实验报告英文

determination of heavy metals in soil by atomic absorption spectrometry(aas)

name: xufei group: the 3rd group

date: sep. 20th 2012

part 1 the introduction

1.1the purposes

(1)learn how to operate the atomic absorption spectrometry;

(2)learn how to do the pretreatment of soil samples;

(3)get familiar with the application of atomic absorption spectrometry.

1.2the principles

atomic absorption spectrometry (aas) is a technique for measuring quantities of chemical elements present in environmental samples by measuring the absorbed radiation by the chemical element of interest. this is done 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 .

the concentration is calculated based on the beer-lambert law. absorbance is directly proportional to the concentration of the analyte absorbed for the

existing set of conditions. the concentration is usually determined from a calibration curve, obtained using standards of known concentration. calibration curve method: prepare standard solutions of at least three different concentrations, measure the absorbance of these standard solutions, and prepare a calibration curve from the values obtained. then measure the absorbance of the

test solution adjusted in concentration to a measurable range, and determine the concentration of the element from the calibration curve.

part 2 the materials and apparatus

part 3 the procedure

3.1 operating procedure for aas

(2) instal l required hollow cathode lamp. select ¡°t¡± before turning to the power and hollow cathode lamp. then select appropriate la mp current and preheat for 30min.

(3) make sure electrical meter to point to zero and then turn on high-voltage power.

(4) select appropriate slit width.

(5) rotate monochromator and select required wavelength. if the power meter

is too high or low, adjust negative high voltage until the meter reads full scale.

(6) adjust light point and wavelength so that the meter represents the maximum value.

(8) inject distilled water into the flame and continue to preheat the burner. inject distilled water into the flame after each sample.

(9) select ¡°e¡±, inject blank solution into the flame and adjust the meter to zero.

(10) optimize analysis conditions and measure standard solution and samples.

(12) select ¡°t¡± before turning off high voltage power, decrease lamp current and then turn off the lamp. at the same time, all buttons should be on original positions.

(13) check the equipment before leaving the laboratory.

3.2 determination of soil samples