We have an Applied Automation Optichrome GC which is connected in a gas stream having the following composition : Methane, Ethane, Propane, IC4, NC4, IC5, NC5, C6+.

The GC is presently measuring Methane, Ethane, Propane, IC4, NC4.

We would additionally like to measure IC5, NC5, C6+.

The coloumns used are :

COL# LENGTH COLOUMN DESCRIPTION FUNCTION OF COLOUMN

1A 2FT 10% C-WAX 20 M CHROMT - 40/60 BACKFLUSHES WATER, HEAVIES

1B 1FT 1% TCEP CPACK B - 80/100

2 1FT 1% TCEP CPACK B - 80/10 SEPARATE N2, C1, CO2, C2 FOR
TRAP

3 8FT HYESCP Q - 80/100 SEPARATE N2, C1, CO2, O2

4 2FT CHROMP 750-80/100 BUTTER

My question is how can we measure the additional components by modifying the GC. Are some new coloumns required for measuring the additional components ? or can we use the same coloumns and decrease the flow rate and increase the sample loop size to measure the additional components or is there any other suitable method.

An early response will be highly appreciated.

The present system backflushes the iC5+ hydrocarbons and water with the 1A and 1B column.

To allow the iC5 and nC5 to pass through simply make the backflush happen later so only the iC6s and heavier are backflushed. The cost will be a longer cycle time, but no changes in the system are required. Make sure the water is still backflushed. If the C5s are too broad then you will have to change the 1B column, possibly also the column #2. I would use a 2ft 20% SP-2100 on Chrom P-AW 80/100 column for the 1A and 6ft 20% SP-2100 on Chrom P-AW 80/100 for column #2.

Other faster columns are available but these are std equipment and well proven.

These lengths are guesses based on experience. Length modifications may be neccessary. If water is not backflushed with the later BF time other solutions are available.

Supelco offers columns with 5 or 10µm 316SS screens like the OEM AAI columns but possibly at a cheaper cost.

Pardon the commercial.

Please call or email me if I can answer any specific questions.

Rodney George
Senior Research and Development Scientist
Multidimensional GC Applications
Gas Separations Research
Supelco
595 North Harrison Road
Bellefonte, PA 16823

814-359-5737 voice
814-359-5702 fax
rgeorge@sial.com

Sorry, I mistyped my response above.

"I would use a 2ft 20% SP-2100 on Chrom P-AW 80/100 column for the 1A and ..."

should read

"I would use a 2ft 20% SP-2100 on Chrom P-AW 80/100 column for the 1B column and ..."

my apologies.

Rodney George