Simultaneous enantiomeric separation of linagliptin and clopidogrel by capillary electrophoresis for the individual, combined, and enantiomeric ecotoxicity evaluation on Pseudokirchneriella subcapitata

An analytical methodology was developed in this work enabling the simultaneous enantioseparation of linagliptin and clopidogrel by Capillary Electrophoresis (CE). The use of 10.4 mg/mL carboxymethyl-β-CD (CM-β-CD) as chiral selector in 25 mM phosphate buffer (pH 7.0), at 25 °C and a separation voltage of 30 kV, made possible the chiral separation in 7.4 min, with resolution values of 3.9 and 2.7 for linagliptin and clopidogrel enantiomers, respectively. The analytical characteristics of the developed methodology were evaluated in terms of linearity, precision, trueness, LODs and LOQs, and found adequate for the enantiomeric determination of both drugs. The method was applied to study the stability under abiotic and biotic conditions and the ecotoxicity of both drugs on Pseudokirchneriella subcapitata at individual, combined, and enantiomeric level. Both studies were carried out for each enantiomer of linagliptin, racemic linagliptin, S-clopidogrel, racemic clopidogrel, a mixture of the active enantiomers (R-linagliptin and S-clopidogrel), and a mixture of both racemates. Results obtained showed that individual solutions of S-linagliptin, R-linagliptin, S-clopidogrel, RS-linagliptin, and a mixture of the active enantiomers of both compounds, were stable under abiotic and biotic conditions, regardless of the incubation time; however, the concentration of racemic clopidogrel after 96 h of incubation showed a decay which ranged from 18 to 24 % under abiotic and biotic conditions, respectively. Experimental determination of ecotoxicological parameters demonstrated that all compounds studied (individual enantiomers, racemates, the combination of active enantiomers, and racemic mixtures) are highly toxic to algae. In mixtures, different degrees of antagonisms and synergism were observed.