A post-probe upstream metering pump for insuring phase change completion of a multi-phase fluid such as Natural Gas Liquid (NGL) in a sample conditioning system having a pipeline sample take-off probe for fluid extraction, a sample conditioning unit for conditioning the extracted fluid to a select range of temperature and pressure for analysis of the fluid sample by an associated analyzer without dew point dropout or phase separation, and a metering pump disposed in-line between the sample take-off probe and the sample conditioning unit to pressurize the fluid sample to condense into a substantially fully liquid phase and to reduce lag time between extraction and fluid sample conditioning.