How important is the purity of the nitrogen used for LC-MS separations? Whatcontrol do researchers have over this?

In LC-MS, most applications recommend 95% pure nitrogen because oxygen, whichmakes up the remaining 5% of the gas, has not been found to be detrimental toanalysis when supplied by a gas generator.When developing nitrogen generators in close cooperation with LC-MSmanufacturers, it has been found that contaminants, such as phthalates andbutylated hydroxytoluene (BHT) have significantly more impact on the quality of theanalysis results than O2content.Are there any analytical advantages of using nitrogen that is generated on-siteinstead of nitrogen stored in a cylinder or dewars?Having agas generatorin place ensures that that Lab Managers and staff can focusfully on their analysis as they will not need to monitor gas levels in cylinders. Inaddition to this, LC-MS typically require more than 20 L of nitrogen per minute. For atypical 8 hour working day this can equate to 9,600 L of nitrogen. This is a significantvolume of gas, which would mean replacement of a cylinder per day.