Procedure for the Laboratory Analysis of Halocarbons
| Gas Samples | Water Samples |
|---|---|
|
Dry the gas using Mg(ClO4)2. |
|
|
Introduce the gas into a loop of known volume. |
Introduce water into a stripping cell. |
|
Measure the temperature and pressure of the gas. |
Strip halocarbons with N2 Gas flow >40cc/min for 4 min. |
|
Inject the gas through a trap of Mg(ClO4)2 and Ascarite (NaOH)to remove H2O, H2S and CO2(H2S interferes with the analysis of CFC-11). |
Same as for gases |
|
Trap the halocarbons on Porasil C and Porapak T at -30°C. At -30°C O2 and most of the very high N2O not trapped (N2O interferes with the analysis of CFC-12). |
Same as for gases |
|
Heat trap to 95°C to release halocarbons. |
Same as for gases |
|
Inject release halocarbons through a pre-column of Porasil C into a Column of Porasil C. |
Same as for gases |
|
Reverse the flow in the pre-column after about 40 sec. The reversal of flow vents out the highly retentive halocarbons and greatly reduces the time for the analysis. |
Same as for gases |
|
The halocarbons are separated in the column. Time required is 7 to 15 min. |
Same as for gases |
|
Halocarbons passed through an Electron Capture Detector (ECD) containing 63Ni. By beta (e-) radioactive decay (CFCs+e- = CFCs-), the CFCs- move to the cathode in the detector and produce a small current. The current is amplified. |
Same as for gases |
|
Integrator measures areas. Areas are converted to concentrations. |
Same as for gases |
