Since the introduction of ion chromatography over 30 years ago, there has been much progress in the development of innovative IC systems. Capillary IC was introduced to provide a technique that is always ready and provides excellent eluent and waste economy. The first commercial capillary IC systems became available in 2010, but uptake of the technique has been slow, even though it has many benefits. This article assesses these benefits and presents selected application areas where capillary IC is proving especially useful.
There are a number of benefits to capillary ion chromatography (IC):
Lower Sample Volume: Capillary IC operated as a RFIC system can provide trace-level determinations using sample volumes of up to 250 µL. One approach is to perform a large-volume direct injection that is suitable for samples with low levels of matrix ions. A 10 µL injection onto a 0.4-mm i.d. column in a capillary IC system is equivalent to a 1000 µL injection onto a 4-mm i.d. column. An alternative approach is to load a 250 µL sample onto a capillary concentrator rather than loading a 25-mL sample onto a 4-mm concentrator. Capillary IC can offer significant benefits in trace analysis where sample volumes might be limited.
Higher Resolution: Capillary IC can be performed under high pressure at up to 5000 psi when configured as an RFIC system. These high-pressure capillary IC systems can support higher back pressure 4-µm particle ion exchange columns. The advantage of using a 4-µm particle ion exchange column is improved chromatographic efficiency because of the smaller particle size. A 150-mm length column can be used at higher flow rates to increase productivity; a 250-mm length column can provide higher resolution separations of complex sample matrices.