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Information about LC-NMR-MS

Published on March 21, 2014

Author: naveen.gokanapudi


LC/NMR/MS :  LC/NMR/MS Presented by G.Naveen , G.Dinesh Kumar, Y12MPH206 & 207, M.Pharm -Pharmaceutics, Hindu college of pharmacy , Guntur. Table of Contents: Table of Contents Introduction LC/NMR LC/MS Linking of LC/NMR/MS Sample collection Applications of LC/NMR/MS Disadvantages of LC/NMR/MS Conclusion References 1. Introduction : 1. Introduction From 1970 LC/MS evolved into standard technique from this the detection sensitivity can reach very low levels. LC/NMR relatively recent design improvements have improved sensitivity and the technique is now established. Integrated LC/NMR/MS system is progression involving combination of two systems. LC/NMR:  LC/NMR Modes of operation in LC-NMR system:: Modes of operation in LC-NMR system: Continuous-flow Stopped-flow Loop collection. Continuous-flow: Continuous-flow Stopped - flow: Stopped - flow Loop - flow: Loop - flow Advantages of LC/NMR: Advantages of LC/NMR Non destructive method Isomer identification (structural, conformational or optical) Fractions can be recovered after analysis and stored Volatile and non-volatile buffer mobile systems are suitable Common interfaces: Common interfaces Electron spray Atmospheric pressure chemical ionization Particle beam Thermo spray LC/MS: LC/MS Ion detectors employed: Ion detectors employed Single quadrapole Triple quadrapole Ion trap Fourier transform ion cyclotron resonance TOF analysers Applications : Applications Molecular weight determination Fragmentation patterns Isotope determination Elemental analysis Pharmacokinetic & protein studies Linking LC/NMR/MS : Linking LC/NMR/MS Two types A. Series Difficult correlation as sample analyzed at different times in each detector Pressure difference between MS & NMR induces leaks from NMR flow probe B. Parallel Analyte output is spitted simultaneously to two systems Series connection : Series connection Pump Column UV cell MS NMR Parallel connection: Parallel connection PowerPoint Presentation: If UV cell is positioned before the splitter , it can be used to initiate the next step when an analyte is detected. If the UV detector is positioned after the splitter , the eluent can be directed to the MS and a peak observed before that peak reaches the UV cell. When that same peak is subsequently detected at the cell, it can be used to initiate a stopped-flow experiment on the peak in the NMR instrument. Solvent systems : Solvent systems Solvents minimizing 1 H spectrum are more suitable Ex: Formic acid (P H adjusted with ammonium formate ) Deuterated solvents (D 2 0, acetonitrile-d 3 , methanol-d 4 ) Acetonitrile in D 2 0 (P H adjusted with sodium phosphate) Disadvantage: phosphate salts deposits in MS system Aqueous tri fluroacetic acid Disadvantage: suppress ionization of acid analytes Interferences during operation: Interferences during operation Strong magnetic field of NMR interfere with MS operation Remedy: Highly shielded modern superconducting NMR magnets In lab built equipments older NMR instruments linked with MS are positioned away from MS Solvent signal interference during NMR analysis: Solvent signal interference during NMR analysis Presaturation Technique of solvent signal suppression, where a long low-power pulse is applied on the solvent resonance before the pulse sequence. Water suppression enhanced through T1 effects Uses selective pulse and transverse signal cancellation with pulsed field gradients Current scenario: Current scenario Commercial LC-NMR-MS systems are produced by “ Bruker Analytik ” They sold only 24 systems till September 28, 2005 They are available with magnetic strengths from 500-800 MHz with mass spectrometer – the Esquire ion trap Consisting removable cartridge with 36 sample loop which collect eluting samples for analysis and they can be transported as such A: The HPLC pump, B: The NMR-MS interface, C: The ion trap mass spectrometer, D: the LC-NMR rack with the DAD/UV detector. Applications : Applications Drugs and metabolites: Drugs and their metabolites in urine, blood, sweat, milk are analysed Drugs in phase I,II trails are mostly analyzed by LC-NMR-MS system Ex: Di hydroquinoxaline carboxylate GW320867(anti HIV) Triazolopyridine GI265080 (bipolar disorder treatment) Natural products: Natural products Plant extracts Ex: Flavonoid glycosides, Napthodianthrones from Hypericum perforatum Flavonoids like Arabinoside , Galacturonide of Quercetin are seperated Flavonoid glycosides from fruit peels like apple Ecdysteroids from extract of Lychnis flos-coculi Toxic steroid glycoside called asterosaponins extracted from starfish Asterias rubens Disadvantages of LC-NMR-MS : Disadvantages of LC-NMR-MS high costs long experiment times partial use of 2H solvents It is hard to find an HPLC method that makes LC, NMR, and MS experts all uniformly. Examples: TFA,phosphate buffers(great for NMR, but not MS) Triethylamine (great for MS, but not NMR). Flow systems can clog up, and get dirty, and be hard to clean Conclusion: Conclusion Use of either LC/MS or LC/NMR alone can often solve analytical problems but there are occasions when they fail and extra techniques are required to solve the problem. In these cases, using both LC/MS and LC/NMR can provide extra information and structural identity. It seems a natural progression to combine the two systems into one integrated LC/NMR/MS system. Abbreviations: Abbreviations API atmospheric pressure chemical ionization DAD diode array detector FT Fourier transform GC gas chromatography HPLC high-performance liquid chromatography ICP inductively coupled plasma IR infrared LC/MS liquid chromatography/mass spectrometry LC-NMR liquid chromatograph-nuclear magnetic resonance spectrometer LC/NMR liquid chromatography/nuclear magnetic resonance spectrometry References : References A Primer on LC/NMR/MS: Education Article Published: Sep 28, 2005 article pdf  www.wikedpedia Pharmaceutical methods - International journal  

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