HP 5989A GC/MS

 

 

 

 

 

GC/MS –Running Procedure for Software

 

Turn the Helium gas on. Gas pressure should be 8psi.

Set the Oven Temp = 60

Set Injector B Temp = 250

Set Detector B on Temp = 280

Turn Purge Valve A on.

Turn Purge Valve B on.

The GC-MS is operated from the MS Windows workstation located next to the instrument. Programs to acquire and analyze data from the GC/MS are accessed through the Mass Spec Top program as described in the procedure below. It is advisable to limit the number of additional programs running during data acquisition since the system has been known to crash and there is a risk of losing data.

Editing Acquisition Parameters

The instrumental parameters used for data acquisition are specified in the analytical method and may be modified by selecting Edit Entire Method. from the Methods menu of the 5971 Instrument Top window. A series of dialog boxes is displayed through which the instrumental acquisition parameters may be specified.

1)     Method Information: Descriptive comments for a method and designation of which sections of a method are to be executed.

2)     Set Inlet: Select HP 5890 GC

3)     Select 5971 Tune File: Should normally be set to ATUNE.U

4)     Select Acquisition Mode: Select scan mode. In scan mode the mass analyzer is swept continuously through a designated mass range.

5)     Normal Scan Acquisition:

·        Solvent Delay- 1.00 mi. This tells the mass spec when to start    detecting. One wants the solvent to come off the GC before any effluent is sent to the MS source. A one minute solvent delay is good for diethyl ether, a two minute solvent delay for solvents with bp’s below 100 C and a higher solvent delay for solvents like DMSO. You may override the solvent delay by selecting Yes to the Override Solvent Delay prompt that appears after the acquisition has started. Make sure that the solvent front has passed through the analyzer by monitoring the source pressure on the ion gauge before overriding the solvent delay. The solvent delay might be set to 0 minutes in a number of unusual instances:

Ø     Analyses involving the injection of the sample as a vapor – headspace analysis, for example. The sample loading unto the system is very low in this case.

Ø     The analysis of a mixture of many components, such as gasoline, where no solvent is used but the concentration of no single component is enough to overpressure the source.

Ø     The analysis of less volatile analytes using a heavy solvent such as hexadecane. In this case, the run is terminated after the analytes have eluted but before the solvent. The GC oven is ramped to a temperature sufficient to elute the solvent after the MS has turned off.

·        EM Voltage=0. The electron multiplier voltage or detector gain. Increasing this voltage will increase the abundances of the ions reported in the scan. The eM voltage is normally set relative to the voltage set when the instrument is tuned - typically is just left at the tuning voltage or 0 relative.

·        MS Scan Param:

Ø     Real time, plot Param-default-ok.

Ø     This GC/MS is not equipped to do the following-

                                             Inlet Temperature Program-ok

                                             Select inlet-A

                                             Inlet A pressure Program: Initial  

                                             Pressure 21 kPa

                                             Initial Time: 480.00 min

                                             GC Pressure Unit: kPa

 

Ø     You can change the following stuffs-

                                                  Entered Values:

                                                        Column length-30.00m

                                                        Column Diameter-.25mm-ok    

                                                        Gas-He: Vacuum Comp On

                                                         No Aux Channel-ok

                                                   Calculated Values:

                                                         Oven Temp: 50 C

                                                         Press=0kPa

                                                         Flow=0kPa

                                                         Velocity=0 cm/sec

Ø     Aux Pressure Program

                                                         Aux Channel C

                                                         Aux Pressure Program

                                                         Initial Pressure=0kPa

                                                         Initial Time=480.00 min

                                                         GC Pressure Unit kPa.

6)     Temp Information(you can change this too)-

·        Zone Temperature:

Ø     Injection port B- SetPoint 280, Actual 0

Ø     Detector B-290

These zones should be set slightly above the boiling point of the least volatile compound to be injected into the system to insure that all of the sample reaches the mass spectrometer without condensing.

·        Oven Program:

Ø     Initial temperature-50/60C. Actual -0C. The initial temperature should ideally be above the boiling point of the solvent but below the boiling point of the analytes. A lower temperature will retain the compounds on the column longer.

Ø     Initial time-2.0 min. The initial time is the length of time the GC will remain at the initial temperature before the temperature will be started.

Ø     Level 1- Rate (20)   Temp (280)   Time (10.0). The rate specifies how fast the GC oven temperature will rise. A slower temperature ramp will separate compounds with similar boiling points with the trade off of a longer analysis time.

Ø     Final Temp: The final temp should be above the boiling point of the least volatile compound in the sample to ensure that none of the sample will remain on the column to contaminate subsequent

analyses.

Ø     Final Time: The final time is the length of time the GC oven will be maintained at the final temperature.

Ø     Oven on-ok

Ø     The total run time is automatically calculated.

          

·        Oven Param:

Ø     Oven max-325C. he maximum temperature for the GC.

Ø     Oven on.

Ø     Oven Equil Time: .50 min. This is the time that must elapse after the oven has reached the initial temperature before the Not Ready light on the GC control panel goes out.

Ø     Ambient = 25

·        Injector Information:

                                Sources:

Ø     Manual

Ø     Auto

                                Location:

Ø     Rear-B

                                 ALS:

Ø     Sample Wash-1-Wash once

Ø     Sample Volume-1stop-1microliter

Ø     Sample pump-2

Ø     Solvent A wash=0

Ø     Solvent B wash=3

Ø     On column-no

Ø     Viscosity Delay-5sec(The less the better,injector will slowly inject sample)

Ø     Purge A/B –ontime-0.0, offtime-0.0

Ø     Purge A:off

Ø     Purge B-on

Ø     Purge inj-ok

Ø     MS Run Table –ok

Ø     Select Reports –ok

Ø     Percent Report Option –ok

Ø     Save method as Default-ok

7)     Method

·        Run

·        Name:

·        Sample name:    Vial = 1/2/3(number of place where you put the sample in carousal)

·        Run, Override-yes

If injection is successful you will hear a sound.

8)     Data Analysis:

·        Main Panel, Data Analysis, File, File load-ok

·        Put mouse on graph and double click on right side of mouse. You will see the mass spec.

          After done do the following:

·        Purge Valve A off

·        Purge Valve B off.

 

Additional Information:

Flow Meters:

To determine the carrier gas flow rate we use bubble flow meter. It consists of reservoir of soap solution, a calibrated glass tube and a squeeze bulb. Bubble flow meters are normally calibrated in 0-2, 0-10, and 0-60. A rubber tube connects the GC exit port (septum purge vent and inlet vent) to a side arm on the calibrated flow meter. The GC column effluent causes the soap film to form bubbles that traverse through the calibrated column. The flowrate is determined by timing how long the bubbles take to travel the calibrated column. For example to start the stop watch press time in GC/MS two/three times, it will show t=,1/t= (this is the stop watch for GC/MS), hit enter when bubble passes 0-mL calibration mark. Hit enter again when bubble passes 1-mL calibration mark. If it takes 15 secs (.25) min the flow rate is 1ml/.25 min=4ml/min.

Flow rate for septum purge = 4.0 mL/min

Flow rate for Inlet vent= 1.0 mL/min. It should always remain less than 1.5 mL/min.

Pressure=8psi.

To wash the syringe:

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