A Brief Story of an Analyte’s Isolation, Preparation, and Detection
Scientific research is a vast compilation of techniques used to progress the well-being of Earth’s inhabitants. Many of these techniques are placed into subcategories based on their generalities. A sub-category of techniques is known as the “omics”, which directly translates to the “study of”. In current studies, innovation involves studying physiology through analyses of the “omics,” specifically: proteomics, genomics, and molecular pathology (Bennet 2005). Today, an emerging field of study receiving more focus from the science community is metabolomics. Metabolomics is defined as the study of metabolites as they are produced from physiological processes of living organisms (Jordan 2009). Metabolomics is comprised of the specific techniques of separation, ionization, and detection.
Separation methods are essential to initiating an effective study involving a metabolic process. In order to separate chemical species within a sample it is imperative that a target may be identified; more importantly, a target’s potential interactive qualities (Gika 2007). With the qualities in mind, there will need to be a technique that is proven to be useful, and reproducible. These techniques are known as chromatography. The chromatography methods that are commonly used today are gas chromatography (GC), high-performance liquid chromatography (HPLC), and capillary electrophoresis (CE) (Gika 2007). Gas chromatography is a technique used in a wide array of scientific areas of study for separation of chemical species which are both volatile, and not volatile. HPLC uses a liquid phase to separate chemical species and allows the scientist to use more sensitive methods for elution of specific chemical species in a sample. Lastly, CE is simply the most effective separation method for chemical species in a sample that have distinct charges (Soga 2003).
Ionization methods of metabolomics coupled directly to separation methods but not limited to separation methods. The importance of ionization methods is simply to prepare a sample of analytes for detection (Morrow 2010). In order to properly prepare a sample for detection of the analytes must be charged. The common methods for imparting a charge on metabolites is electric ionization (EI), chemical ionization (CI), and electrospray ionization (ESI). Electric Ionization is generally coupled to gas chromatography because of the low pressures used in separation (Morrow 2010). Chemical ionization is able to be used with most chromatography methods; however, this chromatography is generally used for less polar compounds. Finally, electrospray ionization is more often used with liquid chromatography containing analytes that are polar.
Without an accurate detection method, the separation and ionization processes become more or less useless. Science has a necessity of proper detection instrumentation and methods that are accurate and precise. The best detection methods in tandem with chromatography and ionization methods are mass spectrometry (MS), proton nuclear magnetic resonance (hNMR) and carbon proton nuclear magnetic resonance (cNMR), and surfaced based mass analysis. Mass spectrometry is a widely used method for identifying and quantifying analytes in a sample after chromatography and is the first detection method to be developed (Griffiths 2009). Nuclear Magnetic Resonance is a unique technique relative to MS. A sample containing multiple analytes is able to be measured all at once using NMR and is currently known as an effective method of detection (Griffin 2003). With NMR a scientist is able to use minimal preparation methods and receive a highly reproducible set of data involving the contents within a sample. As for the third method stated there is a growing concern in the field of science regarding the ability of MS to measure the present analytes in a complex sample; therefore, a component of surface-based mass analysis known as nanostructure-initiator mass spectrometry is emerging as a significantly necessary technique in modern metabolomics.
Scientific studies today demand a consistent and reproducible means of identifying and quantifying chemical species in a sample derived from an organism’s physiological processes. The techniques of isolation, preparation, and detection have applications which allow scientists to further understand physiological processes. These applications involve but are not limited to toxicology, nutrition analysis, and genomics. Generally, doing a toxicology analysis for a human involves extraction and analysis of urine, blood serum, or plasma of a subject (Gika 2007). Nutrition analysis further allows scientists to take into consideration the dietary contribution to pathologies based on which components help or hurt the organism, and this study is coupled to genomics in some cases to identify phenotypes based on changes in genetic expression. In summation, the contributions made by the development of metabolomics positions modern research to progress in a very collaborative mode.
References
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