The first request I’m going to address is how to add or change  internal standard and surrogate compounds in a calibration using Enviroquant and Enhanced Chemstation, and how to configure the software to automatically calculate concentrations and surrogate percent recoveries using the internal standards. I will be using  the 524.3 list as an example. This technique is particularly useful if your lab is expanding the tests offered from hazardous waste (series 8000 methods) to waste water (series 600). Your compound lists and analytical columns will see little to no change, but your internal standard and surrogate compounds may be different. The technique is also useful if you are converting an external standard calibration to an internal standard calibration (for example, 8081) to avoid the closing calibration verification requirements.

Table 4 on page 35 of EPA Method 524.3 lists the target compounds, the internal standard compound each is associated with, and a recommended quant ion. The recommended column for this analysis is the 30m x 0.25mm x 1.4µm Rtx-VMS.

If you use these conditions, you should be able to match your compound list to the published elution order and retention times. The easiest way to reorganize the compound list is in Enhanced ChemStation  under the “Calibrate” menu. If your compound list does not contain the correct internal standards, or they are not configured as internal standards, you will need to use the Edit Compounds option found under the Calibrate menu in Enhanced ChemStation (or Initial Calibration menu in Enviroquant) to add them.

If you don’t have any configured internal standards, your quant database should look similar to the image above. If you have the wrong compounds configured as internal standards, delete them by right clicking on the compound and choosing the delete option. In order to add the first internal standard compound, right  click “Compound Database” at the top of the list, and chose the option “Insert ISTD Compound Below current Group” and then fill out the relevant information for the compound. Make sure you change the quant signal to “Target Ion” and use the recommended ion 114 (taken from EPA method 524.3 Table 4). Do the same for the other two internal standards. You’ll notice, however, that the internal standards are at the bottom of the compound list.

In Enhanced ChemStation, choose “Reorder Compounds” under the “Calibrate” menu, and a popup will open that allows you to move compounds by assigning them a new order number. You want to make sure you list all the compounds associated with internal standard  (IS) 1  before the compounds associated with IS 2, which should be listed before the compounds associated with IS 3. You will want to move the internal standard compounds above the compounds they are associated with. In the case of 524.3 on the Rtx-VMS, you will move 1,4-difluorobenzene above dichlorodifluoromethane, chlorobenzene-d5 between cis-1,3-dichloropropene and toluene, and 1,4-dichlorobenzene-d4 between isopropylbenzene and 4-bromofluorobenzene. I have not been able to find this functionality in Enviroquant.

At this point, if you were to calculate your results, you would see the Internal standards grouped above the target compounds, but we want to calculate the surrogate percent recoveries too.

To calculate the surrogate recoveries, the surrogates need to classified as such in the software. This is done by entering “S” in the edit compound type field under edit compounds on the “Identification” tab.

The expected spike amount for the surrogate and the control ranges are entered on the “Reporting” tab in Edit Compounds.

 

Now, when you calculate results, you should see the surrogate compounds grouped under the internal standard compounds with a calculation of the percent recovered.

I hope this first guide was helpful; don’t hesitate to add questions or suggestions in the comments below. Unless someone suggests something better, the next walk-through will be on running versions of MSD ChemStation that are incompatible with Windows 7 from the Virtual XP machine.

 

 

This entry was posted on Thursday, January 31st, 2013 at 11:49 pm and is filed under Enviro, GC/MS, Optimizing Applications, Tips & Tricks. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.