Development of a novel spectrometric-based temperature probe and the investigation of atomic cloud generation in a tungsten coil atomizer

Abstract

A new two-element atomic emission temperature probe is developed and applied to gas phase temperature determinations in both a tungsten coil atomizer and an air/acetylene flame. Results are comparable to the traditional Sn two-line method, with variances as low as 0.08%. The spectrometric-based thermometer is composed of a handheld spectrometer, a fiber optic and a laptop computer. The method is an interesting alternative for a wide range of applications due to its simplicity, portability and high temperature capabilities. Its spatial resolution is especially desirable for spectroscopic studies. An updated version of the Sn two-line method is used to determine the temperature profile of a tungsten coil atomizer and study processes involved in atomic cloud generation in both atomic absorption and atomic emission spectrometry. Tungsten coil atomizers present significant temperature gradients and spectrometric methods based on them are critically dependent on some interrelated parameters such as gas phase temperatures, protecting gas composition, and ultimately, atomizer positioning relative to the detector. Sn atomic absorption, and Li and Cr atomic emission profiles were determined and compared with the atomizer temperature profile. Elements determined by atomic emission are more dependent on gas phase temperatures while Sn absorption signal is more dependent on the reducing atmosphere provided by H₂ molecules present in the protecting gas mixture. Cr presents higher emission signals in a H₂-rich, more reducing environment, whereas Li is less dependent on both temperature and protecting gas composition. Those results reflect Li lower excitation energy and Cr refractory characteristics.