[31,32]. The sprayer consists of a concentrically shaped stainlesssteel capillary surrounded by an outer stainless steel tube and wasused as the nebulizer of the ICP-MS. As shown in Fig. 1, the CEcapillary passed through the inner stainless steel capillary of thesprayer with a gap between them and protruded approximately0.1 mm out of the sprayer tip. Sheath flow liquid was added intothe inner stainless steel capillary to close the electric circuit anddeliver a suitable flow rate to produce a stable electrospray. Thecarrier gas was added at the outer stainless steel tube. The sheathflow liquid is mixed with the CE effluent at the sprayer tip and themixture is then nebulized by the carrier gas from the outer tube. Tomaintain a steady separation voltage, the stainless-steel shell of thesprayer was grounded. The sprayer was then installed at the baseof the spray chamber to ensure that the liquid from the capillarycan be directly introduced into the ICP-MS after nebulization.Fig. 1. Schematic diagram of the interface coupling CE with ICP-MS.A mixture of water and methanol (95:5, v/v) with 100 ng mL−1Rh solution was used as the sheath flow liquid and was introducedinto ICP-MS by an Agilent 1200 series quaternary pump (Agilent,Germany) in conjunction with a built-in active 1:100 flow-splitter(Agilent, USA), which provided a constant flow rate of 5 L min−1.Using the proposed interface, solution at the sprayer tip wascollectively nebulized by the carrier gas with high nebulization effi-ciency. As the outlet of the CE capillary was directly inserted intothe sprayer chamber of ICP-MS, the dead volume was also signifi-cantly reduced and the analytes could be effectively transported tothe ICP-MS after nebulization. The advantages of the sprayer makeit very suitable as an interface for coupling CE with ICP-MS.2.5. Sample analytical procedureThe species of water-soluble arsenic in ground water, TORT-2(lobster hepatopancreas), DORM-3 (fish protein), two herbal plants(flower of Chrysanthemum morifolium Ramat which is also calledFlos Chrysanthemi and root of Rehmannia glutinosa Libosch) andchicken meat purchased from local market were determined bythe CE-ICP-MS system after pretreatment.The ground water sample used in the experiment was obtainedfrom Shanyin town (Shanxi, China) and stored at −20◦C after sam-pled.The herbal plants and chicken meat were lyophilized andhomogenized before the following extraction procedure: (1) 0.5 gof freeze-dried samples or the dried TORT-2 and DORM-3 wereweighed into a 15 mL centrifuge tube and 10 mL de-ionized waterwas added. (2) The tube was vortexed for 1 min, sonicated for30 min and then centrifuged at 4000 rpm for 10 min. (3) The super-natant was collected and another 5 mL de-ionized water was addedinto the precipitate. Thereafter, the procedure (2) was repeated. (4)The supernatant in the procedure (2) and (3) was mixed together.The extracted solution and water samples were filtrated through0.22 m nylon filter membranes and then analyzed by CE-ICP-MS.