How to Get Equivalent GC-MS Results Faster Using the EZGC Method Translator and GC Accelerator Kit

Description

This video will show you how to adjust your run conditions when switching to a column with smaller dimensions for the purposes of reducing your run time. The combination of using a GC Accelerator oven insert kit and adapting an existing method to a scaled down, more efficient column using our EZGC method translator is a surprisingly simple means of speeding up your analyses to get similar results faster. 

Additional Resources

• EZGC Method Translator

Restek Recommended Tools & Parts

• GC Accelerator Oven Insert Kit

Transcript

How to Get Equivalent GC-MS Results Faster Using Restek’s EZGC Method Translator and GC Accelerator. 

In this video we will show you how the combination of using a GC Accelerator oven insert kit and adapting an existing method to a scaled down, more efficient column using our EZGC method translator is a surprisingly simple means of speeding up your analyses to get similar results faster.  

Faster analyses can be obtained on any GC by moving to a shorter column with a narrower inner diameter (ID) and thinner film. A smaller ID and thinner film results in more efficient columns that produce narrower peaks, which allow relative peak separations to be maintained and compressed into shorter run times. When changing column dimensions, it’s important to adjust the inner diameter and film thickness proportionally so the phase ratio stays the same.  The more efficient column should also be shorter than the original.  The scaled-down, more efficient column will have more plates/meter, but we want to keep the total number of plates the same between the two, so you’ll end up with a shorter final column length for this reason. However, just properly scaling down your column won’t give you the same results in less time.  

For our demonstration, let’s say you’re performing PCB analyses on an Agilent GC-MS using the conditions shown. You’re happy with the separation, but want to shorten analysis time so you can analyze more samples per shift. The first step is to select a scaled-down column with the same phase ratio and the same number of theoretical plates.    

In this example, we are switching from a 30 m, 0.25 mm, 0.25 µm column to a commercially available 20 m, 0.15 mm, 0.15 µm column, which will have very nearly the same number of total plates. To obtain the translated method conditions that provide the same chromatographic separation in less time on the new column, use the following steps. Go to www.restek.com/ezgc-mtfc if you’d like to try using the EZGC method translator yourself as we move through the example. 

Start by selecting the correct carrier gas for your method, then input your existing method conditions into the translator. Next, enter your current column dimensions. Then enter your current method’s column flow. Note that average velocity, holdup time, and inlet pressure will autofill based on the column flow you specify. Because this is a MS method, make sure the outlet pressure value is set to 0 psi and the vacuum button is selected. These are the default selections, but note that the modeler output would be different if you were using an FID, for instance, and the outlet pressure was atmospheric pressure instead of the vacuum generated by a mass spectrometer.  

Enter your current oven program. Make sure the control method is correct and the default radio button “Translate” is selected. By choosing the “Translate” option you are asking the EZGC method translator to balance speed and efficiency. Enter the new column dimensions and the EZGC method translator will do the rest of the work by providing a new column flow and the subsequently calculated flow-related parameters and new oven ramp rates, giving you a shorter analysis time for the same separation on the scaled down column you selected. In this example, we’re seeing a savings of almost 8 minutes, almost 30%, in analysis time. Put simply, this change would allow an instrument to complete a sequence of samples that normally would take 8 hours in a little more than 5.5 hours. Note that the translated method calls for oven ramp rates that a standard GC oven may not be able to achieve. If this is the case, the use of the GC Accelerator oven insert kit for Agilent 6890 & 7890 instruments may be the solution. The GC Accelerator kit reduces oven volume, which shortens heating/cooling times and allows aggressive ramp rates to be met.   

The last thing you’ll need to keep in mind if you implement these changes is moving to a narrower, thinner film column is best paired with the adoption of a split injection mode. The value of the split injection is two-fold. First, if there were any loading capacity concerns with a thinner film producing overloaded, fronting peaks, the split injection will take care of that. Second, the biggest benefit is the very rapid transfer of the sample onto the column, which will help keep the bands of molecules narrow, and, as a result, your peaks narrow.   

In summary, equivalent chromatographic results can be obtained in much faster analysis times for many applications by moving to a scaled down, more efficient column with the same phase ratio. EZGC method translation software from Restek makes it exceptionally easy to do this on any GC system, and the translated method can be even further optimized if desired. When moving to a translated method, make sure that the new oven program does not exceed the capabilities of your oven. Agilent 6890 and 7890 GC-MS users can use the GC Accelerator kit to achieve more aggressive oven programs. These inserts reduce oven volume, which allows the oven to heat and cool faster, ultimately resulting in faster analyses.