J. Sep. Sci. 2013, 36, 3165–3175 3165 Katarina Nikolic 1 Nata ˇ sa Djordjevi ´ c Filijovi ´ c 2 Borislava Mari ˇ ci ´ c 2 Danica Agbaba 1 1 Institute of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia 2 Hemofarm AD, Vr ˇ sac, Serbia Received May 7, 2013 Revised June 25, 2013 Accepted July 21, 2013 Research Article Development of a novel RP-HPLC method for the efficient separation of aripiprazole and its nine impurities The development of an RP-HPLC method for the separation of aripiprazole and its nine impurities was performed with the use of partial least squares regression, response surface plot methodology, and chromatographic response function. The HPLC retention times and computed molecular parameters of the aripiprazole and its nine impurities were further used for the quantitative structure–retention relationship (QSRR) study. The QSRR model, R 2 : 0.899, Q 2 : 0.832, root mean square error of estimation: 4.761, root mean square error of prediction: 6.614, was developed. Very good agreement between the predicted and observed retention times (t R ) for three additional aripiprazole impurities (TC1–TC3) indicated the high prediction potential of the QSRR model for t R evaluation of other aripiprazole impurities and metabolites. The developed HPLC method is the first reported method for the efficient separation of aripiprazole and its nine impurities, which could be used for the analysis of an additional three aripiprazole impurities (TC1–TC3). Keywords: Aripiprazole / Chemometry / Experimental design / HPLC / QSRR DOI 10.1002/jssc.201300477  Additional supporting information may be found in the online version of this article at the publisher’s web-site 1 Introduction Aripiprazole is a novel atypical or second-generation antipsy- chotic drug used for the treatment of schizophrenia and acute manic or mixed episodes associated with bipolar I disorder. It is administered orally once daily as a solution or tablet [1]. This atypical antipsychotic drug has a unique profile, as it pri- marily demonstrates partial agonist activity at dopamine D 2 , serotonin 5-hydroxytriptamine 1A receptors, and antagonist activity at 5-hydroxytriptamine 2A receptors [1, 2]. Chemically, aripiprazole is 7-[4-{4-(2,3-dichlorophenyl)-1-piperazinyl} butoxy]-3,4-dihydroquinolin-2(1H)-one (Fig. 1). Organic impurities found in active pharmaceutical ingredients (APIs) and drug products could be starting ma- terials, intermediates, byproducts, reagents, and degradation Correspondence: Dr. Katarina Nikolic, Faculty of Pharmacy, In- stitute of Pharmaceutical Chemistry, University of Belgrade, Vojvode Stepe 450, 11000 Belgrade, Serbia E-mail: knikolic@pharmacy.bg.ac.rs Fax: +381-11-3974-349 Abbreviations: API, Active pharmaceutical ingredients; CRF, Chromatographic response function; HBA, Hydro- gen bond acceptor; HBD, Hydrogen bond donor; 5-HT, 5- Hydroxytriptamine; LogD, Distribution coefficient; MS, Con- nolly molecular area; Na-PS, Sodium pentanesulfonate; PLS, Partial least square; QSRR, Quantitative structure–retention relationship; RMSEE, Root mean square error of estimation; RMSEP, Root mean square error of prediction; VIP, Variable importance in the projection products [3, 4]. Since current pharmacopoeias do not contain a monograph for aripiprazole, the evaluation of its impurities relies on data gathered from relevant scientific literature and information provided by API manufacturers. Bearing in mind that different API manufacturers usually have different routes of synthesis with different possible impurities, this could be a difficult task. In this work, the chromatographic properties of aripiprazole and its nine impurities, namely, a piperazine impurity: 1-(2,3-dichlorophenyl)piperazine hydrochloride; an aza-azonispirodecan impurity: 8-(2,3- dichlorophenyl)-8-aza-5-azonispiro[4,5]decano bromide; a chlorobutoxyquinoline impurity: 7-(4-chlorobutoxy)-3,4- dihydroquinolin-2(1H)-one; a bromobutoxyquinoline im- purity: 7-(4-bromobutoxy)-3,4-dihydroquinolin-2(1H)-one; a hydroxyquinoline impurity: 7-hydroxy-3,4-dihydro quinolin- 2(1H)-one; a diquinoline impurity: 7,7 ′ -(butylenedioxy)di-3,4- dihydroquinolin-2(1H)-one; a quinoline aripiprazole impu- rity: 7-[4-{4-(2,3-dichlorophenyl)-1-piperazinyl}butoxy]-1-[4- (2-oxo-3,4-dihydro-1H-quinolin-7-yl)butoxy]-3,4-dihydroqui- nolin-2(1H)-one; a dehydro aripiprazole impurity: 7-[4-{4-(2, 3-dichlorophenyl)-1-piperazinyl}butoxy]quinolin-2(1H)-one; and an N-oxide aripiprazole impurity: N-oxide-7-[4-{4-(2,3- dichlorophenyl)-1-piperazinyl}butoxy]-3,4-dihydroquinolin- 2 (1H)-one, were evaluated (Fig. 1). A literature survey has revealed several analytical tech- niques for the determination of aripiprazole. In biolog- ical samples, the analysis of aripiprazole and its main metabolite, dehydroaripiprazole, was performed using CE [5], HPLC or GC coupled with MS [6–9], and HPLC with UV C  2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com