Determining a specific gravity of a sample

A method comprising:

• applying a first light pulse to a sample at a first angle-of-incidence;
• detecting an intensity of a first fluorescence emission as the intensity of the first fluorescence emission fades;
• applying a second light pulse to the sample at a second angle-of-incidence;
• detecting an intensity of a second fluorescence emission as the intensity of the second fluorescence emission fades;
• comparing, by a processor, the fading of the first fluorescence emission with the fading of the second fluorescence emission;
• and
• determining a specific gravity of the sample based on a ratio calculated based on a comparison of the fading of the first fluorescence emission and the fading of the second fluorescence emission.

An API gravity measurement system comprising:

• a fluorescence-measuring apparatus, comprising:
• a first single-wavelength light source configured to generate a first excitation light pulse to contact a sample at a first angle-of-incidence;
• a second single-wavelength light source configured to generate a second excitation light pulse to contact the sample at a second-angle of incidence;
• a sample holder configured to hold the sample;
• and
• a detector configured to detect an intensity of a fluorescence emission from the sample;
• a processor;
• and
• a computer-readable storage medium storing instructions executable by the processor, the instructions comprising:
• applying a first light pulse to a sample at a first angle-of-incidence;
• detecting an intensity of a first fluorescence emission emitted from the sample over a first time interval and a second time interval;
• applying a second light pulse to the sample at a second angle-of-incidence;
• detecting an intensity of a second fluorescence emission emitted from the surface over a third time interval and a fourth time interval;
• calculating, by a processor, a first ratio based on the intensity of the first fluorescence emission over the first time interval and the intensity of the first fluorescence emission over the second time interval;
• calculating, by a processor, a second ratio based on the intensity of the second fluorescence emission over the third time interval and the intensity of the second fluorescence emission over the fourth time interval;
• calculating, by a processor, an intensity ratio based on the first ratio and the second ratio;
• and
• determining a specific gravity of the sample based on the intensity ratio.