Liquid chromatography is Among the most effective tools in the analytical lab. It is very popular for the separation and analysis of mixtures of substances of all kinds. When coupled with the sensitivity and selectivity of mass spectrometry its power is significantly enhanced. In Liquid chromatography a Liquid the mobile phase/eluent under high pressure flows through an inert tube column packed with a fine powder which might be coated in a liquid stationary phase. A sample is injected into the eluent until the column; as it moves through the column the time taken by each chemical in the sample to get to the end of the column is regulated by its interaction with the eluent and the stationary phase. This is determined by the chemical’s properties and may be used to separate mixtures of very similar substances. Once separated, the chemicals can be quantified as they emerge from the column with a range of sensors, both non-selective and discerning, including mass spectrometers.
Separation using High Performance Liquid Chromatography relies on the distribution of the analyte between the mobile phase eluent and the stationary phase. The specific intermolecular interactions between the molecules of a part of the sample as well as the packaging material result, in effect, in such molecules being consumed transitorily to the stationary phase. The greater the interaction with the stationary phase compared with the mobile phase, the longer the time spent interacting with the stationary phase, the longer the time spent on the pillar and the longer the retention period for this component. The ability of this technique comes from the broad array of stationary and mobile phases which might be used to fine tune separations. Different packing materials support different separation mechanisms –normal-phase, reversed-phase, size exclusion, ion exchange, affinity, chiral, or hydrophilic interaction HPLC. Normal-phase LC uses a polar stationary phase and a less polar or non-polar eluent. In reverse-phase LC these polarities are reversed.
Ion chromatography IC is a Variant on hplc testing in which the stationary phase interaction relies on ion exchange. It is, therefore, applied to different ions or charged species. Anions and cations are split on different columns. Unlike HPLC where a lot of the focus is on separating similar substances, in IC that the separations are normally standard and the emphasis is on precision and sensitivity. Because of the various properties of ions, conductivity sensors are often used; to boost sensitivity that the background conductivity of the eluent is eliminated before detection of the ions. To achieve higher sensitivity the ions might be preconcentrated on a brief ion exchange column and then eluted to the eluent flow for separation. This offers a very powerful method of determining trace amounts of several anions. IC is often utilised to match the ICP-MS determination of metals in a sample.