Chaotropic effect of trifluoroacetic and perchloric acid on β-cyclodextrininclusion complexation process with risperidone, olanzapine and their selected impuritiesN

Abstract

Effective method development together with method`s eco-friendly character are gaining importance in drug analyses nowadays. One of the strategies often applied to improve the efficacy of separation methods, especially in the case of basic ionizable analytes is adding chaotropic salts into the mobile phases. Moreover, the development of the green liquid chromatography method could also be achieved with certain mobile phase additives such as cyclodextrin (CD). The study aims to investigate whether adding chaotropic agents could improve the complexation process by disrupting the analytes’ water solvation shell. The model mixture consisted of risperidone, olanzapine, and their related impurities. Method development was aided with experimental design methodology, while optimal separation conditions were selected using Derringer’s desirability function. Mathematical models obtained for each of the examined responses enabled the explanation of the single and simultaneous influence of β-CD concentration, chaotropic agents type, and content, as well as the content of acetonitrile in the mobile phase. Retention factors appeared to be the most influenced by acetonitrile content in the mobile phase. The type of chaotropic agent as well as its concentration lead to retention prolongation, but if acetonitrile content in the mobile phase is high, the effect of chaotropic agent becomes negligible. Interaction between analyte and β-CD are relatively weak in comparison to the interaction of analyte form with either chaotropic agent or acetonitrile. Interaction leading to complexation are outperformed by other analyte related interactions in this complicated system, so complexation based retention reduction is not fully exposed. However, increasing β-CD concentration shows a positive effect on the resolution between critical peak pairs. Optimal separation conditions were selected based on 3D plots of Derringer’s desirability function. For olanzapine and its impurity, they included the following: acetonitrile content 16% (v/v), trifluoroacetic acid as a chaotropic agent with 0.95% (v/v) content, and 9 mM β-CD concentration. Further, optimal separation conditions for risperidone and its impurity were 25% (v/v) acetonitrile content in the mobile phase, trifluoroacetic acid as chaotrope agent with 0.27% (v/v) content and 5mM β-CD concentration.

U novije vreme sve više pažnje se poklanja efikasnom razvoju metode uz istovremenu procenu njenih ekoloških karakteristika. Jedna of često primenjivanih strategija za razdvajanje baznih jonizacionih supstanci jeste dodatak haotropnih soli u mobilnu fazu. Sa druge strane, ekološki prihvatljiva metoda tečne hromatografije može se razviti dodatkom ciklodekstrini (CD) kao aditiva mobilne faze. Cilj ovog rada je bio da se istraži mogućnost dodatka haotropnih agenasa u mobilnu fazu u kojoj se već nalaze CD. Na ovaj način moglo bi doći do narušavanja solvatacionog omotača oko analita, što bi ubrzalo proces kompleksiranja analita i CD. Model smeša se sastojala od risperidona, olanzapina i njihovih srodnih supstanci. Metoda je razvijana primenom metodologije eksperimentalnog dizajna, dok su optimalni uslovi birani primenom Deringerove funkcije poželjnih odgovora. Matematički modeli koji su dobijeni za svaki posmatrani odgovor, omogućili su dase ispita pojedinačni i zajednički uticaj koncentracije β-CD, tipa i koncentracije haotropnog agensa, kao i količine acetontrila u mobilnoj fazi. Pokazalo se da najveći uticaj na retencioni faktor ima količina acetonitrila u mobilnoj fazi. Povećanje koncentracije haotropa dovodi do produženja retencionog faktora, ali ukoliko je količina acetonitrila u mobilnoj fazi visoka efekat haotropa postaje zanemarljiv. Interakcija između analita i β-CD su slabe u poređenju sa interakcijama koje analit ostvaruje sa haotropnim agensom ili acetonitrilom, te proces kompleksiranja biva prevaziđen drugim vrstama interakcija u ovom komplikovanom sistemu. Iz tog razloga smanjenje retencionog vremena kao posledica kompleksiranja ne dolazi do izražaja. Uočeno je i da povećanje koncentracije β-CD dovodila je do povećanja rezolucije kritičnih parova. Optimalni hromatografski uslovi odabrani su na osnovu 3D grafikona Deringerove funkcije poželjnih odgovora. Za razdvajanje olanzapina i njegove srodne supstance, optimalni uslovi su obuhvatali 16% acetonitrila, 0,95% trifluorosirćetnu kiselinu kao haotropni agens i 9 mM β-CD. Optimalni uslovi u slučaju razdvajanja risperidona i njegove srodne supstance obuhvatali su 25% acetonitrila, 0,27% trifluorosirćetne kiseline i 5mM β-CD.