Double tungsten coil atomic emission spectrometry: signal enhancement and a new gas phase temperature probe

Abstract

A new double atomizer arrangement for tungsten coil atomic emission spectrometry is described. Two small constant current power supplies, a Czerny–Turner spectrograph, and a charge coupled device (CCD) detector are used to determine refractory elements in water samples. The analytical figures of merit for Ba, Sr, Ti, and V are reported and compared with the single coil arrangement. The use of two atomizers provides more energy for the atomization and excitation of the analytes and consequently improves sensitivity. Addition of a second coil improves limits of detection for refractory elements by a factor of 40 (V) and 5 (Ti). Using 25 µl sample volumes, the limit of detection for V is 10 µg l⁻¹ at the 437.9 nm emission line, and 400 µg l⁻¹ for the 399.9 nm Ti emission line. Vanadium is determined in a polluted water certified reference material, and the results agree with the certified value (250 mg l⁻¹) at the 95% confidence level. For Ba and Sr, which emit strongly with a single coil, the double coil detection limits are improved by less than a factor of two: 0.007 µg l⁻¹Ba and 0.4 µg l⁻¹Sr. Emission signals for Ag, Cu and Sn are observed for the fist time with a tungsten coil atomic emission spectrometry (WCAES) system. A new method to determine the gas phase temperature by atomic emission spectrometry is also presented. Emission intensities for Dy (418.7 and 421.1 nm) and Eu (462.7 and 466.2 nm) are used to calculate Boltzmann temperatures for both the single and double coil arrangements. Temperature values calculated by this method agree with the traditional optical two-line absorption method using Sn (284.0 and 286.3 nm).