ASTM D5996 Measuring Anionic Contaminants in Water by On-Line Ion Chromatography

Scope:

ASTM A247 is used as a reference to define concisely the graphite microstructure required. To permit accurate reporting of the microstructure and to give the comparison reports of cast iron microstructure, these standards are offered primarily by the investigators or labs.

Test Procedure:

In ASTM D5996, a continuously flowing sample is injected into the instrument through a sample injection valve. The sample is pumped through a concentrator column where the anions of interest are collected on an ion-exchange resin. After a suitable sample volume has been passed through the concentrator column, sample flow is diverted, and the eluent is pumped through the concentrator column to remove the trapped anions. This eluant then flows through an analytical column set where the anions are separated based on the retention characteristic of each anion relative to the eluent used. The eluant stream containing the anions of interest passes through a suppressor device where the cations from the eluent are exchanged for hydrogen ions, converting the anions to their acid form. After the suppressor device, the eluent solution is made to pass through a conductivity detector to detect the separated anions. Detection limits for the anions are enhanced because the anions are in the acid form rather than the salt. The anions are identified based on the retention time compared to known standards. The anions can be quantified by measuring peak height or area and comparing the detector response to known standards.

Video 01: Ion Chromatography

Test Specimen:

For ASTM D5996, the temperature control should be at ± 0.5°C or better. Anion contaminants should be at less than 0.02 μg/L.

Conclusion:  

ASTM D5996 determines the analysis of high-purity water by Ion Chromatography (IC). The concentration of acetate, formate, chloride, fluoride, phosphate, nitrate, and sulfate in a continuously flowing sample is measured by this technique.