ACTA FACULTATIS PHARMACEUTICAE UNIVERSITATIS COMENIANAE Tomus LVII 2010 CHIRAL CAPILLARY ELECTROPHORESIS WITH ON-LINE SAMPLE PRETREATMENT AND SPECTRAL DETECTION IN PHARMACEUTICAL AND BIOMEDICAL ANALYSIS Mikuš, P. Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University, Bratislava The aim of this review is to present briefly the recent advances in the pharmaceutical and biomedical analysis. Herein, we focused at the on-line coupled capillary electrophoresis separation methods hyphenated with UV-VIS absorbance spectral detection for the enantioselective analysis of trace drugs (antihistaminics, cardiovascular drugs) in solid dosage forms and body fluids. The drugs (pheniramine and its analogues) and matrices (tablets, urine) presented here have been chosen as representatives illustrating remarkable potentialities of the proposed analytical approach (isotachophoresis-capillary zone electrophoresis-diode array detection, ITP-CZE-DAD) in pharmaceutical and biomedical field. The ITP-CZE-DAD methods were characterized by the favorable performance parameters and they were applied for the enantiomeric purity control of the drugs, enantioselective pharmacokinetic and metabolic studies. Key words: isotachophoresis – capillary zone electrophoresis – column-coupling – spectral detection – pheniramine analogues – charged cyclodextrin – enantiomer purity – pharmaceuticals – clinical analysis – multicomponent mixture INTRODUCTION Nowadays, conventional single column separation techniques (chromatographic, electrophoretic) are usually accompanied by off-line sample preparation procedures when analyzing trace analytes present in complex matrices with variable qualitative and quantitative composition. An external sample handling has several limitations and disadvantages which can be improved by using on-line sample preparation approaches offering enhanced (i) reliability, (ii) automatization and (iii) miniaturization of the analysis. Spectral detection is suitable for (i) evaluating of separation process and (ii) more or less detailed structural characterization of separated compounds (depending on the type of the spectral method). The aim of this review is to show that a hyphenation of these two particular approaches, i.e. the column coupling electrophoresis with the spectral detection, creates a powerful tool for solving advanced analytical problems. Column coupling electrophoresis methods with diode array detection (DAD) were developed for the enantioselective analysis of trace drugs (pheniramine and its derivatives) in the directly injected (unpretreated) pharmaceutical (tablets) and clinical samples (urine). The drugs and matrices presented here [1-3] have been chosen as representatives illustrating potentialities of the proposed analytical approach in pharmaceutical and biomedical field. Anyway, the importance of this approach is further highlighted by other related applications (pharmacokinetic studies of various chiral cardiovascular drugs in urine) in this area [4-10]. 1 EXPERIMENTAL Material Disophrol-repetabs tablets (3 mg of dexbrompheniramine in the surface layer of one tablet) were treated in the following way: ten tablets were put into 100 ml of distilled water and vortex for 3 minutes at 2000 rpm. Rest of the tablets (cores) was removed from the solution after 3 minutes. The stock solution of tablet extract was kept in the refrigerator until the use and it was filtered before the use through the disposable membrane filter made of Nylon of a 1.2 µm pore size (Millipore, Molsheim, France). Clinical sample was prepared by the following way: one dose of the commercial pharmaceutical preparation Fervex (25 mg of pheniramine per dose) was administered per-orally to female volunteer. The urine samples were taken in different time periods after Fervex was administered (8.5 hours, 16.17 hours and 23.17 hours, resp.) to investigate the elimination of pheniramine and its metabolites in urine. Each urine sample was frozen (-18°C) immediately after the sampling and kept in the refrigerator until the use. The sample was thawed out just before the manipulation and preparation of the sample. Each sample was 10 times diluted with pure water and immediately injected into the sampling loop of the electrophoretic analyzer. Methods An ITAChrom EA-101capillary electrophoresis analyzer (J&M, Aalen, Germany), assembled in the column-coupling configuration of the separation unit, was used in this work for performing the ITP-CZE runs. The samples were injected by a 30 µl internal sample loop of the injection valve of the analyzer. An ITP column was provided with an 800 µm I.D. capillary tube made of FEP (fluorinated ethylene-propylene copolymer) and an on-column conductivity sensor. Its total length was 90 mm. A CZE column was provided with a 320 µm I.D. capillary tube made of fused silica (J&W, Folsom, Canada) of a 240 mm total length (180 mm to the detection cell). A TIDAS, multiwavelength photometric absorbance diode array detector (J&M) was connected to an on-column photometric detection cell, mounted on the CZE column, via optical fibers (J&M). The detector operated under the following conditions: (1) scanned wavelength range 200 – 400 nm; (2) integration time 15 ms; (3) scan interval 0.225 s; (4) number of accumulations 15. The spectral data were acquired and processed by the Spectralys program (version 1.82, J&M). RESULTS AND DISCUSSION On-line coupled isotachophoresis-capillary zone electrophoresis (ITP-CZE) separation methods with diode array detection (DAD) were developed (optimized, validated and applied) for the enantioselective analysis of trace drugs (pheniramine and its analogues) in pharmaceutical (tablets) and clinical samples (urine). Benefits of the on-line coupled isotachophoresis (ITP) stage in isotachophoresis-capillary zone electrophoresis (CZE) combination presented in our work were (i) high sample load capacity, (ii) preseparation and purification of drugs, (iii) preconcentration of sample constituents. In this way ITP served as an ideal injection technique of on-line pretreated samples for the CZE stage. The CZE stage provided final analysis of the drugs and their enantiomers. Here the enhanced (enantio)separation selectivity was achieved by a ionizable chiral selector, carboxyethyl-β-cyclodextrin. Potentialities of this chiral buffer additive were demonstrated in the recognition between the enantiomers of the drugs on one hand as well as between the drugs and sample matrix constituents (including also accompanied drugs in dosage forms, e.g. pseudoephedrine, paracetamol, vitamin C) on the other hand. This (enantio)separation selectivity enabled to obtain pure zones of the analytes, suitable for their detection and quantitation. DAD in comparison with single wavelength UV detection can enhance the value of analytical information when analytes and interferents have different spectra. In this context DAD was used to 2 examine the purity of analytes zones. Obtained results indicated the pure zones confirming effective ITPCZE (enantio)separation process. Moreover, distinguishing the trace analytes signals superposed on the baseline noise was provided with sufficient reliability (for this purpose the background correction and smoothing procedure had to be applied to the raw DAD spectra). The proposed ITP-CZE-DAD methods were characterized by favorable performance parameters (sensitivity, linearity, precision, recovery, accuracy, robustness, selectivity). Validated methods were successfully applied to (i) enantiomeric purity testing of dexbrompheniramine in commercial pharmaceutical tablets and (ii) an enantioselective metabolic study of pheniramine (and its metabolites) in human urine. Minimized sample handling / pretreatment makes this analytical approach suitable for (i) a wide scale of samples and/or analytes, (ii) routine use, and (iii) analyses where enhanced reliability of results is required. Optimal separation conditions Table 1. Electrolyte systems Parameter ITP1 Solvent water ITP2 water Parameter solvent CZE1 water CZE2 water leading cation concentration [mmol/l] Na+ 10 Na+ 10 carrier cation concentration [mmol/l] glycine 25 EACA 25 counter ion concentration [mmol/l] acetate 20 acetate 20 counter ion concentration [mmol/l] acetate 100 acetate 20 pH EOF suppressor concentration [%, w/v] terminating kationt concentration [mmol/l] 4.75 HEC 0.1 Glycine 5 4.75 HEC 0.1 EACA 5 pH EOF suppressor concentration [%, w/v] complexing agent concentration [mg/ml] 3.1 HEC 0.1 CE-β-CD 5 4.5 HEC 0.1 CE-β-CD 5 counter ion Acetate acetate concentration [mmol/l] 10 10 pH 3.5 4.5 Abbreviation: EOF – electroosmotic flow; HEC – hydroxyethylcellulose; CE-β-CD – carboxyethyl-β-cyclodextrin; EACA – ε-aminocaproic acid Figure 1. Direct ITP-CZE analyses of trace drugs enantiomers in unpretreated model samples. (a) Enantioseparation of dexbrompheniramine standard in electrolyte system ITP1-CZE1 (Tab.1). LBP:DBP ratio was 0.16:99.84 and concentration of trace enantiomer (impurity), LBP, was 9.10-8 mol.l-1 in the injected sample. (b) Enantioseparation of pheniramine racemic standard in electrolyte system ITP2-CZE2 (Tab.1). Concentration of PHM was 7.10-8 mol.l-1 in the injected sample. The detection wavelength in CZE step was 261 nm. The driving currents in the ITP and CZE stages were 200 µA and 80 µA, respectively. Other working conditions are in the part Experimental. 3 Validation parameters Table 2. Performance parameters of ITP-CZE methods applied for enantioseparations of racemic drugs Parameter t [min] st [min] a [mAU.s.min-1] sa [mAU.s.min-1] b [mAU.s.min-1.mg-1.l] sb [mAU.s.min-1.mg-1.l] RSS R r2 QC LOD [µg.l-1] LOQ [µg.l-1] N H [µm] R repeatability (RSD) [%] recovery [%] accuracy (RE) [%] robustness (∆R) [%] a ITP1-CZE1, water sample LBP DBP 8.022 8.340 0.0356 0.0359 0.3166 0.3385 0.0369 0.0643 48.8466 50.4837 0.26191 0.4570 0.0162 0.0494 0.99993 0.99980 0.99990 0.99960 0.88267 1.48727 2.5 4.2 7.5 12.7 33400 30450 5.5 6.1 2.94 0.99 1.65 98.1 97.8 -1.9 -2.2 < 3.9 ITP2-CZE2, urine samplea PHM 1 PHM 2 27.67 29.95 0.360 0.400 -0.191 -0.287 0.061 0.081 74.47 74.96 0.607 0.811 0.0625 0.1116 0.99980 0.99965 0.99960 0.99930 1.62825 2.19733 5.2 6.8 7.7 10.1 17600 17600 10.2 10.2 4.4 1.30 1.33 98.5 98.3 -1.5 -1.7 < 2.7 Comparable data were obtained also for PHM dissolved in demineralized water. Figure 2. Spectral evaluation of analytes zones using ITP-CZE-DAD method. DAD spectra of the drugs enantiomers, (a) BP and (b) PHM, were taken from the concentration maxima of their zones (peaks). Upper traces illustrate raw (unprocessed) spectra while lower traces final (processed) spectra (passed through the background correction and smoothing procedure). Samples, separation and other working conditions as in Fig. 1. 4 Table 3. Proof of selectivity of the proposed methods. Pearson ' s correlation coefficients for DAD spectra of the drugs in real samplesa Raw spectrumc Corrected spectrumc Analyteb LBP 0.8125 0.98958 DBP 0.8347 0.99825 PHM1 0.9419 0.9971 PHM2 0.8853 0.9995 M1 0.8507 0.9942 M2 0.8945 0.9950 I 0.0827 0.1153 a DAD spectra of real samples were compared with DAD spectra of reference samples (racemic standards). b LBP, DBP in pharmaceutical tablets and PHM1, PHM2, M1, M2, I in clinical urine samples; c Average values from 5 measurements of pharmaceutical tablets Disophrol Repetabs (batch №.1) and clinical urine samples taken 16.67 hours after Fervex per oral application Application examples Figure 3. Electropherograms from CZE step of ITP-CZE-DAD combination during the chiral analyses of the drugs in real pharmaceutical and clinical samples. (a) Enantiomeric purity testing of BP in tablets Disophrol Repetabs (batch №.1, obtained data are in Tab. 4). (b) Enantioselective metabolic study of PHM in clinical urine sample taken 16.67 h after Fervex was administered to female volunteer (obtained data are in Tab. 5). For the samples preparations see the part Experimental. Separation, detection and other working conditions as in Fig.1. Table 4: Enantiomeric purity testing of DBP in pharmaceutical samples Disophrol tablets Batch №. Content (mg per tablet) RSD %, n=5 Enantiomeric ratio % DBP LBP DBP LBP DBP:LBP 1 5.82 0.128 0.81 2.84 97.85 : 2.15 2 5.77 0.111 1.15 3.57 98.11 : 1.89 3 5.71 0.089 0.96 3.31 98.47 : 1.53 4 5.78 0.098 0.91 3.02 98.33 : 1.67 5 Table 5: Enantioselective metabolic study of PHM in clinical urine samplesa Time [hours] 8.50 16.67 23.83 M1 0.773 0.812 0.274 Concentration level [mg.l-1] PHM1 M2 1.087 0.630 0.483 0.692 0.295 0.229 PHM2 0.959 0.371 0.293 a Urine samples taken at different times after using 1 dose of Fervex (equivalent to 25 mg PHM) by female volunteer. Clinical urine samples significantly differed from each other in qualitative and quantitative composition of sample matrix constituents. CONCLUSION The performance parameters of the ITP-CZE-DAD methods (limit of detection/quantification, linearity, precision, accuracy, recovery, robustness, selectivity, separation efficiency), as well as the application examples (enantiomeric purity control of the commercial drugs, enantioselective pharmacokinetic and metabolic studies) clearly illustrated potentialities of this unique analytical approach in the pharmaceutical and biomedical field. Hence, it can be concluded that the ITP-CZE-DAD methods are suitable for a routine use in advanced analytical applications, i.e. ultratrace determinations, complex matrices, enantioselective separations, direct injections of unpretreated samples, basic structural characterization of separated analytes and spectral information in composition of separated zones, as well as combinations of these particular tasks. Acknowledgment: This work was supported by the grant from the Slovak Grant Agency for Science under the project VEGA №. 1/0003/08. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. MARÁK, J. – MIKUŠ, P. – MARÁKOVÁ, K. – KANIANSKY, D. – VALÁŠKOVÁ, I. – HAVRÁNEK, E.: Enantioselective analysis of pheniramine in urine by charged cyclodextrin-mediated capillary zone electrophoresis provided with a fiber-based diode array detection and an on-line sample pretreatment by capillary isotachophoresis. Electrophoresis 28, 2007, p. 2738-2747. 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MIKUŠ, P. – MARÁKOVÁ, K. – MARÁK, J. – NEMEC, I. – VALÁŠKOVÁ, I. – HAVRÁNEK, E.: Pharmacokinetic study of amlodipine in human urine using on-line coupled isotachophoresis-capillary zone electrophoresis with diode array detection. Curr. Pharm. Anal. 5, 2009, p. 171-178. MIKUŠ, P. – MARÁKOVÁ, K.: Advanced capillary electrophoresis for chiral analysis of drugs, metabolites and biomarkers in biological samples. Electrophoresis 30, 2009, p. 2773-2802. 6 10. MIKUŠ, P. – MARÁKOVÁ, K.: Chiral capillary electrophoresis with on-line sample preparation. Curr. Pharm. Anal. 6, 2010, p. 76-100. Registred: October 12, 2010 Accepted: November 29, 2010 doc. RNDr. Peter Mikuš, PhD. Faculty of Pharmacy Comenius University Odbojárov 10 832 32 Bratislava Slovak Republic CHIRÁLNA KAPILÁRNA ELEKTROFORÉZA S ON-LINE PREDÚPRAVOU VZORKY A SPEKTRÁLNOU DETEKCIOU VO FARMACEUTICKEJ A BIOMEDICÍNSKEJ ANALÝZE Mikuš, P. Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University, Bratislava Cieľom tohto review je stručne prezentovať najnovšie pokroky vo farmaceutickej a biomedicínskej analýze. Tu sme zamerali pozornosť na on-line spojené separačné metódy kapilárnej elektroforézy v kombinácii s UV-VIS absorpčnou spektrálnou detekciou pre enantioselektívne analýzy stopových liečiv (antihistaminiká, liečivá s kardiovaskulárnym účinkom) v pevných liekových formách a telových tekutinách. Liečivá (feniramín a jeho analógy) ako aj matrice (tablety, moč) prezentované v tejto práci boli vybrané ako reprezentatívne na ilustráciu pozoruhodných možností navrhnutého analytického prístupu (izotachoforéza-kapilárna zónová elektroforéza-diode array detekcia, ITPCZE-DAD) vo farmaceutickej a biomedicínskej oblasti. ITP-CZE-DAD metódy sú charakterizované priaznivými validačnými parametrami a boli aplikované na kontrolu enantiomérnej čistoty komerčných liekov, ako aj enantioselektívne farmakokinetické a metabolické štúdie. Acta Facult. Pharm. Univ. Comenianae 57, 2010, p. strana-strana. 7
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