Chemstation 101: Quickly Update Your Retention Time Windows Using the Run Times Provided by the EZGC Method Translator

Jason, Jack and Michelle have all recently posted on using the EZGC Method Translator. Whether you are changing carrier gasses or performing column trimming maintenance (while maintaining the same elution profile), you can quickly adjust all your compound retention times using the Global Update feature built into MSD ChemStation. The following screenshots show where to find global update in the Enhanced Data Analysis version F.01.00 (those of you running different versions may have different menus).

When you use the "translate" function of the EZGC Method Translator, the elution profile (i.e. elution temperatures AND relative retention times) is preserved. Therefore, we want to enter the retention time shift as a % change. Lets use Jack's Recent column trimming post as an example.

 

You'll notice that the EZGC Method Translator provides a speed factor. This the how much faster the analysis is after translation (Tinit/Tfin). However, we need the percent change in the analytical method's compound retention times. In this case, it is 100 x (Tfin-Tinit)/Tfin, or ((29.34-19.95)/29.34) x 100 = 32.00%

 

Because the retention times are decreasing, it is important to make sure you enter the percentage as a negative number. We can check our work using an early, mid, and late eluting compound from Jack's example pesticide method.

Dichlorvos:  5.72 x (1-.32) = 3.89 min

Chlorpyrifos:  15.45 x (1-0.32) = 10.51 min

Deltamethrin:  22.47 x (1-0.32) = 15.28 min