Combination of a multimode sample introduction system with a pre-evaporation tube to improve multi-element analysis by ICP-OES

Abstract

A pre-evaporation tube (heated to 400 C) was inserted between a multi-mode sample introduction system (MSIS) and the plasma torch in inductively coupled plasma optical emission spectrometry (ICP-OES) to improve the simultaneous determination of hydride-forming and other elements. Multivariate optimisations were conducted to find operating conditions improving plasma robustness. Under these conditions and compared to conventional sample introduction with a pneumatic nebulizer and spray chamber, using MSIS with a pre-evaporation tube (PET) improved sensitivity and detection limits for hydride-forming elements (As, Sn, Hg, Sb and Bi) and other elements as well. In order to obtain a significant improvement for all elements, irrespective of hydride formation or not, the pneumatic nebulizer was replaced by an ultrasonic nebulizer (USN) and the same experimental conditions were used for the simultaneous introduction of aerosol and hydrides (from the MSIS) into a PET. With USN-MSIS-PET, the figures of merit of ICP-OES improved by over an order of magnitude for both hydride-forming elements and other elements compared to those with a conventional sample introduction system. Furthermore, using either PN-MSIS-PET or USN-MSIS-PET increased plasma robustness, likely as a result of the hydrogen gas by-product of hydride generation, which was reported to increase energy transfer within the plasma, and from the introduction of water vapor (with PET), which was reported to improve plasma stability as well as sensitivity. Good agreement with certified values was obtained when this approach was applied to the determination of hydride-forming and other elements in environmental certified reference materials.

Improvement of analytical performance in inductively coupled plasma optical emission spectrometry without compromising robustness using an infrared-heated sample introduction system with a pneumatic nebulizer

“…The enhancements in sensitivity are in agreement with those reported for the TISIS (8-15 fold), 28 PN-MSIS-PET (1-50 fold) 29 and USN-PET(IR) (10-25 fold) 2 systems, and are not due to a sole increase in R.F. power.…”

“…The sample introduction components did not need to be cleaned any more frequently than with PN at room temperature, unlike the previous PN-MSIS-PET system, which had to be cleaned aer only two days. 29 The washout time was about 3-4 s longer than that with the standard system at room temperature, despite the fact that the sample pumping rate was over 10 times smaller. Operating at 1.7 kW, i.e.…”

“…19 Signicant improvement in sensitivity and detection limit was also demonstrated using a low sample consumption system with a spray chamber heated to 105 C. 28 Coupling a multi-mode sample introduction system (MSIS) with a USN-PET improved sensitivity and detection limits, in particular for hydride-forming elements. 29 Replacing the heating tape with an infrared (IR) heater in a USN-PET system allowed vastly increased sample uptake rates because IR heating is more uniform and efficient than convective heating. 2 The efficacy of IR heating over conduction-convection based heating had also been demonstrated in earlier studies with the Mistral desolvation system for ICP OES.…”

Atomic spectrometry update: review of advances in atomic spectrometry and related techniques

“…The method was characterized, optimized, and applied to the determination of Co in a drug preparation, Pb in whole blood, and Sn in food samples without any sample pretreatment. Beauchemin et al 60,61 described the use of a preevaporation tube (PET) heated to 400 C, inserted between a multi-mode sample introduction system (MSIS) and the plasma torch for sample introduction to an ICP-AES. This modication improved the simultaneous determination of hydride forming and other elements compared with conventional sample introduction.…”

Effect of temperature on direct chemical vapor generation for plasma optical emission spectrometry: An application of programmable temperature spray chamber

“…A continuous-flow in-situ nebulizer/hydride generation system (MSIS) was coupled with ICP torch by means of a pre-evaporation tube heated to 400°C. This combination improved the analytical performance of multi-element analysis by ICP-OES as described by Asfaw and Beauchemin [4]. Also, the advantageous effect of spray chamber cooling on the analytical results obtained by ICP-OES and ICP-MS has been claimed for PN [5,6].…”