HJ 737-2015Soil and sediment. Determination of total beryllium. Graphite furnace atomic absorption spectrophotometry (English PDF)

7.1 Sample collection and storage

According to the relevant provisions of HJ/T 166 collection and preservation of soil samples; in accordance with GB 17378.3 and HJ/T 91 of the relevant provisions of mining Set and store sediment samples.

7.2 Sample preparation

According to the requirements of HJ/T 166 and GB 17378.3, the collected samples were air-dried, coarsely and finely ground in the laboratory Pore size 0.15 mm (100 mesh) sieve. Sample collection, transport, preparation and preservation should avoid contamination and loss of element to be measured.

7.3 Sample preparation

7.3.1 Electric plate digestion method

Weigh the sample 0.1 ~ 0.3 g (accurate to 0.1 mg) in 50 ml polytetrafluoroethylene crucible, wet with water and add l0 ml Hydrochloric acid (5.1), in the fume hood on the hot plate at low temperature (95 ± 5 °C) heating, so that the initial decomposition of the sample, to be evaporated to about 3 ml (5.2), 5 ml of hydrofluoric acid (5.3), capped on the hot plate at the temperature (120 ± 5 °C) heating 0.5 ~ 1 h, After cooling, add 2 ml of perchloric acid (5.4), capped at medium temperature for 1 h, open the cover fly silicon (in order to achieve good flying silicon effect, should Often shake the crucible), when heated to take a thick perchloric acid white smoke, stamped, so that the black organic carbide decomposition. To be on the wall of the crucible Black organic matter disappeared, open the lid, drive white smoke (temperature control at 140 ± 5 °C) and steamed to near dry (hot observation of the content was Non-flowing liquid beads). As the digestion, can add 3 ml of nitric acid (5.2), 3 ml of hydrofluoric acid (5.3), 1 ml Perchloric acid (5.4), repeat the above digestion process. Remove the crucible slightly cold, add 1 ml of nitric acid solution (5.5), warm dissolved can be Soluble residue, transferred to 50 ml volumetric flask, the water volume to the mark, shake, stored in the polyethylene bottle.

Some soil and sediment organic matter content is high, should increase the amount of nitric acid; in the digestion process, should pay attention to observe, the 3 kinds of acid dosage and digestion time visualization of the situation as appropriate increase or decrease; hot plate temperature should not be too high to prevent the polytetrafluoroethylene crucible change Shape and sample evaporated.

7.3.2 Microwave digestion method

Weigh the sample 0.1 ~ 0.3 g (accurate to 0.1 mg) in the microwave digestion tank, with a small amount of water wet after adding 6 ml of nitric acid (5.2) 2 ml hydrochloric acid (5.1), 2 to 5 ml hydrofluoric acid (5.3), digested according to a certain warming procedure (see Table 1), after cooling (or Transfer the solution to 50 ml of polytetrafluoroethylene crucible) Add 1.0 ml of perchloric acid (5.4), heat on a hot plate, System at 150 ° C, heated to take a thick perchloric acid white smoke and the contents were not flow state, remove the crucible slightly cold, add 1 ml of nitrate Acid solution (5.5), dissolve the soluble residue in warm, transfer to 50 ml volumetric flask, water volume to the mark, shake, save in Polyethylene bottle.

Table 1 Microwave digestion temperature program reference table

Heating time (min) Digestion temperature (°C) Holding time (min) 7 room temperature ~ 120 3 5 120 ~ 160 3 5 160 ~ 190 25

7.4 Preparation of laboratory blanks

Instead of the sample with deionized water, the same procedure and reagents were prepared using the sample to prepare a laboratory blank.

7.5 Determination of dry matter content and moisture content of samples

The dry matter content of soil samples was determined according to HJ 613. The moisture content of the sediment samples was determined according to GB 17378.5.

8.1 Instrument reference measurement conditions

According to the instrument specification requirements to select the measurement conditions, the instrument reference measurement conditions in Table 2.

Table 2 Instrument reference measurement conditions

Element Be

Determination of wavelength (nm) 234.9 Passband width (nm) 0.5 Drying temperature (°C)/time (s) 85 ~ 120/55 Ashing temperature (°C)/time (s) 1200 ~ 1400/10 ~ 15 Atomization temperature (°C)/time (s) 2600/2.9 Clear temperature (°C)/time (s) 2650/2 Whether the atomic phase is stopped Argon flow rate (ml/min) 300 Injection volume (µl) 20 (autosampler or manual injection) Substrate modifier addition (µl) 2

8.2 Calibration curve

Accurate removal of beryllium standard use of liquid (5.10) 0.00,0.50,1.00,2.00,3.00,4.00 ml in 10 ml volumetric flask, 4 with nitric acid solution (5.7) constant volume shake. The concentration of beryllium in this standard series is 0,0.50,1.00,2.00,3.00,4.00 µg/L.

According to the instrument measurement conditions (8.1), from the low concentration to high concentration followed by adding 20 µl of the standard solution to the graphite tube and 2 µl of the base solution Addition (5.11), measuring absorbance. With the corresponding absorbance as the ordinate to beryllium standard series of mass concentration for the abscissa, drawing beryllium of the calibration curve.

8.3 Determination

The laboratory blank and the absorbance of the sample were measured under the same conditions as the calibration curve. By the absorbance value in the calibration song Check the beryllium content online. If the sample is diluted before the measurement, the measurement result should be multiplied by the corresponding dilution factor.

9.1 Results calculation

9.1.1 Calculation of soil samples

The content of beryllium in the soil omega1 (mg/kg) calculated according to formula (1).

Dmwm

Where. 1 - the content of beryllium in the soil, mg/kg;

- Check the calibration curve to determine the mass concentration of beryllium in the test solution, µg/L;

0 - mass concentration of beryllium in blank solution, µg/L;

V - the volume of the sample volume, ml;

M - the quality of the sample, g;

Dmw - dry matter content of soil samples,%.

9.1.2 Calculation of the results of sediment samples

Sediment beryllium content omega2 (mg/kg) calculated according to formula (2).

2 10) 1 (

Where. 2 - the content of beryllium in the sediment, mg/kg;

- Mass concentration of beryllium in the test solution from the calibration curve, µg/L;

0 - mass concentration of beryllium in blank solution, µg/L;

V - the volume of the sample volume, ml;

M - the quality of the sample, g;

F - sediment sample moisture,%.

9.2 The result is shown when the determination result is less than 1.00 mg/kg, two digits after the decimal point are retained; when the result is greater than or equal to 1.00 mg/kg, Keep three valid digits.

10.1 Precision

5 laboratory tests were carried out on the actual soil samples (chernozem) and sediment samples (Songhua River sediments) (N = 6), the results show that.

The relative standard deviations in the laboratory range from 2.8% to 12% and 1.2% to 9.1%, respectively;

The relative standard deviations were 7.3% and 8.4%, respectively.

The reproducibility limits (r) were 0.465 mg/kg and 0.419 mg/kg, respectively;

Reproducibility limits (R) were 0.665 mg/kg and 0.736 mg/kg, respectively.

10.2 Accuracy

Seven samples of soil were tested for soil standard samples with a concentration of 2.0 ± 0.4 mg/kg and a concentration of 1.8 ± 0.3 mg/kg the relative error of the standard samples is -18% ~ 9.2% and -13% ~ 13% respectively. The mean values of the relative errors are (-5.7% ± 22%) and (0.8% ± 17.6%).