Acrylonitrile analysis method

suuuuuu 1 month ago

Dear Sir/Madam,

I hope this message finds you well.

We are currently attempting to analyze acrylonitrile (m/z 53, 52, 51) using the Perkin Turbo Matrix 40 HS, 6890N GC, and 5975 MSD.

While we have successfully detected substances such as vinyl chloride and bromoform, we are encountering difficulties with acrylonitrile, as no peaks are appearing.

Even when diluting the sample in a solvent and injecting it directly, rather than using the headspace method, we are still unable to obtain satisfactory results.

Could this issue be related to the MSD?

For your reference, we are using a VF-624MS column (30 m × 0.32 mm × 1.8 μm).

We would greatly appreciate any advice or guidance you could provide on this matter.

Thank you for your assistance.

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0 paulsalverda 28 days ago

The 30×320µM column does not have enough restriction for use with a Mass Spectrometer. Your column flow at 1.5 ml/min, a bit too high for optimal MS, only results in 1.65 psi inlet pressure at your 35° C oven initial temperature. For decent pressure/flow control the inlet must never be less than 5 psi when running samples. It would be best to replace that column with a 30×250µM or even narrower column.

In Windows Explorer underneath your run method's METHOD.M subdirectory is a file called ACQMETH.TXT. Please upload that file or copy/paste it for review.
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0 suuuuuu 24 days ago in reply to paulsalverda

Fullscreen 7853.acqmeth.txt Download

                               INSTRUMENT CONTROL PARAMETERS:    GCMSD
                               ---------------------------------------

   C:\MSDCHEM\1\METHODS\VINYL CHLORIDE, ACRYLONITRILE, BROMOFORM METHOD\VC,AN,BROM SIM-20240614.M
      Fri Jun 14 10:13:54 2024

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

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


 No Sample Prep method has been assigned to this method.

=============================================================================
                                6890 GC METHOD
=============================================================================


OVEN
   Initial temp:  35 'C (On)               Maximum temp:  275 'C
   Initial time:  4.00 min                 Equilibration time:  0.50 min
   Ramps:
      #  Rate  Final temp  Final time
      1 10.00      230        1.50
      2   0.0(Off)
   Post temp:  0 'C
   Post time:  0.00 min
   Run time:  25.00 min


FRONT INLET (SPLIT/SPLITLESS)           BACK INLET (UNKNOWN)
   Mode:  Split
   Initial temp:  250 'C (On)
   Pressure:  1.62 psi (On)
   Split ratio:  5:1
   Split flow:  7.5 mL/min
   Total flow:  11.6 mL/min
   Gas saver:  Off
   Gas type:  Helium


COLUMN 1                                COLUMN 2
   Capillary Column                        (not installed)
   Model Number:  Agilent VF-624ms

   Max temperature:  280 'C
   Nominal length:  30.0 m
   Nominal diameter:  320.00 um
   Nominal film thickness:  1.80 um
   Mode:  constant flow
   Initial flow:  1.5 mL/min
   Nominal init pressure:  1.63 psi
   Average velocity:  44 cm/sec
   Inlet:  Front Inlet
   Outlet:  MSD
   Outlet pressure:  vacuum


FRONT DETECTOR (NO DET)                 BACK DETECTOR (NO DET)


SIGNAL 1                                SIGNAL 2
   Data rate:  20 Hz                       Data rate:  20 Hz
   Type:  test plot                        Type:  test plot
   Save Data:  Off                         Save Data:  Off
   Zero:  0.0 (Off)                        Zero:  0.0 (Off)
   Range:  0                               Range:  0
   Fast Peaks:  Off                        Fast Peaks:  Off
   Attenuation:  0                         Attenuation:  0


COLUMN COMP 1                           COLUMN COMP 2
   (No Detectors Installed)                (No Detectors Installed)


THERMAL AUX 2
   Use:  MSD Transfer Line Heater
   Description:
   Initial temp:  280 'C (On)
   Initial time:  0.00 min
      #  Rate  Final temp  Final time
      1   0.0(Off)


                                        POST RUN
                                           Post Time: 0.00 min


TIME TABLE
   Time       Specifier                     Parameter & Setpoint




                               GC Injector


     Front Injector:
          Injector not configured, use these parameters if it becomes configured
        Sample Washes                 0
        Sample Pumps                  6
        Injection Volume           1.00 microliters
        Syringe Size               10.0 microliters
        PostInj Solvent A Washes      0
        PostInj Solvent B Washes      0
        Viscosity Delay               0 seconds
        Plunger Speed              Fast

     Back Injector:
No parameters specified

 Column 1 Inventory Number : CP9104
 Column 2 Inventory Number :  

                                MS ACQUISITION PARAMETERS


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

Tune File                : atune.u
Acquistion Mode          : SIM


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

Solvent Delay            : 1.00 min

EMV Mode                 : Relative
Relative Voltage         : 0
Resulting EM Voltage     : 1412

[Sim Parameters]

GROUP 1
Group ID                 : 1
Resolution               : Low
Plot 1 Ion               : 62.00
Ions/Dwell In Group      (  Mass,  Dwell) (  Mass,  Dwell) 
                         ( 62.00,    100) ( 64.00,    100) 

GROUP 2
Group ID                 : 2
Resolution               : Low
Group Start Time         : 3.00
Plot 1 Ion               : 53.00
Ions/Dwell In Group      (  Mass,  Dwell) (  Mass,  Dwell) (  Mass,  Dwell) 
                         ( 51.00,    100) ( 52.00,    100) ( 53.00,    100) 

GROUP 3
Group ID                 : 3
Resolution               : Low
Group Start Time         : 6.00
Plot 1 Ion               : 96.00
Ions/Dwell In Group      (  Mass,  Dwell) (  Mass,  Dwell) 
                         ( 77.00,    100) ( 96.00,    100) 

GROUP 4
Group ID                 : 4
Resolution               : Low
Group Start Time         : 9.00
Plot 1 Ion               : 82.00
Ions/Dwell In Group      (  Mass,  Dwell) (  Mass,  Dwell) 
                         ( 82.00,    100) (117.00,    100) 

GROUP 5
Group ID                 : 5
Resolution               : Low
Group Start Time         : 12.00
Plot 1 Ion               : 173.00
Ions/Dwell In Group      (  Mass,  Dwell) (  Mass,  Dwell) (  Mass,  Dwell) 
                         (171.00,    100) (173.00,    100) (175.00,    100) 
                         (254.00,    100) 

GROUP 6
Group ID                 : 6
Resolution               : Low
Group Start Time         : 14.00
Plot 1 Ion               : 152.00
Ions/Dwell In Group      (  Mass,  Dwell) (  Mass,  Dwell) (  Mass,  Dwell) 
                         (115.00,    100) (150.00,    100) (152.00,    100) 

[MSZones]

MS Source                : 230 C   maximum 250 C
MS Quad                  : 150 C   maximum 200 C

Timed Events
----- ------

[Timed MS Detector Table Entries]

Time (min)          State (MS On/Off)
17.00                    Off


                             END OF MS ACQUISITION PARAMETERS


                              TUNE PARAMETERS for SN: US60522243
                        -----------------------------

 Trace Ion Detection is OFF.

 EMISSION    :      34.610
 ENERGY      :      69.922
 REPELLER    :      25.432
 IONFOCUS    :      90.157
 ENTRANCE_LE :      35.000
 EMVOLTS     :    1411.765
                               Actual EMV  :    1411.77
                               GAIN FACTOR :       0.82
 AMUGAIN     :    1621.000
 AMUOFFSET   :     122.000
 FILAMENT    :       1.000
 DCPOLARITY  :       0.000
 ENTLENSOFFS :      16.314
 MASSGAIN    :    -680.000   
 MASSOFFSET  :     -33.000   

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



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

당신의 응답을 주셔서 감사합니다. 파일을 첨부했습니다.

0 paulsalverda 24 days ago in reply to suuuuuu

Here are some recommendations. Please change to a 30×0.250 or narrower/longer column. The inlet pressure must be >5 psi for good pressure control. The split ratio/total flow is too low for good control. What is the flow coming out of your headspace sampler? At this low pressure and flow, it is possible for air to diffuse into the inlet and oxygen to damage the column, too. Do you use a matrix modifier in your headspace vials as described in this GC method ? 5991-8096EN.pdf (agilent.com)
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0 paulsalverda 24 days ago in reply to suuuuuu

Here are some recommendations. Please change to a 30×0.250 or narrower/longer column. The inlet pressure must be >5 psi for good pressure control. The split ratio/total flow is too low for good control. What is the flow coming out of your headspace sampler? At this low pressure and flow, it is possible for air to diffuse into the inlet and oxygen to damage the column, too. Do you use a matrix modifier in your headspace vials as described in this GC method ? 5991-8096EN.pdf (agilent.com)
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0 suuuuuu 22 days ago in reply to paulsalverda

Perkin Turbo Matrix 40 HS의 현재 상태는 다음과 같습니다.

20mL 헤드스페이스 바이알에 증류수 10mL와 K2CO3(탄산칼륨) 6g을 첨가하여 분석합니다.

온도(℃)	바늘	110	옵션	약병 통풍구	~에
	옮기다	120
	오븐	80
타이밍(분)	압력을 가하다	2	PPC(psi)	열	20
	주입하다	0.05		주입하다	20
	철회하다	0.1
	온도	30
	GC주기	34

예비 컬럼이 없고 30 x 0.32mm 컬럼을 사용하여 분석해야 하는 경우 어떻게 해야 합니까?
주입구 압력을 5psi 이상으로 높이기 위해 컬럼 흐름을 3mL/분으로 변경할 수 있습니까?
염화비닐은 1.4분에 용출되므로 용매 지연 시간을 1분으로 설정했습니다. 어떻게 진행해야 합니까?
그룹 1은 용매 지연이 끝나면 시작하지만 용매 이온을 찾지 못합니다. 이것이 무엇을 의미하는지, 더 알아보고 싶습니다.

아직 배울게 너무 많아서 답변해주시면 정말 감사하겠습니다.
답변을 제공해 주셔서 감사합니다.

-------------------------------------------------------------------------------------------------------------------------------------------------------(+)-----------------------------

I have a few additional questions:

After setting the column flow to 3, when I switch to Splitless mode, the pressure and total flow appear to be abnormal, as shown in the attached image.

What is the typical range for the split vent flow that should be used?
Is this issue related to the column inner diameter?
What adjustments need to be made in order to use the Splitless mode?

Thank you.

+1 paulsalverda 21 days ago in reply to suuuuuu

Column flow 3 is too high for a GCMS system. Column flow 0.8 to 1.4 ml/min is the optimal range. If you don't have the proper sized column, do you have any other columns at all? Using the proper connector you could connect two columns together to make one longer one and get the proper column flow and inlet pressure.

Splitless mode is not used with headspace or purge & trap systems. It is used with liquid injections. Purge flow to split vent is typically 50 to 75 ml/min at 0.8 minutes, but that time is related to the actual column flow. Then set gas saver on at 20 ml/min at 2.00 minutes. Setting purge flow to split vent at 15 ml/min at 0.00 minutes is the same as running split.

You are running in SIM mode, which only looks at specific ions and not all of the ions that are being created in the ion source. Please edit your method to SCAN mode, 35-500 amu, N=2, and Gain=1, save it as a new method name, and run it once. If the solvent peak is there then you need to adjust your methodology so that the solvent peak elutes completely before the peaks of interest.

There is so much to learn! Please take a look at the Agilent University courses to begin the training path... Agilent University | Agilent
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0 suuuuuu 21 days ago in reply to paulsalverda

Thank you for the response.

It seems the only thing I can do is to replace the columns.

Thank you for your help.
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