Ion chromatography

Ion chromatography is a separation technique that resolves ions and polar molecules in a liquid sample by passing them through a column packed with an ion-exchange resin, then measuring each species as it elutes. It is used for anion and cation analysis, as well as for polar compounds that carry a charge in solution.

In practice it means separating a mixed sample into its individual charged components so each can be identified and quantified. A pump drives an eluent through an ion-exchange column, the column separates the ions by their affinity for the resin, and a detector records them one after another as they come off the column.

A sample is injected into a stream of eluent that carries it onto an ion-exchange column, where ions bind to the resin and release at different rates depending on their charge and size. As each ion elutes it passes a detector, usually a conductivity detector, which produces a peak whose area corresponds to the amount present.

The catalogue covers complete ion chromatography systems and ion chromatographs, plus the separate modules that build them: conductivity detectors, autosamplers, broader analytical chromatography instruments, and electrolytic sample preparation systems. A conductivity detector is the component most often listed on its own, bought to replace a failed unit or to extend an existing stack.

It is used for anion and cation analysis in water, for nucleotide and oligonucleotide separation in molecular biology, for protein fractionation run as ion-exchange chromatography, and for carbohydrate and glycan profiling where pulsed amperometric detection reads sugars. In bioprocessing it handles counter-ion and excipient analysis for cell culture media testing and final-product release.

Start with the ion-exchange chemistry, since anion and cation analysis use different column resins and eluents, and a system set up for one does not switch to the other without changing the column and often the suppressor. Once the ion class is fixed, pick the detection method: suppressed conductivity for routine inorganic work, or electrochemical and UV detectors for sugars, iodide and species conductivity reads poorly.

A used unit is sold in its existing condition, while a refurbished unit has been serviced or reconditioned before sale. Both are listed below the price of new equipment, and the listing itself states what was done to a refurbished unit, so read it to see whether the pump, detector and suppressor were checked or replaced.

Prices on Questpair run from EUR 86 to EUR 137.475, with an average of EUR 6.128. The lower end covers individual modules such as a bare conductivity detector or an autosampler, while the upper end covers complete, recently serviced platforms.

The makers behind most of these listings are Thermo Scientific, Dionex, Thermo Fisher Scientific, Metrohm and Fisher Scientific. These are the names a laboratory is most likely to already run, which makes a second-hand unit easier to fold into an existing method.

A warranty is often possible and is arranged in consultation for the specific listing. Because terms are set per listing rather than centrally, check the individual unit you are considering.

Parts can be sourced via Questpair. For the leading platforms, columns, suppressors and eluent cartridges remain in regular supply, so a used system can be kept running without hunting for discontinued consumables.

The instrument frame and detector can run for many years, while the pump seals, check valves and suppressor are consumables with a finite life. Electrolytic suppressors in particular wear out and a replacement is a real cost, so lifespan depends more on how these parts are maintained than on the age of the chassis.

Used and refurbished units are listed at lower prices than new ones, and the saving is largest when a single module can be added to an existing stack rather than replacing a whole system. Where you need to weigh the two, compare the specific listing and note that warranty is arranged in consultation.

The listings on Questpair come from 12 verified suppliers and distributors across 6 countries, covering 114 listings for this technique. Because the listings cluster around a handful of makers, you can compare one model against another on completeness and condition rather than across incompatible designs.

Lead time and shipping depend on the individual supplier and the unit's location, which spans 6 countries. The listing shows who holds the instrument, and Questpair specialists respond within one hour if you need to confirm availability.

On a used instrument, verify the pump and detector first, since both wear and drift, and ask whether the seller ran a recent calibration and whether a certificate exists. A conductivity detector that sat unused can look stable on paper but show elevated noise once eluent is flowing, and pump seals and check valves are routine replacements on a system that has pumped hundreds of litres.

Complete ion chromatography systems and ion chromatographs are bought by laboratories setting up or replacing a full analysis, while conductivity detectors are the single module listed most often, bought to replace a failed unit or extend a stack. Autosamplers go to labs running unattended overnight sequences, and electrolytic sample preparation systems handle inline matrix elimination and eluent generation ahead of the column.

Thermo Scientific, Dionex, Thermo Fisher Scientific, Metrohm and Fisher Scientific account for most of what is listed. That concentration means columns, suppressors and replacement parts are easier to find, and that a used unit is likely to match a method a laboratory already runs, so it can be folded in rather than revalidated from scratch.

The lower end covers individual modules, such as a bare conductivity detector or an autosampler sold on its own, while the upper end covers complete, recently serviced platforms from the established makers. Completeness and brand matter more than age: a system with an impressive datasheet limit is worth little if its pump cannot hold a steady flow.