Improved Sensitivity and Characterization of High-Speed Ion Chromatography of Inorganic Anions

The continuous flow gradient and its effect on chromatographic parameters were investigated for the separations of inorganic anions on a monolithic porous disk with bonded hydroxyproline residues.The general definition of high-performance liquid chromatography assumes a maximum number of resolved chromatographic peaks in the shortest possible time. There are two main approaches to high-speed ion-chromatography (IC). One is the use of short columns (3-5 cm) packed with fine particles 1.5-3.0 µm in diameter. 1 A reasonable efficiency can be achieved with such columns in a short time, but a high backpressure does not allow a significant increase of the flow-rate of the eluent and hence a further decrease of the analysis time.Another possibility for achieving fast IC consists in the use of monoliths or continuous stationary phases. Monoliths have through pores, which result in a low backpressure, and mesopores providing a large surface area. The pores are highly interconnected and form a network of channels, 2 which allow a very large increase in flow-rate with little loss in efficiency, thus drastically reducing the time of analysis. For a monolithic column 5 cm in length with an internal diameter of 4.6 mm, the flow-rate can be increased up to 16 ml min -1 providing the separation of a mixture of anions in a minute. 3 Of course, gradient elution can also be used to reduce the time of chromatographic analysis. A rarely used alternative approach of flow programming has very limited applications in HPLC with packed columns because of a sharp increase of the backpressure, which limits the flow-rate to a relatively narrow range. 4,5 Note that a flow gradient can often be used only in tandem with a temperature gradient, 6,7 which diminishes the growth of backpressure.Schafer et al. 8 considered flow-gradient elution on monolithic silica-based Chromolith (Merck) columns with the use of a sharp increase in the flow rate to speed up the elution of one or two strongly retained peaks, which are widely separated from others on an isocratic chromatogram. The programming of flow-gradient elution for separation on monolithic columns could be more efficient. We studied the separations of inorganic anions on a chemically modified monolithic column with programmed flow gradients during the entire run.We used a Shimadzu LC-10AT pump (Germany) with programmed eluent flow rate, a Rheodyne 7125 injection valve (USA) and CD-510 conductivity detector (Aquilon, Moscow, Russia). The CIM ® (Convective Interaction Media) disk monolithic column consisted of a CIM ® Epoxy disk (thickness, 3 mm; diameter, 16 mm; active bed volume, 0.34 ml; macropore diameter, 1500 nm; mesopore diameter, 100 nm 9 ) and a CIM ® housing (BIA Separations, Slovenia).L-Hydroxyproline (Sigma) (pK 1 = 1.92; pK 2 = 9.73) was chosen as an ion-exchange functionality because of the tertiary nature of the amino group in the bonded state, which provides anion-exchange properties and high ion-exchange selectivity. 10,11 The attachment of L-hydroxyproline to the disk was perfo...

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“…3 The flow-gradient separation can be considered as a kind of isocratic separation in respect to a constant composition of the Br -…”

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confidence: 99%

The use of a continuous flow gradient for the separation of inorganic anions on a monolithic disk

Nesterenko

Rybalko

2004

Mendeleev Communications

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“…The rapid degradation of silica-based stationary phases at alkaline pH implies that these materials have limited suitability for hydroxide eluent suppressed conductivity detection. Some of the work described above [20] has utilised suppressed conductivity detection using o-cyanophenol titrated to pH 7.0 with sodium hydroxide and this approach has provided the lowest detection limit in the above examples. As electrostatic shielding of hydroxide by equivalent charged surfactant layers affords some degree of protection, a variation of this method may become a viable option for mild hydroxide shielding of silica monoliths using a suitable array of charged surface coatings.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Studies using unmodified commercial silica monolith columns have already reported considerable improvement in selectivity, efficiency and LOD over conventional columns simply by allowing higher sample throughput while maintaining the favourable mass transfer characteristics, which is not possible with conventional packed particle columns [34]. Several examples of postmodification have been reported, including surfactant-coated RP silica monoliths for ion-exchange [20,21], covalent attachment of functional group substrates [35][36][37], as well as silica monoliths fabricated in a capillary and coated via electrostatic interaction [38].…”

Section: Monolithic Silica Stationary Phasesmentioning

confidence: 99%

“…2) using RP ion-interaction chromatography with direct conductivity detection and reported detection limits in the low ppm range. A surfactant coating procedure employed by Connolly and Paull [42] in packed ODS particle columns was also adapted by Hatsis and Lucy [20] to perform a high speed ion-exchange separation on a surfactant coated, RP monolithic silica column. Seven anions were separated with baseline resolution in 30 s (Fig.…”

Section: Ic On Modified Commercial Columnsmentioning

confidence: 99%

“…Examples such as the Chromolith RP-18 range (Merck) and the Onyx Monolithic C18 range (Phenomenex) are becoming more popular for inorganic and biological analysis due to their advantages over packed particle columns [9]. For analytes such as small molecules and ions, the RP C18 silica structures have recently been coated with ionic surfactants to create anionic [19], cationic [20][21][22] or zwitterionic [23,24] stationary phases suitable for fast IC.…”

Section: Introductionmentioning

confidence: 99%

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Monolithic stationary phases for fast ion chromatography and capillary electrochromatography of inorganic ions

Schaller

Hilder

Haddad³

2006

J of Separation Science

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Review Monolithic stationary phases for fast ion chromatography and capillary electrochromatography of inorganic ionsThe focus of this review is on current developments in monolithic stationary phases for the fast analysis of inorganic ions and other small molecules in ion chromatography (IC) and capillary electrochromatography (CEC), concentrating in particular on the properties of organic (polymer) monolithic materials in comparison to inorganic (silica-based) monoliths. The applicability of these materials for fast IC is discussed in the context of recent publications, including the range of synthesis and modification procedures described. While commercial monolithic silica columns already show promising results on current IC instrumentation, polymer-based monolithic stationary phases are currently predominantly used in the capillary format on modified micro-IC systems. However, they are beginning to find application in IC particularly under high pH conditions, with the potential to replace their particle-packed counterparts.

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Monolithic High‐Performance Liquid Chromatography Columns

Desire

Hilder

Arrua

2017

Encyclopedia of Analytical Chemistry

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Monolithic HPLC (high‐performance liquid chromatography) columns have emerged over the recent decades as highly attractive alternatives to conventional HPLC technology. A monolith is considered to be a continuous piece of porous material. Two types of monolithic columns have been developed for liquid chromatography (LC) applications; they are polymer monoliths and silica monoliths, which differ based on their porous properties. Polymer monoliths consist solely of macropores (pores larger than 50 nm), while silica monoliths possess both macropores and mesopores (pores between 2 and 50 nm). Silica monoliths therefore possess higher surface areas than polymer monoliths and have mainly been utilied for the separation of small molecules, where excellent separation performance has been demonstrated. Polymer monoliths on the other hand have been shown to provide excellent separation performance for larger molecules, where the convective transport of these molecules is unhindered by the presence of mesopores. Polymer and silica monoliths can be prepared in a variety of ways, resulting in varied surface chemistries and flow properties, thus allowing their application in a wide range of chromatographic modes, including reversed‐phase (RP), ion‐exchange, hydrophilic interaction, and hydrophobic interaction chromatography (HIC), to name a few. This has allowed for the separation of a variety of analytes, from small molecules such as alkylbenzenes, to larger molecules such as peptides and proteins. They have also found application for the separation of DNA. In recent years, significant attention has been focused on improving and understanding the behavior of these materials and alternative synthetic routes for their preparation.

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Improved Sensitivity and Characterization of High-Speed Ion Chromatography of Inorganic Anions

Cited by 81 publications

References 38 publications

The use of a continuous flow gradient for the separation of inorganic anions on a monolithic disk

The use of a continuous flow gradient for the separation of inorganic anions on a monolithic disk

Monolithic stationary phases for fast ion chromatography and capillary electrochromatography of inorganic ions

Monolithic High‐Performance Liquid Chromatography Columns

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