关键词: 土壤, 重金属, 快速检测, 电热蒸发, 固体进样, 基体干扰

Abstract:

Recently, with the high-speed development of industry and agriculture in China, the contamination of heavy metal has become a severe environmental problem caused by immoderate mining operation, "three wastes" emissions, vehicle exhaust, and misuse of agricultural chemical inputs. So, it is very important to monitor the contamination of heavy metals in soil. However, the national and industrial standards of detecting heavy metals in soil mainly focus on the traditional analytical approaches employed in laboratory at present. So, it is still difficult to achieve the on-site and fast detection of heavy metals in soil, which gives rise to such difficulty of monitoring and preventing the source contamination effectively and timely. In view of the matrix of soil sample, solid sampling analysis should be feasible to the fast detection of heavy metals, including electrothermal vaporization (ETV), X-ray fluorescence spectrometry (XRF), laser ablation (LA), laser induced breakthrough spectrometry (LIBS), X-ray photoelectron spectroscopy (XPS), and instrumental neutron activation analysis (INAA). The solid sampling techniques do not require digestion treatment and is thereby fast and efficient. However, among them, the detection limit and stability of XRF, LA, and LIBS cannot satisfy the all demands in standards of soil quality; on the other hand, it is too difficult to reach the miniaturization and on-site testing for LA, XAS, and INAA. By comparison, ETV is a kind of solid sampling tool with excellent advantages such as high analytical sensitivity, favorable stability, and being easy to be miniaturized, using electric heating to introduce analyses via aerosol from the sample into the atomizer or exciter for measurement. ETV is able to introduce heavy metals fast and efficiently, which is versatile to atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), atomic emission spectrometry (AES), and induced coupled plasma mass spectrometry (ICP-MS). As usual, many materials such as carbon, metals, and quartz can be utilized for ETV, which are frequently processed into graphite furnace, porous carbon tube, tungsten coil, rhenium coil, quartz tube and so on. Among various ETV approaches, electromagnetic induction ETV is characterized with no cold zone, fast heating or cooling and miniaturization. Considering the complicated soil matrices, however, ETV has been always confronted with the bottleneck problem, namely matrix interference. Through integrating these advanced techniques including gas phase enrichment (GPE), dielectric barrier discharge, matrix modifier, background correction and so on, the matrix interference will be eliminated completely for the detection of heavy metals in soil when solid sampling by using ETV atomic spectrometers. Especially for GPE, it can realize both two aims at one time: eliminating matrix interference and improving analytical sensitivity. This review is about to bring some valuable suggestions for innovating the fast detection of heavy metals in soil, to play parts in the environmental monitoring and protection in the future.

Key words: soil, heavy metals, fast detection, electrothermal vaporization, solid sampling, matrix interference