min. A comparison between the traditional, wet chemistry methods commonly used for commercial explosive analysis and this new ion chromatographic method is presented.

Enhancing the anion separations on a polydivinylbenzene-based anion stationary phase

Abstract A new anion-exchange stationary phase is described for the separation of inorganic anions by ion chromatography. This stationary phase is made of polydivinylbenzene (P-DVB) based resin with dimetylethanolamine functional groups. The highly cross-linked P-DVB backbone makes this material chemically and mechanically stable under extreme chromatographic conditions. It withstands organic solvents and is stable at a wide range ofpH, temperature and pressure. The separation of anions on this stationary phase can be enhanced by simple modification of the chromatographic conditions. The resolution and peak shape can be improved by adding organic additives to the eluent. These improvements can also be achieved by changing the column operating temperature. This stationary phase is useful for the separation of inorganic anions by suppressor-based and single-column ion chromatography methods.