Solution Cathode Glow Discharge Based on Charge Coupled Device Detector

In 21st century, many countries pay much attention to lithium because lithium is an ideal material for green energy and light alloys as well as an important kind of strategic resources. The main source of lithium is from salt lake brine. China has rich resources of salt lake brine, but these brine resources are mainly distributed in the remote western region, which are in urgent need of portable analytical instrument for on-site exploration and exploitation. However, the available experimental techniques at present can not achieve the target of on-site analysis. Over the past decade, based on atmospheric pressure solution cathode glow discharge-atomic emission spectrometry (SCGD-AES) has been paid attention to analytical researchers because it runs without common air conditions such as fuel gas, carrier gas and vacuum environment. On the basis of previous studies of other researchers, we have developed a portable SCGD based on a charge coupled device (CCD) detector by ourselves, which is short for Li-K analyzer. The length, width, height and weight of the portable Li-K analyzer is 35 cm, 19 cm, 27 cm and 10 kg, respectively, which is very conducive to carry. This work selected the wavelength of 670.78 nm as the characteristic spectral line of Li and has established a rapid analytical method for Li in salt lake brine based on two different types of brines from Tibet. Under the optimum operating conditions, the detection limit of Li was 4 ng·mL-1 and the measured precision (RSD) was better than 2%. The analytical results of Li were much different from those obtained by inductively coupled plasma-mass spectrometry (ICP-MS) with different dilution ratios by standard curve method, which may be related to the matrix effect of solution. However, the analytical results of Li agreed well with the results obtained by ICP-MS using standard addition method, which showed that standard addition method can effectively reduce the matrix effect and improve the analytical accuracies. A great deal of experimental results showed that standard addition method could obtain accurate results of Li using only two points and can greatly reduce the workloads. This work laid a methodological foundation for on-site determination of Li in salt lake brine by the portable Li-K analyzer.