9.14 : 分析样品制备：概述

Sample preparation is a critical step in obtaining accurate analysis results. It comprises three main objectives: extraction, purification, and concentration.

Firstly, extraction involves isolating a mixture with the analyte of interest from a sample matrix. Secondly, if interfering substances are present, they are removed to obtain a pure sample. Thirdly, if the extracted analyte is of low concentration, it is concentrated to a level that can be detected accurately.

The common forms of the sample are solid, liquid, and gas. Solid chunks too large to be directly analyzed are powdered by physical methods such as grinding, crushing, and milling.

Sieving and blending this mixture results in a homogeneous fine powder, which is then dried and dissolved in a suitable solvent to extract the analyte into the solution.   

Unlike solids, liquid suspensions are filtered or centrifuged before analysis to remove impure solid particles.

As solid sorbents selectively adsorb the gaseous analyte, sample preparation is not required for gases.