HJ 779-2015Ambient air. Determination of hexavalent chromium(Ⅵ). Ion chromatography with post-column method (English PDF)

Foreword

In order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on the Prevention and Control of Atmospheric Pollution, Protection of human health, regulate the ambient air particles in the determination of hexavalent chromium, the development of this standard.

This standard specifies the determination of hexavalent chromium in ambient air particulate matter by ion chromatography.

This standard is the first release.

This standard is organized by the Ministry of Environmental Protection Science and Technology Standards Division.

The main drafting of this standard. China Environmental Monitoring Station, the National Environmental Analysis and Testing Center.

The standard verification unit. Beijing Environmental Protection Monitoring Center, Beijing Chaoyang District Environmental Protection Monitoring Station, Tianjin Ring Environmental Monitoring Center, Jiangsu Province Environmental Monitoring Center, Hunan Provincial Environmental Monitoring Center Station, Chongqing Environmental Monitoring Center, Sichuan Province Environmental monitoring terminus.

This standard is approved by the Ministry of Environmental Protection on December 4, 2015.

This standard has been implemented since January 1, 2016.

This standard is explained by the Ministry of Environmental Protection.

Determination of hexavalent chromium in ambient air - post - column derivatization ion chromatography WARNING. Potassium dichromate and diphenylcarbonylate used in this method are highly toxic and should be avoided during contact with skin and clothing.

1 Scope of application

This standard specifies the determination of hexavalent chromium in ambient air particulate matter by ion chromatography.

This standard is applicable to the determination of hexavalent chromium in ambient air particulate matter.

When the sampling volume is 21 m3 (standard state), the volume of the extract is 10 ml and the injection volume is 1 ml.

The limit is 0.005 ng/m3 and the lower limit of determination is 0.020 ng/m3.

2 Normative reference documents

The contents of this standard refer to the following documents or their terms. Those who do not specify the date of the reference file, the effective version of the appropriate for this standard.

Technical specification for manual monitoring of ambient air quality Technical Requirements and Test Methods for HJ 93 Environmental Air Particulate (PM10 and PM2.5) Sampler Determination of ambient air PM10 and PM2.5 by HJ 618

3 Principle of the method

In the ambient air particulate matter, hexavalent chromium present in the form of chromate and dichromate is collected into the finely treated fibers Filter, under alkaline conditions by ultrasonic extraction, anion column separation, and the developer diphenyl carbonyl hydrazine formation the absorbance, and the concentration of hexavalent chromium in the sample were measured at 530 nm with a UV-visible detector is proportional to it.

4 Interference and elimination

When the ambient air of ferrous iron, nitrite, thiosulfate and other strong reducing ion concentration is high, with hexavalent chromium the occurrence of redox reaction, resulting in negative interference. A higher content of soluble ferric ions may also cause negative interference to the assay.

The extraction and determination in the alkaline environment can inhibit the conversion of hexavalent chromium, and can avoid the interference of ferric ions.

5 Reagents and materials

Unless otherwise stated, analytical pure chemical reagents are used in accordance with national standards. Experimental water for the resistivity >= 18.2 Mohm · cm of deionized water.

5.1 sodium bicarbonate (NaHCO3). excellent grade pure.

5.2 ammonium sulfate. rho [(NH4) 2SO4] = 1.77 g/ml, excellent grade pure.

5.3 ammonia. rho (NH3 · H2O) = 0.91 g/ml, excellent grade pure.

5.4 Diphenylcarbazide (C13H14N4O).

5.5 Methanol. rho (CH3OH) = 0.79 g/ml, HPLC grade, purity greater than 99.9%.

5.6 Sulfuric acid. rho (H2SO4) = 1.84 g/ml, excellent grade pure.

5.7 potassium dichromate (K2Cr2O7). reference reagent or excellent grade pure.

Weigh 5.0 g of potassium dichromate in a porcelain crucible, placed in an oven at 105 ° C for 2 h, cooled to room temperature and placed in a dryer Save, spare.

5.8 Sodium bicarbonate solution. c (NaHCO3) = 0.12 mol/L.

Weigh 5.0 g of sodium bicarbonate (5.1), dissolve in water and dilute to 500 ml.

5.9 Sodium bicarbonate solution. c (NaHCO3) = 20 mmol/L.

3.36 g of sodium bicarbonate (5.1) was weighed and dissolved in water and diluted to 2000 ml.

5.10 potassium dichromate stock solution. rho (Cr (VI)) = 1000 mg/L.

Accurately weighed 0.2829 g potassium dichromate (5.7) dissolved in water, transferred to 100 ml volumetric flask, dilute the volume to the line.

You can also purchase a commercially available standard material or a certified standard solution.

5.11 Potassium dichromate solution. rho (Cr (VI)) = 10 mg/L.

Accurately remove 0.5 ml of potassium dichromate stock solution (5.10) in 50 ml volumetric flask, dilute with sodium bicarbonate solution (5.9) Release the line.

5.12 potassium dichromate standard use of liquid. rho (Cr (VI)) = 100 ng/ml.

Accurately remove 0.5 ml of potassium dichromate intermediate solution (5.11) in a 50 ml volumetric flask with sodium bicarbonate solution (5.9) Dilute the volume to the mark.

5.13 eluent. 250 mmol/L ammonium sulfate 100 mmol/L ammonium hydroxide.

Weigh 66 g of ammonium sulfate (5.2) dissolved in water, add 14 ml of ammonia (5.3), shake, dilute the volume to 2000 ml.

Immediately transferred to the eluent bottle, can be added nitrogen protection, to slow down the alkaline eluent to absorb CO2 in the air and failure.

6 Instruments and equipment

6.1 ambient air particulate sampling equipment. sampling device from the sampling head, sampling pump and flow meter components. Sampling head is equipped with different Cutter can collect TSP, PM10 and PM2.5 particles; flow meter for small flow, range 7 samples

8 Analysis steps

9 Results calculation and representation

10 Precision and accuracy

11 Quality assurance and quality control

11.1 Environmental Air Particulate Sampling Equipment (6.1) Flow calibration and air tightness checks are required before each sampling, other qualities Warranty and quality control measures are carried out in accordance with the relevant requirements of HJ/T 194.

11.2 Due to the low detection limit of this method, high purity reagents must be used in standard solution preparation and sample pretreatment to reduce the measurement Set the blank value.

11.3 The correlation coefficient of the standard curve should be greater than or equal to 0.999. Each batch of samples (<= 20) should be analyzed for a standard Curve of the middle point of the concentration of the standard solution, the determination of the results and the standard curve of the relative error between the point should be <= 10%. otherwise, the standard curve should be redrawn.

11.4 each batch of samples should be analyzed at least two laboratory blank samples, laboratory blank determination results should be lower than the lower limit of determination, the level the relative deviation of the two-way measured value should not be greater than 10%. Each analysis of a batch (<= 10) samples at least do a full program blank Sample, the whole program blank determination results should be lower than the lower limit of determination. Otherwise, the cause should be identified and the sample should be resampled until qualified to determine the sample.

11.5 each batch of samples (<= 20) at least to do a spike recovery determination, the actual sample spiked recovery should be controlled at 80% to 120%.

12 Waste treatment

Potassium dichromate and dibenzoyl hydrazine is highly toxic, the waste and waste generated in the experiment should be collected collectively and properly kept, Commissioned by qualified units for processing.

13 Precautions

13.1 If there is interference with the determination of hexavalent chromium peak, should be based on laboratory needs to adjust the eluent flow rate, so that the interference peak and Target peak separation.

13.2 post-column derivatization process, the pump pressure instability or changes in room temperature generated by the bubble will affect the determination, can be pressurized by nitrogen Protect to reduce the impact.

13.3 The equipment used in the experiment shall not be cleaned by acid soaking, and the polypropylene (PP) or polytetrafluoroethylene (PTFE) material of the disposable utensils, to avoid the blank value is higher.

13.4 Sampled filters impregnated with sodium bicarbonate solution may cause a decrease in flow during sampling and high performance of the sampling system.

13.5 Preparation and pretreatment of filters should be carried out in a clean environment to avoid contamination. Conditional laboratory, can be related to the operation for use in a glove box with nitrogen purge.