change retention time with Gas Saver Time

Hi, 

Are you running split or splitless inlet conditions?  What is your total inlet flow at the time of injection?   Have you tried to run the split vent trap diagnostic to see if you have some restriction in the line?

Hi Dear,
my mode is split and its flow 200ml/min.
total flow is 205 ml/min.
how i can run this diagnosis ?

Thanks for clarifying.  Of note, at the time your Gas Saver is enabled (2min), you have just finished a ramped flow increase, so your column flow at that point is 4mL/min, not 2.  The diagnostic trace will tell you when the system is stable at the new flow.  I would recommend waiting until that time before you turn on gas saver, like 2.5 or 3 minutes.  Alternatively, is there a chromatographic reason why you cannot simply start your run at 4 mL/min?   That would simplify the inlet conditions - at least for troubleshooting. 

A few other things I want to make sure I'm understanding correctly.  Under a 2min Gas Saver, your RT is around 4.7min.  When you delay the Gas Saver, your RT is later, but still elutes before the time you enabled Gas saver (RT of 7.9 min with Gas Saver enabled at 10 or 15 minutes).  This indicates that Gas Saver isn't creating the problem, but is masking it.  If you turn Gas Saver off completely, when does your MeOH peak elute? 

I will try to turn off gas saver and kindly allow me tell you what's the result.

Of course!  I look forward to hearing your results.  I think we are getting somewhere

Hi Abbey,
I did some trials as the following :
 gas saver is on ( 20 ml/min after 2 min ) and column constant flow at 4ml/min
- the RT for methanol is 4.56 min.
gas saver is off and column constant flow at 4 ml/min.
- the RT for methanol is 7.610 min.
gas saver is off and column constant flow at 5ml/min
- the RT for methanol is 5.626 min.
 gas saver is off and column constant flow at 7ml/min
-the RT for methanol is 3.679 min.
Since this issue is appeared, i observed the response is doubled ( before issue the response of methanol is around 5000 but when this issue is appeared the response of methanol become around 16000 !)

Hi Abbey 

I did some trails as the following 

1- gas saver is on ( 20ml/min after 2 min ) and the column flow is constant at 4 ml/min, so the rt for methanol is 4.561 min.

2- Gas saver is off and the column flow is 4 ml/ min, so the rt for methanol is 7.610 min.

3- gas saver is off and the column flow is 7 ml/min to achieve 5psi, so the rt for methanol is 3.679 min.

Since this problem is appeared, I observed the response is increased by more than doubled ( before problem the response of methanol is around 5000 but after problem the response become 16000)

Good morning!  Thanks for running these experiments.  I have a few suggestions and follow-up questions.  

Were you able to run the split vent restriction test I mentioned earlier in the thread?  What were the results?

I suggest also running the Leak and Restriction test from the same menu. 

Have you recently changed liners?  What is the part number of your current liner?  

Did you see the response of your methanol peak change with the increased column flow?  I would also be interested to see how the RTs behave if you run 3 repeat injections under the same conditions.   

Do you have access to a flowmeter and/or leak detector?  

Good morning!  Thanks for running these experiments.  I have a few suggestions and follow-up questions.  

Were you able to run the split vent restriction test I mentioned earlier in the thread?  What were the results?

I suggest also running the Leak and Restriction test from the same menu. 

Have you recently changed liners?  What is the part number of your current liner?  

Did you see the response of your methanol peak change with the increased column flow?  I would also be interested to see how the RTs behave if you run 3 repeat injections under the same conditions.   

Do you have access to a flowmeter and/or leak detector?  

Abbey, I hope you're doing well and am grateful for your follow-up.

i implemented what you recommended.

alfausett said:

Were you able to run the split vent restriction test I mentioned earlier in the thread?  What were the results?

yes, sir 

for the split vent restriction test, I opened the split valve ( that I circulated in the attached photo ) then I did the test and passed.

alfausett said:

I suggest also running the Leak and Restriction test from the same menu. 

I also did it and passed.

alfausett said:

Have you recently changed liners?  What is the part number of your current liner?  

No, I never changed the linear and for type and part number, kindly review the attached photo.

alfausett said:

Did you see the response of your methanol peak change with the increased column flow?  I would also be interested to see how the RTs behave if you run 3 repeat injections under the same conditions.   

for the response of methanol to the increased column flow, I attached the results files, and the flow value is known by sample name and considering normal = 4ml/min.

for measuring repeatability of injections, kindly review the attached result files.

alfausett said:

Do you have access to a flowmeter and/or leak detector?  

unfortunately, I don't have.

I posted a reply but it needs approval from the moderator because it has a lot of photos and result files.

Hi Abbey,

I look forward to knowing your diagnosis.

Greetings, and thank you for compiling all of this information!  

A few comments.  On the diagnostic tests, you don't need to open any connections for them to run.  The images on the instructions just describe the system control applied for that test.  The split vent test is actually testing the filter restriction in the housing between the Swagelok fitting circled and the vent on top of that metal housing, so we should reconnect everything and re-run that test to be sure there are no issues.  

Liner selection is good, and is my personal go-to liner for split methods.  

Quickly compiling the basics from your flow variation, I see the following

For the repeatability, 

The repeatability seems good for manual injections.  However, the RTs are significantly later than the flow rate runs, so I presume this is using the original method with the flow ramp on the column and Gas Saver enabled?  

Comparing both sets of data, the RT seems off for the 4mL/min run.  I would expect the 4mL/min RT to be longer than the 5mL/min.  Was there any flow programming or differences in injection for that first run?  

For repeability, the gas saver was off and the column flow was constant at 4ml/min.

Yes, I repeat split vent restriction test without open valve by myself and passed.

alfausett said:

Comparing both sets of data, the RT seems off for the 4mL/min run.  I would expect the 4mL/min RT to be longer than the 5mL/min.  Was there any flow programming or differences in injection for that first run?  

The three runs was exactly the same condition ( flow rate constant )

hi abbey,

kindly let me share with you my method parameters for the repeatability test and column flow changing.

for repeatability, 

for column flow 

4 ml/min 

5 ml/min

7 ml/min

this problem exhausts me, kindly guide me to remedy it as soon as possible.