Arsenic speciation by coupling capillary zone electrophoresis with mass spectrometry

Abstract

SummaryCapillary zone electrophoresis (CZE) has been coupled with mass spectrometry to enable the identification of mineral and organometallic compounds of arsenic in speciation studies. The electrophoretic effluent was introduced through a concentric interface into the mass spectrometer. Make-up liquid was added to enable electric contact at the outlet of the separation capillary and to assist the electronebulization process. After ionization, the ions were analyzed and quantified with an ion-trap detector. Optimization of the coupling conditions (geometry of the concentric interface, composition and flow rate of the sheath liquid, electronebulization and detection conditions) is described. The results show that the geometry of the concentric interface and the positioning of the outlet of the separation capillary have a critical effect on stability and sensitivity. Programming the electronebulization and detection conditions throughout the analysis enabled identification and quantification of the seven arsenic compounds of interest (neutral, and positively or negatively charged species) in less than 20 min at the ppm level. Limits of detection ranged from 0.5 to 3.3 mg L 1, corresponding to amounts injected ranging from 15 to 60 pg. The linear dependence of mass spectrometric response on arsenic concentration was verified for concentrations ranging from 5 to 200 mg L 1. For the two positively charged species, arsenobetaine and arsenocholine, an on-line preconcentration technique (field-amplified sample injection) enabled reduction of the detection limits by aP?arOXimately one order of magnitude to 110 and 160 #g L-, respectively.

Arsenous acid ionisation in aqueous solutions from 25 to 300°C

“…A recent study of Debusschere et al (2000) of arsenic speciation using capillary zone electrophoresis coupled mass spectrometry supports the HAsO 2 stoichiometry. The As-containing species produced in the gas phase had mass-to-charge-ratios (m/z) of 107 and indicated the presence of the AsO 2 À ion (molecular mass of AsO 2 À = 75 + 2.16 = 107).…”

Recent advances and trends in capillary electrophoresis of inorganic ions

“…A great deal of research work over the last two years proves that CE techniques keep playing an increasingly important role in discriminating the speciation pattern of various environmentally and biologically important metals, metalloids, and nonmetals (e.g., mercury [61,62,68,70,72], chromium [65,75,84,138], vanadium [141], iron [132], cobalt [74], platinum [85], rhodium [230], arsenic [63,65,67,74,77,187,216,[231][232][233], selenium [65,66,80,86,87,105,187,234], tellurium [187], antimony [105], sulfur [235][236][237][238][239], nitrogen [240][241][242][243][244]; see also below). Less optimistic, however, look the method's accomplishments regarding speciation analysis from real-world samples.…”

“…This mode of MS detection appears useful for adding an extra selectivity dimension to CE data and particularly for obtaining structural information in order to facilitate the identification of (unknown) analytes. This attracting feature of ESI-MS may compensate for poorer detection limits compared to ICP-MS (also due to very low tolerance of nonvolatile electrolytes) and make CE-ESI-MS widely practiced for structural characterization, in the first instance, for elemental speciation purposes [20,67,69,71,73,81,90], including applications related to the field of pharmacology [91][92][93].…”

Recent advances in capillary electrophoresis and capillary electrochromatography of pollutants

“…In the last two years, several research groups have described the development of CE-MS methods to analyze environmental pollutants [26][27][28][29][30]. Poiger et al [27] coupled CE with negative ion electrospray MS for sensitive and selective identification and characterization of negatively charged metallized dyes.…”