Field-amplified on-line sample stacking for separation and determination of cimaterol, clenbuterol and salbutamol using capillary electrophoresis

Fluorescent sensing platform based on green luminescence carbon dots and AuNPs for clenbuterol detection in pork liver

In this paper, water-soluble green fluorescent carbon dots (G-CDs) were prepared using p-phenylenediamine and glutathione (GSH) as the precursors. The G-CDs exhibit excellent optical properties, and the maximum emission wavelength is located at 522 nm (under 410 nm excitation), which greatly overlaps with the absorption spectrum of AuNPs. Consequently, an effective “off–on” fluorescent sensing platform involved in G-CDs and AuNPs for detection of clenbuterol (CLB) was constructed. The fluorescence of G-CDs was strongly quenched by AuNPs due to the inner filter effect (IFE). As CLB was introduced, the quenched fluorescence intensity was recovered due to the specific interaction between the AuNPs and CLB. The recovered fluorescence intensity is linear to CLB concentration in the range of 13–270 ng mL⁻¹ with a low detection limit of 3.75 ng mL⁻¹. The prepared sensor has been successfully applied for CLB detection in pork liver and could be utilized in food analysis.

Carbon dots (G-CDs) with bright green fluorescence are synthesized by hydrothermal treatment of p-phenylenediamine and glutathione. Employing the G-CDs and AuNPs as sensing platform, a simple fluorescence sensor to detect clenbuterol was established.

Determination of sulfa antibiotic residues in river and particulate matter by field-amplified sample injection-capillary zone electrophoresis

In the present research, field-amplified sample injection-CZE (FASI-CZE) coupled with a diode array detector was established to determine trace level sulfa antibiotic. Sulfathiazole, sulfadiazine, sulfamethazine, sulfadimethoxine, sulfamethoxazole, and sulfisoxazole were selected as analytes for the experiments. The background electrolyte solution consisted of 70.0 mmol/L borax and 60.0 mmol/L boric acid (including 10% methanol, pH 9.1). The plug was 2.5 mmol/L borax, which was injected into the capillary at a pressure of 0.5 psi for 5 s. Then the sample was injected into the capillary at an injection voltage of -10 kV for 20 s. The electrophoretic separation was carried out under a voltage of +19 kV. The capillary temperature was maintained at 20˚C throughout the analysis, and six sulfonamides were completely separated within 35 min. Compared with pressure injection-CZE, the sensitivity of FASI-CZE was increased by 6.25-10.0 times, and the LODs were reduced from 0.2-0.5 to 0.02-0.05 μg/mL. The method was applied to the determination of sulfonamides in river water and particulate matter samples. The recoveries were 78.59-106.59%. The intraday and interday precisions were 2.89-7.35% and 2.77-7.09%, respectively. This provides a simpler and faster method for the analysis of sulfa antibiotic residues in environmental samples.

Clenbuterol Hydrochloride

Clenbuterol (Broncodil and trade) is a direct-acting sympathomimetic agent with mainly beta-adrenergic activity and a selective action on β2 receptors (a β2 agonist). It has properties similar to those of salbutamol. It is used as a bronchodilator in the management of reversible airways obstruction, as in asthma and in certain patients with chronic obstructive pulmonary disease. The uses, applications, and the synthetic pathways of this drug are outlined. Physical characteristics including: ionization constant, solubility, X-ray powder diffraction pattern, thermal methods of analysis, UV spectrum, IR spectrum, mass spectrum are all produced. This profile also includes the monograph of British Pharmacopoeia, together with several reported analytical methods including spectrophotometric, electrochemical, chromatographic, immunochemical methods, and capillary electrophoretic methods. The stability, the pharmacokinetic behavior, and the pharmacology of the drug are also provided.

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.

Contemporary sample stacking in CE

Sample stacking techniques remain an important tool for enhancement of the selectivity and sensitivity of analyses in contemporary CZE. This contribution reviews new knowledge on this topic published since 2006. It is organized according to the operational principles used, which include concentration adjustment, application of a pH step, MEKC and sweeping, and transient ITP. Techniques combining several of these principles and comparative studies are also included.

Electric field gradient focusing in microchannels with embedded bipolar electrode

The complex interplay of electrophoretic, electroosmotic, bulk convective, and diffusive mass/charge transport in a hybrid poly(dimethylsiloxane) (PDMS)/glass microchannel with embedded floating electrode is analyzed. The thin floating electrode attached locally to the wall of the straight microchannel results in a redistribution of local field strength after the application of an external electric field. Together with bulk convection based on cathodic electroosmotic flow, an extended field gradient is formed in the anodic microchannel segment. It imparts a spatially dependent electrophoretic force on charged analytes and, in combination with the bulk convection, results in an electric field gradient focusing at analyte-specific positions. Analyte concentration in the enriched zone approaches a maximum value which is independent of its concentration in the supplying reservoirs. A simple approach is shown to unify the temporal behavior of the concentration factors under general conditions.

On-line concentration of neutral analytes by complexation and acetonitrile sweeping in nonionic microemulsion electrokinetic chromatography with direct ultraviolet detection

To separate and detect neutral solutes in nonionic microemulsion electrokinetic chromatography (MEEKC), a novel method was developed, combining complex formation and acetonitrile (ACN) sweeping. In this report, dynamic borate complexation and on-line sweeping occurred simultaneously during a run. The operating parameters which affected the performance of analyte sweeping in nonionic MEEKC were examined in terms of borate complexation, ACN content, Brij-35 concentration and sample plug length. In addition, the validation of the method included tests of the limit of detection, reproducibility and sensitivity enhancement. 60-110-Fold of magnitude improvement in detection sensitivity for model compounds (ginsenoside Rf, ginsenoside Rb2, ginsenoside Re) using Brij-35 microemulsion was demonstrated. Furthermore, the method was applied to the determination of glucosides in the plant extract.