Samples with high ion concentrations require loading less volume or diluting prior to injection into an ion chromatography system to avoid exceeding the column capacity and to ensure that the concentrations determined fall within the calibration range.This Technical Note discusses automated dilutions using the Dionex AS-AP Autosampler with and without the Dionex Sample Conductivity and pH Accessory, reviews experimental data, and recommends conditions for obtaining optimal results.

In this Application Update, ion chromatography coupled with pulsed amperometric detection is used to determine iodide in brine (approximately 30% sodium chloride). This method is specific, sensitive, and rapid. Sample preparation is a simple sample dilution. Iodide is separated on the Dionex IonPac AS11 column, which contains a hydrophilic resin that is well suited to the chromatography of iodide, a relatively hydrophobic anion. Using a nitric acid eluent, the iodide ion elutes from the column in under five minutes.

Sodium chloride brines are used in chlor-alkali cells and must have low concentrations of alkali and alkaline earth metals to prevent membrane poisoning. When brines are prepared from seawater, the manganese concentration is also a concern. This application update uses the same separation conditions as AN 120, but alters the online sample preparation with the MetPac column to effectively concentrate manganese from 10 times more sample than used in AN 120.

Perchlorate, a human health concern, has been found in drinking water wells in regions of the U.S. where aerospace material, munitions, or fireworks were developed, tested, or manufactured. This application note shows that perchlorate can be quantified at the 2 μg/L level using a Dionex IonPac AS16 column, hydroxide eluent generation, a large-loop injection, and suppressed conductivity detection. Refer to AU148 for a description of how detection levels of 1 μg/L or less can be obtained using an improved suppressor.

To prevent membrane poisoning, new membrane technology in chlor-alkali cells requires feed brine that is relatively free of alkaline earth metals.This Application Note describes a method for determining low μg/L amounts of calcium and magnesium in a 30% sodium chloride brine by ion chromatography. A MetPac column is used to concentrate calcium and magnesium from the brine, which is then separated on an IonPac CS12A cation-exchange column and detected by suppressed conductivity detection. AU158 updates this method to achieve 10 ppb manganese by concentrating 10 times more sample.