Ion Chromatography - The Separation of Anions 2



Another example of anion analysis using ion chromatography is the determination of different anions in foodstuffs. Anion analysis is needed in milk production, the soft drink industry, alcoholic beverages, soups etc. An example of the use of ion chromatography to determine the chloride content of two Mariana soups and a beef broth is shown in figure 35. The column used was the Metrosep ASUPP5, 15cm long, 4mm in diameter and fitted with a reverse phase guard column. The mobile phase was a 3.2mMol sodium carbonate and 1.0mMol sodium bicarbonate solution at a flow rate of 0.7ml/min. The sample volume was 20ml. Suppressed conductivity was used for the detector system. The chromatogram is very simple and it is clear that an external standard procedure was employed for quantitation. In addition, this procedure could, obviously be easily automated and
could be used for automatic quality control or even plant process control.

(Randy Benton Metrohm-Peak Inc.)

Figure 35. Chromatogram from the Determination of Chloride in Soups.


The use of alcohol as a fuel is increasing and will continue to increase in the future. Unfortunately inorganic salts are significantly soluble in alcohol and consequently can produce problems when used in an internal combustion engine. Different salts can deposit in the fuel system, block fuel lines and nozzles and induce corrosion. It is therefore important to be able to determine the presence of anions in liquid (and mostly hydrocarbon) fuels. Figure 36 shows a chromatogram resulting from a direct injection of alcohol into the ion chromatograph. The black trace is and injection of the alcohol sample, the blue trace from the same alcohol sample spiked with 4ppm each of chloride, chlorate, bromide, nitrite phosphate and sulphate. The column employed was a Metrosep ASUPP5 with a mobile phase containing 3.2mM 0f sodium carbonate and 1.0mM of sodium bicarbonate at a flow rate of 0.7ml/min.

(Jay Gandhi Metrohm-Peak Inc.)


Figure 36. Chromatogram of Some Anions in Ethyl Alcohol.


It is clear that the method can be very useful to the manufacturers of ethanol, the vendors and the users.