Costech Elemental Combustion System CHNS-O (ECS 4010)

Active

Replaces Carlo Erba NA1500 SeriesII Combustion Analyzer

In use from 2004-01-01

Abstract

The Costech Elemental Combustion System 4010 is an automated combustion analyzer used to determine total carbon and nitrogen in soil and plant samples. This system employees a helium carrier gas to bring combustion gases to a gas chromatographic separation column and thermal conductivity detector. More information about the analyzer can be obtained from Costech Analytical Technologies (26074 Avenue Hall, Suite 14
Valencia, CA 91355 – USA or http://www.costechanalytical.com/)

Protocol

Preparing for analysis:

Cylinder gases used:

  • Helium, 99.999% – carrier gas
  • Oxygen, 99.995% – purge gas, accelerates combustion
  • Air, water and oil free – pneumatics

Reactor column replacement

  1. Pack a new column with chromium and cobalt oxides according to the ECS 4010 manual page 6.1.1 (Standard Reactor Packing for N, N/C, and N/C/H Analysis). Position a rubber seal about 3mm down from the top. Set this aside.
  2. Remove the autosampler from the top of the reactor column using a latex glove and wrench. Move to the side, out of the way.
  3. Remove the front panel of the analyzer to allow access to the bottom of the column.
  4. Move the stage to the side and unscrew the metal fitting from the combustion/reduction connection.
  5. Remove the rubber seal, steel washer, metal fitting, and thermal collar. Be careful, these could be very hot.
  6. Lift the spent column out of the analyzer from above and replace with the new column.
  7. Return the autosampler to the top of the reactor column. Tighten using a wrench with a latex glove over the fitting.

Reduction column replacement

  1. Pack a new column with copper wires according to the ECS 4010 manual page 6.1.2 (Reduction Reactor Packing for N, N/C, and N/C/H). Position a rubber seal about 3mm down from the top. Set this aside.
  2. Remove the fitting from the top of the reduction column using a latex glove and wrench. Carefully move the fitting aside.
  3. Remove the front panel of the analyzer to allow access to the bottom of the column.
  4. Move the stage to the side and unscrew the metal fitting from the combustion/reduction connection.
  5. Remove the rubber seal, steel washer, metal fitting, and thermal collar. Be careful, these could be very hot.
  6. Lift the spent column out of the analyzer from above and replace with the new column.
  7. Return the fitting to the top of the reduction column. Tighten using a wrench with a latex glove over the fitting.

Water trap replacement

  1. Pack a new water trap according to the ECS 4010 manual page 6.2 using Magnesium perchlorate.
  2. Remove the small panel located beneath the digital display to reveal the water trap.
  3. Unscrew both red connections and remove the glass column.
  4. Attach newly packed trap with red connections.
  5. Dispose of contents of spent trap as hazardous waste through ORCBS. Once emptied, the glass column can be cleaned with ethanol and reused.

Calibration and check standards

    Each run should begin with a bypass (sample #1) followed by a blank tin cup (sample #2) and four calibration standards (samples 3 thru 6). Chose a calibration standard with carbon and nitrogen values in the range of samples to be analyzed. Use Acetanilide, Atropine or Phenacetin packed in the following weight ranges:
    • Standard 1 should weigh 0.2 – 0.3 mg
    • Standard 2 should weigh 0.5 – 0.6 mg
    • Standard 3 should weigh 1.0 – 1.2 mg
    • Standard 4 should weigh 2.0 – 2.8 mg
    The 7th sample to be run should be a blind standard of either soil or plant material, depending on the type of samples in the run. Following this initial check, the blind standard should be analyzed every 12 – 15 samples to ensure confidence in the analysis.

Packing tins

  1. All sample material must be dried and ground or pulverized to a fine powder.
  2. Turn on the micro balance.
  3. Use forceps to handle tin sample cups. Place a cup on the weighing tray of the balance and close the doors.
  4. Tare the balance.
  5. Remove the cup from the weigh tray. Using a small spatula add sample material to the tin.
    • weight range for soil samples is 15 – 20 mg
    • weight range for plant samples is 2 – 5 mg
  6. Fold the cup into a sphere or cube shape using two pairs of forceps. Once completely closed, drop onto the weighing plate to ensure no sample leaks out. If the prepared cup leaks, discard it and begin again.
  7. Place the folded cup onto the weighing pan and record the weight (in mg) on the provided datasheet.
  8. Carefully move the prepared sample cup to a plexiglass well-plate.
  9. Use laboratory wipes to clean the forceps, spatula, and weighing tray between each sample.
  10. Plates of samples should be stored in a vacuum desiccator until analyzed.

Change reactor column insert

  1. Remove the autosampler from the top of the reactor column using a wrench on the fitting with a latex glove over it to protect it.
  2. Remove the insert from within the reactor column. The back end of a sharpie marker works well for this. The insert will be very hot.
  3. Replace with a new insert, vent end down. Include a small amount of quartz wool in the bottom of the new insert to keep ash inside the insert and out of the column itself. It is okay for the quartz wool to stick out of the insert slightly as this will make removal easier later. Wipe the portion of the insert and column sticking out of the machine with 95% ethanol.
  4. Return autosampler to the top of the reactor column. Tighten using a wrench with a latex glove over the fitting.

Start computer/Ramp up ovens

  1. Push Work and then Enter on the analyzer’s key pad. This will start the heating of the furnaces. Indicator lights on this display will change from solid red = resting, to blinking red = heating, to solid green = ready. The running temperatures are 1000C for the reactor column and 650C for the reduction column.
  2. Open the EAS32 software on the computer and enter your password.
  3. Choose the project with which your samples for analysis correspond.
  4. Select the monitor icon in order to track the baseline.

Leak check (once the baseline has leveled out and ovens are ready)

  1. Plug the Helium vent (vHe). First finger-tighten, then wrench snug the plug. The baseline should drop to about -17.
  2. Open the He all the way by turning the He dial on the machine counterclockwise until it loosens.
  3. The pressure gauge associated with the He dial should not drop. Watch for a drop for about 30-60 seconds. No drop in pressure means that the system is air tight.
  4. Once check is complete, unplug the vHe first and then adjust the He pressure back up to 20 psi.

Calibration and Analysis:

Sample table/Run initiation

  1. Choose File, then New Specified to create a new sample table. Name the file and indicate the length of the run. We fill in our sample table in Excel and then paste it into the EAS32 sample table.
  2. Remove run marks from all samples except the bypass by selecting these lines and choosing Edit-Clear run marks.
  3. Push Remote and then Enter on the analyzer’s key pad. This will start communications between the computer software and the analyzer. REM will appear on the digital display.
  4. The autosampler has 3 stacking carousels into which samples should be loaded. Position the cell “1” on the bottom carousel over the opening to the reactor column. Place the bypass (sample #1) into cell 1 of the autosampler. Be sure to replace the plexiglass cover after loading samples.
  5. Start the combustion and analysis of the bypass by choosing Sample table-Run. Analysis of each sample takes 5 minutes.

Calibration

  1. Choose Sample table-Window-Calibration. Remove all compounds except Nitrogen and Carbon by selecting the others and choosing delete compounds.
  2. Adjust retention times based on N and C peaks for the bypass.
  3. Next load and analyze the blank, calibration standards, and blind standard.
  4. Choose automatic calibration in order for the software to integrate for you.
  5. The calibration correlation coefficient should be at least 0.99
  6. Check the results for the blind standard. If the percentages for N and/or C are off by more than 10% from the expected levels, the run should be stopped.

Sample analysis

  1. Analysis of samples can begin once you are satisfied with the calibration.
  2. Samples should be loaded into the carousels and the plexiglass cover replaced.
  3. Mark the rest of the sample table for run and choose Sample table-Run.

Run completion

  1. When all the samples have been analyzed, save the summary table.
  2. The results can be copied and pasted into a spreadsheet.
  3. Push Abort and then Enter on the analyzer’s key pad to stop communication between the analyzer and computer. Push St-By then Enter to put lower the column temperatures.
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Datatables