New infrared-heated sample introduction system for enhanced analytical performance of inductively coupled plasma optical emission spectrometry

Abstract

The analytical performance of a new infrared (IR)-heated modified cyclonic spray chamber (MC) with a regular 12 mm/5 mm female joint (MC12/5(IR)) was evaluated. The MC12/5(IR) consists of a 50 mL cyclonic spray chamber that was modified to allow the insertion of an IR lamp heater at its centre for more effective heating. The 7 cm base of the torch was also heated with a ceramic bead rope heater to prevent condensation in this region. Another MC(IR) with a 28 mm/15 mm female joint connected to a 38.1 cm pre-evaporation tube (PET) (MC28/15(IR)PET) was also tested. Multivariate optimisations were conducted to find operation conditions maximising analyte sensitivity and plasma robustness in inductively coupled plasma optical emission spectrometry (ICPOES). Under optimised conditions, a 2–5 fold improvement in sensitivity and 2–7 fold improvement in detection limit were achieved for 26 elements using MC12/5(IR) and MC28/15(IR)PET. For a given element, the improvement was larger for ionic emission lines than for atomic emission lines. The results were attributed to an enhancement in transport efficiency and to the conversion of the aerosol into vapour, which significantly improved plasma excitation conditions. The MC(IR) systems were applied to the accurate analysis of two certified reference materials (drinking water and digests of contaminated soil) by ICPOES using a simple external calibration without internal standardization or matrix-matching. The best precision was achieved with the most compact system, i.e. MC12/5(IR).