Influence of the SDS concentration on the analysis of febuxostat's impurities by MEKC

Urični artritis (giht) je najčešća metabolička, reumatska upalna bolest čija incidencija i prevalencija posljednjih godina rastu, a taj je porast povezan sa starenjem stanovništva, promjenama životnih i prehrambenih navika te porastom komorbiditeta. Najvažniji rizični čimbenik za pojavu gihta jest kronična hiperuricemija pa je fokus liječenja upravo na lijekovima koji smanjuju serumsku razinu mokraćne kiseline. Jedan od novijih hipouremika jest febuksostat koji je u Hrvatskoj odobren 2012. godine za bolesnike sa gihtom kod kojih lijek prve linije liječenja, alopurinol, nije bio učinkovit ili je bio kontraindiciran zbog bubrežnog oštećenja. Budući da je terapija febuksostatom kronična, od velike je važnosti razviti prikladnu metodu za analizu njegovih onečišćenja. U ovom je radu optimizirana koncentracija surfaktanta SDS-a predložene MEKC metode za razdvajanje febuksostata i onečišćenja: DEE-a, febuksostat amida te etil febuksostata pri temperaturi od 25°C, naponu od 30 kV i valnoj duljini detekcije od 237 nm. Na temelju dobivenih rezultata zaključeno je da su pri koncentraciji surfaktanta u otopini radnog pufera od 50 mM dobiveni najbolji elektroferogrami s obzirom na izgled pikova i trajanje analize (1,8 min). Također je, s porastom koncentracije SDS-a, uočeno povećanje razlučivanja pikova febuksostata i unutrašnjeg standarda pravastatina sa 1,45, pri koncentraciji od 50 mM, na 2,42 koliko je iznosilo pri 80 mM-om SDS-u, ali se pri tome produljilo vrijeme analize na 2,5 min te je došlo do povećanja širine pikova na baznoj liniji. Oblik i simetrija pika etil febuksostata je prerastao okvire ovog rada te je ostao izazov za budućnost.Gouty arthritis is the most common metabolic rheumatic inflammatory disease characterized by the increasing incidence and prevalence related to lifestyle and dietary changes, as well as comorbidities and ageing population. Hyperuricemia is the single most important risk factor for developing gout so the focus of treatment is on drugs that reduce uric acid. In 2012 a new uricostatic agent, febuxostat, was approved in Croatia for the treatment of patiens who are not responsive to allopurinol, which is drug of choice in gout treatment. It is also used in cases where use of allopurinol becomes contraindicated due to renal impairment. Because of the fact that febuxostat treatment is long-lasting, the method for controlling its impurities in drug products in needed. This research is concentrated on the optimization of SDS concentration in micellar electrokinetic chromatography method for simultaneous determination of febuxostat and its impurities: DEE, febuxostat amide and ethyl febuxostat. The research was conducted under following conditions of 25°C, 30 kV and 237 nm. The results show that 50 mM is the optimal concentration of SDS, since it could obtain short migration time (1,8 min), separation of all analytes and satisfying (symmetrical) peak shapes. In addition, the resolution of febuxostat and an internal standard, pravastatin, became higher when the concentration of SDS increased from 50 mM (1,45) to 80 mM (2,42). On the other hand, migration times became longer, as well as the deterioration of peak shapes showed up. At the end, ethyl febuxostat peak shape issues remained an analytical challenge for the future