thanks,
I did a test with the software from Prode, for the mixture C1 0.8 C2 0.1 C3 0.04999 CO2 0.05 H2O !.0E-4 (100 ppm) molar fractions I calculated these dew points

P 3 Bara 239.94 K
P 5 Bara 244.77 K
P 10 Bara 251.6 K
P 50 Bara 268.149

I have some data collected in the past which confirm the accuracy in low pressure range, what is the expected unceartainty of the method ?