New torch design for inductively coupled plasma optical emission spectrometry with minimised gas consumption

Abstract

A new torch design for inductively coupled plasma optical emission spectrometry was developed. The torch was made of one quartz tube with a ball-shaped excitation zone. Under optimised working conditions of the 27.12 MHz Ar plasma with 1.1 kW RF power, the total argon gas flow could be reduced to only 0.6 L min⁻¹ with external air cooling integrated in the fastening of the torch. Fundamental studies of selected element emissions, emission profiles, the effect of auxiliary plasma and sample carrier gas flow rates were carried out. The attainable excitation and rotational temperatures in the new torch were determined at different sample carrier gas flow rates. For 1.1 kW RF power and total gas flows between 50–800 mL min⁻¹ they were found to be in the order of 6000–10 000 K for the excitation temperatures and 3700–4100 K for the rotational temperatures. The new torch was coupled with an ultrasonic nebuliser and detection limits between 0.03–2.9 μg L⁻¹ could be determined for the elements Ba, Li, Mg, Ca, Cd, K and Al. The new torch delivered promising results that raise hopes of having a new generation of torches allowing low argon consumption.