Giant Peak in Chromatogram

Instrument: 7890B Agilent GC & 7010B TQMS

Hello, our issue started when we noticed a giant peak on a DB-Wax column in the front inlet – it has ions indicative of ethyl ether, which we often use as the solvent in our injections and was injected with the sample that this chromatogram is representing, however, we typically never see the solvent, as it disappears in the solvent delay. Before this front inlet run took place, we ran DHS on our back inlet with the same column, and the chromatogram looked normal with no large peak. There was no solvent in the DHS run, but this proved to us that it likely wasn’t a column or detector issue.

Sample with giant peak (sample was a mix of ~45 flavor standards in diethyl ether solvent), this was a splitless injection on a DB-Wax column and the method has been used previously with no issues:

Mass spectrum of giant peak - looks like ethyl ether:

We ran an air blank (remove solvent from the equation) and the giant peak was still present.

Air blank on DB-Wax (syringe was on and wash station had ethyl ether as it normally does):

We ran a system blank (ran the same method but removed the injection syringe) and the giant peak disappeared, the baseline looked normal.

System blank on DB-Wax (no syringe):

Overlay of the 3 chromatograms:

At this point, we thought the syringe or wash station bottles could be contributing to the issue, so we changed those out with new parts + solvent (which is ethyl ether) and ran another air blank. We also put in a new liner and septum just in case something was going on with our current ones, though they looked visibly fine. The giant peak was still present.

Air blank with new liner, septum, wash station, and syringe:

At this point, we swapped to a DB-5 column (that we know is in good condition) because we thought maybe something might be wrong with the DB-Wax column. We ran an air blank after installing the new column and there is still an elevated baseline due to the solvent peak…though we are not injecting any solvent into the system (aside from washing the syringe at the wash station). We have run the same method many times before and never have had this type of issue. To note, this issue is reproducible, we ran the air blank twice and the chromatograms overlay almost perfectly.

Air blank on DB-5 column:

After calling Agilent, we checked the gold seal (looks completely fine) and the attempted the clean the channel that leads to the split vent line with solvent- it was clean. We ran an ethyl ether solvent blank, an air blank, and a system blank after performing these actions. The system blank looks normal, while the solvent and air blanks have the giant peak.

Chromatogram overlay (DB-5) of ether solvent blank, air blank, and system blank after cleaning/checking gold seal and solvent vent line (the system blank is the blue line):

The only thing in the front inlet that we have not replaced (that we can think of) is the split vent filter cartridge, but we have just ordered parts to do so. Could this be the issue? Is there something else that we are missing or that might be worth trying?

Note: The only thing that happened in the time span between functioning instrument and giant peak was that various solvent mixtures were run on the front inlet. Testing extraction solvents, someone was running DCM/ether, hexane/ether, DCM/hexane on a DB-Wax column – there may have been some water in the samples (we are not sure), but likely not much.

Tune: The tune looks like previous tunes and nothing is out of the ordinary (normal air/water levels)

Any help you can offer would be greatly appreciated, thanks!

0 paulsalverda 3 months ago

All of these peaks are gigantic - they're in the millions to tens of millions when typical peaks should be in the tens to hundreds of thousands.

How much sample is injected? What type of sampler? What syringe volume? What are your splitless parameters? What injection port temperature? Oven temperature profile? What column dimensions, configuration, flows, carrier gas, etc...in short, all of the method parameters as found in the acqmeth.txt file that is located in Windows Explorer underneath your run methods' XXX.M subdirectory? There is also a flle called qqqacqmethod.xml. Would you please upload both of those?

The simplest thing to do is a bit much as once the inlet is cold and apart there are parts to change that might as well all be done together. Replace the septum, liner, swab the inlet body, liner O ring, gold seal, column ferrule, the copper split vent line that goes from the inlet to the split vent trap, swab out the side arm of the injection port weldment, the split vent trap cartridge itself.... and reinstall the parts with the column inserted 6 to 8 millimeters above the end of the ferrule - a bit higher is better than too low.

Diethyl ether should be gone very quickly at higher temperatures. A seven minute wide peak means that the solvent is going to a dead, unswept volume or a very cold spot or both.
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0 IsabelG 3 months ago in reply to paulsalverda

Attached below are the two files you mentioned for the most recent DB-5 run:

1) acqmeth.txt file:

Fullscreen 5633.acqmeth.txt Download

                    INSTRUMENT CONTROL PARAMETERS:    GCMSQQQ
                    -----------------------------------------

   D:\MassHunter\GCMS\1\methods\Isabel\FrontInlet\Front_DB5_SR5.M
      Wed Jul 03 14:54:51 2024

Control Information
------- -----------

Sample Inlet             : GC
Injection Source         : External Device
Mass Spectrometer        : Enabled

Injection Location:  Front


 No Sample Prep method has been assigned to this method.


GC
GC Summary
Run Time                                     41 min
Post Run Time                                0 min

Oven
Temperature
Setpoint                                     On
(Initial)                                    40 °C
Hold Time                                    1 min
Post Run                                     40 °C
Program
#1 Rate                                      6 °C/min
#1 Value                                     250 °C
#1 Hold Time                                 5 min


Equilibration Time                           0.5 min
Max Temperature                              325 °C
Maximum Temperature Override                 Disabled
Slow Fan                                     Disabled

Collision Cell/Backflush
He Quench Gas                                On    2.25 mL/min
N2 Collision Gas                             On    1.5 mL/min
He Backflush EPC                             Supplies Column 2

Front SS Inlet He
                                             ***Excluded from Affecting GC's Readiness State***
Mode                                         Split
Heater                                       On    250 °C
Pressure                                     On    27.993 psi
Total Flow                                   On    10.2 mL/min
Septum Purge Flow                            On    3 mL/min
Gas Saver                                    On    20 After 3 min mL/min
Split Ratio                                  5 :1
Split Flow                                   6 mL/min
Liner                                        Agilent 5190-2293: 900 μL (Splitless, single taper, ultra inert )

Back PTV Inlet He
Mode                                         Solvent Vent
Pressure                                     Off
Total Flow                                   Off
Septum Purge Flow                            Off
Purge Flow to Split Vent                     60 mL/min at 2 min
Vent Flow                                    50 mL/min per min
Vent Pressure                                23.081 psi Until 0 min

Thermal Aux 2 (MSD Transfer Line)
Temperature
Setpoint                                     On
(Initial)                                    250 °C
Post Run                                     0 °C


Column
Column #1
Flow
Setpoint                                     Off
(Initial)                                    1.2 mL/min
Post Run                                     1.2 mL/min

Agilent 122-5562                             
DB-5ms                                       
-60 °C—325 °C (350 °C): 60 m x 250 μm x 0.25 μm
Column lock                                  Unlocked
In                                           Front SS Inlet He
Out                                          Backflush EPC 
(Initial)                                    40 °C
Pressure                                     27.993 psi
Flow                                         1.2 mL/min
Average Velocity                             17.992 cm/sec
Holdup Time                                  5.558 min

Column #2
Flow
Setpoint                                     Off
(Initial)                                    1.4 mL/min
Post Run                                     1.2 mL/min

Agilent 160-2635-1                           
-59 °C—449 °C (449 °C): 1 m x 100 μm x 0 μm  
Column lock                                  Unlocked
In                                           He Backflush EPC
Out                                          MSD 
(Initial)                                    40 °C
Pressure                                     11.484 psi
Flow                                         1.4 mL/min
Average Velocity                             262.74 cm/sec
Holdup Time                                  0.0063434 min

Column Outlet Pressure                       0 psi

Signals
Signal #1:  Test Plot
Description                                  Test Plot
Details                                      
Save                                         Off
Data Rate                                    50 Hz
Dual Injection Assignment                    Front Sample

Signal #2:  Test Plot
Description                                  Test Plot
Details                                      
Save                                         Off
Data Rate                                    50 Hz
Dual Injection Assignment                    Back Sample

Signal #3:  Test Plot
Description                                  Test Plot
Details                                      
Save                                         Off
Data Rate                                    50 Hz
Dual Injection Assignment                    Back Sample

Signal #4:  Test Plot
Description                                  Test Plot
Details                                      
Save                                         Off
Data Rate                                    50 Hz
Dual Injection Assignment                    Back Sample






                            GERSTEL MAESTRO


SYSTEM SETTINGS
   Maestro Runtime         : 41.00 min
   GC Cool Down Time       : 6.00 min
   Cryo Timeout            : 25.00 min



                               GERSTEL CIS


   CIS                     : not used  -  use these parameters if it becomes 'used'

CRYO COOLING
   Cryo Cooling            : used

TEMPERATURE PROGRAM
   Heater Mode             : Standard

   Liner Type              : 013882-010-00 glass liner CIS4, baffled, non deactivated
   Liner Max Temperature   : 400 'C

   Initial Temperature     : -40 'C
   Equilibration Time      : 0.50 min
   Initial Time            : 0.10 min
   Ramp 1                 
       Rate                : 12.00 'C/s
       End Temp            : 250 'C
       Hold Time           : 5.00 min
   Ramp 2                 
       Rate                : 0.0 'C/s



                               GERSTEL MPS PREP


   Sample Prep             : not used


                        GERSTEL MPS Liquid Injection

   Syringe                 : 10ul

SAMPLE PARAMETERS
   Sandwich                : not used

   Inj. Volume             : 1.0 uL
   Air Volume below        : 1.0 uL

   Inj. Speed              : 50.00 uL/s
   Fill Volume             : 2.0 uL
   Fill Strokes            : 2

   Fill Speed              : 5.00 uL/s
   Viscositiy Delay        : 1 s
   Eject Speed             : 50.00 uL/s

   Pre Inj. Delay          : 0 s
   Post Inj. Delay         : 0 s

   Inj. Penetration        : 35.00 mm
   Sample Tray Type        : VT98
   Vial Penetration        : 30.00 mm

CLEANING PARAMETERS
   Preclean Sample         : 0

   Wash Station 1          : Wash1
   Preclean Solv.1         : 2
   Postclean Solv.1        : 2
   Clean Volume Solv.1     : 70 %
   Fill Speed Solv.1       : 5.00 uL/s
   Viscosity Delay Solv.1  : 0 s
   Eject Speed Solv.1      : 50.00 uL/s

   Wash Station 2          : Wash2
   Preclean Solv.2         : 2
   Postclean Solv.2        : 2
   Clean Volume Solv.2     : 70 %
   Fill Speed Solv.2       : 5.00 uL/s
   Viscosity Delay Solv.2  : 0 s
   Eject Speed Solv.2      : 50.00 uL/s



                      END OF INSTRUMENT CONTROL PARAMETERS
                      ------------------------------------

2) qqqacqmethod.xml file:

Fullscreen 7268.qqqacqmethod.xml Download

<?xml version="1.0"?>
<MSAcqMethod xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <msInstrument>QQQ</msInstrument>
  <ionSource>EI</ionSource>
  <tuneFile>atunes.eihs.tune.xml</tuneFile>
  <stopMode>ByChromatographTime</stopMode>
  <stopTime>1</stopTime>
  <solventDelay>7</solventDelay>
  <collisionGasOn>true</collisionGasOn>
  <sourceParameters>
    <sourceParameter>
      <id>SourceHeater</id>
      <posPolarityValue>230</posPolarityValue>
      <negPolarityValue>230</negPolarityValue>
    </sourceParameter>
  </sourceParameters>
  <isTimeFilterEnabled>false</isTimeFilterEnabled>
  <timeFilterPeakWidth>0.0133333337</timeFilterPeakWidth>
  <timeFilter>
    <activeCount>0</activeCount>
    <definition>
      <time>0</time>
      <peakWidth>0.0133333337</peakWidth>
    </definition>
    <definition>
      <time>10</time>
      <peakWidth>0.05</peakWidth>
    </definition>
  </timeFilter>
  <useGain>true</useGain>
  <timeSegments>
    <timeSegment>
      <index>1</index>
      <startTime>0</startTime>
      <isDataSaved>true</isDataSaved>
      <scanSegments>
        <scanSegment>
          <index>1</index>
          <scanType>MS2Scan</scanType>
          <scanTime>200</scanTime>
          <dataStorage>PeakDetected</dataStorage>
          <threshold>100</threshold>
          <scanElements>
            <scanElement>
              <index>1</index>
              <ms2LowMz>35</ms2LowMz>
              <ms2HighMz>300</ms2HighMz>
              <ms2Stepsize>0.1</ms2Stepsize>
              <gain>0.1</gain>
            </scanElement>
          </scanElements>
        </scanSegment>
      </scanSegments>
    </timeSegment>
  </timeSegments>
  <instrumentCurves>
    <samplingRate>5</samplingRate>
  </instrumentCurves>
  <chromatograms>
    <chromatogram>
      <index>1</index>
      <chromType>TIC</chromType>
      <label>TIC</label>
      <offset>0</offset>
      <yRange>1E+07</yRange>
    </chromatogram>
    <defaultExtractionWindow>
      <minus>0.3</minus>
      <plus>0.7</plus>
    </defaultExtractionWindow>
  </chromatograms>
</MSAcqMethod>

We did some of the things you mentioned before posting in the forum (replace the septum, liner, swab the inlet body, liner O ring, gold seal, column ferrule, swab out the side arm of the injection port weldment), but have not swapped out the copper split vent line or split vent cartridge (waiting for some parts).

Thank you for the reply and helping us figure this out

0 paulsalverda 3 months ago in reply to IsabelG

In that acqmeth.txt file...the column flow setpoints for both columns are set to "Off" ? Please make sure that both are checked ON and save the method.

They don't say the control type - Constant Flow is typical. What version of MassHunter Acquisition is running?

One concern is the very low split ratio of 5:1 with a total flow during injection of only 10.2 ml/min. That is too low for decent inlet pressure/flow control. If you think you need to go to lower split ratios that result in less than 20 ml/min of total flow try either a more concentrated sample, more injection volume that still fits in the liner, or splitless mode.

This could be allowing some expanded vapor to push backwards up the carrier gas supply line and then bleed back into the injection port during the run. Try a blank run with the split ratio set to 25:1.

Since you have two columns configured they are probably connected to a Purged Ultimate Union (PUU) in the GC oven. To get this to work properly, there should be a 1 m × 0.005" i.d. metal tubing bleed restrictor installed in the supply line between the Backflush EPC module and the PUU that would be resting on top of the GC oven underneath the top cover. This is there to ensure that the Backflush EPC module always has enough forward flow for good control.

With some sample/column/flow/pressure combinations if that bleed line is not installed it is possible for stuff to go back up the PUU supply line and then bleed back into the PUU during the run.
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