Steroselective determination of trihexyphenidyl using carboxylmethyl-β-cyclodextrin by capillary electrophoresis with field-amplified sample stacking

A Novel Reduced Graphene Oxide Modified Carbon Paste Electrode for Potentiometric Determination of Trihexyphenidyl Hydrochloride in Pharmaceutical and Biological Matrices

A novel promising carbon paste electrode with excellent potentiometric properties was prepared for the analysis of trihexyphenidyl hydrochloride (THP), the acetylcholine receptor and an anticholinergic drug in real samples. It contains 10.2% trihexyphenidy-tetraphenylborate ionic pair as the electroactive material, with the addition of 3.9% reduced graphene oxide and 0.3% of anionic additive into the paste, which consists of 45.0% dibutylphthalate as the solvent mediator and 40.6% graphite. Under the optimized experimental conditions, the electrode showed a Nernstian slope of 58.9 ± 0.2 mV/decade with a regression coefficient of 0.9992. It exhibited high selectivity and reproducibility as well as a fast and linear dynamic response range from 4.0 × 10⁻⁷ to 1.0 × 10⁻² M. The electrode remained usable for up to 19 days. Analytical applications showed excellent recoveries ranging from 96.8 to 101.7%, LOD was 2.5 × 10⁻⁷ M. The electrode was successfully used for THP analysis of pharmaceutical and biological samples.

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.

Recent advances of enantioseparations in capillary electrophoresis and capillary electrochromatography

A comprehensive survey of recent developments and applications of capillary electromigration techniques for enantioseparations from January 2006 to June 2010 is presented. The techniques include capillary electrophoresis, chip capillary electrophoresis and capillary electrochromatography. The separation principles and the chiral recognition mechanisms are discussed. Additionally, on-line preconcentrations in chiral capillary electrophoresis are also reviewed.

Advanced CE for chiral analysis of drugs, metabolites, and biomarkers in biological samples

An analysis of recent trends indicates that CE can show real advantages over chromatographic methods in ultratrace enantioselective determination of biologically active compounds in complex biological matrices. It is due to high separation efficiency and many applicable in-capillary electromigration effects in CE (countercurrent migration, stacking effects) enhancing significantly (enantio)separability and enabling effective sample preparation (preconcentration, purification, analyte derivatization). Other possible on-line combinations of CE, such as column coupled CE-CE techniques and implementation of nonelectrophoretic techniques (extraction, membrane filtration, flow injection) into CE, offer additional approaches for highly effective sample preparation and separation. CE matured to a highly flexible and compatible technique enabling its hyphenation with powerful detection systems allowing extremely sensitive detection (e.g. LIF) and/or structural characterization of analytes (e.g. MS). Within the last decade, more as well as less conventional analytical on-line approaches have been effectively utilized in this field and their practical potentialities are demonstrated on many new application examples in this article. Here, three basic areas of (enantioselective) drug bioanalysis are highlighted and supported by a brief theoretical description of each individual approach in a compact review structure (to create integrated view on the topic), including (i) progressive enantioseparation approaches and new enantioselective agents, (ii) in-capillary sample preparation (preconcentration, purification, derivatization), and (iii) detection possibilities related to enhanced sensitivity and structural characterization.

Direct chiral analysis of primary amine drugs in human urine by single drop microextraction in-line coupled to CE

Three-phase single drop microextraction (SDME) was in-line coupled to chiral CE of weakly basic amine compounds including amphetamine. SDME was used for the matrix isolation and sample preconcentration in order to directly analyze urine samples with the minimal pretreatment of adding NaOH. A small drop of an acidic aqueous acceptor phase covered with a thin layer of octanol was formed at the tip of a capillary by simple manipulation of the liquid handling functions of a commercial CE instrument. While the saline matrix of the urine sample was blocked by the octanol layer, the basic analytes in a basic aqueous donor phase were concentrated into the acidic acceptor drop through the octanol layer by the driving force of the pH difference between the two aqueous phases. The enantiomers of the enriched amines were resolved by using (+)-(18-crown-6)-tetracarboxylic acid as a chiral selector for the subsequent CE separation. From 10 min SDME with the agitation of the donor phase by a small stirrer retrofit to the CE instrument, enrichment factors were about a 1000-fold, yielding the LOD of 0.5 ng/mL for amphetamine. This low LOD value as well as the convenience of in-line coupled SDME make the proposed scheme well suited for the demanding chiral analysis of amphetamine-type stimulants.

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.