EQUIPMENT

  1. PSA MERLIN Mercury Fluorescence Instrument
  2. CEM Model MDS-2000 Microwave oven
  3. Microwave pressure digestion vessels.
  4. Convection Oven

REAGENTS

1 Nitric Acid HNO3
2 Sulfuric Acid H2SO4
3 Hydrochloric Acid HCl
4 Potassium Persulfate K2S2O8
5 Potassium Permanganate KMnO4
6 Hydroxylamine Hydrochloride NH2OH •HCl
7 Sodium Chloride NaCl
8 Stannous Chloride SnCl2•2H2O

GAS

  1. Argon 99.99%

STANDARDS

  1. Stock solutions
    1. 1000 ppm Mercury - Use certified, NIST traceable standard.
    2. 10 ppm Mercury - Pipet 10 mL of 1000 ppm mercury standard into a 1 liter volumetric flask. Dilute to volume with deionized water and mix well.
    3. 100 ng/mL mercury - Pipet 10 mL of 10 ppm mercury standard into a 1 liter volumetric flask. Dilute to volume with deionized water and mix well.
  2. Instrument Calibration Standards
    1. Pipet the designated mL of 100 ng/mL mercury standard into 100 mL volumetric flasks, Dilute to volume with deionized water and mix well.
      StandardmL
      100 ng/mL Mercury      		Final Mercury
      Concentration (ng/mL)
      100
      211
      333
      455

PUMP SOLUTIONS

  1. Stannous chloride, 5%
    1. Add 50 mL hydrochloric acid into a 500 mL volumetric flask containing 300 mL deionized water.
    2. Add 25 g stannous chloride and heat to dissolve.
    3. Allow to cool, dilute to volume with deionized water and mix well.
  2. Nitric acid, 5%
    1. Add 50 mL nitric acid into a 1 liter volumetric flask containing 600 mL deionized water. Dilute to volume with deionized water and mix well

SPIKING SOLUTION

  1. Use the 5 ng/mL mercury instrument calibration standard.

DIGESTION SOLUTIONS

  1. Potassium persulfate, 5%.
    1. Weigh 5 g potassium persulfate into a 500 mL volumetric flask. Dissolve and dilute to volume with deionized water and mix well.
  2. Potassium permanganate, 5%
    1. Weigh 5 g potassium permanganate in a 500 mL volumetric flask. Dissolve and dilute to volume with deionized water and mix well.
  3. Hydroxylamine hydrochloride, 11.6% / sodium chloride, 12%
    1. Weigh 60 g sodium chloride into a 500 mL volumetric flask containing 300 mL of deionized water. Swirl to dissolve.
    2. Add 58 g hydroxylamine hydrochloride. Dissolve, dilute to volume with deionized water and mix well.

SAMPLE DIGESTION

  1. Liquid Samples.
    1. Pipet 50 mL of sample into a 100 mL volumetric flask.
    2. Add 5 mL of sulfuric acid.
    3. Add 2.5 mL of nitric acid.
    4. Add 5 mL of 5% potassium persulfate solution.
    5. Add 5 mL of 5% potassium permanganate solution.
    6. Place in a convection oven for 2 hours at 95 degrees C.
    7. Remove sample from oven and let cool.
    8. Add hydroxylamine hydrochloride/sodium chloride solution in 1 mL increments, until the solution becomes colorless.
    9. Let stand for 15 minutes. Add additional hydroxylamine hydrocholride/sodium chloride solution if the sample does not remain colorless.
    10. Dilute to volume with deionized water and mix well.
  2. Solid Samples
    1. Weigh 1 g sample into a microwave digestion vessel.
    2. Add 5 mL of deionized water.
    3. Add 5 mL of nitric acid.
    4. Place vessel in the microwave oven and digest for 56 minutes, using the sludge program.
    5. Allow the vessel to cool and transfer sample into a 100 mL volumetric flask.
    6. Dilute to volume with deionized water and mix well.
  3. Animal Tissue
    1. Weigh 1 g sample into a microwave digestion vessel.
    2. Add 5 mL deionized water.
    3. Add 5 mL nitric acid.
    4. Place vessel in the microwave oven and digest for 50 minutes, using the fish program.
    5. Allow the vessel to cool and add an additional 5 mL nitric acid.
    6. Digest the sample a second time in the microwave oven for 50 minutes.
    7. Allow the vessel to cool and then transfer sample into a 100 mL volumetric flask.
    8. Dilute to volume with deionized water and mix well.

SPIKING PROCEDURE

  1. Client samples
    1. Pipet 10 mL of the sample digest into a 50 mL volumetric flask.
    2. Pipet 10 mL of the 5 ng/mL mercury instrument calibration standard to the flask.
    3. Dilute to volume with deionized water and mix well.
  2. Digest blank - liquid samples.
    1. Pipet 50 mL deionized water into a 100 mL volumetric flask.
    2. Pipet 10 mL of 5 ng/mL mercury instrument calibration standard into the 100 mL volumetric flask.
    3. Follow steps 1b through 1j of the sample digestion section, page 154.
  3. Digest blank - solid samples
    1. Pipet 10 mL of 5 ng/mL mercury instrument calibration standard into a microwave digestion vessel.
    2. Follow steps 2b through 2f of the sample digestion section, page 154.
  4. Digest blank - animal tissue
    1. Pipet 10 mL of 5 ng/mL mercury instrument calibration standard into a microwave digestion vessel.
    2. Follow steps 3b through 3h of the sample digestion section, page 155.

ANALYSIS PROTOCOL

  1. Analyze one quality control sample with each set of client samples.
  2. Analyze a reagent blank, digest blank, spiked digest blank, and spiked client sample with each set of samples.
  3. Analyze a 3 ng/mL mercury instrument calibration standard after each 10th client sample for reslope purposes.

PROCEDURE

  1. Turn on:
    1. Computer monitor
    2. Printer
    3. Mercury Florescence System
    4. Argon
  2. Click on "Start".
  3. Click on "Shut Down".
  4. Click on "Restart the computer in MS-DOS mode?".
  5. Click on "YES"
  6. Type "CD:\TS" and press "Enter".
  7. Type "TS LOAD" and press"Enter".
  8. Using the arrow keys select "Analyse" from the main men, and press "Enter".
  9. Using the arrow keys go to "Program" and press "Enter". The last program entered will appear.
  10. Press F4-EDIT.
  11. Construct a sample table in the following manner:
    1. Using the up or down arrow keys, highlight the first line.
    2. Press the proper F key in order to identify and change anything on the line.
    3. After each change press "Enter". If no change is made press "Enter" in order to progress to the next column.
    4. Proceed in this manner until all samples have been entered. Include one quality control sample, one spiked sample, one spiked digest blank, and a 3 ng/mL mercury standard following each 10th client sample for reslope purposes.
    5. PRESS "S".
    6. Type the name of the program and press "Enter".
    7. Press "Escape" - the new program will appear. Press "Escape" a second time in order to return to the main menu.
  12. Select "Calibrate" from the main menu and press "Enter".
  13. Go to "New Curve" and press "Enter".
  14. If the settings are correct, press "Enter" after each prompt. If they are not correct, change them to the correct setting and press enter after each entry. The correct settings are listed below.
    Units:PPB
    Option of 4 curve fit parameters: 2
    No. of standards: 4
    No. of runs per standard: 1
    Concentration of standard 1 0
    Concentration of standard 2 1
    Concentration of standard 3 3
    Concentration of standard 4 5
  15. After the last "Enter" is pressed, "Settings correct and ready to analyse - reading STD 1 Y/N" will appear.
  16. Place the pump tubes in their proper containers, and turn on the pump.
  17. Place the sample uptake line in standard 1 (deionized water) and press "Y".
  18. When the screen goes to memory, remove the sample uptake line from standard 1 and place it into a beaker of deionized water.
  19. Repeat this process for standards 2, 3, and 4.
  20. Press "Escape" in order to return to the main menu.
  21. Go to "Analyse", and press "Enter".
  22. Press F5-RUN.
  23. Analyze samples in the same manner as standards, following the instrument prompts.
  24. After analysis is complete, press "Escape" in order to return to the main menu.
  25. Go to "Results" and press "Enter".
  26. Go to "Quit" and press "Enter".

QUALITY CONTROL

  1. Values on the quality control sample must lie between the limits established by the supplier.
  2. Recovery of mercury for the spiked samples and spiked blank digests must lie between 75% and 125%.
  3. The range of acceptable values for the reslope, using the 3 ng/mL mercury instrument calibration standard is 2.27-3.30 ng/mL (10%).

REFERENCES

  1. Cold Vapor Atomic Absorption Spectrometric Method, 3112B, in Standard Methods for the Examination of Water and Wastewater, 19th Edition, 1995, chapter 3, p 18-20.
  2. Scifres, J., V. Cheema, M. Wasco, and W. McDaniel, Determination of ultratrace-level total mercury in sediment and tissue by microwave digestion and atomic fluorescence detection: Part 2. American Environmental Laboratory, 6/95.