Determination of thallium at trace levels by electrolyte cathode discharge atomic emission spectrometry with improved sensitivity

An analytical method using electrolyte cathode discharge atomic emission spectrometry (ELCAD-AES) has been described for the trace determination of thallium after improving its sensitivity. Parameters influencing the sensitivity of thallium are investigated at its emission wavelength of 377.572 nm. Maximum enhancement of sensitivity is obtained with the combination of a surfactant (Triton X-114) and potassium iodide. Sensitivity of thallium is improved 12 times with the use of an optimised composition of 3.5% v/v Triton X-114 and 0.2% w/v of KI. Under the optimized conditions, the achieved detection limit is 1 mu g L-1 which is 100 times better compared to the detection limit obtained without addition of the surfactant and KI. The precision of the method is 2% for thallium of 500 mu g L-1 concentration. The accuracy of the proposed method has been validated by analyzing a NIST 1633b coal fly ash certified reference material and a IAEA 394 coal fly ash material. On comparison, the ELCAD-AES results are found to be in agreement with the certified values and the results obtained by high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS). The detection limit of thallium for coal fly ash has been found to be 134 ng g(-1). Determinations of spiked thallium at trace levels in ground water samples are carried out by ELCAD-AES and HR-CS-AAS and the results are in agreement with each other.