Determination of polysulfide anions and molecular sulfur via coupling HPLC with ICP-MS†

A novel method for the speciation and quantification of polysulfide anions and molecular sulfur in lithium polysulfide solutions in organic solvents is reported. The technique is based on hyphenation of high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS). A sector-field mass-spectrometer was utilized which made it possible to quantify various sulfur compounds without the need for single component standards and conduct the direct detection of the main isotope of sulfur regardless of interferents such as highly abundant ¹⁶O₂. Key aspects of separation and sample preparation were considered which allowed complete separation of derivatized polysulfide anions. Gradual adjustment of essential parameters and hardware is described. Variation of plasma settings allowed for obtaining chromatograms with desired analyte peak shapes. The optimized method was applied for the quantification of various lithium polysulfide mixtures in organic solvents showing the accessibility of the corresponding polysulfide distributions with this technique.