Background

Ion exchange chromatography of carboxylic acids can be performed using an anion exchange stationary phase. The capacity of this anion exchanger is important since the capacity needs to be sufficiently high to separate carboxylic acids of similar charge, but low enough for the ionic strength of the mobile phase to permit the use of conductivity detection. The development of new high-efficiency, low- and medium-capacity columns combined with a new generation of micromembrane suppressors capable of handling concentrated mobile phases has made the determination of carboxylic acids by anion exchange chromatography a practical proposition.

One disadvantage of anion exchange chromatogra-phy is that groups of mono-, di- and tricarboxylic acids must be analysed separately. However, the use of gradient elution (water, sodium hydroxide and methanol) has made it possible to separate these compounds in a single run, as well as simultaneously separating inorganic anions (Figure 7).

Ion exchange chromatography of carboxylic acids has been performed on anion exchange resins in the hydroxyl, carbonate, sulfate, chloride, nitrate, formate, acetate or borate form. The mobile phase usually consists of an alkaline solution such as sodium hydroxide or sodium carbonate and sodium hydrogen carbonate, with detection achieved using a suppressor column and conductivity. Solutes are usually low-molecular-weight, saturated or unsaturated acids and hydroxy acids. Factors which affect retention include molecular dimensions, pKa and specific adsorption of organic acid molecules on the organic matrix of the ion exchanger.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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