Characterization of replacement-ion chromatography employing cation replacement and flame-spectrometric detection

Abstract

A relatively new detection method for ion chromatography (IC) called replacement-Ion chromatography (RIC) Is critically evaluated. The capabilities and limitations of cationreplacement RIC for cation and anion separatlon and determination were explored by uslng a conventlonal dual-column IC system followed by a continuously regenerating Nafion cation-exchange fiber (the replacement column). This third cdumn converts all lonk solutes into their lithium salts, whlch are detected by an acetylene-air flame-emission spectrometer. Although poor figures of merit were observed for cation chromatography, the method is analytically useful for anion chromatography. Anlon detection llmits are 3-50 ng and depend upon the replacement-Ion background produced by the eluent. This background llmitatlon of RIC and the infiuence of varlous system parameters are dlscussed in detail.

Universal Anion Detection by Replacement-Ion Chromatography with an Atmospheric-Pressure Solution-Cathode Glow Discharge Photometric Detector

“…Second, portions of analytes that are not dissociated clearly cannot displace Li + in the replacement column and thus would exhibit lower signals. Both effects were suggested by Galante and Hieftje, who observed similarly low sulfate response with a flame photometer Li + -based RIC system …”

“…Detection limits reported earlier were estimated with a Li + background bleed of approximately 0.15 mM (1.0 μg·mL –1 ). Notably, Li + background in the present system is nearly an order of magnitude larger than in past RIC methods that used packed-bed columns or fiber suppressors for both the ion suppressor and replacement column. − Despite its higher background bleed, the present system exhibits superior performance over past RIC methods that employed photometric detection. This result indicates that multiplicative noise (or the flicker factor, k , in eq ) of the SCGD system is smaller than in prior RIC setups.…”

“…The replacement column is functionalized with a desired “replacement ion”, and separated analyte ions (or their counterions) that enter the replacement column are stoichiometrically exchanged for the replacement ions, which are then monitored downstream with a suitable detector. In its first embodiment, RIC employed Li + as the replacement ion and detection was achieved via flame photometry. , Since then, RIC was implemented with a variety of other detection methods, including ultraviolet–visible absorption spectrometry, microwave-induced nitrogen discharge emission spectrometry, and potentiometry. , …”

“…The SCGD, described in detail elsewhere, − is particularly attractive for RIC. The SCGD is much simpler than past RIC systems based on atomic emission spectrometry, ,, as no compressed (or flammable) gases or nebulizer is required and the discharge operates in the ambient atmosphere. Additionally, because the SCGD samples directly from a flowing stream of sample solution, the detector response is very rapid, promoting chromatographic resolution.…”

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

“…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). Alternatively, anions can be detected by RIC utilizing a cation-replacement method (12,34,35).…”