Simultaneous analysis of small cations and anions from a lithium-ion battery anode surface using liquid extraction...

For the simultaneous analysis of both cations and anions using a single capillary electrophoresis (CE) run of reasonable duration, two capacitively coupled contactless conductivity detectors (C⁴Ds) were installed on a single capillary with weak and reversed electroosmotic flow (EOF). This CE/2C⁴D was synergistically combined with liquid extraction surface analysis (LESA) to investigate the ionic composition of a solid surface. In LESA, a liquid microjunction was formed between the surface and the inlet of a separation capillary to extract analytes from the surface. The extract was then hydrodynamically injected into the capillary and positioned between the two C⁴Ds. Subsequently, a reverse voltage was applied to perform CE/2C⁴D. Both the cationic and anionic compositions of a standard solid surface sample (salts-sprayed graphite sheet) or a lithium-ion battery anode surface were obtained within 30 min, including the time required for extract positioning and electrophoretic separation. In LESA-CE/2C⁴D of a standard solid surface sample, the relative standard deviations of the peak areas for small cations and anions were 3.6-4.6 % and 1.2-5.1 %, respectively, using azide as an internal standard. The limits of detection for cations and anions were 50-80 ng/cm² and 20-100 ng/cm², respectively.