Atomic Absorption Spectrometry (2)

2.

(1) Scope of application

It is suitable for the determination of barium in solid waste leachate and total barium in solid waste

(2) Method principle

The solid waste leachate or solid waste is digested and injected into the graphite furnace atomizer.

(3) Reagents and materials

(1) Deionized water: first-grade pure water

(2) Sulfuric acid , nitric acid , hydrochloric acid , oxyfluoric acid , perchloric acid , and hydrogen peroxide are all top grade pure

(3) Barium standard stock solution, 1000mg/L: Purchase a standard solution with a national standard material certificate

(4) Barium standard intermediate solution, 10mg/L: Pipette 10.

(5) Barium standard use solution, 1mg/L: Pipette 10.

(4) Instruments and equipment

(1) Graphite furnace atomic absorption spectrometer with barium hollow cathode lamp and pyrolytic graphite tube

(2) Electric heating plate: with constant temperature function

(3) Microwave digestion instrument: output power 1000～1600W

(4) Digestion tank: a closed tank made of fluorocarbon (soluble polytetrafluoroethylene PFA or modified polytetrafluoroethylene TFM), which can resist pressure (170-200psi), acid and corrosion, and has pressure relief Function

(5) Analytical balance: the accuracy is 0.

(6) Triangular flasks, small glass funnels, PTFE crucibles, volumetric flasks and other common laboratory instruments and equipment

Note: All conical flasks, volumetric flasks, pipettes and other glassware used in the experiment were soaked in 10% dilute nitric acid overnight, rinsed with deionized water, and dried

(5) Analysis and testing

1.

The solid waste leachate is in accordance with "Solid waste leaching toxicity leaching method: sulfuric acid and nitric acid method" (HJ/T299), "solid waste leaching toxicity leaching method acetic acid buffer solution method" (HJ/T300), "solid waste leaching toxicity leaching method horizontal oscillation method" (HJ557) to prepare
.

Take HJ/T299-2007 as an example to prepare the extractant: add a mixture of concentrated sulfuric acid and concentrated nitric acid with a mass ratio of 2:1 to pure water (about 2 drops of 1L water) to make the pH 3.
20
.
After the sample is crushed and sieved, according to the moisture content of the sample, calculate and add the volume of the required extract at a liquid-to-solid ratio of 10:1 (L/kg), adjust the speed to 30r/min, and oscillate at 23°C for 18h
.
Filter after the above steps
.
Perform digestion according to the electric hot plate digestion method or microwave digestion method, and transfer to a 25mL volumetric flask after cooling, dilute to the mark with pure water, and shake well for testing
.

2.
Solid waste

Weigh 0.
5g of sample (accurate to 0.
1mg) that has passed a 100-mesh sieve into a polytetrafluoroethylene crucible or digestion tank, moisten it with a small amount of water, and add an appropriate amount of hydrochloric acid, nitric acid, hydrofluoric acid, and perchloric acid in the order required by the method.
Perform digestion according to the electric hot plate digestion method or microwave digestion method, transfer to a 50mL volumetric flask after cooling, and dilute to the mark with experimental water, shake well for testing
.

3.
Instrument measurement conditions

The temperature setting of the graphite furnace is shown in Table 5-2, and the reference measurement conditions of the instrument are shown in Table 5-3
.

Table 5-2 Graphite furnace temperature setting

Table 5-3 Instrument reference measurement conditions

4.
Standard curve

Pipette 1mg/L barium standard solution 0mL, 0.
50mL, 1.
00mL, 2.
00mL, 3.
00mL, 4.
00mL, 5.
00mL into a 100mL volumetric flask, dilute to the mark with nitric acid solution (1+99), shake well
.
This standard series contains 0ug/L, 5.
0ug/L, 10.
0ug/L, 20.
0ug/L, 30.
0ug/L, 40.
0ug/L, 50.
0ug/L
.
According to the measurement conditions of the instrument, add 20uL standard solution to the graphite tube from low mass concentration to high mass concentration to measure the absorbance
.
Use the corresponding absorbance as the ordinate and the mass concentration of the barium standard series as the abscissa to draw a barium calibration curve
.

Refer to Table 5-4 for the reference standard curve, the correlation coefficient is greater than 0.
999, Abs=0.
01330C+0.
07007
.

Table 5-4 Standard Curve Series

5.
Blank experiment and detection limit

Under the same conditions as drawing the calibration curve, take 11 blank samples to be tested prepared by the same operation as the sample, measure the absorbance of the laboratory blank, and check the barium content on the calibration curve from the absorbance value
.
Refer to Table 5-5 for reference data
.
The relative deviation of the determination result of the extract is 0.
46ug/L, and the detection limit of the calculated method is 1.
27ug/L; the relative deviation of the total digestion determination result is 1.
91ug/L, and the detection limit of the calculated method is 6.
43ug/L (16.
8mg/L).
kg)
.

Table 5-5 Blank experiment results

Note: The detection limit of the method is MDL=SD×t(n-1.
99%), where t(5.
9%)=3.
365 and t(10.
90%)=2.
764 are found by looking up the table
.

6.
Method precision

The relative standard deviation in the laboratory of the solid waste sample leaching liquid electric heating plate method is 0.
87% to 13%; the relative standard deviation among the laboratories is 14%
.
The relative standard deviation of the leaching liquid microwave method in the laboratory is 1.
6% to 7.
0%; the relative standard deviation between the laboratories is 8%
.

The relative standard deviation in the laboratory of the total digestion liquid electric heating plate method for solid waste samples is 1.
5% to 8.
6%; the relative standard deviation between laboratories is 3.
3%
.
The relative standard deviation in the laboratory of the complete digestion solution microwave method is 2.
9% to 8.
4%; the relative standard deviation among the laboratories is 5.
4%
.

It was verified that the relative standard deviations of the determination results of the extract and total digestion were 10.
1% and 7.
6%
.
The results are shown in Table 5-6
.

Table 5-6 Method precision

7.
Recovery rate determination

For standard samples CSS-4 and CSS-5 in different laboratories, the relative errors of the fully digested electric heating plate method were -8.
0%～1.
9%, -5.
4%～1.
0%; the relative errors of the complete digestion microwave method were -6.
6%～2.
3 %, -5.
4%～1.
7%
.

Different laboratories measured the recovery rate of standard addition of solid waste samples.
The recovery rate of the addition of the electrothermal plate method of the leachate was 78.
0%~110%, and the recovery rate of the addition of the leachate by the microwave method was 79.
0%~101%
.

To verify the standard addition recovery determination of the extract, the standard addition amount is 20.
0ug/L
.
The recovery rate is 82.
0%～125%, and the measurement results are shown in Table 5-7
.
Because the mass concentration of the total digestion sample was too high, the spike recovery test was not carried out
.

Table 5-7 Recovery rate measurement results

Related Links: Atomic Absorption Spectrometry (1)