What is Ion Chromatography?

The term chromatography refers to different methods of molecular separation between a mobile phase and a stationary phase based on various physio-chemical properties. There are many types of chromatography that are used as analytical tools in environmental science, forensics, metallurgy, biology, etc. Some common examples are thin layer chromatography (TLC), gas chromatography (GC), high performance liquid chromatography (HPLC) and ion chromatography. Ion chromatography (IC) was introduced as an analytical technique by Small, Stevens, and Bauman in 1975. According to IUPAC in IC “separation is based on differences in the ion exchange affinities of the individual analytes. If inorganic ions are separated and can be detected by conductivity detectors or by indirect UV detection then this is also called ion chromatography” (Eith 17).

IC is a blanket term for various other types of chromatography based on the same principle such as ion exchange chromatography, ion exclusion chromatography, ion pair chromatography, etc. Charged ions can be separated and the separated chromatogram can be simultaneously detected using IC. Earlier IC systems used to have a separator column for ion separation and a suppressor column that reduced the conductance of the eluent used to elute the ions (Fritz and Gjerde 3). An alternative method was discovered where a single column could be used for the whole process by using eluent solutions that had naturally reduced conductance but had good eluting capabilities. The reason that led to the development of this single column IC was the resin in the suppressor column. Some of the analytes interacted with the resin, resulting in extended elution times, the variation in peaks and degradation by the resin. This d...

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...mple injector has two positions, namely, load and inject. During the load phase, the injector loads the sample into a coiled sample loop. Simultaneously, the eluent that is being pumped, is obstructed from entering the sample loop and is by-passed into the column. The samples are loaded using syringes that are devoid of rubber components to prevent contamination. Care must be taken to prevent the formation of air bubbles in the sample loop. At the inject position, the obstruction is removed and the eluent passes through the sample loop, carrying the analytes through the two columns. The load volume ranges from 20 to 100 μl. Nearly 2 times the amount of the sample to be analyzed is taken in the syringes for loading where the excess sample overflows and exits via a waste pipe. This prevents bubble formation and rinses the sample loop with the sample for even flow.