the minispec ProFiler
The minispec ProFiler is a handheld NMR instrument for relaxation measurements in the near surface volume of unrestricted size samples.
Single-Sided NMR is the generic name associated with these types of NMR devices.
Nuclear Magnetic Resonance (NMR) methods are among the most useful non-destructive techniques of material analysis. Non-invasive examination of the body by means of NMR is extensive and has many useful applications, particularly with Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS). TD-NMR uses similar NMR technology, providing analysis of fat tissue, lean tissue and free fluid by the same physical selection rules that give rise to contrast in MRI. Tissue contrast is high between fat and muscle based on relative relaxation times.
mq-ProFiler: a bench-top spectrometer for single-sided NMR
The mq-ProFiler is a compact NMR relaxometer, equipped with single-sided magnet and RF probes for performing 1H-NMR experiments within the first few millimeters below the surface of arbitrarily shaped samples.
The system is based on Bruker`s well-proven minispec mq series console, a broadbanded electronics unit which works with any kind of minispec probe. The magnet assembly of the mq-ProFiler consists of two rectangular magnets, placed in an antiparallel configuration and fixed to an iron yoke, and generates a static surface field. The winning features that distinguish the mq-ProFiler from other single-sided NMR tools are mainly related to its RF probe design.
Applications
In view of the features discussed above, the mq-ProFiler is suitable for QC solutions in industrial environments.
For example, relaxation time experiments provide insight into the characteristics of rubber or polymer products in general. Through the magnetic dipole-dipole interaction, the time-evolution of the 1H magnetization is strongly coupled to the internal molecular dynamics of polymer materials. Thus, 1H relaxation rates provide quantitative information concerning cross-link density and, thus, the stiffness of the products examined.
Not only nuclear relaxation rates can be exploited to investigate physical properties. The static B0 field gradient inherent in the single-sided NMR devices suggest the application of diffusion-weighted NMR measurement schemes. Recently, Casieri et al. have reported a method for determining self-diffusion coefficients (without prior knowledge of T2) that was developed using a prototype of the mq-ProFiler. Moreover, Maddinelli and Peron showed that the mq-ProFiler can be successfully used to distinguish water and oil fractions in saturated sandstone rock cores.
The need for quality control in the food industry has led to exploratory investigations with the mq-ProFiler. Most applications are devoted to distinguishing fat and water compartments. The classic CPMG spin-echo pulse sequence is frequently applied to food emulsions and fish. Specially designed sequences were developed by Bruker which exploit differences in both relaxation rates and diffusion coefficients for water and lipids leading to improved accuracy of the measurements. The overall sample preparation and measurement times for single-sided NMR and the accuracy of the results are now comparable with the capabilities of conventional low-field NMR. Many other applications of single-sided NMR are currently being developed in various research areas.
