Development of a multicommuted flow analysis procedure for simultaneous determination of sulfate and chloride in petroleum coke employing a homemade syringe pump and a LED-based photometer

Abstract

The current paper deals with procedures for simultaneous determination of sulfate and chloride in petroleum coke samples after microwave-induced combustion (MIC), which were implemented employing a multicommuted flow analysis process. The setup comprised a homemade syringe pump and two individual flow system manifolds, each coupled to a homemade LED-based photometer. Dedicated software enabled sampling and reading steps to be performed while displacing the syringe pistons forward and backward, allowing a sampling rate of 150 determinations per hour. The procedure for sulfate determination was based on the reaction of barium with sulfate and turbidimetric detection, while the procedure for chloride determination was based on the photometric mercury/thiocyanate method. In order to investigate the feasibility of both the equipment setup and the proposed procedures, samples of petroleum coke previously digested by microwave induced combustion (MIC) were analyzed. For accuracy assessment, samples were also analyzed employing ion chromatography and inductively coupled plasma optical emission spectrometry to determine chloride and sulfate, respectively. The paired t-test indicated no significant difference between the results for our method and those of the established methods, at a 95% confidence level. Linear responses (r = 0.999) were obtained with concentrations ranging from 10 to 700 mg L⁻¹ for sulfate, and from 0.25 to 10 mg L⁻¹ for chloride.