Spectroscopic characterization of low power argon microwave-induced plasma with gaseous species produced from ethanol–water solutions in continuous hydride generation process

Abstract

Low power microwave-induced argon plasma generated by resonant TE 101 rectangular cavity was investigated upon introduction of volatile species formed in the reaction with sodium tetraborohydrate(III) in hydrochloric acid–ethanol solution. The molecular emission bands of OH and CH were used for rotational temperature ( T rot) determination, while the atomic emission lines of Ar, H and Sb were applied for excitation temperature ( T exc) measurement. Assuming a Boltzmann distribution, the temperatures were calculated with the aid of the least squares method. Electron number density ( n e) derived from Stark broadening of the H β line was found to be between 2.5×10 15 and 0.57×10 15 cm −3. The detection limits (DL) were determined for Hg and Sb. The influence of ethanol concentration in analyte solution and microwave power on measured parameters, was investigated. The results showed that T rot(OH) increased from 2970 to 3820 K while T rot(CH) decreased from 6100 to 4540 K with ethanol concentration in the solution, ranging from 10 to 90%. Under the same experimental conditions the excitation temperature for Ar, H and Sb varied in the following ranges: 5670–4800, 6190–3950 and 10500–7390 K, respectively. It was observed that element DL were significantly influenced by the presence of ethanol in the sample solution. The DL values for Hg and Sb were, as follows: 0.5–11 and 5.3–35 μg l −1, respectively.