Replacement ion chromatography with flame photometric detection

Detectors

“…Flame photometric detection [76,77] has been used to detect alkali, alkaline earth, and some rare earth metals. Most of these detectors have been used only in special cases.…”

Universal detection of ions by replacement-ion chromatography employing an anion-replacement method and an ultraviolet-visible spectrophotometric detector

“…Better success with anion determinations might be obtained if the fiber were fabricated from a different ionomer. Recently, Dasgupta (34) evaluated the performance of several types of anion-exchange membranes that permit the sensitive determination of anions by postsuppression ion exchange chromatography, identical in concept to the original RIC (12). Several detection modes were investigated by using anthranilate, a fluorescent and optically absorbing anion, as the replacement ion with no apparent problem from unusual peak tailing (34).…”

“…A few years ago, a method called replacement-ion chromatography (RIC) was described that allows otherwise species-specific detectors to be used as general detectors for suppressed IC (12). In RIC, a third ion-exchange column called the replacement column is used to replace solute ions 0003-2700/88/0360-0995$01.50/0 (or their co-ions) with another ion (the replacement ion) that can be sensitively monitored by a suitable detector.…”

“…In RIC, a third ion-exchange column called the replacement column is used to replace solute ions 0003-2700/88/0360-0995$01.50/0 (or their co-ions) with another ion (the replacement ion) that can be sensitively monitored by a suitable detector. In the first demonstration of RIC (12), ionic solutes eluting from the suppressor column were converted to their lithium salts by a replacement column containing a cation-exchange resin in the lithium form. Solutes were subsequently detected (indirectly) by monitoring their lithium atomic emission in a hydrogen-air flame. There are several fundamental advantages to RIC.…”

In-line tubular ion-exchanger to enhance selectivity in enzyme-based flow-injection potentiometry; application to determination of l-glutamine in bioreactor media

“…The concept of usmg ion-exchange to reduce background levels of ammoma/ammoruum in samples 1s not completely new Indeed, Mascmi and Palleschl [12] as well as Meyerhoff and Rechmtz [13] used ion-exchange resins to pretreat urine and blood samples for subsequent enzymeelectrode measurements of creatmme Smularly, post-analytical column ion-exchange 1s the method of choice for reducing the background conductlvlty of the eluent m modem Ion chromatography systems (e g , suppressed systems [14,15]) In replacement Ion-chromatography, an approach pioneered by HleftJe and coworkers [16,171, ions separated on a conventional suppressed Ion-exchange system are further exchanged quantitatively for more readily detected replacement Ions within a third ion exchanger incorporated mto the chromatographlc system In these various chromatographlc arrangements, suppressor and replacement stages of the systems can be classical Ion-exchange columns, although newer monomer membrane-based exchangers, used either m flat or tubular form, offer attractive advantages Indeed, the tubular Ion-exchange fibers can be incorporated conveniently mto flowmg arrangements and mamtamed m their approprlate Ion loaded state by bathing the tubing m a reservoir of surtable electrolyte For efficient cation exchange, varymg lengths of narrow bore Naflon tubing have proved to be quite effective [15,181 In this work, the feaslblhty of usmg Nafion tubing m-line to reduce endogenous catlon mterferences when employmg enzymes that liberate ammoma/ ammomum m conjunction with a flow-mjectlon (FIA) system equipped with an ammoruum Ion electrode detector was examined As a model, the FIA arrangement was configured to determme L-glutamme m bloreactor media via the use of unmoblhzed glutammase This enzyme catalyzes the followmg reactlon L-glutamme --, L-glutamate + NH: Figure 1 illustrates the basic manifold arrangement used for L-glutamme measurements m bloreactor media Evaluation of the efflaency of the m-hne ion-exchange system and the practical Improvements m the selectlvlty were camed out with a very sumlar arrangement, except that the stream of NaCl solution (A) was ehmmated The NaCl stream was added to the final system to help mmlmlze electncal noise and drift, and to enhance basehne recovery In all cases, solution delivery was accomplished with a Ramm multlchannel penstaltlc pump (Woburn, MA) A PTFE a rotary mJectlon valve (Rheodyne, Cotatl, CA) with a 20-~1 sample loop was used for sample and standard mtroductlon…”