[Determination of heat stable salt anions in alkanolamine desulphurization solution by ion chromatography]

To control the potential risk of natural gas purification plants, an ion chromatographic method has been developed to determine the heat stable salts (HSS) in alkanolamine desulphurization solution. Seven HSS anions, including CH3COO(-), HCOO(-), Cl(-), SO4(2-), C2O4(2-), S2O3(2-), SCN(-), were determined in a single injection. Before the chromatographic analysis, these industrial samples were pretreated by three steps, i.e. filtration, solid phase extraction and dilution. Using the gradient elution with KOH solution, all of the seven anions have been separated and determined by a conductivity detector. As the calibration results, the linear range of this method was 0.01 - 0.5 mmol/L for the 7 anions. The limit of detection (LOD, S/N = 3) was 0. 1 mg/L for each anion. By spiked standard solutions in the samples, the recoveries were in the range of 80.0% - 100.3%. The repeatability of this method was evaluated at five different concentrations. The relative standard deviations (RSD, n = 10) of the peak areas were in the range of 0.94% to 3.99%. Moreover, the reproducibility of the method was also tested in three different laboratories and it was acceptable with the RSD <5%. The proposed method has been applied to the determination of HSS in eight gas purification plants, three oil refineries and one coal gas plant and to monitor a gas purification plant continuously in 15 days. It's shown that the accuracy and precision of this method are satisfactory.