A self-contained analysis system operable to assess gas to oil ratio (GOR), shrinkage of reservoir fluid, and composition of pressurized reservoir fluids. The analysis system can be used for extended compositional analysis of rich flashed gas and lean gas samples as well as flashed equilibrium liquids, condensates, and black oils. Analysis of the various samples is achieved without cross contamination, for example, between rich flashed gases and lean gases or between extended natural gas and liquids (e.g., black oils and condensates). The system yields accurate results up to and including C20 for gas samples and up to and including C36+ for liquid samples, and entrained water.