An externally air-cooled low-flow torch for inductively coupled plasma mass spectrometry

A low-flow torch specifically designed for inductively coupled plasma mass spectrometry (ICP-MS) was developed and evaluated. The outside of the torch is cooled externally by pressurized air flowing at similar to 70 1 min(-1) through a fourth tube sealed onto the usual 'outer' tube of a standard min itorch. This external air flow merely cools the outer tube of the torch and does not enter the plasma. Although plasmas can be sustained at operating power as low as 400 W with a 2 1 min(-1) outer Ar flow, somewhat higher pow er and Rows are advisable. A stable and analytically useful. Under optimum operating conditions, plasma can be obtained at 850 W with an outer. Ar how rate of only 4 1 min(-1) the externally air-cooled plasma produces compara ble sensitivities, M2+/M+ signal ratios, matrix effects and other analytica l figures of merit as those produced by a conventional torch while using mu ch less argon. MO+/M+ signal ratios are slightly higher with the externally cooled torch. (C) 2000 Elsevier Science B.V. All rights reserved.