Differences between propane in nitrogen versus air matrix analyzed using gas chromatography with flame-ionization...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Metrology

Background:

• New US Federal low-level automobile emission requirements necessitate certified reference materials for accurate hydrocarbon measurements.
• Automobile manufacturers require 100 nmol/mol (ppb) propane in air gas standards for calibrating emission measurement instruments.
• National Institute of Standards and Technology (NIST) traceable reference materials are mandated by law for instrument calibration.

Purpose of the Study:

• To develop a NIST Standard Reference Material (SRM) for 100 nmol/mol propane in air.
• To investigate the effect of the matrix (air vs. nitrogen) on propane concentration measurements using flame-ionization detectors.

Main Methods:

• Development of two suites of primary propane standards: one in air and one in nitrogen.
• Analysis of both suites using NIST methods, including gas chromatography/flame-ionization detection (GC/FID).
• Comparison of determined propane concentrations between the air and nitrogen matrices.

Main Results:

• A NIST Standard Reference Material (SRM) containing 100 nmol/mol propane was successfully developed.
• A difference of 0.63% was observed in the determined propane concentration between the air and nitrogen primary standards.
• This indicates a potential matrix effect of oxygen on flame-ionization detector response for propane.

Conclusions:

• The matrix composition can influence the accuracy of low-level propane measurements in air.
• Further investigation into oxygen's effect on hydrocarbon analyzers is warranted for precise emission monitoring.
• The developed NIST SRM provides a crucial tool for meeting new stringent automotive emission regulations.