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Chapter Nineteen
Non-Medical Applications

19-01 Introduction

he applications of NMR and MR imaging in industry are widespread and in­volve the analysis of both inorganic and or­ganic compounds. Routine exa­mi­na­tions of che­mi­cals are proba­bly the most common applications.

However, the NMR technique is suf­fi­ci­ent­ly flexible to be used, for example, to mea­sure the water-fat ratio in foods (Figure 19-01), monitor the flow of corrosive flu­ids in pipes, or to study the complex struc­tures of molecules, among them ca­ta­lysts.

Figure 19-01:
Nottingham Evening Post, 22 October 1974: Waldo Hinshaw, Peter Mansfield, and Bill Derbyshire — and their NMR equipment. Derbyshire worked on relaxation time measurements of fish muscle and the change of taste of salmon after its violent death. More applications in food science followed rapidly.

This chapter wants to give a general idea of possible applications. The over­view is not meant to be exhaustive, but it shows some highlights. It also un­der­lines the dif­fi­­cul­ties, chal­len­ges, and possibilities of in­terdisciplinary research and teaching.

In­dustrial applications can be divided into chemical, biological, paramedical (pro­te­in), data processing, and non­de­struc­ti­ve testing.

19-02 Applications in Chemistry

spaceholder redGeneral Remarks

Hydrogen (¹H) and carbon (¹³C) NMR spec­troscopy of solutions of chemicals are in­­dis­pen­sab­le to the organic chemist in identi­fying the products of the latest re­ac­tion. The analysis is quick and simple and does not require an especially pure sam­ple. This type of work is probably the most common type of NMR work done through­out the world and will continue to be so for many years. Yet, it does not be­gin to hint at the enormous versatility of the NMR technique and the wide range of in­for­ma­tion which can be obtained from different systems.

spaceholder redOil and Coal Analysis

Analysis of low molecular weight fractions of oils can be done by NMR, although other techniques do exist. The higher molecular weight fractions which are very vis­cous or even solid are more difficult to analyze, but solid-state NMR tech­ni­ques can be very useful.

Solid-state ¹³C NMR has been per­formed on kerogens (an immature type of coal). The information obtained when ap­plied in conjunction with other types of analysis can be used to predict if the kero­gen comes from a site which is gas-form­ing or oil-forming. Such information is ex­tremely valuable when planning an explo­ration and dril­ling program. Among the possible applications in this area is the de­ve­lop­ment of a transportable MRI/MRS system which can be flown into a potential drilling region.

Catalysts called zeolites are used in large quantities by the oil industry to crack the higher molecular weight fractions to pro­duce the smaller carbon molecules used in car and heavy vehicle fuels. The zeolites are a complicated group of mo­le­cu­les com­­po­s­ed mostly of silicon and aluminum.

Solid-state silicon-29 (²⁹Si) and alu­minium-27 (²⁷Al) NMR have been used ex­­ten­si­ve­ly to study the structure of these molecules since an understanding of the way they work can lead to the choosing or designing of more efficient types of cata­lysts.

spaceholder redFlow in Pipelines

The accurate measurement of flow in pipes is a difficult problem for many in­­dus­­tries. For instance, oil in pipes (or even pipelines), fluidized coal, and corrosive fluids have all been measured with NMR, and a commercial NMR flow-meter has been available since 1968. The non-invasive nature of NMR makes it extremely suit­­able for systems with unpleasant chemicals or extreme pres­sures, but despite ex­cel­lent results in a few key examples there is room for much greater use of NMR mo­ni­tor­ing of flow, e.g., flow-meters for oil-pipelines with si­multaneous qua­li­ta­ti­ve as­sess­ment of the transported oil.

spaceholder redDrilling Cores

There has been quite a lot of effort put into spectroscopic and imaging studies of dril­ling cores. The spectroscopic studies have reported correlations between the NMR results and the mineral content, the pore geometry, and the surface chemistry of these rocks. It is hoped that this will either lead to new in­sights into the geology of the rocks or that NMR will be a quicker, sim­pler, or cheaper method at obtaining the same information.

MR imaging is being used to get maps of the three-dimensional distribution of oil and water in the cores and eventually will be able to monitor the flow of oil and water through cores. This information is vital to the models used to predict oil ex­trac­tion from oilfields, where a 1% improvement represents millions of dol­lars of in­come gained or lost.

MR imaging can also be used to image ice cores from glaciers and polar per­ma­frost regions.

spaceholder redPlastics and Polymers

Some samples are mainly of interest as solids. Important examples are found in po­ly­mer scien­ce where it is the properties of the solid which are important and not the individual subunits which go to make up the solid.

Solid-state NMR is used to study how plastics are put together, to relate their che­mis­try with their known physical prop­erties. This information can be used to help im­prove the plas­tics and develop new ones. There are very few alternatives to NMR for get­ting this type of information from poly­mers.

spaceholder redLiquid Crystals

Liquid crystals are used in watches, calcu­lators, and television and computer screens. They are also very difficult to study by other means than NMR. Just like the plas­­tics, information about the packing of the molecules shows how structure re­lates to functional properties and so can help in cre­ating new products.

spaceholder redPharmaceuticals

High resolution NMR is a valuable tool to use when identifying and cha­rac­te­riz­ing new drug molecules and their binding fea­tures. It is possible for molecules to exist in two or more different forms or polymorphs in the solid state. Solid-state NMR can be used to detect this. The polymorphs may have different biological activity which may cause a manufacturer to try to isolate one or another form.

Furthermore it might prove possible for a competitor to by-pass patents if the exis­ten­ce of poly­morphs has not been accurately documented.

Magnetic resonance is also being ap­plied to observe properties and in­ter­ac­tions of pharmaceuticals with proteins, perform toxicology studies, and de­ter­min­ing con­centrations.

spaceholder redCement and Concrete

The study of the hydration process in ce­ment is of great interest to the industry. In­­creas­ing the speed of hydration and the de­gree of hydration are both highly de­si­rable since they increase the speed of setting and the strength of the con­crete.

Until it was shown that they can clearly be seen in solid-state ²⁹Si spectra of ce­ment, both processes were rather difficult to quan­tify. Changes in the concrete can be fol­lowed over periods of 90 days or more and thereby one can cha­rac­te­rize the effect of different additives on the curing process.

spaceholder redWood Pulp and Paper

The pulp and paper industry uses the com­plex mixture of high molecular weight com­pounds from wood pulp as its raw ma­terial. Solid-state NMR has been used to cha­rac­te­rize the pulp and it can be used to determine the effect of different me­­cha­­ni­­cal or chemical treatments of the type of pulp produced. Possibilities might also exist for the monitoring of pulp production in the factory.

spaceholder redExplosives

It is not possible (or at least not safe) to ex­amine explosives directly. However, it is pos­sib­le to study chemical analogues of ex­plosives like acetyl cellulose to im­prove un­der­stand­ing of the chemical structure of such materials. By re­lat­ing che­mi­cal struc­­ture with functional properties one can help in designing of safer and more ef­fi­cient ex­plosives.

spaceholder redLeather and Rubber

Attempts are being made to replace chromium salts in leather tanning by en­vi­r­on­men­tal­ly friendlier aluminum salts. It seems possible that solid-state ²⁷Al spec­tro­sco­py can be used to help to charact­erize tanned leather. In a similar way, tire rub­ber can be analyzed.

spaceholder redImaging of Solid Materials

Imaging of solids is still not very common. Like medical imaging the nucleus being ob­served is ¹H, but unlike medical imaging where the signal is relatively sharp and long lived, the signal from the proton in solid materials is generally rather difficult to de­tect since it is a very broad and only lasts for a relatively short time. The pur­pose of such experiments is to test non-destruct­ively the various plastics and po­ly­­mers used increasingly in modern manufac­turing.

At present most published images are typically of a block of a solid material with holes of varying size drilled in it to demon­strate the resolution of the tech­ni­que.

There is one example of the use of MRI to observe solid rocket fuel prior to com­­bus­tion. The packing of the solid fuel can have a large impact upon the burn­ing pro­p­er­ties. Conventional analytical techniques would either disturb the pack­ing or pre­vent the sample being used in an ignition experi­ment. By the use of solid-state MRI it was possible to image samples before ignition tests and so di­rec­tly correlate the ef­fect of packing on burning properties.