Analyte transport efficiencies in electrothermal vaporization for inductively coupled plasma mass spectrometry

A modified graphite furnace for solid-sampling atomic absorption spectromet ry as an electrothermal vaporizer (ETV) was coupled to a Perkin-Ehner/Sciex ELAN 6000 ICP mass spectrometer. The integrals obtained from electrotherma l vaporization of aliquots containing As, Cd, Cu, Co, Fe, Mn, Pb, Se, and Z n were compared with those obtained from pneumatic nebulization of the same aqueous standard solution. The pneumatic nebulizer was calibrated by weigh ing the mass of aqueous aerosol trapped on a filter. With "wet plasma" cond itions maintained also for measurements with the ETV and reference signals for analyte signals obtained with the calibrated pneumatic nebulization, th e transport efficiency of the ETV system, e.g. the ratio of the analyte amo unt introduced into the plasma to that amount dosed into the vaporizer, was determined. The transport efficiency of two different tube and interface designs has be en evaluated. Investigations with and without the use of trifluoromethane a s reactive gas, with different furnace heating rates, and with varying gas flows were performed. In general, the tube equipped with a nozzle led to ge nerally higher transport efficiency than the standard tube. Without trifluo romethane transport efficiencies ranged from 10% to 35% with the standard t ube and from 15% to 50% with the nozzle-type tube. With addition of 2 mL mi n(-1) trifluoromethane to the argon flow of 400 mL min(-1) through the tube , transport efficiencies from 20% to 70% and from 70% to 100% were achieved with the standard and nozzle-type tubes, respectively.