HJ 503-2009Water quality. Determination of volatile phenolic compounds. 4-AAP spectrophotometric method (English PDF)

5.1 Elimination of oxidants (such as free chlorine)

The sample appeared blue on the starch-potassium iodide test paper (6.23), indicating the presence of oxidant, and an excess of ferrous sulfate (6.2) could be added.

Remove.

5.2 Elimination of sulfides

When there is a black precipitate in the sample, a drop of the sample may be placed on the lead acetate test paper (6.24). If the test paper turns black, it indicates that there is a sulfide.

presence. At this time, the sample was further added with phosphoric acid, and the aeration chamber was stirred and aerated until the generated hydrogen sulfide completely escaped.

5.3 Elimination of organic or inorganic reducing substances such as formaldehyde and sulfite

The appropriate amount of the sample can be separated into a separatory funnel, and the sulfuric acid solution (6.11) is added to make it acidic, and 50, 30, and 30 ml of diethyl ether (6.5) are added in portions.

To extract phenol, combine the ether layer into another separatory funnel, and add 4, 3, 3 ml of sodium hydroxide solution (6.12) in portions to carry out back extraction.

The phenols are transferred to a sodium hydroxide solution. Combine the alkali extract, transfer to a beaker, warm on a water bath to remove residual ether, then use water (6.1) Dilute the alkali extract to the original sample volume.

At the same time, water (6.1) should be used as a blank test.

5.4 Elimination of oils

After the sample is allowed to stand to separate the oil slick, follow the 5.3 procedure.

5.5 Elimination of anilines

Aniline can react with 4-aminoantipyrine to interfere with the determination of phenol, generally under acidic conditions (pH6 reagents and materials the reagents used in this standard are analytically purified according to national standards unless otherwise stated. The experimental water is newly prepared.

Distilled or deionized water.

6.1 phenol-free water. phenol-free water can be prepared according to 6.1.1 or 6.1.2. Phenolic-free water should be stored in glass bottles. When used, avoid with rubber.

The product (rubber plug or latex tube, etc.) is in contact.

6.1.1 Add 0.2 g of activated carbon powder activated at.200 ° C for 30 min per liter of water, shake well, place overnight, and use double-layer medium speed.

Filter paper filter.

6.1.2 Add sodium hydroxide to make the water strong alkaline, and add potassium permanganate until the solution is purple-red, and transfer it to the whole glass distiller for heating and distillation.

Collect the distillate for use.

6.2 Ferrous sulfate (FeSO4·7H2O).

6.3 Potassium iodide (KI).

6.4 Copper sulfate (CuSO4·5H2O).

6.5 Ethyl ether (C4H10O).

6.6 Trichloromethane (CHCl3).

6.7 Refined phenol. Take phenol (C6H5OH) in a distillation flask with an air condenser, heat and distill it, and collect the distillation at 182-184 °C.

After the fraction is cooled, the fraction should be colorless crystals, stored in a brown bottle, and sealed in a cool dark place.

6.8 Ammonia. rho (NH3·H2O) = 0.90 g/ml.

6.9 Hydrochloric acid. rho (HCl) = 1.19 g/ml.

6.10 Phosphoric acid solution, 19.

6.11 Sulfuric acid solution, 14.

6.12 Sodium hydroxide solution. rho (NaOH) = 100 g/L. Weigh 10 g of sodium hydroxide dissolved in water and dilute to 100 ml.

6.13 Buffer solution. pH = 10.7. Weigh 20 g of ammonium chloride (NH4Cl) dissolved in 100 ml of ammonia water (6.8), stuffed in a refrigerator, and placed in the refrigerator.

save. In order to avoid the change of pH caused by the volatilization of ammonia, it should be stored at low temperature, and it should be closed immediately after use, and Formulated in appropriate amount.

6.14 4-aminoantipyrine solution. Weigh 2 g of 4-aminoantipyrine dissolved in water, dissolved and transferred to a 100 ml volumetric flask.

Release to the marking line, purify according to Appendix B, collect the filtrate and store in the refrigerator for 7 days.

6.15 Potassium ferricyanide solution. rho (K3[Fe(CN)6]) = 80 g/L. Weigh 8 g of potassium ferricyanide dissolved in water, dissolve it and transfer it to a 100 ml volumetric flask.

Dilute to the mark with water. Store in the refrigerator for one week.

6.16 Potassium bromate-potassium bromide solution. c (1/6KBrO3) = 0.1 mol/L. Weigh 2.784 g of potassium bromate dissolved in water, add 10 g of potassium bromide, dissolve After dissolving, transfer to a 1 000 ml volumetric flask and dilute to the mark with water.

6.17 sodium thiosulfate solution. c (Na2S2O3) ~ 0.012 5 mol/L. Weigh 3.1 g of sodium thiosulfate, dissolve in boiling water, add Add 0.2 g of sodium carbonate, dissolve it, transfer it to a 1 000 ml volumetric flask, and dilute to the mark with water. Before use, it is calibrated according to GB 7489-87.

6.18 Starch solution. rho = 0.01 g/ml. Weigh 1 g of soluble starch, make a paste with a small amount of water, add boiling water to 100 ml, and after cooling, Transfer to the reagent bottle and store in the refrigerator.

6.19 phenol standard stock solution. rho (C6H5OH) ~ 1.00 g/L. Weigh 1.00 g of refined phenol (6.7), dissolve in water (6.1), and transfer Dilute to the mark with water (6.1) in a 1 000 ml volumetric flask. Calibrate according to Appendix A. Refrigerated in the refrigerator for stable storage for one month.

6.20 Phenol standard intermediate. rho (C6H5OH) = 10.0 mg/L. Take appropriate amount of phenol standard stock solution (6.19) and dilute to 100 ml with water (6.1) in the volumetric flask, it is prepared on the same day of use.

6.21 Phenol standard use solution. rho (C6H5OH) = 1.00 mg/L. Measure 10.00 ml of phenol standard intermediate (6.20) in a 100 ml volumetric flask in the middle, dilute to the mark with water (6.1) and use it within 2 hours after preparation.

6.22 Methyl orange indicator solution. rho (methyl orange) = 0.5 g/L. Weigh 0.1 g of methyl orange dissolved in water, dissolve it and transfer it to a.200 ml volumetric flask.

Dilute to the mark with water.

6.23 Starch-potassium iodide test paper. Weigh 1.5 g of soluble starch, stir it into a paste with a small amount of water, add.200 ml of boiling water, mix well, let cool, Add 0.5 g potassium iodide and 0.5 g sodium carbonate, dilute to 250 ml with water, immerse the filter paper strip, take it out and dry it in a brown bottle.

Save the plug.

6.24 Lead acetate test paper. Weigh 5 g of lead acetate, dissolve in water, and dilute to 100 ml. Dip the filter paper into the above solution and take it after 1 h.

Dry out, in a jar, preserved.

6.25 pH test paper. 1 to 14.

8.1 Sample Collection

Sample collection is performed in accordance with the relevant regulations of HJ/T 91.

At the sample collection site, the starch-potassium iodide test paper (6.23) was used to detect the presence or absence of oxidants such as free chlorine in the sample. If the test paper changes Blue, should be added in time to remove excess ferrous sulfate (6.2).

The sample collection should be greater than 500 ml and stored in a hard glass bottle.

The sample after collection should be acidified to pH about 4.0 in time, and an appropriate amount of copper sulfate (6.4) is added to make the mass concentration of copper sulfate in the sample about it is 1 g/L to inhibit the biooxidation of phenols by microorganisms.

8.2 Sample storage

The collected samples should be refrigerated at 4 ° C and measured within 24 h.

9.1 Pre-distillation

Transfer 250 ml sample into 500 ml full glass distiller, add 25 ml water (6.1), add several glass beads to prevent bumping, add more Drop the methyl orange indicator solution (6.22). If the sample is not orange-red, continue to add phosphoric acid solution (6.10).

Connect the condenser, heat the distillation, and collect 250 ml of distillate into the volumetric flask.

During the distillation process, if the methyl orange red color is found to fade, it should be allowed to cool after the end of the distillation, and then add 1 drop of methyl orange indicator solution (6.22).

If the residue is not acidic after distillation, it should be resampled, and the amount of phosphoric acid solution (6.10) added is increased to carry out distillation.

Note 1. The distillation equipment used should not be mixed with distillation equipment for measuring industrial wastewater or domestic sewage. The entire distillation unit should be cleaned before and after each test.

Note 2. Do not use rubber stoppers or rubber hoses to connect the distillation flask and condenser to prevent interference with the measurement.

9.2 Color rendering

Transfer 250 ml of distillate into a separatory funnel, add 2.0 ml of buffer solution (6.13), mix, pH 10.0 ± 0.2, add 1.5 ml 4-aminoantipyrine solution (6.14), mix well, add 1.5 ml potassium ferricyanide solution (6.15), mix well, close the plug, place 10 min.

9.3 Extraction

Accurately add 10.0 ml of chloroform (6.6) in the above-mentioned color development (9.2) separatory funnel, tightly shake, shake vigorously for 2 min, and place it upside down.

Gas, standing layered. Dry the inner wall of the neck of the separatory funnel with dry absorbent cotton or filter paper, and stuff a small group of dry absorbent cotton or filter paper into the neck tube to dichlorochloride.

The methane layer is passed through a dry skim cotton or filter paper, and after discarding the first few drops of the extract, the remaining chloroform is directly placed into the optical path of 30.

Mm in the cuvette.

9.4 Absorbance measurement

The absorbance of the chloroform layer was determined at 460 nm using chloroform (6.6) as a reference.

9.5 Blank test

Replace the sample with water (6.1) and measure the absorbance according to steps 9.1 to 9.4. The blank should be measured simultaneously with the sample.

9.6 Calibration

9.6.1 Preparation of the calibration series

Add 100 ml of water (6.1) to a set of 8 separatory funnels, and add 0.00, 0.25, 0.50, 1.00, 3.00, 5.00, 7.00 and 10.00 ml of phenol standard solution (6.21), then add water (6.1) to 250 ml.

The measurement was carried out in accordance with the steps 9.2 to 9.4.

9.6.2 Drawing of the calibration curve

The absorbance value measured by the calibration series is subtracted from the absorbance value of the zero-concentration tube, and the curve of the absorbance value to the phenol content (µg) is plotted.

The correlation coefficient of the quasi-curve regression equation should be above 0.999.

11.1 Precision

Five laboratories measured uniform samples containing phenolic concentrations of 0.004 0, 0.020 0, and 0.036 0 mg/L.

The relative standard deviations in the experimental room were. 7.4% to 10.1%, 3.3% to 4.5%, and 1.8% to 2.3%;

The relative standard deviations between laboratories were. 2.9%, 2.3%, 1.3%;

The repeatability limits were. 0.001 0 mg/L, 0.002 3 mg/L, 0.002 0 mg/L;

The reproducibility limits were. 0.001 0 mg/L, 0.002 3 mg/L, and 0.001 8 mg/L, respectively.

11.2 Accuracy

Five laboratories measured standard substances with a phenol concentration of (45.5 ± 3.6) µg/L.

The relative error is. -2.6% to 3.5%;

The final error is. 1.8% ± 5.0%.

18.1 Pre-distillation

See 9.1.

18.2 Color development

Distill 50 ml of the distillate into a 50 ml colorimetric tube, add 0.5 ml of buffer solution (6.13), and mix, at this time, the pH value is 10.0±0.2.

Add 1.0 ml of 4-aminoantipyrine solution (6.14), mix well, add 1.0 ml of potassium ferricyanide solution (6.15), mix well, close the plug, Leave for 10 min.

18.3 Absorbance measurement

At 510 nm, the absorbance of the solution was measured in 30 min using a cuvette with an optical path of 20 mm with water (6.1) as a reference.

Degree value.

18.4 Blank test

Replace the sample with water (6.1) and measure the absorbance according to the procedure of 18.1 to 18.3. The blank should be measured simultaneously with the sample.

18.5 Calibration

18.5.1 Preparation of the calibration series

Add 0.00, 0.50, 1.00, 3.00, 5.00, 7.00, 10.00 and 12.50 ml of phenol to a set of 8 50 ml colorimetric tubes Standard intermediate solution (6.20), add water (6.1) to the marking line.

The measurement was carried out in accordance with the procedures of 18.2 to 18.3.

18.5.2 Drawing of the calibration curve

The absorbance value measured by the calibration series is subtracted from the absorbance value of the zero concentration tube, and the curve of the absorbance value to the phenol content (mg) is plotted.

The correlation coefficient of the quasi-curve regression equation should be above 0.999.

20.1 Precision

Five laboratories tested uniform samples with phenol concentrations of 0.25, 1.25 and 2.25 mg/L.

The relative standard deviations in the laboratory are. 2.0% to 2.1%, 0.6% to 0.9%, and 0.4% to 0.6%;

The relative standard deviations between laboratories were. 2.2%, 0.4%, 0.2%;

The repeatability limits were. 0.01 mg/L, 0.02 mg/L, 0.03 mg/L;

Reproducibility limits were. 0.02 mg/L, 0.03 mg/L, 0.03 mg/L.

20.2 Accuracy

Five laboratories measured standard substances with a phenol concentration of (1.21 ± 0.05) mg/L.

The relative error is. -1.7%~0.8%;

The final value of the relative error is -0.5%±1.8%.