Automated Gasoline Density Measurements with Xsample 530

Introduction 

Gasoline is a highly volatile mixture of hydrocarbons whose composition and vapor pressure make accurate density measurements particularly demanding. During sample transfer and handling, evaporation of light components and bubble formation can alter the sample composition and negatively affect measurement accuracy and repeatability. Consequently, careful sample preparation and a controlled filling process are essential for achieving reliable and repeatable density measurements.

The Xsample 530 provides two approaches for automated measurements of volatile samples. The predefined filling mode "Pressure mode – piston pump controlled" with the "Pressurize after fill" option applies pressure after filling the measuring cell to reduce bubble formation and requires only a 1 bar compressed air supply. For more demanding applications, the Pressurized Measurement Unit (PMU) operates in a closed, pressurized fluidic path using 2 bar pressure, further minimizing evaporation losses and enabling reliable measurements of highly volatile samples.

This report evaluates the automated density measurement of summer gasoline using an Xsample 530 in combination with a benchtop density meter. Special attention is given to sample preparation and filling techniques designed to minimize evaporation and prevent bubble formation. The performance of the "Pressurize after fill" option is compared with the Pressurized Measurement Unit (PMU) with respect to measurement repeatability and suitability for gasoline measurements according to ASTM D4052. The presented workflow also demonstrates practices that support the anticipated trend toward stricter precision requirements and more controlled sample handling.