Method of determining petroleum hydrocarbon fractions in a sample

An apparatus for determining petroleum hydrocarbon fractions (Cn) in a sample, the apparatus including:

• a housing;
• a chamber disposed in the housing for inputting the sample therein;
• an optical light source disposed in the housing for emitting infrared light into the chamber with the sample;
• a detector for detecting a detected infrared light from the chamber;
• and
• a controller disposed in the housing having a processor and a memory in data communication with the processor, the controller being configured to:
• transform the detected infrared light to a Fourier Transform Infrared (FTIR) spectrum of the sample at a processor, wherein the FTIR spectrum has wavenumbers between 4000 and 400 cm−1;
• process the FTIR spectrum to identify sub-bands each having at least one doublet of sub-band peaks at respective wavenumbers in a second derivative curve of the FTIR spectrum using a second derivation algorithm implemented by the processor;
• compare the at least one doublet of sub-band peaks to data indicative of known doublets of sub-band peaks at known wavenumbers for petroleum hydrocarbon fractions in the FTIR spectrum to classify the petroleum hydrocarbon fractions in the sample;
• and
• determine a dominant petroleum hydrocarbon fraction of the petroleum hydrocarbon fractions in the sample based on a ratio of intensities of the sub-band peaks of the at least one doublet for each of the petroleum hydrocarbon fractions in the sample;
• wherein the at least one doublet includes a first doublet of sub-band peaks at wavenumbers between 3000 and 2800 cm−1.