HJ 910-2017Ambient air -- Determination of gaseous mercury -- Gold amalgamation collection and analysis by cold vapor atomic absorption spectrophotometry (English PDF)

6.1 Rich tube

Contains gold particles can be enriched mercury particles. The preparation method and schematic diagram of the rich tube is shown in Appendix A. The tube absorbs saturated mercury the amount is 1 µg. Can also be purchased directly from the sale of gold particles mercury enrichment tube.

Note 1. Due to the different specifications of thermal analyzers used in different instruments, the specifications of the enriched tubes prepared or purchased should be matched with the instruments.

Note 2. Before sampling, the tube is heated in a muffle furnace (6.5) at 750 °C for 3 h. The blank value of the tube should be lower than the detection limit (about 0.15 ng).

After cooling, the ends of the rich tube are plugged tightly with polyethylene or PTFE, placed in a polyethylene self-sealing bag or a special plugged glass tube for preservation, 1 month use.

6.2 Gaseous mercury sampling system

6.2.1 consists of an air sampler (6.2.2), a sampling system connection tube (6.2.3), an enrichment tube (6.1), a membrane holder (6.2.4) and Quartz fiber filter (6.2.5) composition, a schematic view of Figure 1.

1-air sampler; 2-sampling system connecting pipe; 3-rich tube; 4-membrane holder; 5- quartz fiber membrane.

Figure 1 gaseous mercury sampling system composition diagram

6.2.2 Air Sampler. It should have the function of automatically accumulating the sample volume, the flow range of 0.1 ~ 1.5 L/min, flow control the error is ± 2.5%. Flow calibration should be performed before sampling.

6.2.3 Sampling System Connection pipe. Polyethylene or Teflon pipe, and the sampling system interface or connector supporting.

6.2.4 membrane support. polyethylene or PTFE material, diameter 25 mm, and quartz fiber filter (6.2.5) supporting the use of.

6.2.5 Quartz fiber membrane. pore size 0.45 µm, diameter 25 mm. Used to filter out airborne particles when sampling.

Note. quartz fiber filter before use must first muffle furnace (6.5) heated at 500 °C for 1 h to remove the mercury, the treated quartz fiber the filter is wrapped in tin foil and stored in a silica gel dryer for use within 1 month.

6.3 Thermal analysis - cold atomic absorption mercury measurement system

6.3.1 consists of air purification tube (6.3.2), thermal analyzer (6.3.3) and cold atomic absorption mercury analyzer (6.3.4), indicating See Figure 2. Has the function of regulating and controlling the temperature of the thermal analyzer, the temperature control error is ± 1 °C; with constant (0 ~ 1000 ng) and trace (0 ~ 20 ng) two test modes.

1-air purifying pipe; 2-thermal resolver; 3-gas washing buffer bottle; 4-water buffer bottle;

5- Built-in enrichment thermal analyzer; 6-Atomic atomic absorption cell; 7-Mercury detector; 8- Suction pump;

9-flow controller, 10-flow meter, 11 mercury exhaust filter, 12 workstations.

Figure 2 Thermal analysis - cold atomic absorption mercury measurement system

6.3.2 Air Purification Tubes. Blank (6.1) for Thermal Analysis - Cold Atomic Absorption Mercury System Line Inlet Empty Gas purification.

6.3.3 Thermal resolver. can be heated to above 600 °C, the working curve into the preparation of standard enrichment tube preparation, blank Product and sample were measured when the blank and sample collection tube filled with rich tubes.

6.3.4 cold atomic absorption mercury analyzer. from the buffer containing 20 mm high buffer (5.14) gas buffer, in addition to water buffer bottle (Empty bottle), built-in enrichment thermal analyzer with a blank (6.1), cold atomic absorption cell, mercury detector, Pump, flow controller, flow meter, mercury exhaust filter and workstation.

6.4 Mercury enrichment system

6.4.1 by the air purification tube (6.4.2), enrichment system connecting pipe (6.4.3), mercury vapor generation bottle (6.4.4), acid gas absorption Bottles (6.4.5), U-type drying tubes (6.4.6), enrichment tubes (6.1), mercury tail gas filters (6.4.7), adjustable flow meters (6.4.8) and suction pump (6.4.9). Schematic diagram shown in Figure 3.

1-air purifying pipe; 2-rich system connecting pipe; 3-mercury vapor generating bottle; 4-acid gas absorption bottle;

5-U-type drying tube 6-rich tube 7-mercury exhaust filter 8 adjustable flow meter 9 suction pump.

Figure 3 Mercury enrichment system

6.4.2 Air Purification Tubes. Blank (6.1) for the purge of the air at the inlet of the mercury-enriched system piping.

6.4.3 Enrichment system Connecting pipe. Polyethylene or Teflon pipe, which is matched with the enrichment system interface or connecting end.

6.4.4 Mercury Vaporizer Bottles. 25 ml glass vials, ground-tapped stoppers with perforated porous blowheads. Or other and enrichment System to match the reaction device.

6.4.5 Acid gas absorption bottle. 25 ml glass turning bottle, with a bottle-shaped porous blowing head grinding mouth stopper. Built-in 10 ml of hydrogen and oxygen the sodium solution (5.12) is used for the absorption of sour gas in the enrichment system for mercury.

6.4.6 U-shaped drying tube. U-shaped plugged glass with a tube outer diameter of 1.3 cm, a branch tube outer diameter of 0.5 cm and a height of 10 cm Tube, built-in anhydrous calcium chloride (5.1), the ends of the packing stuffed with quartz cotton. Can also be purchased directly commercially available anhydrous calcium chloride drying tube.

6.4.7 Mercury tail gas filter. iodine-containing activated carbon tube, purchased directly or with their own active iodine activated carbon filled tube. Iodine live for the preparation of carbon, see Appendix B.

6.4.8 adjustable flow meter. flow range of 0.1 ~ 1.0 L/min, flow control error of ± 2.5%.

6.4.9 Suction pump. Diaphragm pump, load flow >=1.0 L/min, flow range of use 0.1 ~ 1.0 L/min.

6.5 muffle furnace. can be heated to above 800 °C.

6.6 Air blower. Small flow control consisting of rotameter, pressure reducing valve, pressure gauge, constant flow valve, pipe and fittings Controller, the flow range of 0.1 ~ 1.0 L/min adjustable, flow control error of ± 2.5%.

6.7 glassware. use the A-class glassware in line with national standards.

6.8 General laboratory equipment commonly used.

7.1 Sampling system tightness inspection

Connect a sampling tube of the same size (6.1) to the gaseous mercury sampling system (6.2), open the sampler, Blocking the intake side, if the sampler flow to zero, then the air tightness is good.

7.2 Sample collection

Refer to HJ 194 for sampling of gaseous pollutants for sampling. Remove sampling system air tightness check (7.1) , Connect the other rich tube (6.1) to the gaseous mercury sampling system (6.2), leaving the rich tube at in the vertical position, with the air intake facing up, sample at 1.0 L/min for 60 or 24 h and keep the flow constant. Record mining Sample location, time, environmental conditions, sampling start flow, sampling end flow and sampling tube number and other information.

Note. During the sampler assembly and collection process, the sampler should wear powder-free gloves and located in the downwind of the sample to avoid Pollution caused by objects and breathing. Avoid finger contamination with pipe ends during operation.

7.3 Sample preservation

After sampling, remove the sample collection tube, plug the ends of the sample collection tube with a polyethylene or Teflon plug, Placed in polyethylene ziplock bag or special plugged glass tube, transported to the laboratory, measured within 1 month.

7.4 Full program blank sample

Take one of the same collection tubes (6.1) as the sample collection site to the sampling site and synchronize with the sample collection (7.2) Step connected to the sampling system, immediately removed, according to the sample (7.3) the same procedure for the entire program blank samples sealed, transported and stored until the machine measured.

7.5 Reagents Blank samples

According to 8.2.1 standard series of preparation steps to prepare a blank solution, and the solution into the mercury vapor bottle, take and sample A collection of the same batch of a rich tube (6.1), with reference to 8.2.2 standard preparation steps of the preparation of rich sample blank tube sample enrichment tube, the ends of the rich tube are plugged tightly with polyethylene or PTFE, and are put into a polyethylene self-sealing bag or a special plugged glass tube to be preserved until the machine is measured.

8.1 Thermal analysis - Cold atomic absorption mercury measurement system reference conditions

Determination of wavelength, 253.7 nm; test mode, according to the concentration of mercury in the ambient air range, corresponding to select a constant or trace Test mode; thermal analyzer resolution temperature, above 600 °C, analytical time, 2 min, transfer time, 40 s; built-in enrichment Thermal preconcentrator enrichment Preheat temperature, 160 °C, analytical temperature, 600 °C or more, analysis time, 1 min (trace) or 2 min (Constant); Suction flow, 0.5 L/min.

The actual test should refer to the instrument description, set the best analysis and measurement conditions.

8.2 Working curve

8.2.1 Standard series of preparation

8.2.1.1 Preparation of high concentration standard series of work

The constant test, take six 25 ml mercury vapor bottle, prepared according to Table 1 high concentrations of working standard series. According to actual Mercury concentrations in international samples Adjust the concentration range of the working standard series.

Table 1 high concentrations of mercury standard series

Bottle number 0 1 2 3 4 5 Mercury standard solution I (5.20)/ml 0 0.05 0.10 0.50 1.00 2.00 Sulfuric acid solution (5.15)/ml 5.00 4.95 4.90 4.50 4.00 3.00 Mercury content/ng 0 5.00 10.0 50.0 100.200

8.2.1.2 Preparation of low concentration standard series of work

Trace test, take six 25 ml mercury vapor bottles, according to Table 2 preparation of low concentrations of working standard series.

Table 2 low concentration mercury standard series

Bottle number 0 1 2 3 4 5 Mercury standard use solution II (5.21)/ml 0 0.05 0.10 0.50 1.00 2.00 Sulfuric acid solution (5.15)/ml 5.00 4.95 4.90 4.50 4.00 3.00 Mercury content/ng 0 0.50 1.00 5.00 10.0 20.0

8.2.2 Preparation of standard enrichment tubes

8.2.2.1 Enrichment system leak detection

A mercury vapor generator bottle (6.4.4), a vacant quartz tube (instead of an enrichment tube), are connected in series to the mercury enrichment system (6.4) Open and adjust the enrichment flow rate to 0.8 L/min, block the intake end, if the flow rate to zero, it shows good air tightness.

8.2.2.2 Enrichment system Mercury removal

Remove the vial of mercury vapor with a blow bottle stopper, along the wall to the bottle by adding 5 ml of sulfuric acid solution (5.15) and 0.5 ml the stannous chloride solution (5.11) is then immediately capped and evacuated for 5 min to remove possible mercury in the system.

8.2.2.3 Enrichment

In turn, the standard series of mercury vapor generators and concentrators (6.1) with different concentrations of mercury in 8.2.1 are connected in series to mercury enrichment in system (6.4), open and adjust the enrichment flow to 0.8 L/min, remove the vial of mercury vapor with the blowing head, Add 0.5 ml of stannous chloride solution (5.11) along the tube wall to the vial and immediately close the vial and concentrate for 3 min. Follow Remove the prepared standard enrichment tube, the ends of the rich tube stuffed with polyethylene or PTFE plug, filled polyethylene bag or Special stopper glass tube to save, to be measured on the machine.

8.2.3 Determination of standard enrichment tubes

The 8.2.2.3 prepared standard enrichment tube installed in order to thermal analysis - cold atomic absorption mercury system (6.3) and connected Good pipeline. In accordance with the best instrument set conditions, run the thermal analysis program, the mercury vapor into the cold atomic absorption cell to carry out Test, record the instrument's response value (low concentration standard series record peak height, high concentration standard series record peak area).

8.2.4 Establishment of working curve

The standard series of mercury content (ng) as the abscissa, with its corresponding response to the vertical axis, the establishment of the working curve.

8.3 Sample Determination

8.3.1 Determination of sample collection tube

The sample after the rich pipe connected to the thermal analysis - cold atomic absorption mercury system (6.3), according to the standard with the rich Determination (8.2.3) The same instrument conditions and procedures for the determination of the sample.

8.3.2 Determination of blank rich tubes

Reagent blank sample enrichment tube and full sample blank sample enrichment tube prepared in the same batch with the sample collection are respectively connected to the heat Analytical - cold atomic absorption mercury measurement system (6.3), according to the same sample and sample enrichment tube (8.3.1) the same instrument conditions and instrumentation as a step, the reagent blank sample and the whole program blank sample determination.

9.1 Calculation Results

The mass concentration of gaseous mercury in ambient air is calculated according to equation (1) W - mercury content measured in the sample collection tube, ng;

Vn - sampling volume at standard state (273.15 K, 101.325 kPa), L.

9.2 Results indicated

When the sampling volume is 60 L (60 min, standard state) and the measurement result is less than 100 ng/m3, it is retained to the whole digit;

When the measurement result is 100 ng/m3 or more, 3 significant digits are reserved.

When the sampling volume is 1440 L (24 h, standard state) and the measurement result is less than 10.0 ng/m3, 1 Bit; When the result is greater than or equal to 10.0 ng/m3, 3 significant digits are reserved.

10.1 Precision

Six laboratories respectively prepared the standard enrichment of three concentration levels of 10.0 ng, 50.0 ng and 90.0 ng Tubes (6 for each concentration) were determined. the relative standard deviations in the laboratory were 0.93% ~ 6.8%, respectively, 1.1% ~ 3.1% and 0.47% ~ 2.4% respectively. The relative standard deviations of the two laboratories were 6.7%, 2.8% and 1.4% respectively. The repeatability limit Do not 1.2 ng, 2.7 ng and 3.6 ng, reproducibility limits were 2.2 ng, 4.7 ng and 4.9 ng.

Laboratory concentration of two standard concentration of 0.5 ng and 1.0 ng of mercury prepared standard enrichment tubes (each concentration level each 6) were measured, the relative standard deviations in the laboratory were 7.9% and 7.8%.

The concentration of ambient air samples at the two concentration levels actually collected (24 h) was measured in the laboratory (each concentration the level of the parallel acquisition of six), get the average mercury content of 1.6 ng/m3 and 12.4 ng/m3, the laboratory phase the standard deviations were 11% and 9.5% respectively.

10.2 Accuracy

Six laboratories tested two different concentrations of mercury standard sample solutions (11.4 ± 1.1) µg/L and (20.4 ± 1.6) µg/L the standard sample enrichment tubes with the mercury contents of 11.4 ng and 20.4 ng were separately prepared by the gold membrane enrichment method

6), and their mercury content were determined, the relative errors were -7.0% -9.3%, -6.4% -5.0%; the relative error was the final values were -0.07% ± 13% and -0.24% ± 8.6%, respectively.

11.1 Sampling Flow

The relative deviation of the flow at the beginning and the end of the sampling should be within 10%.

11.2 Calibration

Correlation coefficient of the working curve should be greater than or equal to 0.995, otherwise re-establish the working curve.

Before each analysis should prepare a curve of the middle point of the standard enrichment tube validation curve, such as the determination of concentration deviation greater than 10%, you need to re-establish the working curve.

11.3 Blank

At least one reagent blank should be prepared and analyzed after each working curve is established. Blank value should be below the detection limit (about 0.15 ng). Otherwise, the cause should be identified and the working curve should be re-established if necessary. Only after the reagents have passed the blank can the samples be analyzed.

At least one full program blank should be collected and analyzed for each batch of samples. Blank value should be less than 2 times the detection limit (about 0.3 ng) Otherwise it should be re-sampled for analysis.

11.4 Parallel sample determination

Each batch of samples should be collected at least a parallel sample, the relative deviation should be less than 20%.

11.5 Standard sample determination

Gold membrane enrichment method using commercially available certified standard sample solution of a certain amount of mercury through the mercury enrichment system (6.4) rich Set to enrichment tube (6.1), which is pre...