The Scope and Limitations of Quantitative Nuclear Magnetic Resonance Technique - Coursework Example

The Scope and Limitations of Quantitative NMR The Scope and Limitations of Quantitative NMR Introduction The Nuclear magnetic Resonance Technique (NMR) was discovered in the 1940’s by Purcell and Bloch. Since then, its applications have gone on to grow from one use to another as the technology in use has advanced. Researchers are continuing to take advantage of the diverseness and dynamism that NMR has come to be connected with. The measurements provided by NMR can avail information on various active processes. The active processes can have rates ranging from 10-2 to 10-10 per second. Quantitatively, NMR has done away with the need for calibrations that are usually strenuous. How has it done this? NMR has been shown to have the exceptional capability of containing an even molar reaction for all similar nuclei. Due to this exceptional capability, a solitary standard can be utilised for the precise quantitation of substances (Merkley, et al., 2013). The principle behind NMR is that it senses electrical currents that have been triggered by nuclear magnetic flashes that are found in an even magnetic field that is static (Kleckner & Foster, 2010). Thus, nuclei that have non-zero magnetic flashes are termed to be active to magnetic resonance; hence, they can be sensed. Each nucleus that is active to magnetic resonance has a special frequency. The special frequency is influenced by the magnetic field’s strength, its typical electronic setting, and its isotope’s magnetic features (Dongsheng, et al., 2010). The type of nucleus determines the typical frequency. Hence, NMR can easily differentiate between two Hydrogen isotopes (Merkley, et al., 2013). Because the typical setting of the nuclei affects the precise frequency in the collection of similar nuclei, the applications and importance of NMR has become widespread and diverse (Merkley, et al., 2013). Thus, the application of NMR in quantitative analysis is just one of the many applications there are. The report will focus on quantitative NMR and examine its scope and limit as it has been applied in various research studies. The number of studies that make use of quantitative NMR is not that much. Hence, it can be said that the use of NMR for quantitative evaluation is not that common. Nevertheless, quantitative NMR can precisely and correctly evaluate the concentration of the analyte. The molecules could be in an intricate mixture or in a sample that has been purified. Quantitative NMR does away with the need for strenuous calibrations (Bohni, et al., 2013). Usually, the state of the samples for quantitative evaluation can be semi-solid state or in solid state. Research has helped in the development of protocols. These protocols make use of a solitary external standard that is approved. The protocols are utilised in the calibration of the quantitative NMR instruments (Mazmuder, et al., 2014). The samples can then be quantified using the calibrated system. The signals produced by the quantitative NMR instruments are relational to the nuclei molar concentration. Hence, this permits for the direct contrast and assessment of the concentration of each compound in a mixture. The advantage of quantitative NMR is that there is a recording of the produced spectra. The recording permits for the precise assessment and contrast between various samples that are in various tubes and varying solvents. Hence, it is possible to measure the natural products’ concentrations that are in various tubes. There are benefits about this possibility. The benefits are that; purity is ensured, and the amount of handling that is needed is largely decreased (Kleckner & Foster, 2010). Vu, et al., (2011) describe a design for the quantitative analysis of data obtained from NMR spectrometry. The design involved several steps. These steps were generation of the spectra, finding of the peaks, determining the reference, aligning of the spectrum, and quantification. In the finding of the peaks, the peaks are collected from the NMR spectra. The determination of the reference was done by choosing the main spectrum. The alignment of the peaks was done by approximating the shifts through hierarchical clustering. The BW-Ratio was sued to determine the differential region in the spectra produced by the NMR during quantification. The limitation of this steps was the lack of a standard method for detecting the peaks, which is the initial step. The study was also limited by the inability to apply the peak detection to the whole spectra. The inability was caused by complication in the computations and reduced sensitivity in peaks that were of low intensity. The question that can be asked is, what if a different method that concentrates on getting the differences in the height of the peaks? If such a method is used, would it give the same results? Fisette, et al., (2012) explain how quantitative NMR is applied synergistically with molecular dynamics (MD) to study biological systems. The researchers talk of how the two methods can be used together in applications such as dynamics studies. In the study of protein dynamics, the research indicates that it is possible to derive information regarding the quantitative dynamics using NMR. However, it is noted that this information is normally limited to evaluating the motion rates. Hence, the research shows the way quantitative NMR can be used along with other methods to not only assess the quantity of the proteins or biological samples under study, but also to evaluate the dynamics associated with the sample. It is a study that describes the extent to which quantitative NMR can be manipulated to fit into the aims and objectives of the study (Fisette, et al., 2012). In a study by Gowda, et al., (2012), the researchers examine the quantitative evaluation of metabolites found in blood plasma through the use of NMR methods that have been boosted using isotopes. It is noted that, the quantitative analysis of intricate fluids such as blood plasma is tasking. As Vu, et al., (2011) indicated, the research also states that the use of heteronuclear tests involving 13C on a daily basis is not practical. It is not practical because of the lack of sensitivity in spite of enhanced resolution (Gowda, et al., 2012). Gowda, et al., (2012), talks of the limitations associated with two-dimensional NMR method for quantitation purposes. They include the influence of the volume of the cross-peak in the spectra by many experimental factors. These experimental factors include the distorted excitation outline of the pulses produced by the radio frequency and delays during the transition from one pulse to the next. The peak volumes or intensities are very sensitive to these experimental factors. The sensitivity limits the utilization of two-dimensional NMR in quantitative studies involving metabolomics. The research proposes various methods to mitigate these limitations. Some of these methods include using calibrations curves that have been gotten through 1H-13CHSQC spectra (Gowda, et al., 2012). Hence, the research made use of two-dimensional NMR and isotope tagging so as to mitigate the limitations associated with sensitivity and resolution. The metabolites comprising amino acids and carboxyl were tagged with 13C and 15N respectively. The study indicates that the advantage of tagging the metabolites is to permit the quantitation of numerous metabolites in blood plasma. However, it has not explained how this is achieved (Gowda, et al., 2012). The concentration of the metabolites was obtained by comparison. Comparison of the peak integrals of the blood plasma metabolites with those from the standards or with synthetic analogues. However, what if there were errors during comparison? Wouldn’t the quantitation produce false results? In agreement with the research conducted by Gowda, et al., (2012), Bharti & Roy, (2012) state that, 1H NMR has grown immensely in its utilization in the quantitative analysis of metabolites. The study says that quantitative NMR avails comparative and outright quantification of various metabolites. It does not require the separation of these metabolites into their individual constituents. Conclusion As has been stated, the choosing of the pulse sequence that is to be utilised for quantitative analysis in single-pulse NMR is affected by the concentration of the analyte. Low analyte concentration leads to a strong solvent indicator. The noise produced should lead to a signal-to-noise ratio of 250:1 (Bharti & Roy, 2012). The ratio ensures accuracy. However, it is affected by the resonance of an individual molecule depending on the proton number per resonance. Quantitative NMR requires enough resolution to measure the spectra. A major limitation of quantitative NMR is incorrectness in the baseline. If the baseline is incorrect, then a weighty error during peak integration and quantitation is produced. Nevertheless, it can be corrected using in-built algorithms in the quantitative NMR software used for assessment (Pauli, et al., 2013). In order to calculate an analyte’s concentration, a reference compound is needed. There are two types, an internal and external standard. For the internal standard, the selection is very vital as it is affected by factors like the chemical reaction with the sample and its solubility. Some internal standards bind with the proteins under assessment hence impacting the accuracy. Thus, the external standard is used to avail accuracy where the internal standard cannot (Pauli, et al., 2013). Hence, it is shown that the scope is diverse. It can be combined with other techniques not limited to those mentioned in the paper to quantify and assess a compound. The limitations that quantitative NMR faces have been shown to be limitations that can be overcome through adjustments or addition of various methods to the procedure. References Bharti, S. K. & Roy, R., 2012. Quantitative 1H NMR spectroscopy. Trends in Analytical Chemistry, Volume 35, pp. 5-26. Bohni, N. et al., 2013. Quantitative NMR does away with the need for strenuous calibrations. PLoS ONE, 8(5), p. E64006. Dongsheng, L., Xu, R. & Cowburn, D., 2010. Segmental Isotopic Labeling of Proteins for Nuclear Magnetic Resonance. Methods in Enzymology, 2009(462), pp. 151-175. Fisette, O., Lague, P., Gagne, S. & Morin, S., 2012. Synergistic Applications of MD and NMR for the Study of Biological Systems. Journal of Biomedicine and Biotechnology, Volume 2012, pp. 1-12. Gowda, G. A. N. et al., 2012. Quantitative Analysis of Blood Plasma Metabolites Using Isotope Enhanced NMR Methods. Analytical Chemistry, 82(21), pp. 1-17. Kleckner, I. R. & Foster, M. P., 2010. An introduction to NMR-based approaches for measuring protein dynamics. Biochimica et Biophysica Acta, Volume 2010, pp. 1-28. Mazmuder, A., Kumaar, A. & Dubey, D. K., 2014. A rapid qNMR protocol for the analysis of triclofos sodium in solution state pharmaceutical dosage formulations. Indian Journal of Chemistry , Volume 53B, pp. 95-101. Merkley, N., Burton, I. K. T. & Raymond, T., 2013. Magnetic Resonance Technologies: Molecules to Medicine, Using Old Solutions to New Problems-Natural Drug Discovery in the 21st Century. s.l.:InTech. Pauli, G. F., Godecke, T., Jaki, B. U. & Lankin, D. C., 2013. Quantitative 1H NMR: Development and Potential of an Analytical Method – an Update. Journal of Natural Products, 75(4), pp. 834-851. Vu, T. N. et al., 2011. An integrated workflow for robust alignment and simplified quantitative analysis of NMR spectrometry data. BMC Bioinformatics, Volume 12, p. 405. Read More