文档介绍：Lab 1 1 Determination of heavy metals in soil by atomic absorption spectrometry (AAS) Name: XuFei Group: The 3 rd group Date: Sep. 20 th2012 Part 1 The introduction The purposes (1) Learn how to operate the atomic absorption spectrometry; (2) Learn how todo the pretreatment of soil samples; (3) Get familiar with the application of atomic absorption spectrometry. The principles Atomic Absorption Spectrometry (AAS) isa technique for measuring quantities of chemical elements present in environmental samples by measuring the absorbed radiation by the chemical element of interest. This isdone by reading the spectra produced when the sample is excited by radiation. The atoms absorb ultraviolet or visible light and make transitions to higher energy levels . Atomic absorption methods measure the amount of energy in the form of photons of light that are absorbed by the sample. A detector measures the wavelengths of light transmitted by the sample, pares them to the wavelengths which originally passed through the sample. A signal processor then integrates the changes in wavelength absorbed, which appear in the readout as peaks of energy absorption at discrete wavelengths. The energy required for an electron to leave an atom is known as ionization energy and is specific to each chemical element. When an electron moves from one energy level to another within the atom, a photon is e