EXPLANATION
Benezene is a toxic chemical whose concentration in products is limited by government agencies. This test method is fast, simple to run, and inexpensive. It is applicable for quality control in the production and distribution of spark ignition engine fuels in the concentration range 0.1 to 5 volume %.
TEST SUMMARY
A beam of infrared light is imaged through a liquid sample cell onto a detector, and the detector response is determined. Wavelengths of the spectrum that correlate highly with benzene or interferences are selected for analysis using selective bandpass filters or mathematically by selecting areas of the whole spectrum. A multivariate mathematical analysis converts the detector response for the selected areas of the spectrum of an unknown to a concentration of benzene.
Toluene and other monosubstituted aromatics interfere. Oxygenates can interfere with measurements made with filter apparatus. Proper choice of the apparatus, proper design of a calibration matrix, and proper utilization of multivariate calibration techniques can minimize these interferences.
TEST PRECISION
Where X is the benzene concentration determined.
Bias - Bias against reference materials is not known. However, there appears to be a variable bias against Test Method D5769, of the order of -0.06 vol. % for the FTIR procedure and +0.06 vol. % for the filter procedure.