A Study Towards the Total Analysis of Stretford Liquors Using HPLC Techniques

Abstract

<p> The ultimate objective of this research project was to establish an HPLC method that allows the quantification of most of the major components of a circulating Stretford process liquor using one sample. The criteria that had to be met were reasonable retention times, resolution approaching 1.0 and quantitative results (ie. with an uncertainty in the accuracy and precision of the results less than ± 10%). Ion chromatography was the route chosen since the major components of the circulating liquors are present as either inorganic or organic anions. Ion pair chromatography and ion exchange chromatography were the general methodologies investigated during the study.</p> <p> Ion pair chromatography, specifically soap chromatography, was successful in the isolation of the NaSCN, Na2SO4 and Na2S2O3 species of the circulating Stretford liquors. It was unsuccessful in the quantitative separation of these species. The method was abandoned in order to find a method which could quantify these species as well as the other components of the circulating liquors.</p> <p> The ion exchange chromatography studies fell into two categories, that being columns with a silica based packing and columns with a polymer based packing. The silica based columns had a limited operating range of pH for the analysis and the backbone of these columns degraded at pH values exceeding pH 5.5. The polymer based ion exchange columns had a much wider operating pH range and allowed for the analysis of the Stretford liquors without the need to change the pH of the solution.</p> <p> The best possible method of analysis was the polymer based technique. All of the components of the Stretford liquors, with the exception of the ADA (anthraquinone disulfonic acid) could be quantified in under 15 minutes. The method provided quantitative results and very good resolution between the species eluted.</p>