AN INTRODUCTION AND TROUBLESHOOTING MANUAL A Practical Guide to Ion Chromatography

Revisions and additional material can be found on SeQuant's website (www.sequant.com). Questions and comments regarding the content in this booklet can be e-mailed to [email protected]. An introduction and troubleshooting manual Foreword This guide will show you some of the most common practical issues that occur during analysis of anions by ion chromatography. Many users find the technique difficult and hard to understand. It is our hope that we will be able to explain a few of the most fundamental prerequisites for analysis of water samples. We also want to give you guidance on troubleshooting of the instruments. If your ion chromatographic problems cannot be solved with this guide, SeQuant will be happy to assist you. First of all, we recommend that you visit our web pages (http://www.sequant.com), where you will find more information on applications and our products. Figure 1 shows an ion chromatographic system with suppressor. Eluent is pumped by an eluent pump through an injection valve, where exactly reproducible sample volumes are injected. The sample ions are carried by an eluent flow to a separation column, where interaction with fixed ions of opposite charge (i.e., positive) take place. The ions are thereby slowed down to an extent characteristic of each ion and arrive separated at the " suppressor " , where the eluent and analyte ions are transformed before they reach the detector. The detector measures the electrolytic conductivity of the eluate and the function of the suppressor is both to reduce the background of the eluent and to increase the sensitivity for the sample ions. The detector signals can be evaluated manually from recorder charts or automatically with an integrator or a computer-based data-acquisition system with suitable chromatography software. As with all chromatographic techniques it is very important to recognize the chromatographic terms efficiency, capacity and selectivity. If these factors are kept in mind, it is easier to achieve good separations in a time-saving and economic way: Efficiency An efficient chromatographic system will generally produce high and narrow chromatographic peaks, and thus provide good sensitivity. The efficiency is controlled by the column choice and careful selection of other components of the flow system. Capacity The capacity term has to do with the ability of the column to attract ions and the eluent strength required to elute these through the column. To put it simply, the capacity relates to the retention time of the ions and the ability …