Analytical performance of the Conical torch in inductively coupled plasma optical emission spectroscopy operating methanol and 1-propanol solutions

Abstract

This work explores, for the first time, the strengths and weaknesses of the Conical torch in ICP-OES operating methanol and 1-propanol solutions ranging from 30% to 100% w w⁻¹. To this end, Conical torch performance has been evaluated considering: (i) plasma fundamental properties; (ii) plasma robustness; (iii) carbon-based background emission; and (iv) analytical figures of merit. For the sake of comparison, a Fassel torch has been employed as a reference. Results show that the discharge for the Conical torch is highly robust and plasma characteristics (i.e., excitation temperature and electron number density) are mostly unaffected by the introduction of pure and hydroalcoholic solutions of methanol and 1-propanol. In contrast, the discharge for the Fassel torch is severely affected by organics introduction and it is not feasible to operate methanol solutions above 30% w w⁻¹. Because torch geometry and improved gas flow patterns, the Conical torch affords higher emission signal (2-fold) than the Fassel torch. Nevertheless, the detection limits for both torches are comparable, which is due to the increase in both (carbon-based) background emission and signal noise for the Conical torch. From these results and considering that the Conical torch requires less r.f. power (35%) and argon consumption (55%) than the Fassel one, it is beyond doubt that the former torch is more advantageous for those applications requiring the analysis of alcohol solutions (i.e. extraction procedures and chromatographic separations).