Determination of Arsenic, Antimony, Bismuth, Lead, Cadmium and Tin in Soil by Atomic Fluorescence Spectrometry
Summary
: The hydride generation-atomic fluorescence spectrometry was used to determine the content of arsenic, antimony, bismuth, lead, cadmium and tin in soil. Different pre-treatment methods are applied to different elements to accurately determine the content of the elements to be tested in the soil sample. The method has determined the content of arsenic, antimony, bismuth, lead, cadmium and tin in the four soil standards, and the results are accurate and reliable.
1,
Experimental part
1.1
Experimental reagent
(1)
Hydrochloric acid (excellent grade, 36%, Ï=1.19g/ml); nitric acid (excellent grade, 65%, Ï=1.42g/ml); perchloric acid (excellent grade, 72%, Ï=1.67g/ Ml); hydrofluoric acid (excellent grade, 47%, Ï = 1.15g/ml)
(2)
10%
(thiourea and ascorbic acid): Analytically pure, weigh 10 g of thiourea and ascorbic acid in a beaker, add 100 ml of ultrapure water, and dissolve by heating.
(3)
Standard stock solution of arsenic, antimony, bismuth, lead, cadmium and tin (1000ug/ml): provided by the National Standards Research Center.
(4)
Potassium hydroxide, potassium borohydride, iron: analytical grade
(5)
Cd1
Special analytical reagent, Cd2 special analytical reagent: analytical pure
1.2
Laboratory equipment
(1)
Atomic fluorescence spectrometer (AFS200T);
(2)
High performance hollow cathode lamps of arsenic, antimony, antimony, lead, cadmium and tin;
(3)
Electric heating plate (EGB5B);
(4)
Water bath (HH-4);
(5)
Laboratory grade ultrapure water (RM-200).
1.3
Sample preparation
(1)
Determination of arsenic, antimony and bismuth sample digestion
Accurately weigh 0.2-0.5g of soil sample in 50ml plugged test tube, add a little water to wet the sample, add 10ml (1+1) aqua regia, shake it, shake it in boiling water bath for 2h, low temperature heating drive away digestion solution The remaining nitric acid was taken out and cooled, filtered in a 50 ml volumetric flask, and 2.5 ml of HCl, 10% (thiourea plus ascorbic acid) 5 ml was added, and the volume was adjusted and shaken to be tested.
(2)
Lead and tin sample digestion
Accurately weigh 0.2 -0.5 g (accurate to 0.0002g). The sample is in a 100ml Teflon beaker. After wetting with water, add 10 ml of hydrochloric acid and heat it on the hot plate in the fume hood to make the sample decompose and evaporate. When it is about 3ml left, take it off slightly, then add 5ml of nitric acid, 5ml of hydrofluoric acid, 3ml of perchloric acid, cover it and heat it on the hot plate for about 1h at medium temperature, then open the lid and continue heating to remove silicon. To achieve a good flying silicon effect, the beaker should be shaken frequently. When heated to a thick white smoke of perchloric acid, cover it to fully decompose the black organic matter. After the black organic matter on the wall of the beaker disappears, the lid is opened, the white smoke is driven away, and the contents are viscous. Depending on the digestion, 3 ml of nitric acid, 3 ml of hydrofluoric acid, and 1 ml of perchloric acid may be added to repeat the above digestion process. When the white smoke is again exhausted and the contents are viscous, take a little cold, rinse the lid and inner wall with water, and add 2 ml of hydrochloric acid solution to dissolve the residue warmly. Then transfer the whole amount to a 100 ml volumetric flask, dilute to volume, shake well, and set aside.
(3)
Cadmium sample digestion
The method for digestion of lead and tin is as follows. After the sample is digested, it is taken slightly cold. The lid and inner wall of the clamp are rinsed with water, and 1 ml of hydrochloric acid solution is added to dissolve the residue warmly. Then transfer the whole amount to a 50 ml volumetric flask, add 0.1% (Cd2 special analytical reagent) 2.5ml, dilute to volume, shake well, and set aside.
1.4
Standard curve, current carrying and reductant configuration
Table 1 Configuration of standard solutions of arsenic, antimony and antimony
Current carrying (5% HCl): 25 ml of concentrated hydrochloric acid was weighed and made up to 500 ml with ultrapure water.
Reducing agent (0.5% KOH + 2% KBH 4 ): Weigh accurately 2.5 g of potassium hydroxide dissolved in deionized water, and after confirming that potassium hydroxide is completely dissolved, accurately weigh 10 g of potassium borohydride into the solution. Make up to 500ml with deionized water, dissolve and shake. It is recommended to use the time, it is best not to save overnight, the preparation process can not be reversed.
Table 2 Lead standard solution configuration
Carrier (2% HCl): Measure 10 ml of concentrated hydrochloric acid and make up to 500 ml with ultrapure water.
Reducing agent (1% KOH+2%KBH 4 +1%K 3 Fe(CN) 6 ): Weigh accurately 5g of potassium hydroxide dissolved in deionized water, and then confirm that potassium hydroxide is completely dissolved, then accurately weigh 10g Potassium borohydride and 5 g of iron were placed in the solution, and the volume was made up to 500 ml with deionized water, dissolved and shaken. It is recommended to use the time, it is best not to save overnight, the preparation process can not be reversed.
Table 3 cadmium standard solution configuration
Carrier (2% HCl): Measure 10 ml of concentrated hydrochloric acid and make up to 500 ml with ultrapure water.
Reducing agent (0.5% KOH + 5% Cd1 special analytical reagent): first accurately weigh 2.5g potassium hydroxide dissolved in deionized water, after confirming that potassium hydroxide is completely dissolved, accurately weigh 25g of Cd1 special analytical reagent into the In the solution, dilute to 500 ml with deionized water, dissolve and shake. It is recommended to use the time, it is best not to save overnight, the preparation process can not be reversed.
Table 4 tin standard solution configuration
Carrier (2% HCl): Measure 10 ml of concentrated hydrochloric acid and make up to 500 ml with ultrapure water.
Reducing agent (0.5% KOH + 2% KBH 4 ): Weigh accurately 2.5 g of potassium hydroxide dissolved in deionized water, and after confirming that potassium hydroxide is completely dissolved, accurately weigh 10 g of potassium borohydride into the solution. Make up to 500ml with deionized water, dissolve and shake. It is recommended to use the time, it is best not to save overnight, the preparation process can not be reversed.
2,
Results and discussion
2.1
Linear equations and linear correlation coefficients of each element
The standard curve of each element was configured according to the method in 1.4, and the linear equation and linear correlation coefficient of each element were determined.
Table 5 Linear equations and linear correlation coefficients of each element
2.2
Test results and recovery rate
Table 6 Measured content and recovery rate of each element in three soil standards
By standard
6
The test results show that the recovery of arsenic, antimony and bismuth in the soil samples by the aqua regia bath method is
88.3%
-
91.8%
,
100%
-
105%
,
99.7%
-
102%
between. In the method of digesting soil samples with nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid to completely destroy the soil mineral lattice, the recovery rates of lead, cadmium and tin are respectively
95.2%
-
96.5%
,
93.5%
-
96.7%
,
94.3%
-
95.2%
.
2.3
Experimental considerations
2.3.1
The arsenic, antimony and antimony elements in the test soil samples were digested with aqua regia water bath. After the digestion, a certain amount of nitric acid was present in the digested solution. The nitric acid reacted with the thiourea and ascorbic acid to be added to the sample, thereby affecting the added thiourea and The reduction of ascorbic acid, so after the sample digestion is completed, low temperature heating is required to drive off the remaining nitric acid in the digestion solution.
2.3.2
When measuring lead, the acidity of the digestion solution should be strictly controlled, and the sample digestion solution should be heated and evaporated as much as possible.
2% HCl
Constant volume samples ensure that the acidity of the sample digestion solution and the acidity of the carrier are consistent.
2.3.3
In the standard solution of cadmium and cadmium soil digestion solution, it is necessary to add
Cd2
Special analytical reagents to increase the sensitivity of cadmium. The range of acidity of cadmium hydride reaction is narrow, and the acidity of the solution should be strictly controlled.
3,
in conclusion
In summary, the content of arsenic, antimony, bismuth, lead, cadmium and tin in soil was determined by hydride generation atomic fluorescence spectrometry. The results were accurate and reliable.
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