Sulfobutylether-beta-cyclodextrin-mediated capillary electrophoresis for separation of chlorinated and substituted phenols

Rapid determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration

A rapid, simple and sensitive method was demonstrated for the determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration. With the presence of sulfuric acid, phenol could be transferred into a nitroso-compound by reacting with NaNO2. The titration end-point was obtained by the formation of a sharp cut in the oscillopolarographic with infinitesimal NaNO2 on double platinum electrodes. The results showed that phenol concentration had an excellent linear relationship over the range of 4.82 x 10(-6)-9.65 x 10(-3) mol/L, the RSD of the proposed method was lower than 1.5%, and the spiked recoveries of three real water samples were in the range of 95.6%-106.9%.

Application of water-soluble polymers as modifiers in electrophoretic analysis of phenols

A review of application of water-soluble cationic, anionic and nonionic polymers as pseudostationary phases in capillary electrophoresis (CE) and micellar electrokinetic capillary chromatography (MEKC) is presented. The effect of the structure of the polymers on the selectivity and efficiency of separation is discussed. A novel specially designed cationic polymer, 2,10-ionene, has been used for the separation of phenols. The polymer has hydrophilic and hydrophobic parts in its backbone. The polymer shows the best selectivity as a modifier in capillary zone electrophoresis (CZE)-mode, which allows the selective determination of both hydrophilic and hydrophobic phenols.

Automatic on-line coupling of supercritical fluid extraction and capillary electrophoresis

An interface for the automatic coupling of a supercritical fluid extractor (SFE) with capillary electrophoretic (CE) equipment, both commercially available, was developed with a view to improving sample treatment, which is a crucial step in capillary electrophoresis. Extracted analytes were collected in a trap following depressurization in the SFE and were transferred to the CE equipment across the interface. The key elements of the experimental assembly are a laboratory-made programmable arm and the autosampler of the CE equipment, both of which are controlled by a built-in microprocessor using an appropriate electronic interface and customized software. This combined system was successfully used to determine cresols and chlorophenols in liquid samples (river water and human urine) with increased precision, throughput, and automatability. The proposed arrangement opens up interesting prospects for the direct determination of analyte traces in solid samples without human intervention.

Analysis of polymyxin B sulfate by capillary zone electrophoresis with cyclodextrin as additive. Method development and validation

A capillary zone electrophoresis method for analysis of polymyxin B sulfate is described. In this method, triethanolamine (TEA)-phosphate buffer at pH 2.5 was employed to reduce the adsorption of analyte onto the capillary wall. Methyl-beta-cyclodextrin (M-beta-CD) and 2-propanol (IPA) were found to be necessary for selectivity enhancement. In order to optimize the method and to control its robustness, a central composite design was performed with four parameters, i.e. concentration of M-beta-CD, TEA, IPA and buffer pH. The optimal separation conditions were as follows: capillary, 55 cm (50 microm I.D., 47 cm effective length); 130 mM TEA-phosphate buffer (pH 2.5) containing 5 mM M-beta-CD and 5% IPA; 24 kV (51 microA) applied voltage; column temperature, 20 degrees C. Further, linearity and limits of detection quantification were examined. Three commercial samples were analyzed quantitatively.

Determination of chlorophenols in human urine based on the integration of on-line automated clean-up and preconcentration unit with micellar electrokinetic chromatography

A new method was developed and validated for the determination of chlorophenols in human urine by using micellar electrokinetic chromatography (MEKC) coupled via a mechanic arm to an on-line automatic clean-up and preconcentration unit for urine samples. Separation is accomplished by using a selective buffer consisting of 15 mM borate, 25 mM phosphate and 100 mM sodium dodecyl sulfate (SDS) at pH 9.1 in addition to a positive power supply of 25 kV at 18 degrees C. The proposed capillary electrophoresis (CE) method allows the separation of 11 chlorophenols within 7 min with a reproducibility as relative standard deviation (RSD) between 2.6% and 7.2%, and limits of detection (LODs) between 0.08 and 0.46 microg/mL for all chlorophenols. Urine samples were previously hydrolyzed with 37% HCl at 80 degrees C for 60 min and then cleaned on a C-18 mini-column. Recoveries ranged from 58% to 103%. The preconcentration treatment affords limits of determination between 4 and 12 ng/mL for all chlorophenols except pentachlorophenol and 4-chlorophenol, which could not be determined. The overall analysis time, including on-line clean-up, preconcentration and electrophoretic separation is 20 min per sample.

Capillary electrophoresis and capillary electrochromatography of organic pollutants

Capillary electrophoresis (CE) has a unique capability for separation of analytes of environmental concern, particularly those that are more polar and ionic, based on the complementary separation principle of electrophoresis. In the past few years, CE has been selectively used to analyze various classes of compounds having current or potential environmental relevance. This review outlines the current status of CE for the determination of environmental pollutants, based predominantly on research results published from the beginning of 1997 to early 1999. Covered are environmental pollutants of all types except pesticides and inorganics. Certain naturally produced toxins are also covered because of their significant impacts upon human health and the environment. CE methods, as with all methods, must be judged on their ability to provide approaches that are reliable, sensitive, selective, and rapid, while meeting "green chemistry" initiatives for pollution prevention. We also compare CE methods to benchmark environmental techniques involving gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and high performance liquid chromatography (HPLC).

Achiral selectivity in cyclodextrin-modified capillary electrophoresis

Torus-shaped, circular, and hydrophilic cyclodextrins (CD) have been frequently used in capillary electrophoresis (CE) as buffer modifiers to effect chiral separation of enantiomers of drugs and specialty chemicals. Although less common, both neutral and charged cyclodextrins have also been exploited in CE to optimize the achiral separations of peptides, proteins, small molecules and a variety of positional isomers. Nonionic CDs are only useful for separations of net charged analytes through judicious partitioning of such guest molecules into their hydrophobic cavity of the former. However, they can be used with a surfactant for an effective resolution of neutral solutes as a result of a differential partitioning of such solutes in the micellar and the cyclodextrin-modified buffer phase. Ionic cyclodextrins, particularly, negatively charged derivatives with their own electrophoretic mobilities, increase the separation window and enable better resolution of analytes which weakly complex with or are poorly differentiated by neutral cyclodextrins.