Jumat, 29 April 2011

Ion Chromatography

The ion chromatography is used for analysis of aqueous samples in parts-per-million (ppm) quantities of common anions (such as fluoride, chloride, nitrite, nitrate, and sulfate and common cations like lithium, sodium, ammonium, and potassium) using conductivity detectors. The chromatography also has the capability to analyze aqueous samples for parts-per-billion (ppb) quantities of hydrazine, monomethylhydrazine (MMH), and unsymmetrical dimethylhydrazine (UDMH).
Ion chromatography is a form of liquid chromatography that uses ion-exchange resins to separate atomic or molecular ions based on their interaction with the resin. Its greatest utility is for analysis of anions for which there are no other rapid analytical methods. It is also commonly used for cations and biochemical species such as amino acids and proteins. Most ion-exchange separations are done with pumps and metal columns.
Figure 1 at the left shows the chromatogram of a 0.02 ppm F-, 0.1 ppm Cl-, NO-2, Br-, NO-3, PO4-3, SO4-2 standard.

Ion chromatography is the only technique that can provide quantitative analysis of anions at the ppb level. This technique is used to determine ions in liquids and ionic contamination on the surfaces of wafers, chips, and packages. Aqueous solutions, which may require filtration, dilution, and/or cleaning to remove interferences, are required for analysis. Solid samples are extracted with water to remove ions from the sample surface. Organic liquids may also be extracted with water to obtain an aqueous solution of ions for analysis. The minimum sample required is approximately 10 mL for liquids and 2-3 cm2 for solids. There are no upper limits. 


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