EPR

Electron Paramagnetic Resonance (EPR)

          EPR is the only method for the direct detection of paramagnetic species. Electron paramagnetic resonance (EPR) spectroscopy applications span across a wide range of areas from quality control to molecular research in fields such as material research, structural biology and quantum physics. EPR experiments have provided invaluable information pertaining to metalloprotein structures and to the structures and processes in photosynthesis.

 

What is EPR?

          EPR (Electron Paramagnetic Resonance) is a spectroscopic technique that detects species that have unpaired electrons. It is also often called ESR (Electron Spin Resonance). A surprisingly large number of materials have unpaired electrons. These include free radicals, many transition metal ions, and defects in materials. Free electrons are often short-lived, but still play crucial roles in many processes such as photosynthesis, oxidation, catalysis, and polymerization reactions. As a result EPR crosses several disciplines including: chemistry, physics, biology, materials science, medical science and many more.

 

What kind of information can I get from EPR?

          Only EPR detects unpaired electrons unambiguously. Other techniques such as fluorescence may provide indirect evidence of free radicals, but EPR alone yields incontrovertible evidence of their presence. In addition, EPR has the unique power to identify the paramagnetic species that is detected. EPR samples are very sensitive to local environments. Therefore, the technique sheds light on the molecular structure near the unpaired electron. Sometimes, the EPR spectra exhibit dramatic lineshape changes, giving insight into dynamic processes such as molecular motions or fluidity. The EPR spin-trapping technique, which detects short-lived, reactive free radicals, very nicely illustrates how EPR detection and identification of radicals can be exploited. This technique has been vital in the biomedical field for elucidating the role of free radicals in many pathologies and toxicities. EPR spin-labelling is a technique used by biochemists whereby a paramagnetic molecule (i.e., the spin label) is used to “tag” macromolecules in specific regions. From the EPR spectra reported by the spin label, they can determine the type of environment (hydropho?bicity, pH, fluidity, etc.) in which the spin label is located.

          ESEEM and ENDOR are two EPR methods that measure the interactions of the electron with the surrounding nuclei. They are extremely powerful techniques for probing the structure of “active sites” in metalloproteins. Another important application for quantitative EPR is radiation dosimetry. Among its uses are dose measurements for sterilization of medical goods and foods, detection of irradiated foods, and the dating of early human artifacts.

 

How does EPR work?

          EPR is a magnetic resonance technique very similar to NMR (Nuclear Magnetic Resonance). However, instead of measuring the nuclear transitions in our sample, we are detecting the transitions of unpaired electrons in an applied magnetic field. Like a proton, the electron has “spin”, which gives it a magnetic property known as a magnetic moment. The magnetic moment makes the electron behave like a tiny bar magnet similar to one you might put on your refrigerator. When we supply an external magnetic field, the paramagnetic electrons can either orient in a direction parallel or antiparallel to the direction of the magnetic field. This creates two distinct energy levels for the unpaired electrons and allows us to measure them as they are driven between the two levels.

          Initially, there will be more electrons in the lower energy level (i.e., parallel to the field) than in the upper level (antiparallel). We use a fixed frequency of microwave irradiation to excite some of the electrons in the lower energy level to the upper energy level. In order for the transition to occur we must also have the external magnetic field at a specific strength, such that the energy level separation between the lower and upper states is exactly matched by our microwave frequency. In order to achieve this condition, we sweep the external magnet’s field while exposing the sample to a fixed frequency of microwave irradiation. The condition where the magnetic field and the microwave frequency are “just right” to produce an EPR resonance (or absorption) is known as the resonance condition and is described by the equation shown in the above figure. Below is a diagram of a typical EPR spectrometer.

 

                                                                                  

                                                EMXnano                                                                      microESR

 

 

 

 

EMXnano

 

EMXnano - The New Standard for Bench-Top EPR

          Giving you the power and flexibility you really need in an easy to use compact enclosure, the EMXnano brings affordable highend EPR performance to labs for the first time, delivering a real choice of analysis options.

          For the first time in this instrument category quantitative EPR is offered at your fingertip, thanks to a fully calibrated instrument and inclusion of the Bruker patented spin counting module.

Routine Ease of Use with Unmatched Performance

          Extending Bruker’s renowned EMX spectrometer family to the bench-top class, the EMXnano is a completely new development featuring the latest digital and microwave technologies. Combined with a new generation of magnet system with full range up to 6.5 kG and a highly efficient microwave resonator, this state-of-the-art bench-top instrument is superior in sensitivity and stability, making it ideal for a comprehensive range of analysis and teaching applications.

          The new dedicated bench-top instrument requires minimal infrastructure with a low cost of ownership, making it suitable for a wide range of laboratory types.

Sensitivity and Stability

          No matter what the focus of your application is, the crucial required strengths of an EPR spectrometer are sensitivity and stability. The latest generation magnet and microwave technology delivers class leading performance, enabling the EMXnano to combine both ease of use with highest quality EPR data.

Any customer can confidently add, or enhance, their lab with real world EPR:

  • Integrated, motorized reference standard (marker) for amplitude and g-factor
  • Reference free concentration determination of paramagnetic species (SpinCount)
  • Identification of paramagnetic species by spectrum simulation and fitting (SpinFit)
  • Spectral library including spin traps
  • Dedicated work flows for measurement and analysis

 

Application

EPR in chemistry

Enzyme Reactions

Detection and study of the active site of Cu,Zn-SOD.
          Many enzyme reactions involve one-electron oxidation steps with formation of paramagnetic transient state of the enzyme detectable by EPR. The paramagnetic center where the unpaired electron is located, is usually centered at a transition metal (metalloproteins) or is an amino acid derived radical. Detection and identification of the paramagnetic centers is important to understand the function of the enzymes. For example, in the native SOD1 enzyme, the active site contains one Cu(II) ion that gives a very characteristic EPR spectrum.

                                                                                                                                                  

                                                                                                                            Crystal structure (1E9P.pdb) of Cu(II)-SOD protein                EPR spectrum of Cu(II)-SOD protein at 77 K using finger dewar

 

Reaction Kinetics

Kinetics analysis of vitamin C antioxidant ability.
          Many chemical reactions involve the transfer of one electron. Each electron transfer results in an unpaired electron creating paramagnetic free radicals. EPR is the ideal spectroscopic technique to measure these species as well as to monitor the time behavior of their creation and disappearance. EPR solely has the ability to detect free radicals unambiguously. For example, antioxidants such as vitamin C are important in neutralizing dangerous free radicals in living things and kinetics indicates their effectiveness. 


                                                                                                                              

                                                                                                                Experimental data of the reduction of the                                                       Mechanism of TEMPOL reduction by vitamin C
                                                                                                                nitroxide TEMPOL by ascorbate (vitamin C)

 

 

Photochemistry

Light degradation of hops in beer.
          The majority of photochemical reactions take place through free radical formation as intermediates. For example, hops used in the brewing process contain a mixture of active components that include humulones, cohumulones, adhumulones, beta acids and essential oils. Some forms of these components are photo-active. Light exposure of beer leads to the formation of free radicals that combines with sulfur compounds and gives unpleasant flavor and odor to the beer.

                                                                                                     

                                                                                                             The hop product was exposed to UV/Vis light from 220-600 nm using UV lamp accessory. The light-induced free radicals were recorded
                                                                                                                                 in the presence of the spin trap DMPO and identified as superoxide anion radical and two C-centered radicals.

 

Catalysis

Hydroxyl radical generation through photocatalytic reaction of TiO2.
          The modern chemical industry relies heavily on homogeneous and heterogeneous catalysts. Understanding the operational mode, or reactivity, of these catalysts is crucial for improved developments and enhanced performance. Where paramagnetic centers are involved, ranging from transition metal ions to defects and radicals, EPR spectroscopy is without doubt the technique of choice. For example, photocatalytic oxidation of organic pollutants is frequently carried out using semiconducting polycrystalline powders such as TiO2. A hydroxyl radical is easily formed by light irradiation of TiO2 and detected by EPR using spin traps.

                                                                                                            

                                                                                               Mechanism of hydroxyl radical formation upon light irradiation of TiO2         EPR spectra obtained upon irradiation of aqueous TiO2
                                                                                                                                                                                                                         suspensions in the presence of spin trapping agent PBN

 

Electrochemistry

EPR electrochemistry study of ruthenium complexes.
          Electrochemical generation method combined with EPR has been used to identify and investigate free radicals derived from both organic and inorganic compounds. Inorganic dyes can be used to improve the efficiency of solar cells. In order to optimize the ligands, one must understand the electronic structure of the dye. Here the electrochemistry and EPR combined with DFT calculations and UV/Vis spectroscopy show the unpaired electron is delocalized between the metal and the ligand.

                                                                                

                                                                                                                 Data courtesy of Prof. J. Rochford, University of Massachusetts Boston (Inorg. Chem., 2016, 55 (5), pp 2460–2472)

 

Redox Chemistry

Enzymatic activity of SOD protein studied via Cu(II) reduction.
          Enzymes in the human body regulate oxidation-reduction reactions. These complex proteins, of which several hundred are known, act as catalysts, speeding up chemical processes in the body. Oxidation-reduction reactions also take place in the metabolism of food for energy, with substances in the food broken down into components the body can use. For example, the dismutase activity of Cu,Zn-SOD protein involves reduction of Cu(II)-SOD to Cu(I)-SOD:

 

                                                                          

                                                                                                          Reduction of Cu(II)-SOD (EPR active) to Cu(I)-SOD (EPR inactive)                                     Cu(II)-SOD has a very characteristic EPR signal
                                                                                                                                                                                                                                                     which decays upon reduction of Cu(II) -> Cu(I).

Antioxidants

Detection of ascorbate radical upon oxidation of vitamin C.
          The delicate balance between the advantageous and detrimental effects of free radicals is one of the important aspects of human (patho)physiology. Imbalanced generation of toxic radicals is highly correlated with the pathogenesis of many diseases which require the application of selected antioxidants to regain the homeostasis.  EPR is used to determine the oxidative status of biological systems using endogenous long-lived free radicals (ascorbyl radical, tocopheroxyl radical, melanin) as markers.

 

                                                                                     

                                                                                                      Reaction of a toxic radical R● with an antioxidant A. Also pictured is                                EPR spectrum of ascorbate (Vitamin C) radical
                                                                                                    the reaction of the antioxidant ascorbic acid (Vitamin C) with a radical

 

EPR in biology

RNA and DNA oxidation

DNA-derived radicals detected upon CuCl2/H2O2 treatment.
          EPR spectroscopy in conjunction with spin trapping has been employed successfully to detect and identify high-molecular-weight species generated as a result of reactive oxygen species (ROS)-induced damage to biological macromolecules, such as DNAs and RNAs. The destruction or alteration of these materials is known to play a key role in a large number of cellular injuries and diseases.

                                                                                                           

                                                                                    EPR spectrum of N-centered radical upon DNA damage after CuCl2/H2O2 treatment                      Mechanism of DNA damage by reactive oxygen species (ROS)
                                                                          using DMPO as spin trap. Spectrum also consists of two other radicals that are not DNA-derived.
                                                                                     Data courtesy of Dr. R. Mason, NIEHS (Free Radic. Biol. Med. 2011 50(11) pp 1536

 

Screening DNP agents

EPR spectrum and dipolar coupling determination of bis-TEMPO.
          Correct concentration of DNP polarizing agents is crucial to the success of a DNP experiment. Samples can be pre-screened before DNP experiments using the patented SpinCount module, even in the MAS rotor. Relaxation times are critical for DNP efficiency therefore P1/2measurements at low temperature to estimate the DNP efficiencies of new polarization agents are invaluable. Another characteristic of importance in DNP measurements is the electron-electron dipolar coupling that is easily measured from solution and frozen solution EPR spectra.

 

                                                                                                                  

                                                                                                                EPR spectrum of DNP agent (bis-TEMPO biradical)                                                                            D [G] = 18562/R3 [Å]
                                                                                                                                                                                                                                                             Dipolar coupling measured: D = 7.9 G.
                                                                                                                                                                                                                                                             Distance determined: R = 13 Å
                                                                                                                                                                                                                                                             Data courtesy of Prof. T. Prisner, University of Frankfurt
                                                                                                                                                                                                                                                             (Angew. Chem. Int. Ed., 2009, 48, 4996)

 

Enzyme Reactions

Detection and study of the active site of Cu,Zn-SOD.
          Many enzyme reactions involve one-electron oxidation steps with formation of paramagnetic transient state of the enzyme detectable by EPR. The paramagnetic center where the unpaired electron is located, is usually centered at a transition metal (metalloproteins) or is an amino acid derived radical. Detection and identification of the paramagnetic centers is important to understand the function of the enzymes. For example, in the native SOD1 enzyme, the active site contains one Cu(II) ion that gives a very characteristic EPR spectrum.

 

                                                                                                                      

                                                                                                                  Crystal structure (1E9P.pdb) of Cu(II)-SOD protein                        EPR spectrum of Cu(II)-SOD protein at 77 K using finger dewar

  

 

EPR in biomedical

Nitric oxide

Binding of nitric oxide to oxyhemoglobin detected at 100 K.
          Nitric Oxide (NO) is a highly reactive regulatory molecule which has many important physiological roles, such as a neurotransmitter in the central nervous system, a regulator of vasomotor tone in the cardiovascular system, and a cytotoxic mediator of the immune system. NO is a free radical and its short half-life (< 30 sec), has rendered direct measurement difficult. The instability of NO can be overcome by using a NO-trapping technique, in which a more stable complex is formed and subsequently detected by EPR. For example, the oxidation of nitric oxide (NO) to nitrate by oxyhemoglobin (oxyHb) is a fundamental reaction in NO biology and binding of NO to the heme can be characterized by EPR.

                                                                                                           

                                                                                                                                Crystal structure of NO-Hb (4G51.pdb)                                  EPR spectrum of NO-Hb complex at 100 K with VT unit

 

Detection of Reactive Oxygen Species (ROS) using spin traps

Quantitative EPR analysis of superoxide and hydroxyl radicals.
          Oxidative stress and damage in cells is associated with the development of cancer, Alzheimer‘s disease, atherosclerosis, autism, infections and Parkinson‘s disease. Reactive Oxygen Species (ROSs) are the main cause of oxidative stress and damage in cells, causing damage to proteins, lipids and DNA. Two leading ROS are radicals such as the superoxide radical (O2•-) and the hydroxyl radical (HO•) as shown here in the Xanthine/Xanthine oxidase system where their generation and decomposition can be accurately followed with the EMXnano.

                                                                                                                           

                                                                                                                    SpinCount provides a report showing the time                             EPR spectra and SpinFit simulations of DMPO radical (superoxide
                                                                                                                    evolution of the concentration of the radicals                                       and hydroxyl) adducts in xanthine/xanthine oxidase                                
 

 

Detection of Reactive Oxygen Species (ROS) using spin probes

Time course of superoxide formation using the spin probe CMH.
          In vascular cells, increased generation of superoxide (O2•-) has been suggested to occur in hypertension, diabetes, and heart failure. Thus the accurate detection and ability to quantify O2•- are critically important in understanding the pathogenesis of these various cardiovascular disorders and other noncardiovascular diseases. As shown here the generation of superoxide over time can be easily monitored with the EMXnano.

 

                                                                                                                                          

                                                                                                        Detection of superoxide radical (O2•-) is confirmed by                                                 EPR spectrum of CM nitroxide due to          
                                                                                                    suppression of the EPR signal by superoxide dismutase (SOD)                                           the reaction: CMH + O2•-–» CM + H2O2



 

EPR in material science

Polymer degradation

HALS successfully prevents polymer photoxidation.
The degradation of polymers due to light exposure leads to discoloration of the polymer and a decrease in the mechanical properties (elasticity, toughness, etc). To prevent this decomposition, hindered amine light stabilizers (HALS) are added to the polymer. By monitoring the EPR signals of these light stabilizers, their effectiveness can be evaluated using the EMXnano.

                                                                                                   

                                                                                                          Photo initiation and radical formation upon light irradiation                      The EPR signal generated in the polymer during UV irradiation (left) is
                                                                                                                                                                                                                                completely suppressed after addition of the HALS where only the HALS
                                                                                                                                                                                                                                EPR spectrum is observed (right)

 

Polymer structure

EPR studies of polyelectrolyte multilayer (PEM) films using nitroxide spin labels.
Multilayers of polyelectrolytes (polymers bearing dissociated ionic groups) are formed by the alternating adsorption of oppositely charged polyelectrolytes, so called layer-by-layer technique. PEM films composed of strong polycation and weak polyanion that is usually spin labeled with free nitroxide (4-amino-TEMPO) are studied by EPR. The growth of the PEM films is monitored and quantitative EPR analysis provides information about each double layer.

                                                                                                                                    

                                                                                                                                                        Signal intensity of polycation/TEMPO-labeled polyanion multilayer films in contact
                                                                                                                                                             with buffer solution of pH 4 in dependence on number of double layers NDL.

 

Paint properties

HALS EPR signal in paint indicating deterioration after UV exposure.
The main cause of paint film deterioration is the degradation of several components, including the binder and certain pigments. This is caused by the formation of free radicals from prolonged exposure to UV light (sunlight), moisture and freeze-thaw cycles. Free radicals are highly reactive and either form or breakdown chemical bonds in substances. In the case of paint durability on exposure, free radicals actually damage the film. This process is very similar to how skin ages. Skin contains free radicals that, when exposed to years of sunlight, will show signs of aging, including wrinkling, peeling, sun spots and overall dryness.
 

                                                                                                                                          

                                                                                                                                                 EPR spectra of HALS (hindered amine light stabilizers) detected in paint after UV exposure

 

Solar cells

Defects in amorphous silicon detected by EPR.
Silicon is the most common material for the production of solar cells in the photovoltaic industry either in mono- or polycrystalline form. Specific characterization of paramagnetic defects can be done by EPR to gain insight into how paramagnetic centers induced by degradation influence the efficiency of solar cell active layers. EPR studies on amorphous silicon photovoltaics demonstrated that a strong relationship exists between the presence of paramagnetic defects and the resulting charge collection efficiency in such material.

                                                                                                                 
                                                                                                                                                    Light-induced defect in amorphous silicon detected by EPR due to breaking of weak Si-Si bonds

 

Screening DNP agents

EPR spectrum and dipolar coupling determination of bis-TEMPO.
Correct concentration of DNP polarizing agents is crucial to the success of a DNP experiment. Samples can be pre-screened before DNP experiments using the patented SpinCount module, even in the MAS rotor. Relaxation times are critical for DNP efficiency therefore P1/2 measurements at low temperature to estimate the DNP efficiencies of new polarization agents are invaluable. Another characteristic of importance in DNP measurements is the electron-electron dipolar coupling that is easily measured from solution and frozen solution EPR spectra.

 

                                                                                                                                        

                                                                                                                       EPR spectrum of DNP agent (bis-TEMPO biradical)                Data courtesy of Prof. Thomas Prisner, University of Frankfurt
                                                                                                                                                                                                                                        (Angew. Chem. Int. Ed., 2009, 48, 4996)

 

EPR in physic

Transition metals

Determination of Mg coordination in wurtzite thin films.
          The transition-group, rare-earth and actinide ions are members of the 3d, 4d, 5d, 4f and 5f groups and are subject of a host of EPR investigations. One aspect that makes transition elements interesting subjects for study by EPR is their variable valence. For example, Zn1xMgxO complex is a versatile functional material for oxide semiconductors and the atomic arrangement in the bulk and at the interfaces determines important properties of the oxides. EPR is used to determine the Mg coordination in heteroepitaxial wurtzite Zn1xMgxO:Mn thin films.

          Experimental and simulated EPR spectra at 297 K of Zn0.99Mg0.01O:Mn (pO2 = 0.016 mbar, cMn = 0.05%) thin film sample G5189 for B?c (top) and BIIc (bottom). Asterisks indicate signals of Fe3+ and Cr3+ impurities in the sapphire substrate.

 

                                                                                                           

                                                                                                                                            Data courtesy Dr. Andreas Pöppl, Universitӓt Leipzig (J. Mater. Chem. C, 2015, 3, 11918)

 

EPR in industry

Oxidative stability of foods and beverages

Oxidative stability of olive oil via quantitative EPR analysis.
          The oxidative stability is a major problem in food related industries and is affected by a number of factors, such as oxygen, temperature, presence of metals and light. For example, extra virgin olive oil (EVOO) oxidation is of particular interest due to the complexity of its distribution channels around the world and the fact that it is an individually packaged product (its final quality reflects either positively or negatively on the producer). The resistance of EVOO to oxidation is related to the high levels of monounsaturated triacylglycerols and the presence of natural phenolic antioxidants. EPR is a useful tool to detect free radicals and to determine the level of free radical formation in olive oil during forced oxidation at different temperatures. Application of EPR to foods can reveal important information about radical reactions that may be responsible for food qualities and deterioration.

 

                                                                                                                

                                                                                                                                            EPR spectrum detected after addition of spin trap                             Concentrations of peroxyl, alkoxyl, alkyl 
                                                                                                                                           (DMPO) to an olive oil sample at 40 C.Experimental                            DMPO-radical adducts,and the oxidized 
                                                                                                                                          spectrum was simulated and each of the three radical                             form of DMPO obtained in olive oil 
                                                                                                                                              components is presented as separate simulation                                            during oxidation at 40 C

 

Antioxidant capacity

DPPH scavenging assay to measure antioxidant activity in beverages.
           Antioxidants play an important role as health protecting factor. Scientific evidence suggests that antioxidants reduce the risk for chronic diseases including cancer and heart disease. DPPH (2, 2-Diphenyl-1-picrylhydrazyl) is a free radical that is widely used to test the ability of compounds to act as free radical scavengers or hydrogen donors and to evaluate antioxidant activity. The DPPH assay method is based on the reduction of DPPH by antioxidants and is a rapid and simple method to measure antioxidant capacity of food and beverages.

 

                                                                                                                                       

                                                                                                                                                       Antioxidant activity in wine and tea samples determined by the DPPH scavenging assay

 

 

Radiation dosimetry
Alanine radical detected by EPR corresponds to the irradiation dose.
Alanine forms a very stable free radical when subjected to ionizing radiation. The alanine free radical yields an EPR signal that is dose dependent, yet is independent of the dose rate, energy type, and is relatively insensitive to temperature and humidity. Thus, alanine dosimetry is equally suited to gamma, e-beam, or x-ray irradiation facilities.

 

                                                                                                                                           
                                                                                                                                                                              EPR signal of Alanine radical and the reference marker

 

Pharmaceutical analysis

Lactose radicals in the tablet filler causes enhanced degradation of the active pharmaceutical ingrediants (APIs)
          EPR spectroscopy has a wide variety of applications within the analysis of pharmaceutical compounds. These include photodegradation and oxidation of APIs, the effects of sterilization techniques such as irradiation, interactions between APIs and excipients, etc. Excipients can initiate, propagate or participate in radical chemistry interactions which may compromise the effectiveness of a medication and studied by EPR. Lactose radicals originating from lactose monohydrate, used as a filler in the tablets, react with the API causing an enhanced degradation.

 

                                                                                                                                        

 

Food science and beverages

Ionizing radiation of poultry and fruits creates very distinctive EPR spectra.
          Food irradiation is used to reduce the health risk associated with food-borne pathogens and to prolong shelf life. In fact, ionizing radiation inhibits the division of microorganisms and creates radiolytic products as well as free radicals. In a dry environment these radicals are very stable. For example, irradiated poultry bones or fruits may contain a substantial amount of stable radicals which can be easily detected by EPR.

 

                                                                                                                    

                                                                                                                                     EPR spectrum of irradiated chicken bone                                                        EPR spectrum of irradiated mango

 

 

Polymer research

Polyethylene radicals detected by EPR can predict premature failure of implants.
          Ultra-high molecular weight polyethylene (UHMWPE) has been used as standard lining material in orthopedic implant industry. Oxidative degradation of the polymer caused by free radical formation can lead to premature aging and wear of the material and implant, causing a painful inflammation. EMXnano is capable of detecting and quantifying polyethylene radicals providing reliable and accurate measurements.

 

                                                                                                                            

                                                                                                                               EPR spectra of two different polyethylene radicals                       Data courtesy of Dr. Gavin Braithwaite, Cambridge Polymer Group

 

Diamond quality evaluation

EPR can detect the N3 and single substitution nitrogen centers in diamonds.
          It is an unambiguous technique for quantifying nitrogen centers and hence provide a tool for color grading. It can also be used to distinguish between synthetic and natural diamonds.

 

                                                                                                 

                                                                                                                                                             Room temperature EPR spectra of diamonds with different grades (colors)

 

EPR in education

           As a company driven by innovation, Bruker recognizes the importance of a broad chemical education, and the importance of not only exposing students to a broad range of analytical techniques but also of teaching students the role each plays in chemical analysis. To introduce the upcoming generation of scientists to this powerful technique, Bruker has developed the ideal EPR teaching package that includes an easy-to-use instrument together with a suite of practical experiments, instructional guides and an introduction to the basic theory of EPR spectroscopy.

EMXnano teaching package includes:
• Easy-to-use X-band continuous wave EMXnano benchtop spectrometer fully optimized for a magnetic resonance teaching environment
• Introduction to the basic theory and practice of EPR spectroscopy
• Real life sample analysis in the classroom
• Quantitative EPR experiments
• Suite of principal experiments for teaching EPR data acquisition and processing skills (with full instructions)
• Collection of samples

 

 

 

 

images/EPR/emx_nano-brochure.pdf

 

 

 


microESR

MicroESR

 

microESR is a small, portable research grade instrument

          The microESR is a small, portable research grade instrument. The spectrometer has a mass of only 10 kg and a 30.5 x 30.5 x 30.5 cm3 foot print. It can easily fit in a fume hood or glove box, or be transported to the field. It requires no special installation or regular maintenance.

          The microESR is also an ideal teaching tool for undergraduate chemistry labs. This instrument enables classroom demonstrations of both simple topics such as free radicals in everyday life to far less intuitive subjects including electron density, spin-orbit coupling, spin-spin exchange, and forbidden transitions. The Education Package is a very good investment for Chemistry Departments as there are a wide range of labs and subjects that can be addressed with the microESR.

  • Operating Frequency: X-Band
  • Continuous Wave
  • Field Sweep Range: 500 G centered at g=2
  • Spectrum simulation and fitting
  • Easily run samples at liquid nitrogen temperature

Application

Education
          Research Grade Teaching Tool

Chemistry
          Reaction kinetics, free radical chemistry, catalysts, DNP

Biology/Biochemistry/Biomedical
          Spin labeling, spin trapping, nitric oxides, ROS and RNS

Materials Science
          Polymer degradation

Industry
          Free radicals in polymers and polymerization, petrochemistry, thermoxidative breakdown of lubricants and fuel, real time analysis of additives, antioxidants in lubricants and fuels.

 

 

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