ABSTRACT
Currently, increasing importance has been attached to heavy metal pollution of water environment. In order to help geologist and environmentalist to obtain on-site experimental data, there is an urgent need to develop portable analysis techniques of water quality, which can be used to give an timely and accurate assessment of water quality of the contaminated area with low cost and to monitor water environment conveniently in daily preventing and controlling work of water pollution. Based on adsorption with Purolite S930 chelating resin at pH 4 and thin-film sample preparation technique, a rapid and simple on-site-oriented analysis method of heavy metal ions, namely Mn, Fe, Ni, Cu, Zn and Pb in aqueous solutions, was developed utilizing a handheld energy-dispersive X-ray fluorescence in this paper. The correlation coefficients of the calibration curves were greater than 0.992 for all six metal ions, the lower limits of detection were between 5.8 and 18.6 µg·L-1. Precision tests carried out on multi-element mixed solutions showed that the relative standard deviations (RSD, n=10) were better than 15%. The method has been used on-site to analysis 21 water samples collected from different river or well sites near a mining area northeast China. Out of the five underground water samples one was found contaminated by Cu and Zn (Class â ¢), one by Zn and Fe (Class â ¡), and one by Fe(in between Class â ¡ to â ¢). Surface water samples showed better qualities. But two out of the sixteen were found to be contaminated by Mn heavily (Class â £). Laboratory ICPMS was used to analyze the same samples. The results for Cu, Ni and Pb were coincident with the on-site data in general. But for Zn and Mn with higher concentrations, on-site data were lower than that by ICPMS. The reason for that might be the inclusion of the fine suspending particles in the samples by ICPMS. We conclude that the on-site data were effective. With the described method, an overall data acquisition time, including sampling, processing and measuring, can be within 12 hours for a batch of 10 samples. The pre-concentration device and the XRF instrument are both small, light, portable and can operate without external power supply. So, the method is suitable for on-site water sample analysis, especially in remote areas.
ABSTRACT
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.
ABSTRACT
A method for evaluation of uncertainty was established with standard deviation of relative error. Utilizing a polarized energy dispersive X ray fluorescence spectrometer (P-EDXRF)X-lab 2000 with pressed polyethylene-backed pellets, 76 national reference materials and 89 geological examination samples were analyzed, the results indicated that the relative errors consist with the normal distribution with confidence level 95%. The section standard deviations of relative errors acted as method global relative uncertainty and expanded factor was 2. The section relative uncertainty caused by precision was analyzed and relative uncertainty caused by accuracy based on the error transfer formula was isolated. The ratio of relative uncertainty caused by accuracy to the global relative uncertainty was different with different levels and elements. Two methods validated that the evaluation of global uncertainty is reasonable, with the first method being the formula of audited results in laboratory, and the second being the comparison of standard value with expanded uncertainty and a revised value with expanded uncertainty.
