Help separating a coeluting peak

I am having trouble separating methyl methacrylate (MMA) from another peak. The interfering compound, appearing in the front, is identified by library as 3,3-dimethyl-2-butanone and it is inherent to the sample. MMA appears as the split/tailing peak. Both compounds have a boiling point around 100 C. Identification by mass spectrum is also challenging because both compounds share m/z values 41, 69, 85, and 100. However the interferent is often identified by m/z 57.1.

How can I separate these two peaks? If I change the detector settings to start looking at m/z 60 (essentially excluding the 57.1) will that improve anything?

                      INSTRUMENT CONTROL PARAMETERS:    1
                      -----------------------------------

      Wed Jan 17 15:49:45 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                                     22.133 min
Post Run Time                                0 min

Oven
Temperature
Setpoint                                     On
(Initial)                                    32 °C
Hold Time                                    7 min
Post Run                                     70 °C
Program
#1 Rate                                      10 °C/min
#1 Value                                     70 °C
#1 Hold Time                                 0 min
#2 Rate                                      30 °C/min
#2 Value                                     320 °C
#2 Hold Time                                 3 min


Equilibration Time                           0.25 min
Max Temperature                              320 °C
Maximum Temperature Override                 Disabled
Slow Fan                                     Disabled

Front SS Inlet He
Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
Mode                                         Split
Heater                                       On    250 °C
Pressure                                     On    17.909 psi
Total Flow                                   On    22.02 mL/min
Septum Purge Flow                            On    3 mL/min
Pre-Run Flow Test                            Off
Gas Saver                                    On    20 After 3 min mL/min
Split Ratio                                  10 :1
Split Flow                                   17.291 mL/min
Liner                                        Agilent 5190-2293: 900 μL (Splitless, single taper, wool, Ultra )

Back PTV Inlet He
Mode                                         Sleep
Pressure                                     Off
Septum Purge Flow                            Off
Pre-Run Flow Test                            Off
Liner                                        Agilent G1544-80730: 675 μL (Direct connect, single taper, bottom )

Column
Column #1
Flow
Setpoint                                     On
(Initial)                                    1.7291 mL/min
Post Run                                     0.57353 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                                           Front SS Inlet He
Out                                          PSD 2 
(Initial)                                    32 °C
Pressure                                     17.909 psi
Flow                                         1.7291 mL/min
Average Velocity                             34.759 cm/sec
Holdup Time                                  1.4385 min
Control Mode                                 Constant Flow

Column #2
Pressure
Setpoint                                     On
(Initial)                                    2 psi
Post Run                                     10 psi

Temperature Range                            -1 °C—325 °C (325 °C)
Dimensions                                   5 m x 200 μm x 0 μm
Column lock                                  Unlocked
In                                           PSD 2 He
Out                                          MSD 
(Initial)                                    32 °C
Pressure                                     2 psi
Flow                                         1.5224 mL/min
Average Velocity                             109.14 cm/sec
Holdup Time                                  0.076352 min
Control Mode                                 Constant Pressure

Column Outlet Pressure                       0 psi

Front Detector FID
Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
Makeup                                       He
Heater                                       On    300 °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)                                    320 °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
Excluded from Readiness                      ***Excluded from Affecting GC's Readiness State***
PSD Purge                                    On    0 mL/min
PSD 2 He                                     Supplies Column 2

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         : 22.13 min
   GC Cool Down Time       : 5.00 min
   Cryo Timeout            : 15.00 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     : -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 MPS PREP


   Sample Prep             : used

PREP ACTION LIST

     Action          Method/Value          Source                Destination
     =============   ===================   ===================   ===================






                        GERSTEL MPS Liquid Injection

   Syringe                 : 10ul 65mm USM

SAMPLE PARAMETERS
   Sandwich                : not used

   Inj. Volume             : 1.0 uL
   Air Volume below        : 0.0 uL

   Inj. Speed              : 50.00 uL/s
   Fill Volume             : 5.0 uL
   Fill Strokes            : 5

   Fill Speed              : 2.00 uL/s
   Viscositiy Delay        : 0 s
   Eject Speed             : 50.00 uL/s

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

   Inj. Penetration        : 40.00 mm
   Sample Tray Type        : VT54/2-CVM
   Bottom Sense            : used
   Fast Injection          : used

CLEANING PARAMETERS
   Preclean Sample         : 2

   Wash Station 1          : Pos1@Standard Wash 1
   Preclean Solv.1         : 2
   Postclean Solv.1        : 6
   Clean Volume Solv.1     : 90 %
   Fill Speed Solv.1       : 5.00 uL/s
   Viscosity Delay Solv.1  : 0 s
   Eject Speed Solv.1      : 50.00 uL/s
   Information Solv.1      : Hexane

   Wash Station 2          : Pos2@Standard Wash 1
   Preclean Solv.2         : 0
   Postclean Solv.2        : 0
   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

MS Information
-- -----------


General Information
------- -----------


Acquisition Mode         : Scan
Solvent Delay (minutes)  : 3.3
Tune file                : D:\MassHunter\GCMS\1\5977\etune.u
EM Setting mode Gain     : 5.000000

Normal or Fast Scanning  : Normal Scanning
Trace Ion Detection      : Off
Run Time (if MS only)    : 23.67 minutes 

[Scan Parameters]
Start Time               : 3.3
Low Mass                 : 40
High Mass                : 300
Threshold                : 300
A/D Samples:             : 4


[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       
     3.192   :   REPELLER     
    89.822   :   IONFOCUS     
    22.672   :   ENTRANCE_LENS
  1665.995   :   EMVOLTS      
                              2022.2  : Actual EMV 
                               5.00   : GAIN FACTOR 
  1873.000   :   AMUGAIN      
   132.813   :   AMUOFFSET    
     1.000   :   FILAMENT     
     0.000   :   DCPOLARITY   
     6.828   :   ENTLENSOFFSET
     9.002   :   Ion_Body     
     3.506   :   EXTLENS      
  -255.000   :  MASSGAIN        
   -32.000   :  MASSOFFSET      

                        END OF TUNE PARAMETERS
                        ----------------------



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

Parents
  • Hi kayleemorton,

    to improve the separation of MMA from 3,3-dimethyl-2-butanone, focus on optimizing the chromatographic conditions rather than adjusting the MS detection settings. Once you achieve better separation, you can then refine the MS settings to enhance the identification and quantification of your target components 

    1. Column Selection:

      • Type and Length: Consider using a column with a different stationary phase that may offer better selectivity for these compounds. Longer columns generally provide better separation.
      • Diameter and Film Thickness: A column with a smaller internal diameter and a thicker film might improve separation due to higher resolution, albeit at the cost of longer analysis time.
    2. Temperature Program:

      • Adjusting the temperature program of the GC oven can help in separating closely eluting compounds. A slower temperature ramp might give the compounds more time to separate on the column.
    3. Carrier Gas Flow Rate:

      • Modifying the carrier gas (usually helium or hydrogen) flow rate can also impact the separation. Slowing down the flow rate can increase the resolution between peaks, but like with longer columns, it will also increase the analysis time.
    4. Injection Technique:

      • Experiment with split or splitless injection techniques and adjust the split ratio if you're using split injection. This can influence the peak shape and resolution.
Reply
  • Hi kayleemorton,

    to improve the separation of MMA from 3,3-dimethyl-2-butanone, focus on optimizing the chromatographic conditions rather than adjusting the MS detection settings. Once you achieve better separation, you can then refine the MS settings to enhance the identification and quantification of your target components 

    1. Column Selection:

      • Type and Length: Consider using a column with a different stationary phase that may offer better selectivity for these compounds. Longer columns generally provide better separation.
      • Diameter and Film Thickness: A column with a smaller internal diameter and a thicker film might improve separation due to higher resolution, albeit at the cost of longer analysis time.
    2. Temperature Program:

      • Adjusting the temperature program of the GC oven can help in separating closely eluting compounds. A slower temperature ramp might give the compounds more time to separate on the column.
    3. Carrier Gas Flow Rate:

      • Modifying the carrier gas (usually helium or hydrogen) flow rate can also impact the separation. Slowing down the flow rate can increase the resolution between peaks, but like with longer columns, it will also increase the analysis time.
    4. Injection Technique:

      • Experiment with split or splitless injection techniques and adjust the split ratio if you're using split injection. This can influence the peak shape and resolution.
Children
No Data
Was this helpful?