Model 7500 icp ms

A model 7500 ICPMS equipped with a collision cell (Agilent Technologies, Mississauga, ON, Canada) was used for all measurements. An ESI spray chamber having two inlets to simultaneously permit sample introduction of both gaseous and nebulized liquid samples was used. Solution nebulization was undertaken with a PFA ST nebulizer (ES-2040, Elemental Scientific; Omaha, NE, USA) operating at 0.40 mL min À1 . During PVG optimization and sample analysis, gas flow to the nebulizer was stopped in order to achieve best sensitivity of As using PVG. A schematic of the UV-PVG photoreactor interfaced to the ICPMS has been presented earlier [30] . The UV-PVG system consists of a 19 W thin film flow-through lamp (Beijing Titan Instruments Co., Beijing, China) loosely covered with aluminum foil to shield the operator from exposure to the UV. Argon carrier gas was introduced through a "Y" connection between the outlet of the photoreactor and a homemade gaseliquid separator (GLS, ~2 mL internal volume) maintained at 0 C by immersion in an ice bath to minimize any transport of liquid droplets derived from condensation of water vapor to the ICP. The generated analyte vapors were directed from the outlet of the GLS to the gas inlet port of the spray chamber via a 0.25 m length of Teflon lined Tygon tubing (0.25 in o.d., VWR International).