Determination of trace sodium in water from high-parameter power plant with fluorescent spectrometry

The fluorescent spectrometry used for trace amount of sodium determination with high sensitivity has been discussed in this paper, which was based on complexation of ortho-methoxyl tetraphenylporphyrin (o-OCH₃TPP) and sodium ion with the excitation wavelength of 242 nm. With the concentration of sodium ion increased, the fluorescence intensity of the complex increased at the emission wavelength of 655 nm. The optimal buffer of Na-o-OCH₃TPP complex was selected as 10mM Tris-HCl solution, pH=8.87. The relative fluorescence intensity was proportional to the logarithmic value of concentration of Na⁺ in the range of 1.00×10^-9 to 1.00×10^-3mol/L, while the concentration of o-CH₃TPP was 1.269×10^-5mol/L, the corresponding correlation coefficient was 0.9804 (n=7), the detection limit can be estimated to about 3.00×10^-10mol/L. No significant interferences were observed from alkali metals and alkaline metals, like K⁺, Ca²⁺,Mg²⁺, and Li⁺. In addition, the proposed method possessed a very nice reproducibility and stability. With standard addition method, the presented method possessed a nice recovery rate of 96.3-104.5% for detection of sodium in water samples from a thermal power plant, indicating that the method can be well used for the determination of trace sodium ion in water in high-parameter power plants.