flow rate decreasing after injection

[alchemydon]

Have HP1100 with G1311A quat pump -- purchased complete used system and I am a novice. Pump pressure and flow rate is constant using any channel, any percentage, any or no column, until an injection is made. Then the flow rate immediately begins changing by about 0.01 mL/min for each min of the run and continues throughout the run. The corresponding pressure decreases with the flow decrease. Why just during a run? Thank you in advance!

[bisnettrj2]

Check your method - sounds like you might have a changing flow rate in the method parameters (e.g. - from 1 mL/min to 0.5 mL/min over the length of the run).

[alchemydon]

Checked that, using Chemstation with my own method with no timetable. Thank you for your quick response!

[Blazer]

Just to clarify for my own sake, when you state that

...the flow rate immediately begins changing by about 0.01 mL/min for each min of the run and continues throughout the run.

you mean that if - for example - your run were 10 minutes and you started at 1.0 mL/min, after 1 minute the flow would be 9.99 mL/min, at 2 minutes it would be 9.98 minutes, at 3 minutes it would be at 9.97 mL/min, etc.? And if so, these are the approximate flow rates you see displayed on the Chemstation graphical user interface?

[Camisotro]

Is it an isocratic method or gradient? Are you using an autosampler or manual flow injection?

[alchemydon]

Isocratic with autosampler. Also tried a run from the Control Module and the same thing occurs.

[alchemydon]

yes, the flow rate decreases at a steady rate (as shown on Chemstation status and on the Control Module if using it) (i.e. starts at 1 mL/min and begins dropping -- after 10 minutes the flow is about 0.9 and continues to drop until the run is over at which time the flow rate immediately returns to normal). Works fine at any flow rate as long as not making an injection.

[bisnettrj2]

Ok, just to clear up any doubts I have, can you (in Chemstation) go to Method --> Print Method, then click the "Check All" button, and select "File" as the "Destination for Printout" to generate the report (it will store as methodname.txt in the same directory as the method on your PC). If you could copy everything from Runtime Checklist to the end of the report in your reply, that would be great. That will show everyone what you're dealing with in your method, and clear up any doubts I have about the method being OK.

[bisnettrj2]

One more question - by Control Module, you mean the handheld controller, right? Is that plugged into the system while the instrument is being controlled by the Chemstation?

[alchemydon]

no, was using the handheld controller without Chemstation attached (and visa versa, when using Chemstation the controller is not attached to the system). Not sure if it ever worked correctly (purchased the whole system at auction then added Chemstation -- hope the auction part is not a big mistake).

[bisnettrj2]

So, did you get some time to print the method? Can you post the parameters I requested in my earlier post, so we can veify the method is OK before we start guessing at other possible causes?

[carls]

Are the firmware versions the same on all modules? Strange things can happen if firmware versions conflict. You can check these using the handheld controller or Chemstation. In Chemstation, if memory serves me, its under the instrument menu.

The firmware can be changed by the user but if the process hangs in the midddle you might be left with an unresponsive module that may require a service technician to resolve. This has never happened to me but I've been told its possible. I assume Chemstation (which version of Chemstation?) is communicating to the LC using ethernet?

If needed, the firmware tools and some instructions are available here:
http://www.chem.agilent.com/_layouts/ag ... whid=34884

[bisnettrj2]

carls - Usually you can't get a stack to communicate if all the firmware versions aren't the same (either you will only see the LAN-connected module, or you'll only see the modules with the same firmware and not the one that is different), so I'd be surprised if that was the issue. This, to me, really sounds method-specific because the problem only presents itself when the method is being run, and at no other (apparent) time. However, without the method info, I assume we're all a little suspect that the issue has nothing to do with the method. If it's not the method, though, I'm really confused as to what it might be - some sort of macro that might be running somewhere? Some external device/module that is influencing the system?

[alchemydon]

thank you bisnettrj2 -- sorry, I did not see that post. Thanks for your help! Here is the requested info:

Run Time Checklist




Pre-Run Cmd/Macro: off

Data Acquisition: on

Standard Data Analysis: on

Customized Data Analysis: off

Save GLP Data: off

Post-Run Cmd/Macro: off


Save Method with Data: off

=====================================================================
1100 Quaternary Pump 1
=====================================================================

Control
Column Flow : 1.000 ml/min
Stoptime : 45.00 min
Posttime : Off

Solvents
Solvent A : 0.0 % (ACN)
Solvent B : Off
Solvent C : 0.0 % (0.2% TFA)
Solvent D : 100.0 % (IPA)

PressureLimits
Minimum Pressure : 50 bar
Maximum Pressure : 300 bar


Auxiliary
Maximal Flow Ramp : 100.00 ml/min^2
Primary Channel : Auto
Compressibility : 100*10^-6/bar
Minimal Stroke : Auto

Store Parameters
Store Ratio A : Yes
Store Ratio B : Yes
Store Ratio C : Yes
Store Ratio D : Yes
Store Flow : Yes
Store Pressure : Yes

Timetable

Time Solv.B Solv.C Solv.D Flow Pressure
|--------|-------|-------|-------|-------|-------|
60.00 0.0 75.0 0.0 0.000 200


=====================================================================
Agilent 1100 Diode Array Detector 1
=====================================================================

Signals

Signal Store Signal,Bw Reference,Bw [nm]
A: No 254 4 360 100
B: No 254 16 360 100
C: No 210 8 360 100
D: Yes 230 4 360 100
E: No 280 16 360 100

Spectrum
Store Spectra : None

Time
Stoptime : As pump
Posttime : Off

Required Lamps
UV lamp required : Yes
Vis lamp required : No

Autobalance
Prerun balancing : Yes
Postrun balancing : No
Margin for negative Absorbance: 100 mAU

Peakwidth : > 0.1 min
Slit : 4 nm

Analog Outputs
Zero offset ana. out. 1: 5 %
Zero offset ana. out. 2: 5 %
Attenuation ana. out. 1: 1000 mAU
Attenuation ana. out. 2: 1000 mAU

Timetable is empty


=====================================================================
Agilent 1100 Autosampler 1
=====================================================================

Injection
Injection Mode : Standard
Injector volume : 10.00 µl
Optimization : none

Auxiliary
Drawspeed : 100 µl/min
Ejectspeed : 100 µl/min
Draw position : 0.0 mm

Time
Stoptime : As Pump
Posttime : Off

========================================================================
Integration Events
========================================================================

Results will be produced with the enhanced integrator.

------------------------------------------------------------------------
Default Integration Event Table "Event"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 1.000 Initial
Initial Peak Width 0.040 Initial
Initial Area Reject 1.000 Initial
Initial Height Reject 1.700 Initial
Initial Shoulders OFF Initial

------------------------------------------------------------------------
Detector Default Integration Event Table "Event_DAD"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 5.000 Initial
Initial Peak Width 0.050 Initial
Initial Area Reject 5.000 Initial
Initial Height Reject 1.000 Initial
Initial Shoulders OFF Initial

------------------------------------------------------------------------
Detector Default Integration Event Table "Event_ADC"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 1.000 Initial
Initial Peak Width 0.040 Initial
Initial Area Reject 1.000 Initial
Initial Height Reject 1.700 Initial
Initial Shoulders OFF Initial

------------------------------------------------------------------------
Detector Default Integration Event Table "Event_FLD"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 1.000 Initial
Initial Peak Width 0.040 Initial
Initial Area Reject 1.000 Initial
Initial Height Reject 1.700 Initial
Initial Shoulders OFF Initial

------------------------------------------------------------------------
Detector Default Integration Event Table "Event_VWD"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 1.000 Initial
Initial Peak Width 0.040 Initial
Initial Area Reject 1.000 Initial
Initial Height Reject 1.700 Initial
Initial Shoulders OFF Initial

------------------------------------------------------------------------
Detector Default Integration Event Table "Event_ECD"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 1.000 Initial
Initial Peak Width 0.040 Initial
Initial Area Reject 1.000 Initial
Initial Height Reject 1.700 Initial
Initial Shoulders OFF Initial

------------------------------------------------------------------------
Detector Default Integration Event Table "Event_MWD"
------------------------------------------------------------------------

Event Value Time
|------------------------------------------------|-------------|-------|
Initial Slope Sensitivity 1.000 Initial
Initial Peak Width 0.040 Initial
Initial Area Reject 1.000 Initial
Initial Height Reject 1.700 Initial
Initial Shoulders OFF Initial

Apply Manual Integration Events: No

Advanced Baseline : No

=====================================================================
Specify Report
=====================================================================

Destination: Screen
Quantitative Results sorted by: Signal
Report Style: Short
Sample info on each page: No
Add Chromatogram Output: Yes
Chromatogram Output: Portrait
Size in Time direction: 100 % of Page
Size in Response direction: 40 % of Page

=====================================================================
Signal Options
=====================================================================

Include: Axes, Retention Times, Baselines, Tick Marks
Font: Arial, Size: 8

Ranges: Full
Multi Chromatograms: Separated, Each in full Scale

=====================================================================
Calibration Table
=====================================================================



Calib. Data Modified :

Calculate : Area Percent

Rel. Reference Window : 5.000 %
Abs. Reference Window : 0.000 min
Rel. Non-ref. Window : 5.000 %
Abs. Non-ref. Window : 0.000 min
Use Multiplier & Dilution Factor with ISTDs
Uncalibrated Peaks : not reported
Partial Calibration : Yes, identified peaks are recalibrated
Correct All Ret. Times: No, only for identified peaks

Curve Type : Linear
Origin : Included
Weight : Equal

Recalibration Settings:
Average Response : Average all calibrations
Average Retention Time: Floating Average New 75%

Calibration Report Options :
Printout of recalibrations within a sequence:
Calibration Table after Recalibration
Normal Report after Recalibration
If the sequence is done with bracketing:
Results of first cycle (ending previous bracket)


=====================================================================
Peak Sum Table
=====================================================================

***No Entries in table***
=====================================================================

[Peter Skelton]

Your timetable shows a flow rate of 0 ml/min after 60 minutes...