Investigation of polar stationary phases for the separation of sympathomimetic drugs with nano-liquid chromatography in hydrophilic interaction liquid chromatography mode.

In this study, the retention and selectivity of a mixture of basic polar drugs were investigated in hydrophilic interaction chromatographic conditions (HILIC) using nano-liquid chromatography (nano-LC). Six sympathomimetic drugs including ephedrine, norephedrine, synephrine, epinephrine, norepinephrine and norphenylephrine were separated by changing experimental parameters such as stationary phase, acetonitrile (ACN) content, buffer pH and concentration, column temperature. Four polar stationary phases (i.e. cyano-, diol-, aminopropyl-silica and Luna HILIC, a cross-linked diol phase) were selected and packed into fused silica capillary columns of 100 µm internal diameter (i.d.). Among the four stationary phases investigated a complete separation of the all studied compounds was achieved with aminopropyl silica and Luna HILIC stationary phases only. Best chromatographic results were obtained employing a mobile phase composed by ACN/water (92/8, v/v) containing 10mM ammonium formate buffer pH 3. The influence of the capillary temperature on the resolution of the polar basic drugs was investigated in the range between 10 and 50°C. Linear correlation of lnk vs. 1/T was observed for all the columns; ΔH° values were negative with Luna HILIC and positive with aminopropyl- and diol-silica stationary phases, demonstrating that different mechanisms were involved in the separation. To compare the chromatographic performance of the different columns, Van Deemter curves were also investigated.

Chiral separation of the ß2-sympathomimetic fenoterol by HPLC and capillary zone electrophoresis for pharmacokinetic studies.

The development of methods for the separation of the enantiomers of fenoterol by chiral HPLC and capillary zone electrophoresis (CZE) is described. For the HPLC separation precolumn fluorescence derivatization with naphthyl isocyanate was applied. The resulting urea derivatives were resolved on a cellulose tris(3,5-dimethylphenylcarbamate)-coated silica gel column employing a column switching procedure. Detection was carried out fluorimetrically with a detection limit in the low ng/mL range. The method was adapted to the determination of fenoterol enantiomers in rat heart perfusates using liquid-liquid extraction. As an alternative a CE method was used for the direct separation of fenoterol enantiomers comparing different cyclodextrin derivatives as chiral selectors.

Chiral separation of sympathomimetics and beta-blockers by ligand-exchange CE using Cu(II) complexes of L-tartaric acid and L-threonine as chiral selectors.

This paper deals with the use of Cu(II) complexes of L-tartaric acid or L-threonine as selectors for the chiral separation of drugs containing amino alcohol structure by ligand-exchange CE. Using Cu(II) ions as a complexing agent, a series of sympathomimetics and beta-blockers were resolved. It was found that the resolution strongly depends on selector concentration and pH. The optimum pH for complexation was 12.

Separation of basic drug enantiomers by capillary zone electrophoresis using glucuronyl glucosyl beta-cyclodextrin as a chiral selector.

Separations of basic drug enantiomers have been investigated using glucuronyl glucosyl beta-cyclodextrin (GUG beta-CD) as a chiral selector in the background electrolyte by capillary zone electrophoresis. The effects of GUG beta-CD concentration and running buffer pH on the migration times and resolution of 16 basic drug enantiomers were precisely examined using a linear polyacrylamide-coated capillary. High resolution of 16 basic drug enantiomers was generally attained with a running buffer pH 2.5 or 3.5 containing 10 mM GUG beta-CD. Next, we compared the chiral resolution abilities of GUG beta-CD with those of beta-CD and maltosyl beta-CD (G2 beta-CD). GUG beta-CD showed higher resolution for basic drug enantiomers tested than beta-CD and G2 beta-CD. This could be due to that hydrogen bonding or ionic interactions of uncharged and charged glucuronyl glucosyl groups of GUG beta-CD with an analyte could stabilize the inclusion complex.

Separation of sympathomimetic amines of abuse and related compounds by micellar electrokinetic chromatography.

Separation of twelve sympathomimetic amines and related compounds by micellar electrokinetic chromatography (MEKC) with UV absorbance detection is described. These amines were well separated within 25 min using 50 mM sodium tetraborate solution containing 15 mM sodium dodecylsulfate (SDS) of pH 9.3 as a running solution and detected at 210 nm. MEKC was performed with an applied voltage of 13 kV at 25 degrees C using a fused-silica capillary (50 cm x 75 mm i.d.) with effective length of 37.5 cm. The detection limits of these compounds were in the range from 4 to 97 fmol/injection at a signal-to-noise ratio (S/N) of 3. The reproducibility of the method expressed as relative standard deviation (RSD) for within-day (n=6) and between-day (n=5) assays was less than 4.8 and 8.8%, respectively. The proposed method could be applied to the determination of an anorectic drug, phentermine, in Chinese tea with a detection limit of 99 microg/g (105 fmol/injection, S/N=3).

Chiral separation of sympathomimetics by ligand exchange capillary electrophoresis.

A rapid and simple approach to the chiral separation of sympathomimetic drugs with amino alcohol structure by ligand exchange capillary electrophoresis is described. An N-(2-hydroxyoctyl)-L-4-hydroxyproline/copper(II) complex is used as chiral selector. Thirteen sympathomimetics were resolved, nine with baseline resolution. The influence of pH and composition of the electrolyte on resolution was investigated. The optimal pH for complexation of these amino alcohols was found to be 12.

Modelling of conditions for the enantiomeric separation of beta2-adrenergic sympathicomimetics by capillary electrophoresis using cyclodextrins as chiral selectors in a polyethylene glycol gel.

A two-factor central composite design was used to determine a mathematical model for prediction of the optimal conditions for the separation of the enantiomers of some widely used beta2-sympathicomimetic drugs (beta2-agonists) by capillary electrophoresis using cyclodextrins (CD) as a chiral selector in a polyethylene glycolgel. The effects of the chemical structure of these drugs along with the addition of polyethylene glycol to the cyclodextrin solution on the resolution of their enantiomers were studied. To allow impurity studies down to 0.1% (distomer eutomer) a resolution of 2.5 should be warranted. Those beta2-agonists containing two hydroxylic groups in the aromatic ring structure show the highest enantiomeric separation, due to the fact that one of their enantiomers has a better geometric structure to fit into the beta-cyclodextrin cavity.

Separation of racemic pharmaceuticals by high-performance liquid chromatography on silica gel modified with carbohydrate residues.

Derivatives of 2-amino-2-deoxyglucose covalently connected to aminopropyl-silica gel were used as chiral selectors in the separation of racemic pharmaceuticals. beta-Receptor blockers, adrenergic drugs and compounds with secondary amino functions could be separated after appropriate derivatization.

Pentafluorobenzoyl derivatives of doping agents. I. Extractive benzoylation and gas chromatography with electron-capture detection of primary and secondary amines.

A sensitive and rapid method for the gas chromatographic (with electron-capture detection) confirmation of derivable sympathomimetic amines is described. Extractive derivatization with pentafluorobenzoyl chloride is performed on 2-ml urine or plasma samples. Especially for primary amines, the method appears to be very sensitive. Mass spectral data allowed confirmation of the monobenzoylation of all congeners.

Thin layer chromatographic identification of some sympathomimetic amines.

Thin layer chromatographic behavior of some sympathomimetic amines in the presence of acids in neutral and organic solvent systems is reported. The sympathomimetic amines were dissolved in 0.1N HCl or ethanol and treated with bromocresol green or p-nitrobenzoyl chloride reagents on fiber sheets or precoated glass plates. Two-, 3-, and 4-, component solvent systems were tested. Benzene-ethyl acetate gave 2 spots for each amine standard; the more polar spots were satisfactorily separated. Amines in pharmaccuticals were not separated by any solvent system tested.