Changing carrier gas from helium to argon

Most applications using Argon as a carrier are packed column applications, and usually they are ECD applications and the Ar has between 5 and 10% methane added. The advantage is greater linearity for the ECD. The van Deemter for Argon is steeper and has a lower u-opt between 7-14 cm/sec) than Nitrogen. This is explained by the resistance to mass transfer term in the van Deemter equation. In capillary columns, this term plays a significant role in column efficiency because of the low relative amount of phase compared to packed columns. In packed columns, it almost doesn't matter what gas you use in terms of efficiency as long as it is oxygen free as the resistance to mass transfer in the stationary phase equation plays a much more significant role in limiting column efficiency