Evaluation of a sampling system coupled to liquid cathode glow discharge for the determination of rubidium, cesium and strontium in water samples

A simple sample introduction system has been successfully developed, and then integrated with liquid cathode glow discharge (LCGD) to form atomic emission spectrometry (AES) for the detection of rubidium (Rb), cesium (Cs) and strontium (Sr) in water samples by using a fiber-optic spectrometer, in which a buffer bottle was employed to improve the stability of microplasma, and a six-port valve equipped with sample loop was used to reduce the sample consumption and enhance the analytical precision and speed. The effects of flow rate, discharge voltage, supporting electrolyte and solution pH on signal intensity were examined systemically. The matrix interferences of major cations and anions in aqueous solution were also evaluated. The results indicated that the optimal operating conditions are 2.4 mL min(-1) flow rate, 660 V discharge voltage and pH = 1.0 HNO3 as supporting electrolyte. Only Al3+ ions interfere with the determination of Rb, Cs and Sr. The limits of detection (LODs) of Rb, Cs and Sr are 0.18, 0.17 and 0.21 mg L-1, respectively, which are basically inferior to those of the closed-type electrolyte cathode atmospheric discharge (ELCAD). The relative standard deviation (RSD) is 2.7% for Rb, 2.0% for Cs and 2.5% for Sr, the correlation coefficients (R-2) of Rb, Cs and Sr are over 0.999, and the power is below 50 W. The measured results of Rb, Cs and Sr are in agreement well with the spiked values, and the satisfactory recoveries of standard addition are obtained between 97 and 111%. The advantages of small size, low sample and power consumption and high stability suggested that the LCGD-AES is a promising technique for the detection of Rb, Cs and Sr in water samples.