ASTM D5827 Standard Test Method for Analysis of Engine Coolant for Chloride and Other Anions by Ion Chromatography
3. Summary of Test Method
3.1 A small volume of working sample is prepared by dilution of the sample with the method eluant. This diluted sample is filtered and pumped through two ion exchange columns and a suppressor and into a conductivity detector. Ions are separated based on their affinity for exchange sites of the resin with respect to the resin's affinity for the eluant. The suppressor increases the sensitivity of the method by both increasing the conductivity of the analytes and decreasing the conductivity of the eluant. The suppressor converts the eluant and the analytes to the corresponding hydrogen form acids. Anions are quantitated by integration of their response compared with an external calibration curve and are reported as milligrams per litre (mg/L).
4. Significance and Use
4.1 This test method provides for the qualitative and quantitative determination of common anions in engine coolant in the milligrams per litre to low percent range and requires only a few millilitres or microlitres of sample per test, with results available in less than 30 min. Acceptable levels of chloride and other anions vary with manufacturer's blending specifications and applicable ASTM minimum or maximum specifications.
5.1 Interferences can be caused by substances with similar retention times, especially if they are in high concentration compared to those of the analyte of interest. Sample dilution will be used to minimize or solve most interference problems.
5.2 A water dip (solvent system peak) can cause interference with some integrators. This is eliminated by dilution with the eluant ifthe sample dilution factor is 49 + 1 (v/v) or greater. Below this dilution, it is best to add a spike of eluant concentrate to the sample such that the sample is not diluted significantly and the resulting test solution matches the eluant used in the system. One method is the addition of 100 µL of 100X eluant concentrate to 10.0 mL of sample or standard.
5.3 Method interferences can be caused by the contamination of glassware, eluant, reagents, etc. Great care must be taken to ensure that contamination, especially by chloride, is kept at the lowest possible levels.
5.4 Pre-rinsing of the sample preparation containers with deionized water is mandatory.
5.5 The use of latex gloves is highly recommended to prevent contamination.