HJ 807-2016Water quality - Determination of molybdenum and titanium by graphite furnace atomic absorption spectrophotometry (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 Water Pollution, Protection of human health, regulate the determination of molybdenum and titanium in water, the development of this standard.

This standard specifies the graphite furnace atomic absorption spectrophotometric method for the determination of molybdenum and titanium in water.

This standard is the first release.

Appendix A and Appendix B of this standard are informative.

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

The main drafting of this standard. Nanjing Environmental Monitoring Center Station.

The standard verification unit. Jiangsu Province Environmental Monitoring Center, Jiangsu Province, physical and chemical testing center, Nanjing Water Company water quality Monitoring center, Changzhou City Environmental Monitoring Center, Zhenjiang City Environmental Monitoring Center Station, Taizhou City Environmental Monitoring Center Station.

This standard is approved by the Ministry of Environmental Protection on June 24, 2016.

This standard has been implemented since August 1, 2016.

This standard is explained by the Ministry of Environmental Protection.

Determination of molybdenum and titanium in water - Graphite furnace atomic absorption spectrophotometric method

1 Scope of application

This standard specifies the graphite furnace atomic absorption spectrophotometric method for the determination of molybdenum and titanium in water.

This standard applies to the determination of molybdenum and titanium in surface water, groundwater, domestic sewage and industrial waste water.

The detection limit of molybdenum was 0.6 µg/L, the lower limit of determination was 2.4 µg/L, the detection limit of titanium was 7 µg/L, for 28 µg/L.

2 Normative reference documents

The contents of this standard refer to the following documents or their terms. Any unspecified date of the reference file, the effective version of the appropriate for this standard.

Technical specification for surface water and wastewater monitoring Technical specification for groundwater environmental monitoring

3 Terms and definitions

The following terms and definitions apply to this standard.

4 Principle of the method

After the sample is filtered or digested, it is injected into a graphite furnace atomizer, dried, ashed and atomized to become a ground state atom Vapor, selective absorption of the characteristic lines emitted by the elemental hollow cathode lamp or the electrodeless discharge lamp. In a certain concentration range, its absorbance is proportional to the mass concentration of the element.

5 Interference and elimination

6 Reagents and materials

Unless otherwise stated, analytical reagents conforming to national standards are used for analysis. Experimental water is a newly prepared deionized Water or water of the same purity.

6.1 nitric acid. rho (HNO3) = 1.42 g/ml, excellent grade pure.

6.2 hydrochloric acid. rho (HCl) = 1.19 g/ml, excellent grade pure.

26.3 sulfuric acid. rho (H2SO4) = 1.84 g/ml, excellent grade pure.

6.4 Hydrogen peroxide. omega (H2O2) = 30%.

6.5 palladium nitrate [Pd (NO3) 2 · 2H2O]. excellent grade pure.

6.6 Magnesium nitrate [Mg (NO3) 2 · 6H2O]. excellent grade pure.

6.7 Ammonium heptamolybdate [(NH4) 6Mo7O 24 · 4H2O]. Excellent grade pure.

6.8 Titanium. Spectral purity, mass fraction >=99.99%.

6.9 Nitric acid solution. 1 1 (v/v), prepared with (6.1).

6.10 nitric acid solution. 1 99 (v/v), prepared with (6.1).

6.11 hydrochloric acid solution. 1 1 (v/v), prepared with (6.2).

6.12 mixed solution of palladium nitrate-magnesium nitrate.

Weigh 0.5 g (exact to 0.01 g) of palladium nitrate (6.5) and dissolve with 1 ml of nitric acid (6.1). Weigh 0.2 g (exact to 0.01 g) of magnesium nitrate (6.6), dissolved in the appropriate amount of water. The two solutions were mixed and bound to 100 ml with experimental water.

37 Instruments and equipment

7.1 Graphite Furnace Atomic Absorption Spectrophotometer. with Zeeman background corrector.

7.2 graphite tube. pyrolytic coated graphite tube (commercially available).

7.3 hot plate. with temperature control function, temperature range 90 °C ~.200 °C, temperature accuracy ± 5 °C.

7.4 microwave digestion instrument. a programmable control function, the output power of 600 W ~ 1500 W, the temperature accuracy of ± 2.5 °C. Equipped with Microwave digestion tank with automatic pressure relief function.

7.5 Analysis of the balance. the amount of 0.1 mg.

7.6 Common laboratory equipment and equipment.

8 samples

8.1 Sample collection the sample collection is carried out in accordance with the relevant provisions of HJ/T 91 and HJ/T 164.

8.2 Preservation of samples

8.2.1 Soluble molybdenum or soluble titanium samples After the sample was collected, the initial filtrate was discarded by filtration with water microporous membrane (6.16), and immediately adding appropriate amount of nitric acid Liquid (6.9) to pH to 1 to 2, and the assay was completed within 14 days.

8.2.2 Total molybdenum or total titanium samples Immediately after the sample collection, the appropriate amount of nitric acid solution (6.9) was acidified to a pH of 1 to 2, and the analysis was completed within 14 days Determination.

8.3 Preparation of sample Soluble molybdenum or soluble titanium samples directly measured. Total molybdenum or total titanium samples shall be digested.

8.3.1 Preparation of total molybdenum test

8.3.1.1 Heater digestion Remove 50.0 ml of shaken samples (8.2.2) In a 100 ml beaker, add 5 ml nitric acid (6.1), cover the surface Dish, in the hot plate at 95 °C ± 5 °C heating to the solution remaining 2 ml ~ 3 ml, cooling, depending on the digestion situation can continue to join Nitric acid (6.1), each time 3 ml, repeat the digestion process until no more brown smoke is generated and cooled. Slowly join 3 Ml of hydrogen peroxide (6.4), covered with a surface dish, in the hot plate 95 ± 5 °C heated reflux, as the case can continue to join the peroxide Hydrogen (6.4), 1 ml at a time until only minor bubbles or no more changes in appearance, remove the surface pan, evaporate the solution to Near dry and cool. Add 1 ml of nitric acid solution (6.9), with the experimental water to wash the beaker inner wall and surface dish at least 3 times, the whole Volume into the 50 ml volumetric flask, with the experimental water volume to the mark, shake. If the sample has insoluble particles, it can be left or Filtration with water microporous membrane (6.16), the clarified liquid stored in the polyethylene bottle.

8.3.1.2 Microwave digestion Remove 25.0 ml of shaken samples (8.2.2) In a microwave digestion tank, add 5 ml nitric acid (6.1) and 1 ml Hydrogen peroxide (6.4), after 30 minutes of standing for microwave digestion, 10 min from room temperature rose to 170 °C ± 5 °C, keep the temperature 10 Min. After digestion and cooling to room temperature, move to the hot plate at 95 °C ± 5 °C heating to close to dry, cooling. Join 0.5 ml nitric acid solution (6.9), with the experimental water rinse digestion tank wall and lid at least 3 times, the whole amount into the 25 ml capacity Bottle, with the experimental water volume to the mark, shake. If the sample has insoluble particles, can be standing or water microporous membrane (6.16), and the clearant was stored in a polyethylene bottle.

4 Note 1. The total volume of the solution in the microwave digestion tank shall not exceed the limits specified by the instrument.

Note 2. The volume of the sample and the volume of the volume after sample preparation can be adjusted according to the sample concentration.

8.3.2 Preparation of total titanium samples

8.3.2.1 Heater digestion Remove 50.0 ml of shaken samples (8.2.2) In a 100 ml beaker, add 5 ml nitric acid (6.1), cover the surface Dish, in the hot plate at 95 °C ± 5 °C heating to the solution remaining 2 ml ~ 3 ml, cooling, depending on the digestion situation can continue to join Nitric acid (6.1), each time 3 ml, repeat the digestion process 1 ~ 2 times. If the digestion is clear and transparent or the appearance is no longer made Change, remove the surface of the dish, the solution evaporated to near dry, cooling; if the digestion turbidity is not clear, add 5 ml sulfuric acid (6.3), Cover the surface of the dish, in the hot plate 95 °C ± 5 °C heating reflux, as the case can continue to add nitric acid (6.1), each 3 ml, Until no more brown smoke is produced. Raise the temperature to.200 °C ± 5 °C, heat reflux to the emergence of SO3 white smoke, and the solution clear Bright or appearance no longer change, remove the surface dish, the solution evaporated to near dry, cooling.

Add 1 ml of nitric acid solution (6.9), with experimental water to wash the inner wall of the beaker and the surface dish at least 3 times, the whole volume into 50 ml Capacity bottle, with the experimental water volume to the mark, shake. If the sample has insoluble particles, can be standing or water microporous filter Membrane (6.16) was filtered and the clearant was stored in a polyethylene bottle.

8.3.2.2 Microwave digestion refer to 8.3.1.2 for operation. If the sample is turbid after digestion, add 3 ml of sulfuric acid (6.3), stamped Heating on the hot plate 95 °C ± 5 °C reflow, as the case can continue to add nitric acid (6.1), each 2 ml until no longer brown Smoke generated. Raise the temperature to.200 °C ± 5 °C, heat reflux to the emergence of SO3 white smoke, and the solution is clear or the appearance of no longer hair Change, open the lid, the solution evaporated to near dry, cooling. Add 0.5 ml nitric acid solution (6.9), with the experimental water leaching elimination Decoction of the inner wall and lid at least 3 times, the full amount into the 25 ml volumetric flask, with the experimental water volume to the mark, shake. in case the sample is insoluble in the particles, can be standing or water microporous membrane (6.16) filter, take the clear liquid stored in the polyethylene bottle.

8.4 Preparation of laboratory blank samples A laboratory blank sample was prepared according to the same procedure for sample preparation (8.3) using the same batch of experimental water instead of the sample.

9 Analysis steps

9.1 Instrument reference conditions Select the optimum measurement according to the instrument manual. Instrument reference measurement conditions in Table 1.

Table 1 Reference measurement conditions

Determination of elemental molybdenum (Mo) titanium (Ti) Light source Molybdenum hollow cathode lamp Titanium hollow cathode lamp Lamp current (mA) 7 20 Determination of wavelength (nm) 313.3 365.4 Passband width (nm) 0.5 0.2 Drying temperature (°C)/drying time (s) 85 ~ 125/55 85 ~ 125/55 Ashing temperature (° C)/ashing time (s) 1200/15 1400/20 Atomization temperature (°C)/atomization time (s) 2800/3.0 2800/5.5

5 Clear temperature (° C)/Clear time (s) 2850/2 2850/2 Argon flow rate (ml/min) 300 300 Whether the atomization stage is stopped Injection volume (µl) 20 20 Background correction method Zeeman background correction Zeeman background correction

9.2 Calibration curve calibration 9.2.1 molybdenum calibration curve Remove 0.00 ml, 0.25 ml, 1.00 ml, 2.00 ml, 3.00 ml, 4.00 ml and 5.00 ml molybdenum respectively Liquid (6.13.3) in a group of 50 ml volumetric flask, with nitric acid solution (6.10) constant volume to the mark, shake. This standard series the concentrations of molybdenum were 0.0 µg/L, 2.5 µg/L, 10.0 µg/L, 20.0 µg/L, 30.0 µg/L, 40.0 µg/L and 50.0 Mg/L. From low concentration to high concentration in turn to the graphite tube into the 20 µl standard series, according to the instrument reference conditions (9.1) measured Absorbance. With the absorbance as the ordinate, the molybdenum standard series mass concentration is abscissa, and the calibration curve is established by linear regression method.

9.2.2 Titanium calibration curve Remove 0.00 ml, 0.50 ml, 1.00 ml, 2.00 ml, 3.00 ml, 4.00 ml and 5.00 ml titanium standard respectively Liquid (6.14.3) in a group of 50 ml volumetric flask, with nitric acid solution (6.10) constant volume to the mark, shake. This standard series the concentration of titanium in the medium was 0 µg/L, 25 µg/L, 50 µg/L, 100 µg/L, 150 µg/L,.200 µg/L and 250 µg/L, respectively.

From low concentration to high concentration in turn to the graphite tube into the 20 µl standard series, according to the instrument reference conditions (9.1) measured absorbance degree. With the absorbance as the ordinate, the titanium standard series mass concentration is abscissa, and the calibration curve is established by linear regression method.

9.3 blank determination Prepare the prepared blank sample (8.4) according to the same conditions as the drawing calibration curve (9.1) and step (9.2) Line determination.

9.4 Sample determination the prepared sample (8.3) was subjected to the same conditions as in the drawing of the calibration curve (9.1) and step (9.2) set. If the measurement results exceed the calibration curve range, the sample should be diluted with nitric acid solution (6.10) and re-determined.

Note 3. If SO42-interference is present in the sample containing molybdenum, 5 µl of palladium nitrate-magnesium nitrate mixed solution (6.12) is added to 20 µl of sample and 20 µl standard series were co-injected into the graphite tube.

10 results are calculated and expressed

10.1 Result calculation the mass concentration of molybdenum or titanium in the sample is calculated according to equation (1) Vf 11 xx-06 (1) where. rho - mass concentration of molybdenum or titanium in the sample, µg/L;

rho1 - from the calibration curve obtained in the sample molybdenum or titanium mass concentration, µg/L;

F - the dilution factor of the sample;

6V - the volume of the sample taken, ml;

V1 - volume of the sample after preparation, ml.

10.2 results are shown 10.2.1 molybdenum results when the determination result is less than 10 µg/L, one decimal place is retained; when the result is greater than or equal to 10 µg/L, Keep three valid digits.

10.2.2 Titanium results when the determination result is less than 100 µg/L, it is retained to the integer position. When the measurement result is greater than or equal to 100 µg/L, Leaving three valid digits.

11 precision and accuracy 11.1 precision Six laboratories with soluble molybdenum concentrations of 1.4 µg/L and 6.4 µg/L of surface water samples and surface water spiked samples Six repeated measurements were made. the relative standard deviations in the laboratory were 10% to 16% and 3.5% to 6.4%, respectively; inter-laboratory phase the standard deviations were 15% and 4.5%, respectively, and the reproducibility limits were 0.6 µg/L and 1.0 µg/L, respectively. The reproducibility limits were 0.8 Mg/L and 1.2 µg/L. The surface water spiked samples with soluble titanium concentrations of 10 µg/L and 30 µg/L were subjected to 6 times Repeat the determination. the relative standard deviation of the laboratory were 7.1% to 12% and 4.0% to 5.0%; the relative standard deviation between the laboratory Respectively, 10% and 2.5%; repeatability of 3 µg/L and 4 µg/L, respectively; reproducibility limit of 4 µg/L and 5 µg/L, respectively.

Six laboratories conducted six replicates of groundwater samples with a total molybdenum concentration of 5.4 µg/L. the laboratory phase Standard deviation of 5.3% to 7.6%; laboratory relative standard deviation of 5.7%; repeatability limit of 1.0 µg/L; reproducibility limit Was 1.3 µg/L. Six replicates of groundwater spikes with total titanium concentrations of 30 µg/L and 52 µg/L were tested for six replicates.

The relative standard deviations in the laboratory were 4.9% ~ 7.0% and 4.1% ~ 4.9%, respectively. The relative standard deviations were 6.0% and 4.2% respectively. The reproducibility limits were 5 µg/L and 7 µg/L, respectively. The reproducibility limits were 7 µg/L and 9 µg/L, respectively.

Six laboratories carried out samples of waste water samples with total molybdenum concentration of 8.0 µg/L and 27.6 µg/L 6 times the repeated determination. the relative standard deviation of the laboratory were 4.5% to 5.6% and 4.5% to 5.8%; inter-laboratory relative standard and the reproducibility limits were 1.2 µg/L and 4.0 µg/L, respectively. The reproducibility limits were 1.5 µg/L and 4.5 µg/L. Six samples of waste water samples with total titanium mass concentration of 30 µg/L and 223 µg/L were collected Repeat the determination. the relative standard deviation of the laboratory were 5.3% to 7.9% and 2.6% to 2.9%; the relative standard deviation between the laboratory Respectively. The reproducibility limits were 6 µg/L and 18 µg/L, respectively. The reproducibility limits were 8 µg/L and 20 µg/L, respectively.

11.2 Accuracy

Six laboratories tested concentrations of 161 µg/L ± 18 µg/L, with a concentration of 503 µg/L ± 49 µg/L of the titanium standard samples were measured. the relative error were -6.2% to 0% and -3.4% to 2.4%, the relative error of the final value Respectively -3.1% ± 4.8% and -1.0% ± 4.0%.

Six laboratories on the surface water samples were spiked recovery test. molybdenum plus standard recovery rate of 95.8% to 106%, plus standard back the final yield was 101% ± 8.2%. Titanium spiked recovery rate of 97.5% to 103%, spiked recovery rate of the final value 101% ± 4.2%.

Six laboratories on the groundwater samples were spiked recovery test. molybdenum plus standard recovery rate of 97.3% to 104%, plus standard back the final yield was 101% ± 4.2%. Titanium spiked recovery rate of 96.1% to 109%, spiked recovery rate of the final value 7101% ± 8.0%.