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Appendix B
5/20/2009
20
16.7.
40 CFR, Part 136, Appendix B. Definition and Procedure for the Determination
of the Method Detection Limit. Revision 1.11.
16.8.
Zimmermann, C. F., Keefe, C. W., and Bashe, J. 1997. Method 440.0.
Determination of Carbon and Nitrogen in Sediments and Particulates of
Estuarine/Coastal Waters Using Elemental Analysis. USEPA
17.
DETAILED PROCEDURE
17.1. Exeter 440 Operation
17.1.1. The following sequence should be followed when initially starting up
the system or when restarting after a shutdown.
17.1.1.1. Make sure the power switches on the computer and on
the CEC- 490 (Interface) are off.
17.1.1.2. Remove the 440 cover from instrument.
17.1.1.3. Check that the helium regulator is set at 18 psig and
oxygen at 20 psig and open the in-line gas valves.
17.1.1.4. If restarting, check that the combustion and reduction
tubes, scrubber and traps are not exhausted.
17.1.1.5. Turn the selector switch to SYSTEM. Turn on the CEC-
490 and the computer. The monitor will now display the
Menu. If this is a cold re-start, set combustion and
reduction furnace temperature controls to values previously
established. Wait until the reduction furnace has reached
operating temperature. DO-NOT PUSH DETECTOR
RESET BUTTON AT THIS TIME!
17.1.1.6. With the combustion to reduction tube end connector
removed, go to “Tube Replacement” in the Service Menu,
then follow the directions under “Combustion Tube
Replacement” to purge the helium and oxygen regulators
twice. This will also serve the purpose of conditioning the
reduction and combustion tubes. Then go to Main Menu
and install the end connectors.
17.1.1.7.After allowing the 440 oven to reach operating temperature
(about one hour) go to the Service Menu and select
Calibrate CEC-490. Calibrate all and follow instructions.
17.1.1.8.Run 2 to 3 blank runs to establish a fill time of about 20 to
40 seconds. If the fill time has been exceeded, increase the
helium pressure by ½ psig, and repeat running until fill time
is achieved. If the system still aborts after the helium
pressure has been increased to 22 psig, go through the leak
test mode.
17.1.1.9.
After the first complete run, push DET RESET. High
concentrations of air or oxygen in the analytical system will
damage the filaments in the detectors if power is applied. To
protect the detectors, a detector safety circuit is provided
which shuts off power when the helium carrier gas becomes