Review on Sample Pretreatment Methods and Determination Techniques for Inorganic Elements in Plant Samples

The determination of inorganic elements in plant samples is very important for the research of environmental geochemistry and biogeochemistry. The content of elements in plant samples is characteristically low, deeming it necessary for the determination technique to be highly sensitive, with excellent precision and an as-low-as-possible detection limit. A comparison of the current pretreatment methods for plant samples is described in this paper, namely, dry ashing, wet digestion, and microwave digestion. Pretreatment method is selected based on the characteristics of samples and target elements. The advantage of dry ashing is less consumption of reagent and low level blank, but is unsuitable for compact-tissue samples and some volatile elements. Wet digestion is a complete digestion method for most samples, but its disadvantages of high consumption of reagent, high level blank and complex procedure. Microwave digestion can avoid loss of some volatile elements with less reagent and rapid digestion, but it is unsuitable for large weighing samples. At present, most instrument techniques are suitable for plant sample analysis, based on the target element, interference correction method and matrix modification method. More than 40 elements can be determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and the detection limit of high resolution ICP-MS is fg/mL level. Inductively Coupled Plasma-Atomic Emission Spectrometry is suitable for determination of high content elements such as P, K and Na in plant samples. Atomic Absorption Spectrometry can determine more than 70 elements, and is one of the most popular techniques. The hydride generation technique coupled with Atomic Fluorescence Spectrometry is widely used for low content elements in plant sample. The new technique, Laser-induced Breakdown Spectroscopy, is also used for plant sample without complex pretreatment, can on-line and on-site simultaneously determine multi-elements with simple and fast operation. Other high selective and sensitive techniques are also vital to determine unusual inorganic elements in plant sample. Based on the previous research, it pointed out that the solid sampling technique is a new development trend for inorganic element analysis in plant sample.