Analysis of sulfide and sulfur oxyanions in water and wastewater using capillary zone electrophoresis with detection by indirect and direct UV-Vis spectrophotometry

Saeed, Angham H. (2017) Analysis of sulfide and sulfur oxyanions in water and wastewater using capillary zone electrophoresis with detection by indirect and direct UV-Vis spectrophotometry. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (1MB)

Abstract

Sulfides and sulfur oxyanions, including thiosulfate, sulfate, and polythionates, can impact environmental quality and have negative economic consequences for industrial processes. For example, anaerobic reduction can produce toxic corrosive hydrogen sulfide, and oxidation can lead to environmental acidification accompanied with mobilization of toxic metals. Understanding the chemistry of various systems so that the reductive or oxidative processes can be curtailed requires methods to quantify key sulfur species. Accurate quantitation requires baseline separation and accommodation for co-migrating interferents, such as thiosulfate which co-migrates with chloride, found in abundance in briny waters. A strategy was developed using two capillary zone electrophoresis (CZE) methods, one with direct detection and the other with indirect detection, for speciation analysis of charged sulfur species (sulfate (SO42-), thiosulfate (S2O32-), tetrathionate (S4O62-), sulfite (SO32-), and sulfide (S2-)) in saline water. Both CZE methods were developed with reverse-polarity in which the anions migrate toward the detector. Hexamethonium hydroxide (HMOH) was added to modify the capillary surface chemistry and reduce EOF toward the inlet, affording methods with shorter time of analysis and better peak resolution. The composition of the background electrolyte (e.g. pH (buffers), flow modifiers, chromophoric probes, etc.) were considered for each method. Also, a chromophoric probe is needed for indirect detection of non-absorbing or weakly absorbing anions. Pyromellitic acid (PMA) was selected because it is non-oxidizing, has high molar absorptivity (high sensitivity), and is a good mobility match for thiosalts. Other factors taken into consideration include capillary length, separation temperature, potential applied, and use of a stabilizing agent to limit spontaneous oxidation of some of the sulfur-containing compounds.

Actions (login required)

View Item