What is my Source Temperature and why do I care?

The MS source temperature is a setting that can be made on an Agilent 7890A/5975C GC/MS. Auto-tunes typically have some sort of default setting. For example a DFTPP specific tune, used for EPA Method 8270, has a default source temp of 230°C. However, if you increase the source temperature, improved peak shape of late eluting analytes such as PAHs results. You may think great! I am going to jack up that source temperature as high as it will go and I will have awesome peak shape. Well, hold on to those horses. Of course all great things come at a cost. The price you pay for better peak shape is stronger fragmentation of your analytes. This could result in a decrease of your quant ion. Check out the figure to see how changing the MS source temp from 230°C to 250°C to 300°C results in better peak shape, but also how it affects 2,4-DNP response. It turns out 250°C looks like the sweet spot for a happy marriage between peak shape and compound response.