LC NMR HYPHENATED TECHNIQUES
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The document discusses hyphenated techniques, specifically liquid chromatography-nuclear magnetic resonance (LC-NMR). It begins by introducing hyphenated techniques as the combination of two analytical methods, usually a separation technique coupled with a spectroscopic technique. It then describes LC-NMR in more detail, explaining how it works to separate components with liquid chromatography and then uses NMR for identification. Key aspects covered include instrumentation, modes of data acquisition (continuous flow, stopped flow, time sliced), and advantages such as automation, reproducibility, and simultaneous separation and quantification.
LC NMR HYPHENATED TECHNIQUES
- 1. IC- NMR PRESENTED BY R.ARULKUMAR M. PHARMACY DEPARTMENT OF PHARMACEUTICS KMCH COLLEGE OF PHARMACY
- 2. INTRODUCTION A hyphenated technique is combination (or) coupling of two different analytical techniques with the help of proper interface. Mainly chromatographic techniques are combined with spectroscopic techniques. In the chromatography, the pure or nearly pure fractions of chemical components in a mixture was separated and spectroscopy produces selective information for identification using standards or library spectra. KMCH COLLEGE OF PHARMACY 2
- 3. The term hyphenated techniques range from the combination of separation -separation, separation-identification & identification- identification techniques. The term “hyphenation” was first adapted by Hirsch Feldin (1980) KMCH COLLEGE OF PHARMACY 3
- 4. Advantages For fast and accurate analysis A Higher degree of automation. Higher sample throughput. Better reproducibility. Reduction of contamination due to its closed system. Separation of quantification at the same time. KMCH COLLEGE OF PHARMACY 4
- 5. Typesofhyphenatedtechniques Double hyphenated techniques. Triple hyphenated techniques. 1. Double hyphenated techniques LC-MS LC-NMR LC-IR CE-MS GC-IR GC-MS HPLC-DAD GC-FTIR 2. Triple hyphenated techniques LC-API-MS APCI-MS-MS ESI-MS-MS LVI-GC-MS LC-ESI-MS LC-UV-NMR-MS-ESI LC-MS-TSPLC-UV-NMR-MS LC-NMR-MS LC-DAD-API-MS LC-PDA-MS LC-PDA-NMR-MS SPE-LC-MS KMCH COLLEGE OF PHARMACY 5
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- 7. LC-NMR Instrumentation and working The use of HPLC-NMR or LC-NMR hyphenated technique in the analytical laboratories started in the latter part of the 1990s only. LC-NMR promises to be of great value in the analysis of complex mixtures of all types, particularly the analysis of natural products and drug-related metabolites in biofluids. KMCH COLLEGE OF PHARMACY 7
- 8. LC-NMR experiments can be performed in both continuous-flow and stop- flow modes. A wide range of bio analytical problems can be addressed using 500, 600, and 800 MHz systems with 1H, 13C, 2H, 19F, and 31P probes. The main prerequisites for on-line LC-NMR, in addition to the NMR and HPLC instrumentation, are the continuous-flow probe and a valve installed before the probe for recording either continuous-flow or stopped-flow NMR spectra. A UV–vis detector is also used as a primary detector for LC operation. Magnetic field strengths higher than 9.4 T are recommended KMCH COLLEGE OF PHARMACY 8
- 9. In fact, the benefits of the closed-loop separation–identification circuit, together with the prospect of using all presently available 2D and 3D NMR techniques in a fully automated way, have prompted the development of stopped-flow modes, e.g., time-slice mode. Generally, in the LC-NMR system, the LC unit comprises autosampler, LC pump, column, and a non-NMR detector (e.g., UV, DAD, refractive index, or radioactivity). From this detector, the flow is guided into the LC-NMR interface, which can be equipped with additional loops for the intermediate storage of selected LC peaks. The flow from the LC-NMR interface is then guided either to the flow-cell NMR probe head or to the waste receptacle. Following passage through the probe head, the flow is routed to a fraction collector for recovery and further investigation of the various fractions analysed by NMR. KMCH COLLEGE OF PHARMACY 9
- 10. An MS can also be attached to the system via a splitter at the output of the LC-NMR interface .In most of the LC-NMR operations, reversed-phase columns are used, employing a binary or tertiary solvent mixture with isocratic or gradient elution. The protons of the solvents of the mobile phase cause severe problems for obtaining an adequate NMR spectrum. The receiver of the NMR spectrometer is not quite able to handle the intense solvent signals and the weak substance signals at the same time. To overcome this problem, solvent signal suppression can be achieved by one of the three major methods: pre-saturation, soft-pulse multiple irradiations or water suppression enhancement through T1 effects (WET) pre-saturation employing a z-gradient. KMCH COLLEGE OF PHARMACY 10
- 11. This problem can also be minimized by considering the following guidelines: 1. Using eluents that have as few 1H NMR resonances as possible, e.g., H2O, Me OH. 2. Using at least one deuterated solvent, e.g., D2O 3. Using buffers that have as few 1H NMR resonances as possible, e.g., ammonium acetate. 4. Using ion pair reagents that have as few 1H NMR resonances as possible, e.g., ion pairs with t-butyl groups create an additional resonance. KMCH COLLEGE OF PHARMACY 11
- 12. Three main types of data acquisition modes have been introduced: continuous-flow acquisition, stopped-flow acquisition, and time-sliced acquisition. Whatever may be the acquisition mode, an optimized HPLC separation is crucial to any LC-NMR analysis. As the sensitivity of LC-NMR is much less than other hyphenated techniques, e.g., LC-MS, or LC-PDA, it is imperative to develop a suitable LC separation where the quantity of the available separated compound is concentrated in the smallest available elution volume. LC-NMR represents a potentially interesting complementary technique to LC- UV-MS 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. KMCH COLLEGE OF PHARMACY 12
- 13. The development of efficient solvent suppression techniques enables the measurement of high-qualityLC-1H-NMR spectra, both on-flow and stop-flow, with reversed-phase HPLC conditions. Non deuterated solvents such as Me OH or Me CN 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 a 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. KMCH COLLEGE OF PHARMACY 13
- 14. 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 hetero nuclear 2D NMR experiments such as 2D total correlation spectroscopy (TOCSY) or 2D nuclear Over Hauser enhancement spectroscopy (NOESY). 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 (800–900 MHz) have offered new impetus to this technique. KMCH COLLEGE OF PHARMACY 14
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- 16. REFERENCES www.wikipedia, encyclopaedia. Ruchira chinholeet.al. Recent applications of hyphenated liquid chromatography techniques. International journal of pharmaceutical sciences review and research: 2012, 14(1); 57-63.3. Pallavi Phalke et.al. International Journal of Chemical Studies Review on Hyphenated Techniques 2013; 1(3): 157-164. Hill technologies KB Item: 35254 Version(1) 1 of 2.5. Sheetal V. Patil*, et al.World Journal of Pharmaceutical Research Volume 4, Issue 2, 214-225. ISSN 2277–7105 pg no: 217-218 Shree Sureshdada Jain Institute of Pharmaceutical Education and Research, Jamner. Kalpesh n Patel, et.al. Introduction to hyphenated techniques and their applications in pharmacy Pharm Methods.2010 Oct-Dec; 1(1): 2–13.doi:10.4103/2229-4708.722227. KMCH COLLEGE OF PHARMACY 16
- 17. Sheetal V. Patil*, et al World Journal of Pharmaceutical Research Volume 4, Issue 2, 214- 225. ISSN 2277–7105pg no: 219-220Shree Suresh dada Jain Institute of Pharmaceutical Education and Research, Jamner. P. R. Griffiths, et, al, University of Idaho, Moscow, ID, USA This article is reproduced from Encyclopaedia ofAnalytical Science, Copyright Academic Press 1995.pg.no:-464-465. M. Hamdan, et. al. Capillary Electrophoresis^ Mass SpectrometryGlaxo Wellcome Medicines Research Centre, Verona, Italy. P. G. Righetti, et.al University of Verona, Verona, Italy Copyright ^ 2000 Academic Press. Pharmaceuticalanalysis modern methods, W.MUNSONpart –a 2001 edition. Ju seopkanget al. Principles and applications of lc-ms/ms for quantitative bio analysisof analytes in various Biological samples. www.intechopen.com. KMCH COLLEGE OF PHARMACY 17