Electrochemically generated standard additions for gas chromatography: case study of O₂ and H₂ analysis

The method of standard additions with electrochemically generated spikes was elaborated and demonstrated on examples of O₂ and H₂ chromatographic analysis in standard mixtures. While oxygen portions may be generated directly in a stream of inert gas by solid-state electrolysis, a standard hydrogen-containing mixture is introduced into the electrochemical cell followed by controlled electrochemical consumption of hydrogen. In both cases the analysis characteristics are similar: the recovery is 90-120% and exhibits a slight sensitivity towards the flow rate of the analyzed oxygen-containing gas. The relative error associated with the non-ideal proportionality between the spike and chromatograph signal is within 10-15% for operation in the optimum concentration region. The major factors affecting the accuracy of the analysis are associated with detector characteristics, particularly influenced by the sample dilution, precision of flow controllers and linearity of the function "signal vs. spike." The lowest errors of determination were found to be for the analyte content range 1-5% while at oxygen and hydrogen concentrations below 0.5% the interference of the signal associated with other components may lead to overestimated results. Graphical abstract Scheme of the gas line used for oxygen determination with electrochemically generated standard additions (method 2). Inset shows an example of oxygen content calculation using the dependency "chromatographic signal vs. current."