Vapor Volume Calculators are Undervalued Tools
Vapor Volume Calculators are probably one of the least utilized FREE tools available to anyone who develops gas-phase chromatography methods. Here is the interesting part – Using this tool will save you time and headaches upfront while saving downtime and possible re-validation of the method later!
A real-life example that I experienced involved a “simple” GC method using water as the solvent (there is almost always a better solution than water!). The validation had been signed off years before, but a new user was running the samples. They could not get reproducible results, after trying unsuccessfully for three days. On top of that, there was excessive carryover and bad tailing on some of the peaks.
After consulting with me on the issue, I asked how much sample was being injected. I cannot remember the exact amount, but when I fed all the numbers into a Vapor Volume Calculator it showed almost 200% vapor volume in relation to the inlet! This would be unacceptable with any solvent, but that much water had created other issues requiring the inlet to be removed and thoroughly cleaned.
In the end, a new style liner was suggested, creating a bigger inlet internal volume, while lowering the amount being injected into the inlet. Samples had to be diluted differently, but the results were much more consistent. Days were lost for the technician, along with other support staff who were involved with the revalidation.
Agilent includes a Vapor Volume Calculator in most of its chromatography software platforms.
Restek has an online tool here: https://www.restek.com/row/tools-and-calculators/tools/solvent-expansion-calculator/
Or, do a Google search for Vapor Volume Calculator to find one you like.