Optimisation of size-exclusion chromatography with diode array detector for aquatic organic matter profiling using design of experiments: application to tropical reservoirs

ABSTRACT

In this article, a size-exclusion chromatography with diode array detector (HPSEC-DAD) method was developed to determine the molecular weight distribution of natural aquatic organic matter. First, a variable screening was performed using sodium polystyrene sulphonate (PSS) standards, verifying the significant effects of ionic strength and flow rate of the mobile phase and the injection volume on resolution and final retention time. The method was then optimised using a Box – Behnken design (BBD), obtaining optimal values of 60 mM (ionic strength), 70 μL (injection volume) and 1.2 mL/min (flow rate). The process was repeated with the same design, using natural water as analyte and introducing peak area as a response, achieving optimum values of 30 mM (ionic strength), 60 μL (injection volume) and 1.17 mL/min (flow rate). In view of this discrepancy, the results of both optimal methods, using standard humic acid, were compared with the results reported in the literature, resulting in lower relative errors with the PSS method than with the natural water method. Under PSS method conditions, different samples of natural water were analysed, and it was possible to distinguish between the molecular weight profiles of organic matter coming from different environments.

KEYWORDS:

• Optimisation
• design of experiments
• size-exclusion chromatography
• molecular weight distribution
• natural organic matter

Acknowledgments

The authors of the article wish to acknowledge EmpresasPúblicas de Medellín (EPM) for the funding given to this research project; as well as María Fernanda Guerra Posada and Julián Sánchez for their technical collaboration in the development of this project.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Funding

This research was supported by Empresas Públicas de Medellín under research project PI09-1-01, Inter-administrative Agreement PC – 2999083845.