Hi Mike

Thanks for your suggestion and happy new year. I has repeated the experiments under 900C with the car. flow at 100 and 80, and oxy. flow at 250 x 3sec and 150 x 3sec individually. The shoulder on mass 30 still existed.

We used the packed collumn from EMA - X1151, and we use the quartz inner tube for collecting ash. 
The chemical packed setting of the collumn (from bottom to top):

quartz wool x 2cm
cobaltous/ic oxide silvered granular x 5 cm
copper wires x 10 cm
quartz wool x1 cm
chromium oxide x 5 cm
quartz wool x1 cm

The height from the tube bottom to the copper top is 17 cm. It's over too much to your suggestion -- 12cm. Temperature might be still too high for upper copper and couse the top copper melting when flash happened.  I guess that I need to reduce some oxide silvered granular and and copper in order to satisfy your suggestion. I will try the experiment again by using the self packing reactor and will let your know the result.