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Ion Chromatograhy (IC) is a versatile analytical technique that is generally applied to detect positive and negative ions. It utilizes an ion's intrinsic affinity for both an “eluent” (typically buffered water) and a “stationary phase” (porous solid support with charge‐bearing functional groups) [3, 7]. It works on any kind of charged molecule, including large proteins, small nucleotides and amino acids.

There are two types of IC, cation‐exchange and anion‐exchange. Cation‐exchange chromatography is used for positively charged molecules (pH < pI). The stationary phase is negatively charged and positively charged molecules are loaded to get attracted toward it. In anion‐exchange chromatography, the stationary phase is positively charged and negatively charged molecules (pH > pI) are loaded to get attracted toward it. It is used in water analysis, protein purification, and quality control. Some of the ideal uses of IC include the analysis of food products and beverages, aqueous solutions such as water, and water‐extractable surfaces. It is more useful for analysis for quality assurance and control, purification of charged molecules, quantitative analysis of ions such as cations (Li, Na, K, Mg, Ca, NH₄ ⁺), anions (bromide, fluoride, nitrate, phosphate, sulfate, etc.), secondary amines, chlorite, sulfate, iodide, bromated, etc. Some of the advantages and limitations are tabulated in Table 1.2.

IC has industrial applications too. Its main advantages in this sector include good precision and accuracy, reliability, high separation efficiency, high selectivity, good speed, and low operating cost. Applications of IC particularly in the field of pharmaceutical industry are being developed. These applications are typically focused on the determination of detection limits in the field of pharmaceuticals. The detection limits corresponding to oxalates, sulfamates, sulfates, iodide, phosphate, and electrolytes like sodium and potassium can be determined too. The IC can also be used for the analysis of drugs having pharmaceutical importance for the development of products with quality control testing. It can be used in pharmaceutical drugs in tablet or capsule form for the determination of the actual dosage of the drugs that can be dissolved within some time. IC can also be utilized for the detection as well as quantification of the inactive or undesirable ingredients that are being used in the pharmaceutical formulations. Sugar and associated alcohol have been detected in such formulations with the help of IC as they are easily resolved in an ion column due to having polar groups. IC can also analyze the impurities present in the drug substances and products. Impurities in the drug can be easily estimated and help to provide an intuition for the minimum and maximum dosage of drugs needed by a person on daily basis.

Table 1.2 Advantages and limitations of ion chromatography (IC) [3, 7].

Advantages	Limitations
Small sample quantity required.Rapid determination of anions and cations (inorganic as well as organic)Sensitivity: μg/l levelAnalysis of ionic speciesStability of the separator columns	Buffer requirementDetermination of only ionic analytesIdentification of peaks based on a retention time match to a standard solutionSmall change in pH greatly alters binding profile of stationary phase and ion statesSamples applied to the IC under conditions of low ionic strength and controlled pHResistant to salt‐induced corrosion