Chromatography Forum

Hello,

Im new to posting here but have found this site to contain some very valuable information and I would like to begin by saying thanks all the effort put in here. You have made my life a bit easier by existing. Thx!
now i am coming to ya'll for some help.
I am having some trouble with a Perkin Elmer Turbomatix ATD 650. My lab purchased one earlier this year. We are using it to run TO-17. Connected to it is a 6890 and 5973n.
column is a rxi 5ms .28x 1µ film x 45meter
1 ml/min col flw

If you are familiar with the Atd650, the instrument has a function to recollect a portion of the sample back on to the desorbed TD tube or to a fresh one. We are specifically interested in using the same tube for recollection. I am writing to see if anyone else has experienced the same phenomena that we are. Basically the ATD is not spiting the sample at the ratio for which it has been set. For example, we have the instrument set to recollect 90% of the sample while 10% is sent down the column. In actuality it is closer to a 3:1 ratio, and while the ratio is incorrect, it is consistent. We have determined this through empirical data and fortunately have been able to run the instrument on a production basis with this knowledge. I would like to solve the puzzle though. I am working with PE right now to solve, but i wanted to ask here as well.

Has anyone experienced this? I am happy to provide more detailed system specs if needed.

Thanks
mike

Have you measured the split flow rate to be 9 mL/min? If the split flow is correct, then the column flow is 3 mL/min, not 1 mL/min.

Yes we have, and it is indeed ~9ml/min. Well as far as column flow, my model has the PPC. The col flow can be set independent of split flow. I have it set for 1 ml/min. Now I have taken the ATD650 out of vacuum compensation mode and measured the column flow directly. It too appears to be correct using this method to verify. Also the vacuum we are pulling is quite low, I would expect much higher if we were at 3 ml/min.

however I maybe mistaken, why should it be 3ml/min?

If you set up to recollect 90% of the sample, the desorb flow should be 10 mL/min (9 mL/min split flow and 1 mL/min column flow). If you are recollecting the sample in the ratio of 3 to 1 and the split flow is 9 mL/min, then column flow should be about 3 mL/min to reach the 3:1 ratio (desorb flow 12 mL/min). Have you tried to recollect the sample on a new tube?

Lee Marotta from PE is an expert on the system. Her email:
Lee.Marotta@perkinelmer.com