Capillary electrophoresis (CE) is a well established separation technique for the study of elemental speciation, however, its low electroosmotic flow nL min(-1) restricts its application in many studies in which low detection limits are required. For this reason, the study of CE coupling (hyphenation) to more sensitive detectors is of great relevance. This work was initiated with a critical evaluation of different interfaces of CE to ICPMS, including a commercial interface, and others, mounted in our laboratory from different micronebulizers and spray chambers. Best results in routine work were obtained with a parallel flow nebulizer (Mira Mist CE, Burgener Research, AU) due to the absence of backpressure on the capillary orifice and its large internal sample channel, which permits that the CE capillary can be inserted up to the nebulizer exit, thus avoiding clogging problems observed in all other nebulizers. Using this nebulizer in combination with a small-volume cyclonic spray chamber (20 mL), a method was developed for the electrophoretic separation and quantification by ICPMS of five arsenic species: AsIII, AsV, MMAV, DMAV and AsB. The systematic study of different experimental parameters resulted in the following optimized separation and nebulization conditions: phosphate buffer (pH = 9.0), 20 mmol L(-1) with 1.5 mmol L(-1) TTAB as electroosmotic flow modifier; injection time (hydrodynamic mode) of 40 s at 50 mbar; make-up solution of NH4NO3 20 mmol L(-1) (pH = 9) containing 10 percent of methanol and injected at flow of 40 (mi)L min(-)1. Iodide was used as a monitor for the electrophoretic separation, whereas Cs was applied for controlling the nebulization efficiency and constancy. Repeatabilities (RSD) in peak location and peak area measurements were better than 10 percent in all cases, and detection limits were about 2.5 (mi)g L(-1) for AsB and 0.5 (mi)g L(-1) for all other species studied. The methodology was applied in the speciation analysis of arsenic in grape juice samples, and in a preliminary study on the uptake, transformation and excretion of Arsenil (MMAV) by horses. In the first study, low concentrations o total arsenic and other toxic elements (e.g Al, Hg, Cd, Sn,Pb, e Al) were measured in 31 samples (20 different brands) and which were in accordance with Maximum Tolerance Levels established by Brazilian laws. Speciation analysis of these samples by CE-ICPMS and FIA- HG-ICPMS revealed the existence, in varying proportions, of only inorganic arsenic species (AsV and AsIII). The investigations on the uptake and excretion of Arsenil (MMAV) by horses showed that the drug is rapidly eliminated from the organism, suggesting a first order kinetics for the excretion/elimination with half lives of about 34 h and 44 h for urine and plasma, respectively, within the time period of seven days here studied. DMAV was the only metabolic alteration product of Arsenil detected already in the first two days after drug uptake and accompanying its absorption and excretion profile. These results indicate that methylation is the principal detoxification pathway, as already observed by other authors but for different biologic systems.