Cadmium, Copper, Zinc and Lead Determination Experiment in Soil
Cadmium, Copper, Zinc and Lead Determination Experiment in Soil
The soil sample is digested and the solution is introduced into the atomizer, the metal atoms formed absorb the characteristic electromagnetic radiation, and the concentration of the elements in the sample is obtained by comparing the measured absorbance of the sample with the absorbance of the standard solution.
Operation method
Flame Atomic Absorption
Principle
The soil sample is digested and the solution is introduced into the atomizer, the metal atoms formed absorb the characteristic electromagnetic radiation, and the concentration of the elements in the sample is obtained by comparing the measured absorbance of the sample with the absorbance of the standard solution. Move I. Instrumentation Caveat 1. Zinc is particularly susceptible to contamination, so special attention should be paid to the contamination of containers and reagents during the determination. 2. The results of the aqua regia-perchloric acid digestion method for the determination of Cd, Cu and Pb are on the low side, especially for the determination of background values. In general, it is recommended to use HF-HClO4-HNO3HF-HClO4-HNO 3 digestion is recommended for the determination of soil background values, and aqua regia-perchloric acid digestion can be used for the determination of contaminated soil. For more product details, please visit Aladdin Scientific website.
Hot plate, atomic absorption spectrophotometer, hollow cathode lamp, rigid beaker or polytetrafluoroethylene crucible, 25 mL and 50 mL volumetric flasks, 1 mL and 5 mL pipettes.
II. Reagents
1. Nitric acid, excellent purity.
2. Perchloric acid, superior purity.
3. Hydrochloric acid, good grade pure.
4. Hydrofluoric acid, superior purity.
5. Metal standard reservoirs.
III. Experimental steps
1. Digestion of soil samples
(1) HF-HClO4-HNO3 digestion: weigh 0.5-1 g (accurate to 0.0001 g) of soil samples that have been dried at 105-110°C and passed through a sieve of 0.149 mm (100 mesh) or more in a 30 mL PTFE crucible, add a few drops of deionized water to moisten the crucible, add 10 mL of HF, and 5 mL of 1:1HClO4-HNO3 mixture. Add 10 mL of HF, add 5 mL of 1: 1HClO4-HNO3 mixture, cover with a low-temperature digestion (below 100 ℃) for 1 hour, remove the lid, increase the temperature (below 250 ℃) and continue to digest until a large number of HClO4 smoke, and then add 5 mL of HF and 5 mL of 1: 1HClO4-HNO3 mixture, and then digest until the HClO4 smoke, cover with a lid, so that the black organic carbons are fully decomposed. When the black organic matter on the crucible disappeared, open the lid to drive the white smoke nearly dry, add 5 mL of HNO3 digestion to the white smoke basically smoke and the contents of the dry cracked, remove while hot and add 5 mL of 2 mol/L HCl, heating to dissolve the residue (can not be smoked), and then transfer it to a 25mL volumetric flask, with deionized water, shaking well to be measured. At the same time to do the blank.
(2) Aqua regia - perchloric acid method: weigh the soil sample 0.5 ~ 1 g (accurate to 0.0001 g) dried at 105 ~ 110 ℃, through 0.149 mm (100 mesh) or more sieve in a 100 mL high beaker, moistened with a small amount of water (such as calcareous soils, can be added dropwise appropriate amount of HCl to the absence of a large number of bubbles), in a fume hood, add 7.5 mL of concentrated HCl, followed by 2.5 mL of concentrated HNO3, put on the electric hot plate at low temperature heating, after intense reaction, add 5 mL of HClO4 cooking until nearly dry. 7.5 mL of concentrated HCl, followed by 2.5 mL of concentrated HNO3, put on the electric hot plate heating at low temperature, to be intense reaction, add 5 mL of HClO4 digestion , until nearly dry (pay attention to do not burn), this time, the residue is white or off-white precipitate, such as the color is darker, you can add 5 mL of HClO4, and continue to meet the requirements of the digested so far (in general, add two times can be). Remove the beaker, add 10 mL of 1 mol/LHCl, stirred with a glass rod and heated to a slight boil under stirring, cooled and filtered to 25 or 50 mL volumetric flasks, washed with deionized water for several times, and then fixed to be measured.
2. Preparation of standard series of solutions for calibration curves: refer to the preparation of solutions for water standard curves.
3. Measurement on the machine: the standard series of solutions together with the specimen solution on the machine.
IV. Calculation of results
C=C1×V×ts/wEq:C - Concentration of an element in soil, ug/g or mg/kg;C1 - measured concentration of an element, ug/mL;V - the volume of the determination, mL;ts - fractionation times;w - sample weight, g.