Field Enhanced Sample Injection for the CE Determination of Arsenic Compounds Using Successive Multiple Ionic Polymer Layer Coated Capillaries

Sensitive arsenic speciation by capillary electrophoresis using UV absorbance detection with on-line sample preconcentration techniques

The World Health Organization (WHO) guideline states that the total arsenic concentration in drinking water must not exceed 10 ppb. However, arsenic toxicity varies significantly, with inorganic arsenic species being more toxic than organic species. Arsenic speciation is therefore important for evaluating the health risks from arsenic-contaminated drinking water. Capillary electrophoresis provides the necessary high performance separation to determine arsenic species in water, but its sensitivity with absorbance detection is far below than needed. Using a coated capillary, several on-line sample preconcentration techniques such as large volume sample stacking with an electroosmotic flow pump, field amplified sample injection (FASI), transient isotachophoresis (tITP), electrokinetic supercharging (EKS) combining FASI and tITP, and counter flow (CF)-EKS, were therefore investigated. With CF-EKS using phosphate and N-cyclohexyl-2-aminoethanesulfonate as leading and terminating electrolytes, respectively, standard samples of arsenite, arsenate, monomethylarsonic acid, and dimethylarsinic acid were preconcentrated from 6,300- to 45,000-fold. The limits of detection obtained with UV absorbance detection were 0.08-0.3 ppb As. For a spring water sample spiked with the four arsenic species, LODs of 2-9 ppb As were obtained, which are lower than the WHO guideline of 10 ppb total As.

Review of recent developments of on-line sample stacking techniques and their application in capillary electrophoresis

Capillary electrophoresis (CE) has become one of the most useful tools in separation science because of its high separation efficiency, low cost, versatility, ease of sample preparation and automation. However, some limitations of CE, such as poor concentration sensitivity due to its lower sample loading and shorter optical path length, limits its further applications in separation science. In order to solve this problem, various on-line sample preconcentration techniques such as transient isotachophoresis preconcentration, field-enhanced sample stacking, micelle to solvent stacking, micelle collapse, dynamic pH junction, sweeping, solid phase extraction, single drop microextraction and liquid phase microextraction have been combined with CE. Recent developments, applications and some variants together with different combinations of these techniques integrating in CE are reviewed here and our discussions will be confined to the past three years (2008–2011).

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2008-2010)

Capillary electrophoresis has been alive for over two decades now; yet, its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with an update published in 2009 and covers material published through to June 2010. It includes developments in the fields of stacking, covering all methods from field-amplified sample stacking and large volume sample stacking, through to ITP, dynamic pH junction and sweeping. Attention is also given to on-line or in-line extraction methods that have been used for electrophoresis.