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Modernized assay for foscarnet following ICH guidelines

New preliminary assay for the antiviral medication foscarnet which is a DNA polymerase inhibitor that is used to combat herpes viruses, including drug-resistant cytomegalovirus, and to treat patients with HIV as part of salvage therapy. This method was developed by Diduco to meet the requirements in the ICH guidelines, as a contribution to the United States Pharmacopoeia initiative for modernized monograph methods.

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“.

Foscarnet assay calibration with XAMS suppressor and ASUREX-A200

Superimposed chromatograms from foscarnet assay calibration acquired on a Shodex IC SI-90 4E column (250×4 mm) using an eluent containing 7.5 mM NaHCO₃ and 7.5 mM Na₂CO₃ in water, pumped at 1.0 mL/min at 25 °C from an EQAX-B1 eluent bottle equipped with an EQAX-TC1 trap cartridge for carbon dioxide removal. Background reduced by XAMS suppressor with ASUREX-A200 automatic regenerator. Eluent pumping and conductivity detection by Metrohm 761 Compact IC. Injection of 20 µL of foscarnet (5, 10, 20, 50, 100, and 200 mg/L) in water, giving calibration signals up to about 9.3 µS/cm, or of phosphate (5 mg/L), to highlight method specificity.

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