A sweeping-micellar electrokinetic chromatography method for direct detection of some aromatic amines in water samples

Rapid separation and sensitive determination of banned aromatic amines with plastic microchip electrophoresis

Rapid analysis of trace amount of aromatic amines in environmental samples and daily necessities has attracted considerable attentions because some of them are strongly toxic and carcinogenic. In this study, fast and efficient electrophoretic separation and sensitive determination of 5 banned aromatic amines were explored for practical analysis using disposable plastic microchips combined with a low-cost laser-induced fluorescence detector. The effect of running buffer and its additive was systematically investigated. Under the selected condition, 5 fluorescein isothiocyanate labeled aromatic amines could be baseline separated within 90s by using a 10mmol/L borate buffer containing 2% (w/v) hydroxypropyl cellulose. Calibration curves of peak areas vs. concentrations were linear up to 40 or 120μmol/L for different analytes and limits of detection were in a range of 1-3nmol/L. Theoretical plate numbers of 6.8-8.5×10(5)/m were readily achieved. The method exhibited good repeatability, relative standard deviations (n=5) of peak areas and migration times were no more than 4.6% and 0.9%, respectively. The established method was successfully applied in the quantitative analysis of these banned aromatic amines in real samples of waste water and textile, recoveries of added standards were 85-110%.

Recent advances in enrichment techniques for trace analysis in capillary electrophoresis

CE is gaining great popularity as a well-established separation technique for many fields such as pharmaceutical research, clinical application, environmental monitoring, and food analysis, owing to its high resolving power, rapidity, and small amount of samples and reagents required. However, the sensitivity in CE analysis is still considered as being inferior to that in HPLC analysis. Diverse enrichment methods and techniques have been increasingly developed for overcoming this issue. In this review, we summarize the recent advances in enrichment techniques containing off-line preconcentration (sample preparation) and on-line concentration (sample stacking) to enhancing sensitivity in CE for trace analysis over the last 5 years. Some relatively new cleanup and preconcentration methods involving the use of dispersive liquid-liquid microextraction, supercritical fluid extraction, matrix solid-phase dispersion, etc., and the continued use and improvement of conventional SPE, have been comprehensively reviewed and proved effective preconcentration alternatives for liquid, semisolid, and solid samples. As for CE on-line stacking, we give an overview of field amplication, sweeping, pH regulation, and transient isotachophoresis, and the coupling of multiple modes. Moreover, some limitations and comparisons related to such methods/techniques are also discussed. Finally, the combined use of various enrichment techniques and some significant attempts are proposed to further promote analytical merits in CE.

Determination of aniline and its derivatives in environmental water by capillary electrophoresis with on-line concentration

This paper describes a simple, sensitive and environmentally benign method for the direct determination of aniline and its derivatives in environmental water samples by capillary zone electrophoresis (CZE) with field-enhanced sample injection. The parameters that influenced the enhancement and separation efficiencies were investigated. Surprisingly, under the optimized conditions, two linear ranges for the calibration plot, 1–50 ng/mL and 50–1000 ng/mL (R > 0.998), were obtained. The detection limit was in the range of 0.29–0.43 ng/mL. To eliminate the effect of the real sample matrix on the stacking efficiency, the standard addition method was applied to the analysis of water samples from local rivers.

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.

Determination of aromatic amines in food products and composite food packaging bags by capillary electrophoresis coupled with transient isotachophoretic stacking

A capillary electrophoretic method was explored to assay aromatic amines in food samples. With an inline-coupled transient isotachophoretic stacking approach, the method has yielded about 200-fold improvement of sensitivity in UV detection of three primary aromatic amines and melamine. By using K(+) as a leading ion and Tris(+) as a terminating ion, a plug of 10 cm (equivalent to 0.44 microL) sample solution was allowed to introduce into a 60 cm (50 cm effective) capillary for separation, giving limits of detection down to 2.0 x 10(-8)M. Baseline separation was achieved within 10 min, with relative standard deviation of 0.41-0.75% (intra-day) or 1.2-1.5% (inter-day) for migration time and 3.8-4.3% (intra-day) or 5.2-6.7% (inter-day) for peak area. The method was directly applicable to assaying the melamine in powder milk samples, with recovery in between 92.0% and 107.1%. The method could also be applied to the analysis of trace primary aromatic amines migrating from composite food packaging bags after combination of a 10-fold off-line concentration step, with limit of detection down to less than 1 microg/L. By this method, 4,4'-diaminophenylmethane and 2,4-diaminotoluene were thus found in three types of composite food packaging bags.