Capillary zone electrophoretic separation of neutral species of chloro-s-triazines in the presence of cationic surfactant monomers

Porous poly(bismaleimide-co-divinylbenzene) microspheres as dispersive solid-phase extraction adsorbent coupled to high-performance liquid chromatography for the determination of triazine herbicide residues in vegetable samples

In this work, monodisperse and nano-porous poly(bismaleimide-co-divinylbenzene) microspheres with large specific surface area (427.6 m2 /g) and rich pore structure were prepared by one-pot self-stable precipitation polymerization of 2,2'-bis[4-(4-maleimidophenoxy) phenyl] propane and divinylbenzene. The prepared poly(bismaleimide-co-divinylbenzene) microspheres were employed as dispersive solid-phase extraction (DSPE) adsorbent for the extraction of triazine herbicides. Under optimized conditions, good linearities were obtained between the peak area and the concentration of triazine herbicides in the range of 1-400 µg/L (R2 ≥ 0.9987) with the limits of detection of 0.12-0.31 µg/L. Triazine herbicides were detected using the described approach in vegetable samples (i.e., cucumber, tomato, and maize) with recoveries of 93.6%-117.3% and relative standard deviations of 0.4%-3.5%. In addition, the recoveries of triazine herbicides remained above 80.7% after being used for nine DSPE cycles, showing excellent reusability of poly(bismaleimide-co-divinylbenzene) microspheres. The adsorption of poly(bismaleimide-co-divinylbenzene) microspheres toward triazine herbicides was a monolayer and chemical adsorption. The adsorption mechanism between triazine herbicides and adsorbents might be a combination of hydrogen bonding, electrostatic interaction, and π-π conjugation. The results confirmed the potential use of the poly(bismaleimide-co-divinylbenzene) microspheres-based DSPE coupled to the high-performance liquid chromatography method for the detection of triazine herbicide residues in vegetable samples.

Microchip capillary electrophoresis based electroanalysis of triazine herbicides

The number of pesticides used in agriculture is increasing steadily, leading to contamination of soil and drinking water. Herein, we present a microfluidic platform to detect the extent of contamination in soil samples. A microchip capillary electrophoresis system with in-channel electrodes was fabricated for label-free electroanalytical detection of triazine herbicides. The sample mixture contained three representative triazines: simazine, atrazine and ametryn. The electropherogram for each individual injection of simazine, atrazine and ametryn showed peaks at 58, 66 and 72 s whereas a mixture of them showed distinct peaks at 59, 67 and 71 s respectively. The technique as such may prove to be a useful qualitative and quantitative tool for the similar environmental pollutants.

Determination of critical micelle concentration of surfactants by capillary electrophoresis

Capillary electrophoresis (CE) has been proven to be a convenient and useful technique for the determination of the critical micelle concentration (CMC) of a surfactant in an electrophoretic system under operating conditions. In this review, methodological approaches to the determination of the CMC of surfactants by CE technique are described. The practical requirements for making such measurements and the CMC values of surfactants determined by CE methods are presented. In addition, difficulties and uncertainty, as well as misconceptions that may arise in the CMC determination are discussed.

Pesticide analysis by capillary electrophoresis

In this work, a critical and updated revision of the current situation of the analysis of pesticides by Capillary Electrophoresis (CE) is presented. The review has been written in two main sections. The first one presents a thorough revision of the various offline and on-line sample preconcentration procedures that have been used in conjunction with CE to analyze these compounds. The second part reviews the various detection strategies (i.e., UV, LIF, MS, and electrochemical) and CE modes that have been applied to the analysis of pesticides. Future trends that can be expected from this hot research area are also discussed.

Estimation of binding constants by capillary electrophoresis

Capillary electrophoresis (CE) has become a useful technique for measuring binding constants. This review is focused on recent trends in the estimation of binding constants by affinity CE. First, we introduce several mathematical equations in which it is assumed that the stoichiometry of the binding between drug and protein is 1:1 as a simple model. In order to calculate accurate binding constants by affinity CE, several experimental considerations are described in this review. In addition, some recent methodologies, such as partial filling technique and multiple-step ligand injection method, are introduced. Among research publications within 3 years, recent applications for determining binding constants are reviewed.

Capillary electrophoresis and electrochromatography of pesticides and metabolites

Synthetic pesticides are important chemicals since they are widely used to control many types of weeds, insects, and other pests in a wide variety of agricultural and nonagricultural settings. This review article is aimed at describing the recent progress made in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of pesticides and metabolites. The various electrophoretic systems and detection schemes that were introduced during the period extending from the second half of 1999 to the first half of 2001 for the CE and CEC of pesticides are discussed. Also included in this review article are the various approaches for trace enrichment that are involved in the analysis of dilute pesticide samples.

Salt effects in capillary zone electrophoresis. V. Adsorption and retention of electrically neutral analytes

Two electrically neutral analytes previously observed to be separated from the neutral marker in capillary zone electrophoresis (CZE) experiments [sulphanilamide (SAA) and sulphaguanidine (SGW)] have been examined to determine the basis for separation. The degree of separation increases markedly with buffer concentration and improves with increasing field strength. On the basis of the apparent electrophoretic mobilities in conventional CZE, migration times in a zero EOF environment were calculated for SAA, SGW and six other sulphonamides that were known to be ionized. These six markers were used to test the legitimacy of our predictions and to correct for small discrepancies between the predicted and observed migration times. It was concluded that SAA and SGW have negligible electrophoretic mobilities and that they are retained in the electrical double layer close to the capillary wall. A mechanism for adsorption is proposed and the generality of the phenomenon is discussed.

On-line concentration of s-triazine herbicides in micellar electrokinetic chromatography using a cationic surfactant

On-line concentration of neutral species of s-triazine herbicides in micellar electrokinetic chromatography using tetradecylammonium bromide (TTAB) as a cationic surfactant was investigated. Factors affecting the stacking of analytes were examined. The results indicate that the stacking efficiency is markedly improved with addition of phosphate buffer in the sample matrix. It was found that, depending on the nature of the analytes, the most effective stacking of these analytes occurs when the ratio of the conductivity of buffer electrolyte to that of sample matrix is in the range 1.4-1.2, with sample matrix containing phosphate buffer. Micelle concentration in the separation buffer is also a crucial factor to enhance the stacking efficiency and detection sensitivity of analytes. Moreover, the stacking efficiency of each individual analyte depends on its binding constant to TTAB micelles. The concentration effect is primarily based on sweeping mechanism which is operated in a normal stacking mode with reversed electrode polarity in the presence of reversed electroosmotic flow. As a result of concentration enhancement, the detection limits of these herbicides can reach about 9-15 ng/ml with UV detection.