PROCEDURE FOR ANALYZING TOTAL INORGANIC CARBON IN LAKE SEDIMENTS AND SOILS BY COULOMETRY
1. open left door of 5240 and slide out tray.
2. empty waste container and rinse everything with water
3. fill DI container with DI water
4. fill acid container with 2N perchloric acid (HClO4Ñ69 ml HClO4 in 400 ml of DI water)
5. hook up all containers and replace the tray in the 5240.
6. turn the main power switch on (this is usually not necessary as the 5240 should be left on)
7. set carrier gas to 20 psi on the tank
8. press CLEAR/INITIALIZE SYSTEM and wait for about 15 minutes for the cell to be conditioned for your run
9. press CLEAR/INITIALIZE SYSTEM to get the unit ready to run
10. adjust carrier gas flow to about 100 cc/min and the purge gas flow to 250 cc/min.
1. start with a clean, dry cell
2. wipe off the exterior walls with a Kim Wipe and acetone
3. place small bar magnet in the bottom of the large diameter cell (cathode cell)
4. fill the cathode cell with 125 ml of cathode solution-DO NOT ALLOW SOLUTION TO SPLASH ON CELL WALLS
5. place the cathode cell cover on the cell so that the electrode and gas inlet tube are at the back of the cell compartment (that is, at the 12:00 position, if the anode cell (small diameter cell is at 6:00)
6. add approximately 1/4Ó of KI powder to the bottom of the small-diameter cell (anode cell); this amounts to one large scoop with the scoop that is kept in the KI bottle
7. fill the anode cell with anode solution so that its level is 1/2Ó lower than cathode solution level
8. place anode top in solution so that silver electrode is in the anode solution
1. place cell in coulometer so that anode cell is to the front right of the compartment
2. attach the gas inlet (blue fitting) to the gas vent in the back of the compartment by attaching blue-blue
3. repeat for gas exit vent (attach red-red)
4. attach platinum electrode (black) and silver electrode(red) to the same colored teminals in the side of the cell compartment (red-red; black-black)
5. adjust (twist) top of cathode cell so that the gas inlet tube and the electrode are NOT in the path of the light beam
IV CO2
Coulometer Operation
1. turn cell current switch off (neutral position)
2. turn on main power supply
3. wait for the UIC logo to come on to the screen
4. press any arrow
5. select RUN DIAGNOSTICS
6. select change run settings, and choose the following parameters (NOTE: BE SURE TO ENTER THE LEADING 0 BEFORE ANY DECIMALÑ SO, 0.1 NOT .1)
á measure C
á by weight
á sample weights entered in mg
á percent difference = 0.1 for most samples; samples low in C content may run more efficiently with a percent difference of 0.2
á dilution factor=1.0
á # of readings=6
á interval=minutes
á select coulometer end point
á autosampler
á select 5200 for TC and 5240 for TIC and be sure to change the A-B box on top of the coulometer to match these settings
á select normal print out
á select write to disk
á
7. return to RUN DIAGNOSTICS menu and select print settings
8. exit RUN DIAGNOSTICS
9. select RUN CELL SET-UP
10. slowly rotate cell in coulometer to find the highest %T valueÑbe sure there are no markings on the outside of the cell, and be sure that the gas inlet and electrode are not blocking light; you may need to take a KIM WIPE and clean the side of the cell
11. once you have found the highest possible %T value (should be >3800), select F2 and from now on shut door and do not move the cell at all!
12. turn cell current on and select RUN ANALYSES.
13. hook incoming gas line up to coulometer, check to see that gas is coming into the cell, and then wait at least 15 minutes for titration to reach end point. NOTE: THE END POINT %T SHOULD BE ~29.5 AND IT SHOULD BE VERY STABLE; IF THE END POINT IS NOT STABLE, DO NOT CONTINUE AS YOU WILL BE WASTING YOUR SAMPLE!!
14. when you have found a stable and low end point, select F2
15. you should run at least 2 air blanks to be sure that all is running well (blank values should be <4 µg of C. Select run sample, and type in the number of samples you wish to run.
16. type the word blank for your air blanks (there is no weight for these samples), and press enter when ready to run
17. after air blanks have been run, you are ready to run your batch of samples; select F2 if your stable end point has been reached, and enter the number of samples to run
18. type the word blank for your blank sample, and STD for your standards. Enter all weights in milligrams (you can enter weights only for your standards and unknowns)
19. when finished, press enter to run
20. be sure that carousel is covered with foil so that no dust can fall on samples
21. beware that the 5200 TC furnace occasionally will require prompting after the first sample is runÑthis only happens after the first sample of the day, so be sure to check on the machine after you start it.
22. blank values should be less than 4.0 µg of C; the standard should be at least 11.6% and preferably closer to 12.0%.
23. be sure that you have PC formatted diskette in the coulometer and that the printer is on.
24. if you need to abort a run, enter ESC and return for each sample (turn printer off first)
25. Be
sure to enter all data for each run on the coulometer clipboard!!
1.
disconnect the 5240 from the coulometer by unplugging
the gas input line
2. turn off the cell current in the coulometer
3. turn off the coulometer main power switch
4. unplug the electrodes and gas inlet and exit lines
5. remove the cell from the cell holder
6. dispose of the contents into the waste container
7. rinse tops thoroughly with DI water and place on paper towels
8. fill cathode solution 1/4 with methanol
9. hook up a water faucet aspirator to top of anode solution
10. turn on water
11. allow methanol to be sucked through the frit until the anode side of the frit is filled with methanol to the level of the top of the frit
12. repeat steps 13-16 twice with DI water
13. unplug aspirator and rinse out sample cell thoroughly with DI water
14. wash cell thoroughly with soap and water and then rinse cell again with DI water
15. turn cell upside down on the top rack of the drying oven to dry
16. place cell tops and electrodes on a clean dry paper towel
17. remove waste container from the left side of the 5240 and dump contents into sink in 303 (with limestone tank), then rinse container and capture all of the Teflon boats
18. wash Teflon boats in soapy water with Q-tips; rinse numerous times and place on a large watch glass covered in KIM wipes, and place this in the drying oven.