Applications
Additional Information
Process Control
The quality of a chemical product, such as petroleum, biodiesel or edible oil, is the result of a carefully controlled process. In process control, industrial and chemical engineers continually check various aspects of the health of a process.
- Monitoring and optimizing reaction dynamics
- Batch sampling for content and purity
- Preprocess analysis
- Dilution control
- Identifying impurities
- Monitoring concentration gradients
Modifications in chemical content arising from oxidative processes, chemical transformation due to prolonged exposure to heat (thermal decomposition) or light (polymerization) or other variations in a chemical process are typically monitored by gas- and liquid-phase chromatography. These are static techniques often requiring chemical modification prior to analysis. This can be costly and time-consuming since samples may need to be sent out for synthesis and analysis.
Process NMR is a method of process control, utilizing NMR for analytical testing. NMR is ideally suited for analyzing changes in reaction mixtures, identifying changes in chemical structure, monitoring concentrations, mixing conditions and detecting impurities. NMR is a noninvasive, nondestructive technique, providing information under static or dynamic conditions – the latter being particularly attractive for in situ monitoring and testing of process applications, without the need for separation and derivatization of chemical species.
The picoSpin-45 NMR spectrometer offers high performance, low cost, and compact size, making it ideal for many process NMR applications:
- Biofuels – fatty acid methyl ester fuels composition analysis
- Food – edible oils composition analysis, oxidation/shelf-life analysis, soluble fat/water content
- Petroleum
- LNG
- Pharmaceuticals
The picoSpin NMR spectra of methyl esters of oleic acid and linolenic acid below suggest applications to process control of fatty acid composition in a range of edible oils and biofuels.
Figure 1. picoSpin-45 NMR Spectrum of Methyl Oleate (neat, 72 scans)
This spectrum of methyl oleate (methyl (Z)-9-octadecenoate), the methyl ester of the monounsaturated fatty acid oleic acid, is characterized by several distinct proton groups. Two olefinic protons produce a signal down field at δ 5.4, three methyl ester protons appear midfield as a single peak at δ 3.62, four allylic protons produce the multiple signal at δ 2.15 and the remaining aliphatic methylene protons produce an intense singlet structure at δ 1.37 with the α-methylene protons adjacent to the carbonyl carbon appearing as a triplet at δ 2.12. The terminal methyl protons appear on the trailing edge of the large methylene singlet at δ 0.98.
Figure 2. picoSpin-45 NMR Spectrum of Methyl Linoleate (neat, 72 scans)
Methyl Linoleate (methyl (Z,Z)-9,12-octadecadienoate) is the methyl ester of the polyunsaturated fatty acid linoleaic acid. This fatty acid methyl ester (FAME) has two vinyl groups in the aliphatic chain resulting in an increase in olefinic (δ 5.4) proton signal relative to the allyic proton signal at δ 2.15, and the appearance of a new signal at δ 2.8 due to 2 divinyl methylene protons at C-11. As the the aliphatic-methylene proton signal decreases, the terminal methyl-to methylene ratio increase giving rise to a more prominent terminal methyl signal at δ 0.96.
Figure 3. picoSpin-45 NMR Spectrum of Methyl Linolenate (neat, 72 scans)
Methyl linolenate (above) is the methyl ester of the polyunsaturated fatty acid linolenic acid with two additional vinyl groups. In the spectrum of methyl linolenate (methyl (Z,Z,Z)-6,9,12-octadecatrienoate), we see an expected increase of the olefinic proton signal (δ 5.4) and a moderately strong allylic proton signal at δ 2.8. The large methylene signal at δ 1.38 is still a dominate feature in the spectrum, but lower in intensity, allowing the α-methylene proton signal (δ 2.13) to appear more prominent. The methyl ester proton signal (δ 3.62) is unaffected by the additional vinyl groups, whereas the terminal methyl signal at δ 1.00 is better resolved due to the narrowing of the large aliphatic-methylene peak.
