A field-adapted sampling and HPLC quantification method for lumefantrine and its desbutyl metabolite in whole blood spotted on filter paper.

A quantitative reverse-phase HPLC method with UV detection, for lumefantrine (LF) and desbutyllumefantrine (DLF) in whole blood spotted on filter paper was developed. The analytes were stabilized on filter paper by treatment of blood with phosphoric acid (1.6 mol/L). Halofantrine was used as internal standard and the analytes were extracted from filter paper using methanol. The methanolic extract was extracted with di-isopropylether after addition of acidic phosphate buffer (pH 2). Chromatographic separation was carried out on a Zorbax Eclipse XDB-phenyl column (4.6 mm x 150 mm, particle size 5 microm) at a flow rate of 1 mL/min using a mobile phase of acetonitrile-ammonium acetate buffer (0.1M ammonium acetate and 0.01 M acetic acid, pH 6.5) (10:90). The absorbance of the compounds was monitored at 335 nm. The average extraction recovery from filter paper ranged between 45-51% for LF and 25-33% for DLF for a concentration range between 300 and 3000 nM. Inter- and intra-assay coefficients of variation for LF and DLF were < or =9.2. Limits of quantification for LF and DLF were 300 nM. The method has been applied in malaria patients. In conclusion, a simple procedure for blood sampling and quantitative measurement of lumefantrine and desbutyllumefantrine suitable for field studies in resource-limited laboratories was developed.