FT-IR (Fourier Transform Infrared) spectroscopy is a technique used to analyze the chemical components and changes of a material by measuring its absorption or emission in the infrared (IR) region. In mineral oil analysis, FT-IR is often used to detect the change of chemical substances in the oil as it ages or is used.

The FT-IR determination is used to detect the following components and changes:

1. **Soot:** Carbon-based particles formed as a result of combustion in engines.
2. **Oxidation:** It is formed as a result of the reaction of oil with oxygen. This is a sign that the oil is aging.
3. **Nitriding:** Compounds formed as a result of the reaction of nitrogen oxides with oil, usually as a result of combustion at high temperatures.
4. **Sulfation:** It is formed as a result of the reaction of sulfur dioxide or sulfur trioxide with oil.
5. **Water:** Indicates the presence of emulsified or dissolved water in the oil.
6. **Glycol:** May form in oil as a result of leaking coolants.
7. **Diesel & Gasoline:** Used to detect fuel dilutions.
8. **ZDDP (Zinc Dialkyl Dithiophosphate):** It is an anti-abrasive and anti-oxidant additive. The concentration of this additive can be monitored with FT-IR.

**How to Determine FT-IR?**
1. First, the FT-IR spectrum of the new and unused oil is taken; this is known as the initial spectrum.
2. When the spectrum of the used oil is taken, it is compared with the initial spectrum.
3. Changes indicate what chemical changes have occurred in the oil and the extent of these changes.
4. The peak heights or areas at certain wavelengths indicate the amount of relevant components or changes.

FT-IR analysis provides fast and accurate information on the condition and quality of lubricants. This technique is invaluable for making important decisions such as whether the oil should be changed, the presence of contamination or other problems.