Quantitative determination of clenbuterol, salbutamol and tulobuterol enantiomers by capillary electrophoresis

Green potentiometric electrode for determination of salbutamol in biological samples

Clinical drug analyses and identification of pharmaceuticals in biological samples are highly crucial for therapeutic drug monitoring, pharmacokinetic studies, and screening of illicit drugs. Various analytical tools, such as potentiometric electrodes, are used to conduct these investigations. These potentiometric electrodes are superior to other techniques in terms of greenness and cost efficacy, and thus present a good alternative for researchers. In this study, we develop an advanced electrode for the in-situ monitoring of salbutamol in plasma, this electrode was synthesized using multiwalled carbon nanotubes (MWCNT) as hydrophobic conductive substance and copper oxide nanoparticle (CuO NP) as a surface modifier, the developed electrode was compared to traditional liquid contact electrode as well as solid contact electrode and proved its superiority. The use of MWCNT improved the stability of the electrode via preventing the formation of this water layer and the CuO NP improved the sensitivity due to its high surface area and rich electronic properties. CuO NP modified electrode was used for the determination of salbutamol with a Nernstian slope of 57.4 over a linearity range of range 1.0 × 10^-7- 1.0 × 10^-2 M, and a detection limit of 4.0 × 10^-7 M. The proposed electrode was effectively applied for the determination of the cited drug in rat plasma without interference and compared with chromatographic reported method. The proposed method is economic as it has a low sample analysis cost, time saving and needs fewer manipulation steps and a simple convenient device. It also proved to be a greener method when compared with chromatographic methods using an eco-scale metric system.

Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis

β2-Agonists (β2-adrenergic agonists, bronchodilatants, and sympathomimetic drugs) are a group of drugs that are mainly used in asthma and obstructive pulmonary diseases. In practice, the substances used to contain one or more stereogenic centers in their structure and their enantiomers exhibit different pharmacological properties. In terms of bronchodilatory activity, (R)-enantiomers showed higher activity. The investigation of stereoselectivity in action and disposition of chiral drugs together with the preparation of pure enantiomer drugs calls for efficient stereoselective analytical methods. The overview focuses on the stereoselectivity in pharmacodynamics and pharmacokinetics of β2-agonists and summarizes the stereoselective analytical methods for the enantioseparation of racemic beta-agonists (HPLC, LC-MS, GC, TLC, CE). Some methods of the stereoselective synthesis for β2-agonists preparation are also presented.

Dialkyl anionic surfactant in field-amplified sample injection and sweeping-micellar electrokinetic chromatography for determination of eight leanness-promoting β-agonists in animal feeds

The beta-adrenergic agonists (β-agonists) working as repartitioning agents that make the carcass leaner and enhance the feeding efficiency in animals have been banned in the European Union, China and Taiwan. Here, traditional anionic surfactants, such as sodium dodecyl sulfate (SDS) were replaced with sodium di-(2-ethylhexyl)-sulfosuccinate (AOT) in field-amplified sample injection and sweeping-micellar electrokinetic chromatography (FASI-sweeping MEKC) for simultaneous analysis of eight β-agonists in animal feeds. The AOT vesicles provided a better resolution of β-agonists than micelles of SDS. The detection limits of the eight β-agonists were above 5ng/mL by using this stacking capillary electrophoresis (CE) method. In comparison of traditional MEKC method (sample injection, 1psi for 5s), the stacking strategy provided 400-2000 fold sensitivity enhancement. After method validation, this method was successfully applied for analyzing four animal feeds, and none β-agonist was detected. This strategy possessing good resolution of eight β-agonists was suitable for serving as a tool for routine analysis of animal feeds.

Analytical methods for the detection of clenbuterol

Clenbuterol is therapeutically used for the treatment of pulmonary diseases such as bronchial asthma or for tocolytic reasons. In cattle feeding as well as in sports it is illicitly misused due to its anabolic properties to promote muscle growth. Sample preparation procedures and analytical techniques used for the detection of clenbuterol are manifold and vary with the objectives of the investigation. Methods for its detection in biological specimens, drug preparations, the environment, food and feed products are reported. They are mainly based on immunochemical, chromatographic and mass spectrometric techniques, or on capillary electrophoresis. Sample preparation primarily includes liquid-liquid extraction and solid-phase extraction. Depending on the aim of the method clenbuterol can be determined in single- or multi-analyte methods. In biological and environmental samples concentrations are generally low due to the potency of the drug. Thus, highly sensitive procedures are required for expedient analyses.

Direct separation and quantitative determination of clenbuterol enantiomers by high performance liquid chromatography using an amide type chiral stationary phase

Enantiomers of clenbuterol were directly separated by a new high performance chromatographic method on Chirex 3005 column. Several parameters such as mobile phase composition, column temperature and flow rate were studied. Baseline enantioseparation was achieved, using the optimized mobile phase of n-hexane-1,2-dicholoethane-methanol (54:38:8, v/v/v) at 17 degrees C and 1.0 ml/min, with the separation factor (alpha) 1.43 and the resolution factor (R(S)) 1.81. The mechanism of separation was also discussed. Standard linear calibration cures were established for the R- and S-enantiomers, over the range of 26.1-1,045.8 and 5.7-229.6 nmol/ml, with the correlation coefficient of 0.9999 for both. The limits of detection were 0.47 and 1.04 nmol/ml for R- and S-enantiomers, respectively. Recovery and precision of the method were also evaluated, which had been successfully used to monitor and identify quantitatively the profile of the clenbuterol enantiomers in human serum.