When I was in chemistry school back in the early 80's, the gas chromatography carrier gas choices were helium, hydrogen, nitrogen, and argon. Choosing the optimum carrier gas involved issues of safety, cost, and what type of analysis was being done. I wrote my master's thesis on the quantitative analysis of barbiturates in urine using GC/MS and nitrogen was the carrier gas of choice for drug analysis. All four of these gases are still used today.