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Category: MSD ChemStation / Data Acquisition Methods

Records returned: 3

MSD ChemStation / Data Acquisition Methods

1. In MS SIM experiment on HP MSD, is it necessary to list the ions in an increasing order. If so, how about if I want to add a new ion that comes in between two ions. Should I delete and add, or should I be able to insert without deletion. (id=117)

You should be able to insert a new SIM ion without having to delete any existing ones. To add another ion to your SIM method: (1) Use the Edit Entire method from the TOP view under Method (2) Get to the MS SIM/Scan Parameter form (3) Set the Acq mode to SIM (4) Get to the MS SIM Parameters section (5) Enter your masses IN ANY ORDER in the M/Z box (6) Later, Save the Method

2. I want to set up a selected-ion-monitoring (SIM) method for one compound using isotope dilution on a 6890/5973 with a purge and trap. There will be 6 m/z values in the group all between m/z 43 and 96. Because of the narrow m/z range, should I do a more tailored tuning for this analysis and what should this tuning involve? (id=118)

First make sure that when you enter your SIM ions and dwell times that the scan-cycle time is about one second or just a little shorter, depending on your GC peak width. Wider peak width can have longer scan-cycle times. You need to have about 8?10 data points (scan cycles) to properly define the GC peak.

As far as tuning is concerned, you will probably have to meet BFB tuning criteria if you work in an EPA lab. In the tuning section of the ChemStation software, you have a choice to tune to target BFB criteria. If you are not in an EPA lab, use Autotune or MAX Sensitivity tune to increase your sensitivity. After tuning your instrument, you may also want to run a sample with moderate concentrations of all of your analytes where you scan over a range that includes all of your SIM ions; e.g., m/z 40?100 in the example you gave. Look at the data and see what the values are for the recorded mass spectral peaks for the specified SIM ions. If necessary, update your method to include these values. This will improve your specificity and possibly your sensitivity.

3. How do I have the calibration gas valve open during an analysis when using the G1701DA MSD ChemStation? (id=127)

In the MS SIM/Scan Parameters dialog box of Edit Entire Method, selected from theMethod menu, click on the Timed Events. This causes the MS Timed Events Table dialog box to be displayed on top of the MS SIM/Scan Parameters dialog box. Select Valve from the dropdown menu for Event Type. This results in a Parameter 1 and a Parameter 2 selection with dropdown menus. One of the selections (only one selection if you do not have other valves configured) Parameter 1 is Calibration valve. Select On for Parameter 2. You should enter the time from the start of the analysis until the calibration valve is to be opened in the Time entry area. Then click on the Add. You should also enter an Off time which should be later than the On time. After you have entered the ON and Off times, Select the OK button to close this dialog box and return to the MS SIM/Scan Parameters dialog box.