Straightforward and rapid determination of sulfadoxine and sulfamethoxazole in capillary blood on sampling paper with liquid chromatography and UV detection

A method for the determination of sulfadoxine and sulfamethoxazole in capillary blood on sampling paper has been developed and validated. The method is straightforward with minimal sample preparation, and is suitable for rural settings. Separation of sulfadoxine, sulfamethoxazole and internal standard was performed using a Purospher STAR RP-18 endcapped LC column (150 × 4.6 mm) with a mobile phase consisting of acetonitrile:sodium acetate buffer pH 5.2, I = 0.1 (1:2, v/v). For sulfadoxine, the within-day precision was 5.3% at 15 μmol/l and 3.7% at 600 μmol/l, while for sulfamethoxazole it was 5.7% at 15 μmol/l and 3.8% at 600 μmol/l. The lower limit of quantification was determined to 5 μmol/l and precision was 5.5% and 5.0% for sulfadoxine and sulfamethoxazole, respectively.