Detection Methods in Ion Chromatography

Spectral properties and G-quadruplex DNA binding selectivities of a series of unsymmetrical perylene diimides

A collaborative study, International Evaluation Measurement Programme-25a, was conducted in accordance with international protocols to determine the performance characteristics of an analytical method for the determination of dissolved bromate in drinking water. The method should fulfill the analytical requirements of Council Directive 98/83/EC (referred to in this work as the Drinking Water Directive; DWD). The new draft standard method under investigation is based on ion chromatography followed by post-column reaction and UV detection. The collaborating laboratories used the Draft International Organization for Standardization (ISO)/Draft International Standard (DIS) 11206 document. The existing standard method (ISO 15061:2001) is based on ion chromatography using suppressed conductivity detection, in which a preconcentration step may be required for the determination of bromate concentrations as low as 3 to 5 microg/L. The new method includes a dilution step that reduces the matrix effects, thus allowing the determination of bromate concentrations down to 0.5 microg/L. Furthermore, the method aims to minimize any potential interference of chlorite ions. The collaborative study investigated different types of drinking water, such as soft, hard, and mineral water. Other types of water, such as raw water (untreated), swimming pool water, a blank (named river water), and a bromate standard solution, were included as test samples. All test matrixes except the swimming pool water were spiked with high-purity potassium bromate to obtain bromate concentrations ranging from 1.67 to 10.0 microg/L. Swimming pool water was not spiked, as this water was incurred with bromate. Test samples were dispatched to 17 laboratories from nine different countries. Sixteen participants reported results. The repeatability RSD (RSD(r)) ranged from 1.2 to 4.1%, while the reproducibility RSD (RSDR) ranged from 2.3 to 5.9%. These precision characteristics compare favorably with those of ISO 15601. A thorough comparison of the performance characteristics is presented in this report. All method performance characteristics obtained in the frame of this collaborative study indicate that the draft ISO/DIS 11206 standard method meets the requirements set down by the DWD. It can, therefore, be considered to fit its intended analytical purpose.

Ion chromatography of Mg, Ca, Sr and Ba ions using a metallic copper electrode as a potentiometric detector

On-line monitoring of μg/L levels of haloacetic acids using ion chromatography with post-column nicotinamide reaction and fluorescence detection

Concentrations and characteristics of organic carbon in surface water in Arizona: influence of urbanization

Application of electrochemical methods for the detection of abiotic stress biomarkers in plants

Teaching a computer ion chromatography from a database of published methods

As modified ligands with a wide range of sources, abundant functional groups, and good biocompatibility, polymers have been widely used in the development of silica-based chromatographic stationary phases. In this study, a poly(styrene-acrylic acid) copolymer-modified silica stationary phase (SiO2@P(St-b-AA)) was prepared via one-pot free-radical polymerization. In this stationary phase, styrene and acrylic acid were used as functional repeating units for polymerization and vinyltrimethoxylsilane (VTMS) was used as a silane coupling agent to link the copolymer and silica. Various characterization methods, such as Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, and Zeta potential analysis, confirmed the successful preparation of the SiO2@P(St-b-AA) stationary phase, which had a well-maintained uniform spherical and mesoporous structure. The retention mechanisms and separation performance of the SiO2@P(St-b-AA) stationary phase in multiple separation modes were then evaluated. Hydrophobic and hydrophilic analytes as well as ionic compounds were selected as probes for different separation modes, and changes in the retention of the analytes under various chromatographic conditions, including different methanol or acetonitrile contents and buffer pH values, were investigated. In reversed-phase liquid chromatography (RPLC) mode, the retention factors of alkyl benzenes and polycyclic aromatic hydrocarbons (PAHs) on the stationary phase decreased with increasing methanol content in the mobile phase. This finding could be attributed to the hydrophobic and π-π interactions between the benzene ring and analytes. The retention changes of alkyl benzenes and PAHs revealed that the SiO2@P(St-b-AA) stationary phase, similar to the C18 stationary phase, exhibited a typical reversed-phase retention behavior. In hydrophilic interaction liquid chromatography (HILIC) mode, as the acetonitrile content increased, the retention factors of hydrophilic analytes gradually increased, and a typical hydrophilic interaction retention mechanism was inferred. In addition to hydrophilic interaction, the stationary phase also demonstrated hydrogen-bonding and electrostatic interactions with the analytes. Compared with the C18 and Amide stationary phases prepared by our groups, the SiO2@P(St-b-AA) stationary phase exhibited excellent separation performance for the model analytes in the RPLC and HILIC modes. Owing to the presence of charged carboxylic acid groups in the SiO2@P(St-b-AA) stationary phase, exploring its retention mechanism in ionic exchange chromatography (IEC) mode is of great importance. The effect of the mobile phase pH on the retention time of organic bases and acids was further studied to explore the electrostatic interaction between the stationary phase and charged analytes. The results revealed that the stationary phase has weak cation exchange ability toward organic bases and electrostatically repels organic acids. Moreover, the retention of organic bases and acids on the stationary phase was influenced by the analyte structure and mobile phase. Thus, the SiO2@P(St-b-AA) stationary phase could provide multiple interactions, as demonstrated by the separation modes described above. The SiO2@P(St-b-AA) stationary phase showed excellent performance and reproducibility in the separation of mixed samples with different polar components, indicating that it has promising application potential in mixed-mode liquid chromatography. Further investigation of the proposed method confirmed its repeatability and stability. In summary, this study not only described a novel stationary phase that could be used in RPLC, HILIC, and IEC modes but also presented a facile "one-pot" preparation approach that could provide a new route for the development of novel polymer-modified silica stationary phases.

New strategies for determination of transition metals by complexation ion-exchange chromatography and post column reaction

Synthesis and fluorescence properties of CdTe:Eu ³⁺ nanocrystals and core–shell SiO ₂ ‐coated CdTe:Eu ³⁺ nanospheres

Hemoglobin (Hb) is a tetrameric hemoprotein that is located in red blood cells (RBCs) and is responsible for O2 transport in the circulatory system. Conventionally, Hb assay is a specific and sensitive indicator for the diagnosis of anemia and other related diseases. To date, various methods have been used for the analysis of Hb, and of these, electrochemical method is the simplest and reliable technique. Therefore, several approaches have been reported for the quantification of Hb, including the direct electron transfer (DET) with or without a mediator onto the electrode surface, molecular imprinted polymer (MIPs), and immunoreaction. To realize the direct electrochemistry of Hb, the modification of the electrode surface either with a mediator or catalyst to promote the redox process, which can be applied for the sensitive and selective detection of Hb. This review contains a comprehensive introduction to electrochemical Hb detection methods using modified electrode surfaces. Finally, the review gives a brief insight into the electrochemical sensing platform developed for the analysis of other type of globins such as, myoglobin and glycated hemoglobin. The objectives of this review are to summarize various electrochemical detection methods for Hb and to facilitate future development of new sensing platforms for the medical and healthcare applications.

The chloride ion (Cl−) is a type of anion which is commonly found in the environment and has important physiological functions and industrial uses. However, a high content of Cl− in water will do harm to the ecological environment, human health and industrial production. It is of great significance to strictly monitor the Cl− content in water. Following the recent development of society and industry, large amounts of domestic sewage and industrial sewage are discharged into the environment, which results in the water becoming seriously polluted by Cl−. The detection of Cl− has gradually become a research focus. This paper introduces the harm of Cl− pollution in the environment and summarizes various Cl− detection methods, including the volumetric method, spectrophotometry method, electrochemical method, ion chromatography, paper-based microfluidic technology, fluorescent molecular probe, and flow injection. The principle and application of each technology are described; their advantages, disadvantages, and applicability are discussed. To goal of this research is to find a more simple, rapid, environmental protection and strong anti-interference detection technology of Cl−.

A new strategy for the preparation of mixed-mode chromatographic stationary phases based on modified dialdehyde cellulose

Zn2+ addition: A facile way to obtain CdTe nanocrystals powders with enhanced fluorescence emission

A sensitive chromatographic method was developed for the determination of trace level bromate in food and drinking water. The method was based on a poly (glycidyl methacrylate-co-ethylene dimethacrylate) monolithic column, which was prepared by in situ polymerization and further modified with quaternary amine groups. Morphology of the stationary phases was studied by scanning electron microscopy. Permeability and mechanical stability of the column were both excellent. Bromate was detected after post-column reaction with potassium iodide at 352 nm. The parameters affecting the detection limit of bromate were studied in detail. Under the optimum conditions, the detection limit for bromate was 1.5 μg/L. This method showed good linearity over the concentration range 5.0–30 μg/L, short analysis time (8.5 min), and satisfactory relative standard deviation of the replicate analysis (n = 6, 0.043 %).