The method uses a carbonate-bicarbonate eluent that is suppressed by the Xenoic® XAMS membrane suppressor continuously automatically regenerated by the Xenoic® ASUREX-A200. This gives low levels of background conductivity and noise, thus resulting in linear calibration curves and stable performance suitable for a routine quality control method. This assay was developed further and validated according to quality-by-design principles as described in the peer-reviewed scientific publication summarized in the application example “Published case study of analytical quality by design method development and validation“.