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Eingeladener Vortrag
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Due to recent advances in technical developments of NMR instruments such as acquisition electronics and probe design, detection limits of components in liquid mixtures were improved into the lower ppm range (approx. 5–10 ppm amount of substance). This showed that modern NMR equipment is also suitable for the observation of hydrocarbon samples in the expanded fluid phase or gas phase. Since Quantitative NMR spectroscopy (qNMR) is a direct ratio method of analysis without the need of calibration it was used to determine impurities in appropriate liquid and liquefied hydrocarbon isomers up to C6, which are used for preparation of primary gas standards, e.g., natural gas or exhaust gas standards. At the same time it is possible to yield structural information with a minimum of sample preparation. Thus, cross contaminations between different isomers of the observed hydrocarbons and their (NMR-active) impurities can be identified and quantified.
In general, most quantitative organic chemical measurements rely on the availability of highly purified compounds to act as calibration standards. The traceability and providence of these standards is an essential component of any measurement uncertainty budget and provides the final link of the result to the units of measurement, ideally the SI. The more recent increase in the use of qNMR for the direct assessment of chemical purity however can potentially improve the traceability and reduce the uncertainty of the measured chemical purity at a reduced cost and with less material. For example the method has beneficially been used by National Measurement institutes for recent CCQM comparisons including the CCQM–K55 series of purity studies.
Traditional ‘indirect’ methods of purity analysis require that all impurities are identified and quantified, leading to a minimum of 4 individual analytical methods (organic impurities, water, solvents, inorganic residue). These multiple technique approaches measure an array of different chemical impurities normally present in purified organic chemical compounds. As many analytical methodologies have compound-specific response factors, the accuracy and traceability of the purity assessment is dependent on the availability of reference materials of the impurities being available.
qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The development of CRMs addressing qNMR specific measurement issues will give analysts compounds ideally suited for the analytical method and also provide full characterisation of qNMR related parameters to enable more realistic uncertainty budgets. These materials will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden of multiple analytical testing.
Online NMR spectroscopy is an excellent tool to study complex reacting multicomponent mixtures and gain process insight and understanding. For online studies under process conditions, flow NMR probes can be used in a wide range of temperature and pressure. This paper compiles the most important aspects towards quantitative process NMR spectroscopy in complex multicomponent mixtures and provides examples. After NMR spectroscopy is introduced as an online method and for technical samples without sample preparation in deuterated solvents, influences of the residence time distribution, pre-magnetization, and cell design are discussed. NMR acquisition and processing parameters as well as data preparation methods are presented and the most practical data analysis strategies are introduced.
Benchtop nuclear magnetic resonance spectroscopy currently develops to an important analytical tool for both quality control and process monitoring. In contrast to high resolution online NMR (HR-NMR), benchtop NMR can be operated under rough environmental conditions. A continuous re-circulating stream of reaction mixture from the reaction vessel to the NMR spectrometer enables a non-invasive, volume integrating online analyses of reactants and products. Here we investigated the esterification of 2,2,2-trifluoroethanol with acetic acid to 2,2,2-trifluoroethyl acetate both by 1H HR-NMR (500 MHz) and 1H and 19F MR NMR (43 MHz and 40 MHz) as a model system. The parallel online measurement was realized by splitting the flow, which allowed the adjustment of quantitative and independent flow rates, both in the benchtop NMR probe as well as in the HR-NMR probe, in ad-dition to a fast bypass line back to the reactor.
Resolving overlapping peaks of multiple components. Relative primary analytical method - Fundamental relationship of qNMR.
As presented at the NAMUR general meeting 2015, the technology roadmap "Process Sensors 4.0" identifies the necessary requirements as well as the communication abilities of such process sensors. We report on the progress of discussions in trialogue between users, software and device manufacturers as well as the research.
An important key is the definition of an appropriate and uniform topology for such smart sensors, which will be driven forward in a new NAMUR AK 3.7 "smart sensors" in mutual exchange with device and software manufacturers and research institutions.
Smart sensors and smart reference materials – an approach to the industrial internet of things
(2016)
The BAM targets within Bonares I4S are adaption of two online sensors being optimised for mobile applications: A LIBS spectrometer (Laser Induced Breakdown Spectroscopy) as well an a XRF spectrometer (X-Ray Fluorescence
Spectroscopy). Beyond , the certification of soil reference materials is scope of I4S at BAM. Therefore, a managable relational database structure is needed, based on a modular Architecture, which is dedicated to spectroscopy. The requirements to such a database are discussed.
Resource Analytics with the help of process analytical technology and the use of online methods is becoming increasingly important for mining and processing technologies and for the recovery of raw materials from secondary raw materials. Current online analytical methods like laser-induced breakdown spectroscopy (LIBS), X-ray fluorescence analysis (RFA), or Raman spectroscopy for the characterization of primary and secondary raw materials are increasingly being used in close association with the technologies for exploration and extraction, mechanical and metallurgical processing, as well as for recycling. Because of the complex matrices such methods are a considerable challenge at the same time. The use of reference materials, which are derived from appropriate matrices, can considerably shorten calibration and method development times. As an example, the development of an online process control method for recovery of phosphorus from sewage sludge ashes is discussed. A combination of LIBS and RFA was developed for the determination of element contents in sewage sludge ashes and their products coming from a thermo-chemical reprocessing step, which removes pollutants.