ON-LINE ENANTIOMERIC SEPARATION OF CARVEDILOL WITH FLUORESCENT DETECTION

SILVA, RAUL; TALÍO, MARÍA CAROLINA; LUCONI, MARTA OLGA; ACOSTA, GIMENA; FERNANDEZ, LILIANA

Sanrta Fe

Congreso; II Reunión Internacional de Ciencias Farmacéuticas; 2012

Universidad Nacional de Rosario

Carvedilol (CDL) is a non-selective β-blocker indicated in the treatment of mild to moderate congestive heart failure. It also has vasodilating properties that are mainly attributed to its α1-blocking activity, as well as ability to prevent oxidative stress in coronary smooth muscle (1). CDL is administered as racemic mixture although both enantiomers exhibit different pharmacological effects; the -receptor blocking activity of the S-(-)-CDL is about 200-fold higher than that of R-(+)-CDL, whereas both enantiomers are equipotent -blockers. Carbon Nanotubes (CNTs) have been the subject of intense research because of their extraordinary physical, chemical, and electrical properties. Spectroscopy studies of single-walled carbon nanotubes (SWCNTs) have demonstrated the existence of three configurations, attending the direction of graphene sheet: two non-chiral structures and, the other denominated chiral (2). In this work, a FIA-methodology with fluorescence detection has been developed using a microcolumn packed with a few milligrams of SWCNTs as chiral selectors for separation of carvedilol enantiomers. Materials and methods A Shimadzu RF-5301PC spectrofluorimeter (Shimadzu), equipped with a Xenon discharge lamp was used in all experiments. For the fluorescent measurements, quartz cells of 1 cm were used in statically assays and for flow measurements a LC flow-cell unit of 12 µL was used. A Rheodhyne low pressure valve Model 5020 was used for FIA configuration. All solutions and reagents were propelled by Gilson Minipuls 3 peristaltic pumps using 0.8 mm i.d, Tygon pumping tubings. Sodium dodecylsulfate (SDS), Triton® X-100 and hexadecyl trimethylammonium bromide were from Tokyo Kasei Industries. SWCNTs were from Merck (Germany). Bidecar tablets were acquired from Baliarda Laboratory. All used reagents and solvents were of analytical or spectroscopic grade. Carvedilol standard solution containing 1 mg mL−1 was prepared dissolving the reagent in ethanol. Standard working solution of 1 µg mL−1 was prepared daily by dilution of standard solution with doubly distilled water. A 0.1 mol L−1 SDS solution was prepared with an adequate weight of SDS and dissolving in doubly distilled water. A 0.1 mol L−1 HCl solution was prepared mixing an adequate volume of concentrated acid with doubly distilled water. CDL was kindly provided by Gador S.A. (Argentina). Results The different variables that influence the chiral separation (i.e., pH and composition of eluent solution, sample injection volume and flow rate, activation mode of SWCNTs and mass of the same in column has been examined in detail. CDL enantioseparation was monitored at 358 nm (λext = 317 nm). Taking into account the effect of surfactants on the enantiomers separations, different solutions were preparing using HCl/SDS mixtures at different ratios. Under the optimized condition: flow rate of 4.2 mL min-1; HCl/SDS 2:1; sample injection volume of 2.8 mL, R(+) and S(-) carvedilol were separated with a resolution factor of 3.16 and a sampling rate of 90 samples h-1. S(-)carvedilol showed a retention time of 23 s when was eluted with water; R(+) carvedilol showed a retention time of 65 s using HCl /SDS mixture. The optimized conditions were successfully applied to determine the enantiomeric purity of commercial sample (Bidecar?). Conclusions The new methodology was successfully applied to S(-) and R(+) carvedilol quantification in pharmaceutical preparations, resulting in an attractive alternative to traditional separative methods being fast, simple, and using low cost instrumentation and producing scarce waste.