In this article we will briefly look into various analysis standards, namely those of the American Society for Testing and Materials (ASTM) but also some others such as IP and EPA. Throughout, we’ll be mentioning the place our FTIR analytical equipment has in certain application areas.
Standards for Oil in Water Detection
According to the World Health Organization, almost 700 million people around the world don’t have access to clean drinking water. Some of this water contamination originates from the excessive presence of chlorinated aromatic hydrocarbons (CHCs) in water supplies.
Over the past twelve months, Google has seen “oil in water” searched for from some top locations around the world, namely those featured in this live graph. As of November 2017, this graph is displaying the Phillippines, USA and Australia among the top searchers of this topic. As this graph is live, it will evolve and change over time.
Solvent Extraction Method (ASTM 7066 / IP 426 / EPA 1664)
Solvents such as chlorotrifluoroethylene (ASTM 7066), tetrachloroethylene (IP 426) or n-heptane (EPA 1664) are used to extract hydrocarbons from water samples.
These are then samples in transmission at pathlengths of 10 mm or longer and the absorbance at 2930 cm-1 is compares with a calibration.
Read about our ‘Oil in Water Kit‘ which is appropriate for this ASTM standard.
Cyclohexane Solvent Extraction Method (ASTM 7678)
This technique for oil in water determination is very similar to the above, only with cyclohexane as the solvent.
Sample in transmission at pathlengths of 1000 μm and an absorbance at 1380 cm-1 is compared to a calibration.
Oil analysis is suitable for the Specac Pearl FTIR Transmission Liquid Cell.
- The Pearl accessory fits in most spectrometers.
- Ideal for analyzing viscous oils and greases.
- It is very easy to use, letting the user quickly change the pathlength, introduce sample and clean.
- The throughput is very high.
- Window material can be switched between CaF2 or ZnSe.
- The windows can be wedged to avoid fringing patterns affecting the spectral readings.
- Pathlengths from 25-1000 μm are available.
Watch this video on the Pearl being used for the analysis of greases and oils using FTIR.
FTIR Transmission method (ASTM D7806 / DIN EN 14078)
Carbonyl peak at circa 1750cm-1 is measured and calibrated against certified standards. The cell must use KBr, NaCl or CaF2 windows for this analysis.
The DIN standard recommends the following pathlengths and dilutions for analysis.
| FAME concentration (% V/V) | Dilution | Pathlength |
|---|---|---|
| 0.05-3.0% | None | 0.5 mm |
| 3.0-20% | 1:5 | 0.1 mm |
| 20-50% | 1:5 1:10 | 0.05 mm 0.1 mm |
The main advantage of this method is the possibility to calibrate the model for low concentration of FAME.
BioDiesel analysis is approrpiate for the Specac Pearl FTIR Transmission Liquid Cell.
ATR Method with PLS Calibration Model (ASTM D7371)
This method is potentially more robust as it does not require dilutions for higher concentrations of FAME. However, it is not as sensitive to the lower concentrations. It includes the use of an attenuated total reflectance FTIR spectrometer accessory.
The Quest ATR is also suitable for the analysis of liquids like BioDiesel.
- It is a robust ATR spectrometer accessory.
- High throughput diamond, extended wavelength diamond, ZnSe, Ge, Silicon and Specular Reflectance pucks
- Easy to introduce sample, quick to clean.
- Accurate and great value.
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