HJ 1191-2021Water quality Determination of azide spectrophotometric method (English PDF)

5.2 Presence of NO2 in the sample

-, it interferes with the determination of azide, which can be eliminated by adding ammonium sulfamate before distillation. 5.0 ml Ammonium Sulfamate the solution (6.12) can eliminate 25.0 mg/L of NO2-interference.

6.13 Standard stock solution of sodium azide. rho(N3

)=1.00 g/L.

Accurately weigh 0.1548 g of sodium azide (6.4), dissolve it with a small amount of sodium hydroxide solution (6.8), transfer it to a 100 ml volumetric flask and Dilute to the mark with sodium hydroxide solution (6.8), shake well, and store in a polyethylene bottle. Refrigerated below 4 °C and protected from light can be stored for 3 months.

6.14 Standard solution of sodium azide. rho(N3

)=25.0 mg/L.

Pipette 2.50 ml sodium azide standard stock solution (6.13) into a 100 ml volumetric flask, dilute it with sodium hydroxide solution (6.8) to Line, shake. Ready to use.

6.15 Glass beads. 4 mm to 6 mm in diameter.

8.1 Sample Collection

Collect the sample in the sampling bottle (7.1) according to the relevant regulations of HJ/T 91, HJ 91.1 and HJ 164, and the sample volume is not less than 500 ml.

8.2 Sample Storage

After sample collection, add an appropriate amount of sodium hydroxide solution (6.6) to adjust the pH value of the sample to 9-11, store it at room temperature in the dark, and finish it within 3 days.

into analysis.

8.3 Preparation of test specimens

Measure 150 ml of sample, transfer it into a distillation flask, add 5.0 ml of ammonium sulfamate solution (6.12), put in several glass beads (6.15), Insert the distillate catheter into the receiving bottle (7.5) containing 10.0 ml of sodium hydroxide solution (6.7), making sure that the catheter is submerged below the liquid surface. Open Condensate the water, add 2.0 ml of hydrochloric acid solution (6.9) to the distillation flask, and quickly close the stopper of the distillation flask. Turn on the electric furnace (7.3), adjust the power rate, slowly raise the temperature, control the distillate to distill out at a rate of 2 ml/min to 3 ml/min, and stop when the distillate in the receiving bottle is close to 100 ml heating. Rinse the distillate conduit with a small amount of water, pour it into the receiving bottle, and make up to 100 ml for testing. The distillation process is controlled within 30 min to 45 min appropriate. The schematic diagram of the apparatus is shown in Figure 1.

8.4 Preparation of blank samples

Replace the sample with experimental water, add an appropriate amount of sodium hydroxide solution (6.6) to adjust the pH of the sample to 9-11, according to the preparation of the sample (8.3) The same procedure is used for the preparation of laboratory blank samples.

9.1 Establishment of standard curve

Take 6 stoppered colorimetric tubes (7.6), add 0.00 ml, 0.20 ml, 0.80 ml, 2.00 ml, 4.00 ml, 6.00 ml of azide respectively Sodium standard use solution (6.14), immediately add sodium hydroxide solution (6.8) to 10.0 ml, and prepare the azide mass concentration of 0.00 mg/L, Standard series solutions of 0.50 mg/L, 2.00 mg/L, 5.00 mg/L, 10.0 mg/L, 15.0 mg/L. Add 0.5 ml to each colorimetric tube Ferric perchlorate solution (6.11), close the stopper tightly and shake well. At a wavelength of 454 nm, using a 10 mm optical path cuvette, with water as a reference, measure the absorbance of each standard series solution was measured, and the measurement was completed within 20 min. Take the mass concentration (mg/L) of azide in each standard series solution as the abscissa is the ordinate, and the absorbance corresponding to the reagent blank (zero concentration) is taken as the ordinate, and a standard curve is established.

Note. The color reaction is carried out at room temperature, above 40 °C will affect the determination.

9.2 Sample Determination

Pipette 10.0 ml of the sample (8.3) into a stoppered colorimetric tube (7.6), and follow the same steps as for establishing a standard curve (9.1).

Determination of samples.

Note. If the determination result exceeds the highest concentration point of the standard curve, the sample should be diluted and the sample should be re-prepared according to the steps of sample preparation (8.3).

9.3 Blank test

Carry out the determination of the laboratory blank sample (8.4) following the same procedure as for the determination of the sample (9.2).

10.1 Result calculation

The mass concentration (mg/L) of azide (calculated as azide) in the sample is calculated according to formula (1).

10.2 Result representation

The number of decimal places of the determination results is consistent with the detection limit, and a maximum of 3 significant figures are reserved.

11.1 Precision

Blank spiking of azide (as azide) at 0.50 mg/L, 4.00 mg/L and 8.00 mg/L by six laboratories the samples were repeatedly determined for 6 times. the relative standard deviations in the laboratory were 2.0%-9.5%, 0.9%-5.0% and 0.4%-3.7%, respectively;

The inter-laboratory relative standard deviations were 4.2%, 2.2% and 2.5%, respectively; the repeatability limits were 0.08 mg/L, 0.34 mg/L and 0.45 mg/L, respectively;

The reproducibility limits were 0.09 mg/L, 0.40 mg/L and 0.67 mg/L, respectively.

Surface water samples spiked with azide (as azide) at concentrations of 0.50 mg/L, 4.00 mg/L and 8.00 mg/L by six laboratories the samples were tested 6 times repeatedly. the relative standard deviations in the laboratory were 3.6%-7.7%, 1.0%-5.5% and 0.6%-3.3%, respectively;

The inter-chamber relative standard deviations were 6.0%, 2.8%, and 2.4%, respectively; the repeatability limits were 0.08 mg/L, 0.33 mg/L, and 0.56 mg/L, respectively;

The limit of detection was 0.11 mg/L, 0.43 mg/L and 0.76 mg/L, respectively.

Groundwater samples spiked with azide (as azide) at concentrations of 0.50 mg/L, 4.00 mg/L and 8.00 mg/L by six laboratories the samples were tested 6 times repeatedly. the relative standard deviations in the laboratory were 2.3%-9.9%, 1.0%-3.7% and 0.5%-4.0%, respectively;

The inter-chamber relative standard deviations were 5.8%, 3.6%, and 2.0%, respectively; the repeatability limits were 0.08 mg/L, 0.24 mg/L, and 0.49 mg/L, respectively;

The limit of detection was 0.10 mg/L, 0.44 mg/L and 0.63 mg/L, respectively.

Six laboratories added azide (calculated as azide) to domestic sewage with concentrations of 0.50 mg/L, 4.00 mg/L and 8.00 mg/L the samples were repeatedly determined for 6 times. the relative standard deviations in the laboratory were 4.2%-10.3%, 0.5%-4.7% and 0.4%-4.2%, respectively;

The interlaboratory relative standard deviations were 5.8%, 3.4% and 2.6%, respectively; the repeatability limits were 0.08 mg/L, 0.25 mg/L and 0.48 mg/L, respectively;

The reproducibility limits were 0.10 mg/L, 0.43 mg/L and 0.71 mg/L, respectively.

The average concentration of azide (calculated as azide root) in the six laboratories was 1.31 mg/L, and the standard concentration was 0.50 mg/L and 4.00 mg/L.

and 8.00 mg/L industrial wastewater spiked samples were determined repeatedly for 6 times. the relative standard deviations in the laboratory were 2.2%-8.8%, 0.9%-6.9%, 0.7%-5.9% and 0.5%-3.2%; the relative standard deviations among laboratories were 9.1%, 6.6%, 1.7% and 1.4%, respectively;

The repeatability limits were 0.17 mg/L, 0.18 mg/L, 0.45 mg/L and 0.45 mg/L, respectively; the reproducibility limits were 0.37 mg/L, 0.37 mg/L, 0.48 mg/L and 0.54 mg/L.

11.2 Correctness

Surface water samples spiked with azide (as azide) at concentrations of 0.50 mg/L, 4.00 mg/L and 8.00 mg/L by six laboratories the samples were subjected to 6 repeated standard addition analysis and determination. the standard addition recoveries were 90.0% to 104%, 91.0% to 98.5% and 92.2% to 98.8%, respectively;

The final values of the spiked recoveries were 98.3%±12%, 96.3%±5.6% and 96.6%±4.8%, respectively.

Groundwater samples spiked with azide (as azide) at concentrations of 0.50 mg/L, 4.00 mg/L and 8.00 mg/L by six laboratories the samples were subjected to 6 repeated standard addition analysis and determination. the standard addition recoveries were 88.0%-102%, 89.0%-102% and 93.4%-99.1%, respectively;

The final values of the spiked recoveries were 94.3%±12%, 95.8%±7.2% and 96.8%±4.0%, respectively.

Six laboratories added azide (calculated as azide) to domestic sewage with concentrations of 0.50 mg/L, 4.00 mg/L and 8.00 mg/L the samples were subjected to 6 repeated standard addition analysis and determination. the standard addition recoveries ranged from 88.0% to 98.0%, 90.5% to 99.0% and 92.5% to 92.5% to 92.5%.

99.4%; the final recovery of standard addition was 90.3%±12%, 95.5%±6.8% and 95.7%±5.2%, respectively.

The average concentration of azide (calculated as azide root) in the six laboratories was 1.31 mg/L, and the standard concentration was 0.50 mg/L and 4.00 mg/L.

and 8.00 mg/L industrial wastewater fortified samples were subjected to 6 repeated standard addition analysis and determination. the recovery rates of the standard addition ranged from 88.0% to 96.0%, respectively.

94.5%~98.0% and 93.0%~98.9%, the final recovery of standard addition was 93.0%±6.6%, 96.3%±2.4% and 96.4%±4.4%, respectively.