Method for measuring API gravity of petroleum crude oils using angle-resolved fluorescence spectra

A computer-implemented method comprising:

• generating, by a single-wavelength light source, an excitation light source provided at a first angle-of-incidence onto a sample held by a sample holder including a surface transparent to the excitation light source;
• generating, by the single-wavelength light source, an excitation light source provided at a second different angle-of-incidence onto the sample;
• obtaining, by a detector, spectra from at least the first angle-of-incidence and the second different angle-of-incidence, the detector and one or more optical components positioned in a path of a fluorescence emission emitted from the surface and configured to guide the fluorescence emission;
• recording, by a recording/analyzing device, the spectra from the first angle-of-incidence and the second different angle-of-incidence;
• normalizing and analyzing, by the recording/analyzing device, intensities of the spectra;
• determining, by the recording/analyzing device, a difference in the spectra by subtracting a first spectrum corresponding to the first angle-of-incidence from a second spectrum corresponding to the second different angle-of-incidence;
• and
• identifying, by the recording/analyzing device, a sample type of the sample based on an American Petroleum Institute (API) gravity that is mapped to the difference.

A non-transitory, computer-readable medium storing one or more instructions executable by a computer system to perform operations comprising:

• generating, by a single-wavelength light source, an excitation light source provided at a first angle-of-incidence onto a sample held by a sample holder including a surface transparent to the excitation light source;
• generating, by the single-wavelength light source, an excitation light source provided at a second different angle-of-incidence onto the sample;
• obtaining, by a detector, spectra from at least the first angle-of-incidence and the second different angle-of-incidence, the detector and one or more optical components positioned in a path of a fluorescence emission emitted from the surface and configured to guide the fluorescence emission;
• recording, by a recording/analyzing device, the spectra from the first angle-of-incidence and the second different angle-of-incidence;
• normalizing and analyzing, by the recording/analyzing device, intensities of the spectra;
• determining, by the recording/analyzing device, a difference in the spectra by subtracting a first spectrum corresponding to the first angle-of-incidence from a second spectrum corresponding to the second different angle-of-incidence;
• and
• identifying, by the recording/analyzing device, a sample type of the sample based on an American Petroleum Institute (API) gravity that is mapped to the difference.