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This paper describes the combined use of carbon nanotubes and an ionic liquid directly coupled in-line to commercial CE equipment for sample treatment. The extraction unit operates as a spin column to preconcentrate the analytes. The extraction unit is inserted into the sample vial. The elution is performed in-line, placing the vial on the carrousel of the CE equipment. The joint use of carbon nanotubes and ionic liquids as sorbent is based on the high adsorption capacity of these materials, which makes them highly suitable for microextraction purposes. The LOQ of analytes were within the range of 0.65-0.83 μg/L with a RSD of less than 7%. The values of recovery range between 90 and 112%. The absolute recovery obtained from samples containing 1 μg/L of analytes was 38%.

This paper reports for the first time the use of microextraction by packed sorbent in combination with CE. The combined system was used to determine anesthetic drugs in human plasma. A microdialysis fiber was coupled on-line to the microextraction unit in order to distinguish between free and total concentrations of drugs. The system was automated by connecting the microextraction unit to a syringe pump and interfacing it to a computer. The ensuing method allows the determination of 10 microg/L concentrations of free drugs and 1 microg/L concentrations of total drugs from only 200 microL of sample with an RSD of less than 9%.

Two electrokinetic methods for the separation of phthalates are proposed. One uses 25 mM sodium borate and 50 mM sodium taurodeoxycholate adjusted to pH 2.8, and the other uses 15 mM ammonium tetraborate, 100 mM SDS, 0.25% w:v hydroxypropylmethyl cellulose (HPMC) and 5% v:v methanol (MeoH) adjusted to pH 9. The BGE containing SDS micelles as the pseudo-stationary phase provided better analytical figures of merit, particularly as regards LOD (0.4-1.4 mg/L) and precision (1.1-6.5%). Adding MeoH and HPMC to the BGE proved essential in order to obtain narrow and symmetric peaks. The proposed method was successfully used to determine phthalates in virgin olive oil. Recoveries from spiked samples ranged from 96 to 106%. The precision obtained in the analysis of real samples, as RSD, was better than 6.8%.

This paper provides an overview of the use of carbon nanoparticles (CNPs) as pseudo-stationary phases (PSPs) in EKC. Specifically, it describes the characteristics and properties of the major types of CNPs used as PSPs in EKC separations, namely C(60) fullerenes, carbon nanotubes and covalently modified carbon nanotubes. Based on such properties, a plausible mechanism for the interactions governing EKC separation with these materials is proposed. Also, the most salient uses of CNPs as PSPs are outlined. Finally, CNPs are compared in terms of performance with other well-established types of nanostructures used to enhance selectivity in EKC over the past decade.

A substantial demand currently exists for analytical methods affording the determination of very low concentrations of analytes in complex matrices, such as those of environmental and biological samples, as simply as possible. However, the pretreatment of complex samples, which is unavoidable prior to CE-MS analysis, is usually complicated and time-consuming. In this work, we used voltage-assisted SPE for the first time as an alternative to conventional treatments for preconcentrating and purifying analytes. To this end, we used a simple flow system coupled on-line to CE-MS equipment. The system is quite robust and provides reproducible peak areas (the precision ranges from 2.5 to 3.8%). Also, it provides increased sensitivity affording the determination of trace amounts (nanogram per liter levels) of analytes in only a few milliliters of sample. The proposed system was applied to the determination of members of two compound families (viz. tetracyclines and amines).

This paper reviews and discusses the analytical combination of ionic liquids (IL) with CE. On the one hand, it shows CE as a powerful technique to separate impurities from IL as well as being capable to determine physical and chemical properties of IL. On the other hand, it also shows how IL are employed in CE separations to enhance resolution, peak efficiency and peak symmetry. Specifically, IL are used as additives in CZE, NACE, and MEKC and as support coatings of the capillary wall in electrochromatography. The integrity of the IL in the electrophoretic system as well as the roles of the cations and anions of the IL in the electrophoretic separation are also discussed.

This work describes an efficient in-line extraction-preconcentration unit coupled to the electrophoretic capillary based on a liquid-phase microextraction (LPME) process, which can be directly assembled to the cartridge of the commercial CE equipment. The unit permits analyte extraction, preconcentration and electrophoretic separation to be automatically performed in the commercial CE equipment without the need for additional hardware or software. This new approach was usefully used for the separation and determination of nonsteroidal anti-inflammatory drugs in human urine permitting at least to analyze 30 consecutive real samples. The LODs were lower than 2 microg/L and the reproducibility, expressed as RSD, was 3.1% for the same unit and only 4.8% between different units.

A capillary electrophoresis-electrospray mass spectrometry (CE-ESI-MS) method for the separation and determination of nine biogenic amines is proposed. Operational variables, such as the voltage, temperature, sheath liquid composition, flow-rate, and MS parameters, were optimized. Samples are injected in the hydrodynamic mode into a 75 cm x 50 microm ID coated capillary and separated by using 25 mM citric acid at pH 2.0. Heptylamine is used as internal standard. The experimental setup includes a flow manifold coupled to the CE system for automatic insertion of samples into the CE vials. The proposed method allows amines to be determined with limits of detection from 0.018 to 0.09 microg x mL(-1) and relative standard deviation (RSD) values from 2.4% to 5.0% (except 6.8% for histamine). The method was successfully used to determine biogenic amines in red and white wines.

The exceptional properties of graphene (G) were exploited here to facilitate capillary electrokinetic separations. Two types of commercially available G consisting of nanoparticles containing-one to three and-four to six G sheets, respectively, were compared for this purpose. Both proved effective in separating the arylpropyl derivatives of nonsteroidal anti-inflammatory drugs. The highest resolution and shortest migration times were obtained with G containing high amount of single and double G nanosheets. G affords higher resolution than other types of nanoparticles; stable suspensions can be easily prepared and used as BGE without the need of adding an additional surfactant. This results in a high reproducibility in migration times and stability in background noise. The LOD and LOQ obtained by using G nanoparticles as pseudostationary phases spanned the range 0.29-1.18 mg/L and 0.95-3.95 mg/L, respectively, and the RSD was less than 4.7% in all instances.

On many occasions, sample treatment is a critical step in electrophoretic analysis. As an alternative to batch procedures, in this work, a new strategy is presented with a view to develop an on-capillary sample cleanup method. This strategy is based on the partial filling of the capillary with carboxylated single-walled carbon nanotube (c-SWNT). The nanoparticles retain interferences from the matrix allowing the determination and quantification of carbohydrates (viz glucose, maltose and fructose). The precision of the method for the analysis of real samples ranged from 5.3 to 6.4%. The proposed method was compared with a method based on a batch filtration of the juice sample through diatomaceous earth and further electrophoretic determination. This method was also validated in this work. The RSD for this other method ranged from 5.1 to 6%. The results obtained by both methods were statistically comparable demonstrating the accuracy of the proposed methods and their effectiveness. Electrophoretic separation of carbohydrates was achieved using 200 mM borate solution as a buffer at pH 9.5 and applying 15 kV. During separation, the capillary temperature was kept constant at 40 degrees C. For the on-capillary cleanup method, a solution containing 50 mg/L of c-SWNTs prepared in 300 mM borate solution at pH 9.5 was introduced for 60 s into the capillary just before sample introduction. For the electrophoretic analysis of samples cleaned in batch with diatomaceous earth, it is also recommended to introduce into the capillary, just before the sample, a 300 mM borate solution as it enhances the sensitivity and electrophoretic resolution.

A simple methodology for converting a commercial CE-MS instrument into an integrated 2-D CE system has been developed. The first-dimensional capillary operates as a typical CE instrument with UV/visible detection. Fractions leaving the first dimension are automatically collected and introduced into the second dimension, performed on a CE-MS apparatus, for analysis. The integrated system allows fractions in the second dimension to be analyzed using various electrophoretic modes. As an example, in this work we performed the separation of two families of antibiotics (nitroimidazoles and tetracyclines) in the first dimension and the subsequent resolution of the antibiotics in each family (nitroimidazoles were resolved by MEKC and tetracyclines by CZE) in the second dimension. The proposed system, which operates in an highly automatic manner, is flexible and allows various combination of electrophoretic modes to be implemented. In addition, the use of a mass spectrometer detector in the second dimension further increases the analytical potential of the system as a result of the high selectivity and wealth of structural information provided by the MS detector.

We developed a new interface for the on-line coupling of a fiber for solid-phase microextraction (SPME) with a CE system with an electrospray interface for MS detection. The on-line interface was a modification of a split-flow interface typically used for coupling flow systems to CE. The modification consists of an additional channel closed with a septum that permits the introduction of the fiber in the interface, right at the inlet region of the separation capillary. The interface was designed to be used with commercial fibers. Although commercial fibers can be used directly, we recommend cutting the stationary phase and using fibers with a 2-mm stationary phase. The system was tested for the analysis of tetracycline antibiotic residues, viz., tetracycline, oxytetracycline and doxycycline in soils. The overall accuracy was assessed by regression analysis of spiked samples, showing successful results at a 95% confidence level. The reproducibility, expressed as RSD, was 5.3% and the LOD of tetracycline antibiotics in soil ranged from 2.9 to 3.2 microg/kg.

A new hexane-in-water microemulsion was investigated as buffer in microemulsion EKC (MEEKC). At difference with other microemulsions, the addition of cosurfactant was not necessary to stabilize the microemulsion. The proposed microemulsion was successfully used to achieve electrophoretic separation of seven antibiotics including nitroimidazoles, cephapirin and tetracyclines. Selectivity and separation efficiency achieved in MEEKC were compared with MEKC. MEEKC technique proved to be more efficient than MEKC for performing the separation of the analytes and the presence of microemulsions was found to be critical to achieve the separation of tetracyclines. The proposed microemulsion also points out that solvents with high volatility, such as hexane, can be stabilized and used as a microemulsion of SDS.

An in-line coupling of a micro-membrane extraction unit, based on supported liquid membrane, with commercially available capillary electrophoresis equipment is described. A main characteristic of this micro-membrane device, made from a simple Eppendorf tube, is that it permits the application of voltage in the acceptor solution to be applied during the extraction process. This has been shown as an alternative to enhance sensitivity, as the analytical signal achieved by applying 10 kV for 20 min was similar to that obtained without the application of voltage and with extraction time of 60 min. In addition, the design has been made permitting both in-line hydrodynamic and electrokinetic sample introduction into the electrophoretic capillary. The analytical potential of the proposed system has been demonstrated by the direct determination of nitroimidazoles from pig liver tissue. The high efficiency of the proposed system allowed the extraction and the determination of the analytes to be performed from a simple tissue homogenate obtained in water. The precision of the analysis of spiked samples, expressed in terms of relative standard deviation, was better than 4.8%.

A new methodology is proposed to automate the monitoring of sulfonamide residues in milk samples. It combines a screening unit for the total amount of sulfonamide with capillary electrophoresis-mass spectrometry (CE-MS) equipment for processing the samples containing a detectable level of sulfonamide. The screening unit consists of continuous-flow system (CFS) to precipitate the proteins connected on-line to the CE-MS equipment, in which a common characteristic ion of all sulfonamides was monitored with the MS detector by flushing the sample through the capillary. The confirmatory method is based on the purification and preconcentration of sulfonamides in a CFS unit and posterior analysis by CE-MS. The sample treatment unit was also on-line connected to the CE-MS equipment. In order to increase sensitivity, the flow rate of the sheath liquid was diminished from 0.5 to 0.2 microL.min(-1) by increasing the content in water from 0 to 50% and the formic acid from 0.5 to 1.5% in this liquid and by applying an overimposed pressure of 5 mbar during the electrophoretic separation. The method allowed the analysis of 30 samples per hour.

A capillary electrophoresis (CE) method with indirect photometric detection was developed to identify and quantify myo-inositol phosphates in food samples. A flow-injection (FI) system including a micro-column containing anionic exchange resin was used for the solid-phase extraction of the myo-inositol phosphates with a view to their preconcentration. The FI system was automatically coupled to CE equipment via a mechanical interface. The overall analysis time was shortened by incorporating an FI system for myo-inositol hexakisphosphate monitoring. The limit of detection for myo-inositol phosphates as determined by FI-CE ranged from 11 to 26 micromol/L and the coefficient of variation from 3.9 to 5.0%. On the other hand, the limit of detection and coefficient of variation for myo-inositol hexakisphosphate as monitored by the FI system were 75 micromol/L and 2.9%, respectively. The proposed method was successfully applied to a variety of food samples with recoveries ranging from 96.0 to 107.7% and the precision from 3.9 to 7.9%. Based on the results, the content of myo-inositol hexakisphosphate in nuts was two or three times higher than that in legumes.