UHPLC-fluorescence method for the determination of trace levels of hydrazine in allopurinol and its formulations: Validation using total-error concept.

The present approach poses an interesting way to quantify residues of the genotoxic impurity hydrazine in allopurinol and its pharmaceutical formulations using ultra high performance liquid chromatography coupled to fluorescence detection. Hydrazine was pre-column derivatized through a unique chemistry with o-phthalaldehyde under acidic conditions. Using highly acidic mobile phase the derivative exhibits a strong fluorescence intensity. Derivatization and chromatographic parameters were thoroughly investigated. The validation of the developed method has been carried out in the range of 10 to 200% of the target concentration limit of the analyte using the accuracy profiles as a graphical decision-making tool. The ß-expectation tolerance intervals did not exceed the acceptance criteria of ±20% which means that 95% of future results will be included in the defined bias limits. The variation of the relative bias ranged between -6.0 and 0.5% and the RSD values for repeatability and intermediate precision were lower than 6.9% in all cases. The limit of detection (LOD) and the lower limit of quantification (LLOQ) were satisfactory and found to be 0.3 ng mL-1 (corresponding to 0.03 µg g-1 in solid sample). Experimental designs were constructed to study the robustness of the instrumental method and the derivatization procedure. The developed method has been successfully applied for the analysis of hydrazine in allopurinol API batches and tablets indicating that this methodology could be adopted from QC laboratories.