HJ 490-2009Water quality. Determination of silver. Spectrophotometry with cation 2B (English PDF)

3.8 EDTA-2Na solution, rho (EDTA-2Na)=0.05 mol/L. dissolve 1.86 g EDTA-2Na (C10H14N2O3Na2·2H2O)

In water, and dilute to 100 ml.

3.9 Sodium tetraborate solution, rho (Na2B4O7)=50 g/L. Dissolve 10 g of sodium tetraborate (Na2B4O7·10H2O) in water and dilute to 200 ml.

3.10 Qu Li Tong X-100 solution, rho (Qu Li Tong X-100) = 5% (volume fraction). 5 ml Qu Li Tong X-100 [Triton X-100, (CH3)3CCH2C(CH3)2-C6H4(OCH2CH2)nOHn~10] is dissolved in 95 ml of water and allowed to dissolve by heating.

3.11 Cadmium reagent 2B Ethanol solution, rho (cadmium reagent 2B) = 0.4 g/L. dissolve 0.080 g cadmium reagent 2B (4-nitronaphthyldiazoaminoazo) Benzene, O2NC10H6N. NNHC6H4N. NC6H5) In.200 ml of ethanol (3.5), add 2 drops of sodium hydroxide solution (3.7), use 4 the sand core funnel was filtered to remove insolubles.

3.12 Silver standard stock solution, rho (Ag)=1.00 mg/ml. accurately weigh 0.157 5 g silver nitrate (AgNO3), dissolve in appropriate amount of water, add 2 ml nitric acid solution (3.6). After dissolving, transfer to a 100 ml volumetric flask and dilute to the mark with water. Store in a brown glass bottle, protected from light, at least one month stable.

3.13 Silver standard solution, rho (Ag)=0.100 mg/ml. Transfer 10.00 ml of silver standard stock solution (3.12) to a 100 ml volumetric flask.

Add 2 ml of nitric acid solution (3.6) and dilute to the mark with water. Store in a brown glass bottle protected from light.

3.14 Silver standard solution, rho (Ag)=4.0 µg/ml. Transfer 20.00 ml silver standard solution (3.13) to a 500 ml volumetric flask for use Dilute the water to the mark and prepare it before use.

3.15 methyl orange solution, w (methyl orange) = 10%. Dissolve 0.010 g of methyl orange in water and dilute to 100 ml.

6.1 Acquisition and preservation

The water sample of silver was measured, collected and stored in a polyethylene bottle, and the water sample was acidified to pH 1-2 with concentrated nitric acid and analyzed as soon as possible.

Wastewater from the production of photosensitive materials, film processing, silver plating, etc., no acid is added after sample collection, and analysis is performed immediately.

Water samples collected should be protected from light.

6.2 Preparation of samples

Unless it is proved that the pretreatment of the sample is unnecessary, the sample may be directly prepared for colorimetry, otherwise the pretreatment should be carried out as follows.

Take 25.0 ml of the homogeneous sample in a 100 ml beaker. If the concentration of silver exceeds 0.8 mg/L, the sample may be appropriately reduced and diluted with water until 25 ml. In the sample, 4 ml of nitric acid (3.1), 1 ml of sulfuric acid (3.2) and 0.5 ml of hydrogen peroxide (3.4) were added in sequence. On the hot plate Heat slowly to white smoke. After removing the cooling, add 1 ml of perchloric acid, cover the watch glass, and continue to heat until near dry. After cooling, add 0.5 ml Nitric acid (3.6), rinse the cup wall with a little water and dissolve the residue slightly. Then, carefully wash into a 25 ml volumetric flask, the volume of the solution should not exceed Over 15 ml.

Samples with precipitates or suspended solids, such as photosensitive materials, printing waste water, etc., should be sampled as evenly as possible.

The sample is complex, contains more organic matter, or precipitates, and can be repeatedly digested with nitric acid. Compared with clean samples, nitric acid and perchloric acid are eliminated.

Just solve it. In the digestion process, it is not suitable to evaporate. Otherwise, silver has a loss.

That is, the water sample is acidified to pH 1-2 using concentrated nitric acid, which is not suitable for storage, and should be analyzed as soon as possible. Especially for printing wastewater, after sample collection, Samples should be prepared for analysis without acid.

7.1 Calibration curve

7.1.1 Add 0.00, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00 ml silver standard solution (3.14) to each of the 7 25 ml volumetric flasks.

7.1.2 Add 0.5 ml of EDTA-2Na solution (3.8) to the above volumetric flask, add 1 drop of methyl orange indicator (3.15), and use hydrogen and oxygen.

The sodium solution (3.7) was adjusted until the indicator just turned yellow. Add 2 ml of sodium tetraborate solution (3.9), 1.0 ml of Triton X-100 solution (3.10) and 1.5 ml cadmium reagent 2B ethanol solution (3.11). Dilute to the mark with water and shake well. After 10 min, use 10 mm colorimetric the dish was measured at 554 nm and the absorbance was measured. The absorbance of the reagent blank (zero concentration) was measured with water as a reference. To subtract the reagent empty the absorbance after white (zero concentration) is plotted against the silver content (µg).

7.2 Sample determination

Accurately pipette 1 to 15 ml of the test sample (depending on the silver content in the water) in a 25 ml volumetric flask, as described below in 7.1.2. From the calibration curve the amount of silver in the sample is determined online or calculated using a regression equation.

9.1 Repeatability

The relative standard deviation of repeatability was 2.2%.

9.2 Reproducibility

The relative standard deviation of reproducibility was 4.0%.

9.3 Accuracy

The relative error is -0.2%.