GE MOA 280i, Operation And Maintenance Manual, Page: 173 / 211

GE Analytical Instruments ©2006
15-5
DLM 14291 Rev. A
install the consumables. Select Install and press ENTER to display the Consumables
Menu. Select the Hopcalite option and press ENTER to display the Hopcalite Menu.
Press ENTER to display a confirmation screen. Select Install and press ENTER to
reset the Hopcalite Timer. The Hopcalite Menu will be displayed with the
remaining time reset to 90 days.
Cleaning the Chemiluminescence Reaction Cell
Ozone will react with organic compounds in air to form an opaque film on the
optical filter and the walls of the reaction cell. Over time, this film will block the
transmission of light and cause a loss in sensitivity. In addition, any liquid that gets
into the reaction cell will also stain the filter and cell, and reduce sensitivity. In
order to restore sensitivity, it is necessary to clean the optical filter and reaction
cell. The recommended schedule is 900 hours of operation with the ozone
generator on. However, it may be necessary to clean the cell more frequently,
particularly if any liquid is drawn into the analyzer. If measuring gas-phase NO, a
calibration outside recommended limits may also indicate a dirty reaction cell.
Also, any loss in sensitivity for measurement of nitrite or nitrate may indicate that
it is time to clean the cell. To clean the cell, it is necessary to allow the PMT
temperature to rise to ambient, and then remove the PMT from the analyzer. A
phillips-head screwdriver, the Allen wrench and PMT cap from the accessories kit
for the NOA, an alcohol wipe or a clean cloth and some reagent grade methanol or
ethanol will be needed. It is not necessary to disconnect the vacuum hose from the
NOA to clean the cell. To clean the cell: