LC-NMR represents a potentially interesting complementary techniq

LC-NMR represents a potentially interesting complementary technique to LC-UV-MS our website for detailed on-line structural analysis. Indeed, recent progress in NMR technology has given a new impulse to LC-NMR, which is now emerging as a powerful analytical tool. The development of efficient solvent suppression techniques enables the measurement of high-quality LC-1H-NMR spectra, both on-flow and stop-flow, with reversed-phase HPLC conditions. Nondeuterated solvents such as MeOH or MeCN can be used, while water is replaced by D2O. Recent advances in both hardware and software for the direct coupling of LC and NMR have given a new life to this hyphenated technique. These developments include new coil and flow-cell design for high sensitivity, new RF system for multiple solvent suppression and improved dynamic range gradient elution capability, and automatic peak-picking/storing capabilities.

As a result, this method is a powerful tool used in many areas such as natural products, organic molecules, biomolecules, drug impurities, by-products, reaction mixtures, and drug degradation products. The potential of HPLC-NMR for the investigation and structural elucidation of novel natural products has been enormously extended by the advent of powerful solvent suppression schemes, and their combination with a series of homo- and heteronuclear 2D NMR experiments such as 2D total correlation spectroscopy (TOCSY) or 2D nuclear Overhauser enhancement spectroscopy (NOESY). LC-NMR, despite being known for about last two decades, has not quite become a widely accepted technique, mainly because of its lower level of sensitivity and higher cost compared to other available hyphenated techniques.

However, the recent advances in technology, especially in relation to the developments in pulse field gradients and solvent suppressions methods, the improvement in probe technology, and the introduction of high-field magnets (800�C900 MHz) have offered new impetus to this technique. CE-MS CE is an automated separation technique introduced in the early 1990s. CE analysis is driven by an electric field, performed in narrow tubes, and can result in the rapid separation of many hundreds of different compounds. The versatility and the many ways that CE can be used mean that almost all molecules can be separated using this powerful method.

It separates GSK-3 species by applying voltage across buffer-filled capillaries, and is generally used for separating ions that move at different speeds when voltage is applied, depending on their size and charge. The solutes are seen as peaks as they pass through the detector and the area of each peak is proportional to their concentration, which allows quantitative determinations. Analysis includes purity determination, assays, and trace level determinations.

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