Logochromatographyshopneu
Ion Exchage & Ion LC

Ion Exchange and Ion Liquid Chromatography Methods

 

ION CHROMATOGRAPHY PHASES

This page is under development

Introduction

Ion-exchange phases separate solutes on the basis of ionic charge. Retention in ion-exchange chromatography is determined by the pH of the eluent, the nature and ionic strength of the buffer and temperature. Column efficiencies are lower than in reversed-phase HPLC. Eluents are normally aqueous but can contain some organic component.

Base Material

Both silica-based and polymer-based ion-exchangers are available. For the former, ionic species are attached to the silica surface, whereas for the latter the ion-exchange groups are distributed throughout the matrix. Silica based materials maintain a mechanical strength and higher efficiency advantage whereas the polymer based materials have greater pH stability.

Application

Ion-exchange is used for the analysis of small ions but its key application area is in the separation of biomolecules such as proteins and nucleic acids. Weak ion-exchangers are used for the analysis of inorganic ions, a technique more specifically termed ion-chromatography.

Ion-Exchange Capacity

The exchange capacity of an ion-exchanger is an important measure of its retentivity (typically measured in milliequivalents per gram material). For any one column the packing density of the phase must also be taken into account. Wide pore materials will typically have lower ion-exchange

Classification

 

Type

Strength  pH

Nomenclature

Typical Functionality

Ionisation Range

Ion-
Exchange

Anion

Weak

Amine

 Ionised at specific pH

Strong

SAX

Quaternary Ammonium

Ionised over complete pH range

Cation

Strong

SCX

Sulphonic Acid

Weak 

WCX

Carboxylic Acid

 Ionised at specific pH

 

 

ION CHROMATOGRAPHY PHASES

Introduction

Ion chromatography (IC) is a special form of ion-exchange chromatography developed as a means of separating the ions of strong acids and bases. The most important form of ion chromatography involves a combination of specific ion-exchange phases with conductivity detection. It is a sensitive technique, in some cases being able to detect ppb levels of ions.Suppressed or non-suppressed detection Eluents used in IC contain a relatively high level of salt ions and therefore exhibit high conductivity. This leads to a high background signal which could inhibit the detection of low level analytes. Suppression of eluent conductivity post column is necessary for efficient detection of sample ions, and is the most common method for anion analyses. Although isocratic elution is more commonly used, the use of suppressors enables gradient elution to be used for complex samples.

Phases

Silica and polymer based phases are available for anion and cation analyses. Silica based columns, although showing better efficiency, have a limited pH range. As a result, they are not compatible with anion IC methods requiring suppressed detection, due to the high pH of the eluents required. Polymer based materials are stable over a wider pH range and have higher capacities. Tables 1 and 2 show typical base materials and bonding for anion and cation chromatography phases respectively. The majority of phases for anion chromatography are bonded with quaternary ammonium groups, with a permanent cationic charge. For cation chromatography phases, sulphonate is the most common functionality.Columns optimised for non-suppressed IC generally have lower capacity than those for suppressed detection, in order to achieve a relatively low background conductivity. They are therefore not suitable for suppressed detection.

Eluents

The choice of eluent for IC depends on whether the method is suppressed or non-suppressed. For suppressed anion IC, carbonate/bicarbonate or hydroxide are the most common eluents. Hydroxide eluents have the advantage of producing water only in the suppressor and thereby giving a very low background conductivity. However, some phases are not stable at the high pH (12) of this eluent. For non-suppressed anion IC analyses, typical eluents include p-hydroxybenzoic acid and phthalic acid. Typical eluents for suppressed and non-supressed cation IC include HCl, HNO3, tartaric acid and succinic acid.

Applications

High sensitivity ion analyses are important in a wide spectrum of industries including pharmaceutical, food, water,semiconductor etc. In addition to the common inorganic anions eg F-, Cl-, NO2-, NO3-, SO42-, acid salts can also be analysed by IC eg formate, acetate. Quantitative analysis of anions at the ppb level can be achieved. Cation chromatography is used for the separation and detection of Group 1 and 11 metal ions, in addition to some transition metal ions, ammonium ions and ethanolamines. Small ions are generally eluted before larger ions and monovalent ions before di- and trivalent ions.

Table 1. Anion Chromatography Phases

Base Material

Functional Group

Typical pH Range

Silica

Quaternary ammonium

2 - 5.5

Polystyrenedivinylbenzene

Quaternary ammonium

2 - 12

Polymethacrylate

Quaternary ammonium

 2 - 10

Polyvinyl alcohol

 Quaternary ammonium

 3 - 12

Table 2. Cation Chromatography Phases

Base Material

 Functional Group

Typical pH Range

Silica

 Carboxylate, sulphonate

2 - 7

Silica

Polybutadiene/maleic
acid coating

2 - 7

Polystyrenedivinylbenzene

Sulphonate

2 - 12

A selection of ion chromatography columns can be found in the following sections:

Hamilton
MCI GEL
Shodex
 

 

© by LCC 1995 -2016 All rights reserved
 Chromatographyshop is a division of LCC Engineering & Trading GmbH, CH-4622 Egerkingen, Switzerland.
Collaboration partners in various countries
Our Company Profile and Summary Product List 2015
Unser Firmenprofil und Produktzusammenfassung 2015
      Our Terms and Conditions

Sample Preparation Tools

[Sample  Preparation]
[MatrixEx]
[QuEChERS]
[SPE]
[Syringe Filters]
[Inert RSA  Glass Vials]
[Flash Chromatography]

General Issues

[Chromatogr. Shop Home]
[Newsletter Archive]
[Our Services & Company]
[Terms & Conditions]
[Mobile Phone]

 Bonuses for you

[Special Deals for you]

Seminars & Workshops

[Knowledge Education]
[Seminars & Workshops]

Analytical Scale Chromatography

[Analytical Columns]
[ACE & ACE  Excel Columns]
[ACE Ultra Core]
[Microsolv Cogent Column]
[Capcell Shiseido]
[Daicel / Chiral Technologies]
[GL Science  Inertsil]
[Hichrom Columns]
[Imtakt Column]
[Kromasil Akzo Nobel]
[Mitsubishi MCI-Gel]
[Merck Lichro...]
[Macherey &  Nagel]
[Princeton  Chromatography]
[PolyLC  Columns]
[SieLC Primesep]
[Capcell Shiseido]
[Ultron by Shinwa]
[Welch  Materials]
[Zirchrom]
[Agilent Zorbax]

Knowledge Tools for Chromatographers

[Knowledge Education]
[Definition of  Terms Used]
[Separation Mechanism]
[Solvent  Selection]
[Buffers for  LC.]
[Column &  Material Care]
[Prep & Process Columns]
[Analytical  Columns]
[HPLC- to-UHPLC]

Resin based Systems (Analytical to Process scale)

[Bioseparation Biopurification]

Special Tools to improve data quality, reproducibility and productivity

[Inert RSA  Glass Vials]

Method & Material  Choices  1

[Knowledge Education]
[Sample  Preparation]
[Reverse_Phase_LC]
[Adsorption-LC RPC & SPE]
[AQ Columns]
[Phenyl Bond Columns]
[FPF_Columns]
[HILIC & Aq. Norm. Phase]
[Electrostat. Repul. HILIC]
[Normal Phase Chromatography]

Process Scale   Chromatography Equipment

[Process  Chromatogr.]
[Process Chromat.Systems]
[Flash &  MPLC Pumps]
[HPLC  Pumps]
[Special  Pumps]
[Fraction Collectors]
[Stainless Steel Columns]
[Glass  Columns]
[Glass  Cartridges]
[Plastic Cartridges]
[Manual  Valves]
[Motor  Valves]
[Efficiency  Tools]

Method & Material Choices 

[Knowledge Education]
[Multi  Mode LC]
[Chiral  Chromatography]
[Ion Exchange  & Ion LC]
[Hydrophobic  Interaction LC.]
[Affinity  LC]
[Size Exclusion Chromatogr.]
[SuperCritical Fluid LC]
[Proteomics]
[Metabolomics]
[Process  Scale LC]
[Kamasutra Inspired Tech]