Gain factor applied to specific time in the TIC?

We are detecting methyl methacrylate monomer using air sampling. The signal is so low, we will need to use gain factors. Can I apply gain to a certain region of the TIC or does it have to be applied to the whole chromatogram? My signal height of MMA is currently at 4E+4, other compounds in the standard are at 6E+6 height, what is the suitable gain factor for us?

Parents
  • This is a chromatogram of my high standard, Still haven't gotten to the low. Note that this is actually just one compound injected on the sorbent tube. The compound is methyl methacrylate. The tube is Carbopack B,X. The library identifies the compound at 3.4 mins. The other peaks are unknown and probably side-products of methyl methacrylate heating up (unsure about this). Eventually the plan is to perform air sampling for MMA during combustion of PMMA. SIM is below.

    As you can see, the signal is pretty low especially in SCAN mode. 

    Here is the acqmeth file: 

                             INSTRUMENT CONTROL PARAMETERS:    1
                             -----------------------------------
    
          Mon Sep 18 12:19:39 2023
    
    Control Information
    ------- -----------
    
    Sample Inlet             : GC
    Injection Source         : External Device
    Mass Spectrometer        : Enabled
    
    Injection Location:  Rear
    
    
     No Sample Prep method has been assigned to this method.
    
    
    GC
    GC Summary
    Run Time                                     16.091 min
    Post Run Time                                0 min
    
    Oven
    Temperature
    Setpoint                                     On
    (Initial)                                    36 °C
    Hold Time                                    1 min
    Post Run                                     70 °C
    Program
    #1 Rate                                      9 °C/min
    #1 Value                                     150 °C
    #1 Hold Time                                 0 min
    #2 Rate                                      33 °C/min
    #2 Value                                     230 °C
    #2 Hold Time                                 0 min
    
    
    Equilibration Time                           0.25 min
    Max Temperature                              230 °C
    Maximum Temperature Override                 Disabled
    Slow Fan                                     Disabled
    
    Front SS Inlet He
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    Mode                                         Sleep
    Heater                                       Off
    Pressure                                     Off
    Septum Purge Flow                            Off
    Pre-Run Flow Test                            Off
    Liner                                        Agilent 5183-4709: 140 μL (Direct, straight (gas samples, HS, P&)
    
    Back PTV Inlet He
    Mode                                         Solvent Vent
    Pressure                                     On    6.8361 psi
    Total Flow                                   On    14 mL/min
    Septum Purge Flow                            On    3 mL/min
    Septum Purge Flow Mode                       Standard
    Pre-Run Flow Test                            Off
    Gas Saver                                    On    20 After 2 min mL/min
    Purge Flow to Split Vent                     10 mL/min at 0.01 min
    Vent Flow                                    50 mL/min per min
    Vent Pressure                                6.83 psi Until 0 min
    Liner                                        Agilent G1544-80730: 675 μL (Direct connect, single taper, bottom )
    
    Column
    Column #3
    Flow
    Setpoint                                     On
    (Initial)                                    1 mL/min
    Post Run                                     1.1952 mL/min
    
    Column Information                           Agilent
    Restek-Rxi5SilMS                             
    Temperature Range                            -60 °C—350 °C (350 °C)
    Dimensions                                   30 m x 250 μm x 0.25 μm
    Column lock                                  Unlocked
    In                                           Back PTV Inlet He
    Out                                          MSD 
    (Initial)                                    36 °C
    Pressure                                     6.8361 psi
    Flow                                         1 mL/min
    Average Velocity                             36.187 cm/sec
    Holdup Time                                  1.3817 min
    Control Mode                                 Constant Flow
    
    Column Outlet Pressure                       0 psi
    
    Front Detector FID
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    Makeup                                       He
    Heater                                       On    275 °C
    H2 Flow                                      Off
    Air Flow                                     Off
    Makeup Flow                                  Off
    Carrier Gas Flow Correction                  Constant Makeup and Fuel Flow
    Flame                                        Off
    
    Detector Evaluation
    Perform Detector Evaluation Test             Off
    Signal Selected                              No Signal Selected
    Checkout Sample                              None
    
    
    MSD Transfer Line
    Temperature
    Setpoint                                     On
    (Initial)                                    280 °C
    
    
    
    Aux EPC 1,2,3
    Aux EPC 1 N2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    
    Aux EPC 2 N2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    
    Aux EPC 3 N2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    
    
    PSD 2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    PSD Purge                                    Off
    
    Signals
    Signal #1: 
    Description                                  None
    
    Signal #2: 
    Description                                  None
    
    Signal #3: 
    Description                                  None
    
    Signal #4: 
    Description                                  None
    
    Signal #5: 
    Description                                  None
    
    Signal #6: 
    Description                                  None
    
    Signal #7: 
    Description                                  None
    
    Signal #8: 
    Description                                  None
    
    
    
    
    
    
                                GERSTEL MAESTRO
    
    
    SYSTEM SETTINGS
       Maestro Runtime         : 16.09 min
       GC Cool Down Time       : 5.00 min
       Cryo Timeout            : 15.00 min
    
    
    
                                   GERSTEL CIS
    
    
       CIS                     : 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     : -10 'C
       Equilibration Time      : 0.50 min
       Initial Time            : 0.50 min
       Ramp 1                 
           Rate                : 12.00 'C/s
           End Temp            : 325 'C
           Hold Time           : 5.00 min
       Ramp 2                 
           Rate                : 0.0 'C/s
    
       Low Split               : not used
    
    
    
                                   GERSTEL TDU
    
    
    TEMPERATURE PROGRAM
       Initial Temperature     : 40 'C
       Delay Time              : 0.50 min
       Initial Time            : 0.50 min
       Ramp 1                 
           Rate 1              : 720.0 'C/min
           End Temp 1          : 320 'C
           Hold Time 1         : 7.00 min
       Ramp 2                 
           Rate 2              : 0.0 'C/min
    
    TDU SETTINGS
       Transfer Temp           : 280 'C
       Transfer Temp Mode      : Fixed
       Desorption Mode         : Splitless
       Sample Mode             : Remove Tube - Standby Cooling
       Standby Temp            : 40 'C
    
    
    TDU LIQUID OPTION
       Liquid Option           : not used  -  use these parameters if it becomes 'used'
       Sample Tray             : Rack 1,VT54/2-CVM
       Fixed Liquid Vial       : used
       Liquid Vial             : 1
       Inject into Micro vial  : not used
    
    PYROLYSIS PARAMETERS
    
       Pyrolysis               : not used  -  use these parameters if it becomes 'used'
       Pyro Mode               : Pyro in last hold (standard)
       Pyrolysis Lead Time     : 0.10 min
       Pyrolysis Followup Time : 1.00 min
       Pyrolysis Initial Time  : 0.50 min
       Pyrolysis Initial Temp. : 500 'C
       Pyrolysis Rate 1        : 0.00 'C/s
       Pyrolysis Rate 2        : 0.00 'C/s
       Pyrolysis Heater        : used
    
    
    
    
                                   GERSTEL DHS
    
    
       DHS                     : not used  -  use these parameters if it becomes 'used'
       DHS Module              : DHS
    
    INJECTION TUBE
       Tube Tray               : TDUTray1,VT40t/Tube
       Fixed Tube              : used
       Tube Number             : 1
    
    PURGE TUBE
       Purge Tube              : not used  -  use these parameters if it becomes 'used'
       Purge Tube Tray         :  
       Tube Number             :  
    
    INCUBATION SETTINGS
       Incubation Temperature  : 30 'C
       Incubation Time         : 1.00 min
    
    AGITATION SETTINGS
       Agitator On Time        : 60 s
       Agitator Off Time       : 1 s
       Agitator Speed          : 500 rpm
    
    TRANSFER HEATER SETTINGS
       TEMP                    : 75 'C
    
    PURGE PHASE SETTINGS
       Volume                  : 0.0 mL
    
    TRAPPING PHASE SETTINGS
       Volume                  : 50.0 mL
       Flow                    : 20.0 mL/min
       Trap Temperature        : 25 'C
       Incubation Temperature  : 30 'C
    
    DRYING PHASE SETTINGS
       Volume                  : 0.0 mL
    
    MS Information
    -- -----------
    
    
    General Information
    ------- -----------
    
    
    Acquisition Mode         : SIM/Scan
    Solvent Delay (minutes)  : 1
    Tune file                : D:\MassHunter\GCMS\1\5977\etune.u
    EM Setting mode Gain     : 1.000000
    
    Number of SIM Groups     : 3
    Run Time (if MS only)    : 16 minutes 
    
    [Scan Parameters]
    Start Time               : 1
    Low Mass                 : 35
    High Mass                : 350
    Threshold                : 100
    A/D Samples:             : 8
    
    
    [SIM Parameters]
    Group 1               Group ID                  : Null
    Resolution                : 0
    Group Start Time          : 1
    Number of Ions            : 1
    Ions
    Dwell In Group            :(  Mass,  Dwell) (  Mass,  Dwell)  (  Mass,  Dwell) 
                               (  450.00,50  ) 
    Group 2               Group ID                  : MMA
    Resolution                : 0
    Group Start Time          : 3.52
    Number of Ions            : 5
    Ions
    Dwell In Group            :(  Mass,  Dwell) (  Mass,  Dwell)  (  Mass,  Dwell) 
                               (  41.00,50  )  (  69.00,50  )  (  85.00,50  ) 
                               (  99.00,50  )  (  100.00,50  ) 
    Group 3               Group ID                  : Null
    Resolution                : 0
    Group Start Time          : 3.9
    Number of Ions            : 1
    Ions
    Dwell In Group            :(  Mass,  Dwell) (  Mass,  Dwell)  (  Mass,  Dwell) 
                               (  450.00,50  ) 
    
    
    [MSZones]
    
    MS Source                   : 230 C   maximum 250 C
    MS Quad                     : 150 C   maximum 200 C
    
    Timed Events
    ----- ------
    Number Events= 0
    
    
    
                         END OF MS ACQUISITION PARAMETERS
    
    
                            TUNE PARAMETERS for SN: US2018M021
                            ---------------------------------
    
     Trace Ion Detection is OFF.
    
        34.593   :   EMISSION     
        70.007   :   ENERGY       
         0.503   :   REPELLER     
        88.835   :   IONFOCUS     
        12.582   :   ENTRANCE_LENS
      1509.614   :   EMVOLTS      
                                  1752.4  : Actual EMV 
                                   1.00   : GAIN FACTOR 
      1869.000   :   AMUGAIN      
       140.125   :   AMUOFFSET    
         1.000   :   FILAMENT     
         0.000   :   DCPOLARITY   
        11.650   :   ENTLENSOFFSET
        10.002   :   Ion_Body     
        -2.800   :   EXTLENS      
      -244.000   :  MASSGAIN        
       -28.000   :  MASSOFFSET      
    
                            END OF TUNE PARAMETERS
                            ----------------------
    
    
    
                            END OF INSTRUMENT CONTROL PARAMETERS
                            ------------------------------------
    

Reply
  • This is a chromatogram of my high standard, Still haven't gotten to the low. Note that this is actually just one compound injected on the sorbent tube. The compound is methyl methacrylate. The tube is Carbopack B,X. The library identifies the compound at 3.4 mins. The other peaks are unknown and probably side-products of methyl methacrylate heating up (unsure about this). Eventually the plan is to perform air sampling for MMA during combustion of PMMA. SIM is below.

    As you can see, the signal is pretty low especially in SCAN mode. 

    Here is the acqmeth file: 

                             INSTRUMENT CONTROL PARAMETERS:    1
                             -----------------------------------
    
          Mon Sep 18 12:19:39 2023
    
    Control Information
    ------- -----------
    
    Sample Inlet             : GC
    Injection Source         : External Device
    Mass Spectrometer        : Enabled
    
    Injection Location:  Rear
    
    
     No Sample Prep method has been assigned to this method.
    
    
    GC
    GC Summary
    Run Time                                     16.091 min
    Post Run Time                                0 min
    
    Oven
    Temperature
    Setpoint                                     On
    (Initial)                                    36 °C
    Hold Time                                    1 min
    Post Run                                     70 °C
    Program
    #1 Rate                                      9 °C/min
    #1 Value                                     150 °C
    #1 Hold Time                                 0 min
    #2 Rate                                      33 °C/min
    #2 Value                                     230 °C
    #2 Hold Time                                 0 min
    
    
    Equilibration Time                           0.25 min
    Max Temperature                              230 °C
    Maximum Temperature Override                 Disabled
    Slow Fan                                     Disabled
    
    Front SS Inlet He
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    Mode                                         Sleep
    Heater                                       Off
    Pressure                                     Off
    Septum Purge Flow                            Off
    Pre-Run Flow Test                            Off
    Liner                                        Agilent 5183-4709: 140 μL (Direct, straight (gas samples, HS, P&)
    
    Back PTV Inlet He
    Mode                                         Solvent Vent
    Pressure                                     On    6.8361 psi
    Total Flow                                   On    14 mL/min
    Septum Purge Flow                            On    3 mL/min
    Septum Purge Flow Mode                       Standard
    Pre-Run Flow Test                            Off
    Gas Saver                                    On    20 After 2 min mL/min
    Purge Flow to Split Vent                     10 mL/min at 0.01 min
    Vent Flow                                    50 mL/min per min
    Vent Pressure                                6.83 psi Until 0 min
    Liner                                        Agilent G1544-80730: 675 μL (Direct connect, single taper, bottom )
    
    Column
    Column #3
    Flow
    Setpoint                                     On
    (Initial)                                    1 mL/min
    Post Run                                     1.1952 mL/min
    
    Column Information                           Agilent
    Restek-Rxi5SilMS                             
    Temperature Range                            -60 °C—350 °C (350 °C)
    Dimensions                                   30 m x 250 μm x 0.25 μm
    Column lock                                  Unlocked
    In                                           Back PTV Inlet He
    Out                                          MSD 
    (Initial)                                    36 °C
    Pressure                                     6.8361 psi
    Flow                                         1 mL/min
    Average Velocity                             36.187 cm/sec
    Holdup Time                                  1.3817 min
    Control Mode                                 Constant Flow
    
    Column Outlet Pressure                       0 psi
    
    Front Detector FID
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    Makeup                                       He
    Heater                                       On    275 °C
    H2 Flow                                      Off
    Air Flow                                     Off
    Makeup Flow                                  Off
    Carrier Gas Flow Correction                  Constant Makeup and Fuel Flow
    Flame                                        Off
    
    Detector Evaluation
    Perform Detector Evaluation Test             Off
    Signal Selected                              No Signal Selected
    Checkout Sample                              None
    
    
    MSD Transfer Line
    Temperature
    Setpoint                                     On
    (Initial)                                    280 °C
    
    
    
    Aux EPC 1,2,3
    Aux EPC 1 N2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    
    Aux EPC 2 N2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    
    Aux EPC 3 N2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    
    
    PSD 2
    Pressure
    Setpoint                                     Off
    (Initial)                                    10 psi
    Post Run                                     10 psi
    
    Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
    PSD Purge                                    Off
    
    Signals
    Signal #1: 
    Description                                  None
    
    Signal #2: 
    Description                                  None
    
    Signal #3: 
    Description                                  None
    
    Signal #4: 
    Description                                  None
    
    Signal #5: 
    Description                                  None
    
    Signal #6: 
    Description                                  None
    
    Signal #7: 
    Description                                  None
    
    Signal #8: 
    Description                                  None
    
    
    
    
    
    
                                GERSTEL MAESTRO
    
    
    SYSTEM SETTINGS
       Maestro Runtime         : 16.09 min
       GC Cool Down Time       : 5.00 min
       Cryo Timeout            : 15.00 min
    
    
    
                                   GERSTEL CIS
    
    
       CIS                     : 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     : -10 'C
       Equilibration Time      : 0.50 min
       Initial Time            : 0.50 min
       Ramp 1                 
           Rate                : 12.00 'C/s
           End Temp            : 325 'C
           Hold Time           : 5.00 min
       Ramp 2                 
           Rate                : 0.0 'C/s
    
       Low Split               : not used
    
    
    
                                   GERSTEL TDU
    
    
    TEMPERATURE PROGRAM
       Initial Temperature     : 40 'C
       Delay Time              : 0.50 min
       Initial Time            : 0.50 min
       Ramp 1                 
           Rate 1              : 720.0 'C/min
           End Temp 1          : 320 'C
           Hold Time 1         : 7.00 min
       Ramp 2                 
           Rate 2              : 0.0 'C/min
    
    TDU SETTINGS
       Transfer Temp           : 280 'C
       Transfer Temp Mode      : Fixed
       Desorption Mode         : Splitless
       Sample Mode             : Remove Tube - Standby Cooling
       Standby Temp            : 40 'C
    
    
    TDU LIQUID OPTION
       Liquid Option           : not used  -  use these parameters if it becomes 'used'
       Sample Tray             : Rack 1,VT54/2-CVM
       Fixed Liquid Vial       : used
       Liquid Vial             : 1
       Inject into Micro vial  : not used
    
    PYROLYSIS PARAMETERS
    
       Pyrolysis               : not used  -  use these parameters if it becomes 'used'
       Pyro Mode               : Pyro in last hold (standard)
       Pyrolysis Lead Time     : 0.10 min
       Pyrolysis Followup Time : 1.00 min
       Pyrolysis Initial Time  : 0.50 min
       Pyrolysis Initial Temp. : 500 'C
       Pyrolysis Rate 1        : 0.00 'C/s
       Pyrolysis Rate 2        : 0.00 'C/s
       Pyrolysis Heater        : used
    
    
    
    
                                   GERSTEL DHS
    
    
       DHS                     : not used  -  use these parameters if it becomes 'used'
       DHS Module              : DHS
    
    INJECTION TUBE
       Tube Tray               : TDUTray1,VT40t/Tube
       Fixed Tube              : used
       Tube Number             : 1
    
    PURGE TUBE
       Purge Tube              : not used  -  use these parameters if it becomes 'used'
       Purge Tube Tray         :  
       Tube Number             :  
    
    INCUBATION SETTINGS
       Incubation Temperature  : 30 'C
       Incubation Time         : 1.00 min
    
    AGITATION SETTINGS
       Agitator On Time        : 60 s
       Agitator Off Time       : 1 s
       Agitator Speed          : 500 rpm
    
    TRANSFER HEATER SETTINGS
       TEMP                    : 75 'C
    
    PURGE PHASE SETTINGS
       Volume                  : 0.0 mL
    
    TRAPPING PHASE SETTINGS
       Volume                  : 50.0 mL
       Flow                    : 20.0 mL/min
       Trap Temperature        : 25 'C
       Incubation Temperature  : 30 'C
    
    DRYING PHASE SETTINGS
       Volume                  : 0.0 mL
    
    MS Information
    -- -----------
    
    
    General Information
    ------- -----------
    
    
    Acquisition Mode         : SIM/Scan
    Solvent Delay (minutes)  : 1
    Tune file                : D:\MassHunter\GCMS\1\5977\etune.u
    EM Setting mode Gain     : 1.000000
    
    Number of SIM Groups     : 3
    Run Time (if MS only)    : 16 minutes 
    
    [Scan Parameters]
    Start Time               : 1
    Low Mass                 : 35
    High Mass                : 350
    Threshold                : 100
    A/D Samples:             : 8
    
    
    [SIM Parameters]
    Group 1               Group ID                  : Null
    Resolution                : 0
    Group Start Time          : 1
    Number of Ions            : 1
    Ions
    Dwell In Group            :(  Mass,  Dwell) (  Mass,  Dwell)  (  Mass,  Dwell) 
                               (  450.00,50  ) 
    Group 2               Group ID                  : MMA
    Resolution                : 0
    Group Start Time          : 3.52
    Number of Ions            : 5
    Ions
    Dwell In Group            :(  Mass,  Dwell) (  Mass,  Dwell)  (  Mass,  Dwell) 
                               (  41.00,50  )  (  69.00,50  )  (  85.00,50  ) 
                               (  99.00,50  )  (  100.00,50  ) 
    Group 3               Group ID                  : Null
    Resolution                : 0
    Group Start Time          : 3.9
    Number of Ions            : 1
    Ions
    Dwell In Group            :(  Mass,  Dwell) (  Mass,  Dwell)  (  Mass,  Dwell) 
                               (  450.00,50  ) 
    
    
    [MSZones]
    
    MS Source                   : 230 C   maximum 250 C
    MS Quad                     : 150 C   maximum 200 C
    
    Timed Events
    ----- ------
    Number Events= 0
    
    
    
                         END OF MS ACQUISITION PARAMETERS
    
    
                            TUNE PARAMETERS for SN: US2018M021
                            ---------------------------------
    
     Trace Ion Detection is OFF.
    
        34.593   :   EMISSION     
        70.007   :   ENERGY       
         0.503   :   REPELLER     
        88.835   :   IONFOCUS     
        12.582   :   ENTRANCE_LENS
      1509.614   :   EMVOLTS      
                                  1752.4  : Actual EMV 
                                   1.00   : GAIN FACTOR 
      1869.000   :   AMUGAIN      
       140.125   :   AMUOFFSET    
         1.000   :   FILAMENT     
         0.000   :   DCPOLARITY   
        11.650   :   ENTLENSOFFSET
        10.002   :   Ion_Body     
        -2.800   :   EXTLENS      
      -244.000   :  MASSGAIN        
       -28.000   :  MASSOFFSET      
    
                            END OF TUNE PARAMETERS
                            ----------------------
    
    
    
                            END OF INSTRUMENT CONTROL PARAMETERS
                            ------------------------------------
    

Children
  • You are running in SIM/Scan mode.   The first chromatogram is TIC Scan. The peak in the second SIM time segment, 3.52 to 3.9 minutes, is still visible even at that scale.  0.1x10^7 is 1 million.  Zoom in on just this portion and let's see how big that peak is in SCAN mode along with some background. That peak only needs to be 3x or 4x the noise to be valid.  The other peaks are huge - 1x10^7.  A spectrum of the background near the peak would be interesting, too. 

    The second chromatogram is TIC SIM.  During that time segment it is summing five ions, 41, 69, 85, 99, and 100.  Because it's SIM there is no extraneous background so the peak can be even smaller and still valid. 

    Method recommendations: Because of your very low initial oven temperature, increase the oven temperature equilibration time to 1 to 2 minutes for better run to run reproducibility.   At Gain 1, the system is already running with the EM at ~243 volts above autotune.  The Scan baseline is very low, too, maybe reduce the threshold to 50 or 75 and see how much the baseline increases first.  Below 50 is not useful except for troubleshooting as you start to see electronic background below that.

    I'll need to chat with someone who has Gerstel Maestro and PTV inlet experience about those parameters, but my guess would be that the MMA peak is not being transferred onto the column as well as those other peaks are. Are those other peaks there in a blank, no inject run?  Are they there in a method blank with no MMA in the sample?

    That retention time seems early based on other applications looking for MMA. Search in this catalog for Methyl Methacrylate::5991-5213EN_GC_Catalog_Applications.pdf (agilent.com) .    I think further experimentation and method development is needed.

    Now to answer your original question.  A search in MassHunter Acquistion Help for SIM/Scan gives this answer.

    This EM setting type and value is fixed for all Scan time segments but its value can be overridden by different values specified in timed events

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