Flucloxacillin (FLU) is a semi-synthetic penicillin active against Gram-positive bacteria such as streptococci
and penicilinase-producing staphylococci, including methicillin-susceptible S. aureus. A simple, rapid and reproducible
stability-indicating micellar electrokinetic chromatography (MEKC) method was developed and validated for analysis of
flucloxacillin sodium in capsules, using nimesulide as internal standard. The MEKC method was performed on a fusedsilica
capillary (50 μm id; effective length of 40 cm). The background electrolyte consists of 50 mM borate and 80 mM
anionic surfactant SDS quantities at pH 8.5. The separation was achieved at 20 kV applied voltage and 27.5 ºC. The injection
was performed using the hydrodinamic mode at 50 mbar for 4s, with detection at 210 nm. The method was linear in
the range of 20-100 μg mL-1 (r = 0.9996) with adequate results for the precision ( ≤1.60%) and accuracy (99.45%). The
specificity and stability-indicating capability were demonstrated through forced degradation studies and with placebo solution,
which showed that there is no interference of the excipients. LOD and LOQ were 3.20 and 9.70 μg mL-1, respectively.
The method proved to be robust by a fractional factorial design evaluation. The method was successfully applied
for the drug analysis and the results were compared to liquid chromatographic method, showing non-significant difference
(p>0.005). The proposed method might be applied in routine quality control in the pharmaceutical industries.
Keywords: Capsules, flucloxacillin sodium, MEKC method, penicillin, quality control, validation.
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