Pharmaceuticals complexation liquid chromatography

Separation-based techniques, especially high-performance liquid chromatography (HPLC) and gas chromatography (GC), have long been the work horses of pharmaceutical analysis laboratories. They are among the most powerful and versatile tools for the detection and quantitation of analytes (chemical components) in complex matrices frequently encountered in the course of PhR D. 

Hyphenated analytical techniques such as LC-MS, which combines liquid chromatography and mass spectrometry, are well-developed laboratory tools that are widely used in the pharmaceutical industry. Eor some compounds, mass spectrometry alone is insufficient for complete structural elucidation of unknown compounds nuclear magnetic resonance spectroscopy (NMR) can help elucidate the structure of these compounds (see Chapter 20). Traditionally, NMR experiments are performed on more or less pure samples, in which the signals of a single component dominate. Therefore, the structural analysis of individual components of complex mixtures is normally time-consuming and less cost-effective. The... 

The concurrent identification and quantification of organic impurities is a principal use of liquid chromatography in the pharmaceutical industry. However, the application of liquid chromatography to this task highlights a weakness of this technique when compared to gas chromatography specifically, the lack of a universal detector. Great strides have been made to create detectors and hyphenated techniques to address these problems. However, multiple detectors and analytical procedures may be necessary to accurately and specifically identify and quantify the impurities in complex systems. 

In the last years, the use of comprehensive liquid chromatography has been greatly increased and it has been widely used to separate and characterize various complex samples, such as biomolecules [10-15], polymers [16,17], lipids [18-21], essential oils [22], acidic and phenolic compounds [23-28], pharmaceuticals and traditional medicines [29-31], etc. Comprehensive LC has been reviewed by several authors [32-37]. 

This pharmaceutical revolution could not have been achieved without the under-girdment of advanced analytical instrumentation. Mass spectrometry (MS) combined with liquid chromatography (LC) has enabled the characterization of novel potential dmgs as well as quantitative measurement in an increasingly complex milieu at an incredibly rapid throughput rate. Quantitation of dmgs in biological media such as... 

With the availability of less expensive and more dependable commercial instruments, liquid chromatography coupled to mass spectrometry is quickly becoming the industry standard. However, the role of electrochemistry in pharmaceutical analysis has been well defined, and will likely continue to be preferentially employed in applications where low analyte concentrations, small sample volumes, or complex sample matrices requiring high specificity challenge the analytical method. 

Many of the most important chemical questions in the pharmaceutical industry involve the analysis of complex mixtures. Identification of low-level metabolites and drug substance impurities usually requires high-performance liquid chromatography for the separation of these mixtures or isolation of a compound of interest from a sample matrix. In these analyses, the structural information obtainable for the low-level compounds is limited by the type of detection used. The coupling of HPLC and mass spectrometry has become routine and provides useful molecular weight and fragmentation information, but this is often not enough for complete structure elucidation. 

The ability to gather more knowledge faster with smaller quantities of complex samples can support these increased demands on pharmaceutical R D. The advanced approaches and technologies associated with liquid chromatography-mass spectrometry (LC-MS) continue to play a significant role within drug discovery because of the inherent sensitivity and selectivity of this analytical platform. Improvements with increased throughput and easier-to-use instruments have allowed researchers unprecedented levels of efficiency and productivity. 

In conclusion, NMR is an essential tool for the successful determination of crucial metabolite structures and is routinely used in the pharmaceutical industry. As discussed, metabolite structure problems could be as simple as hydroxylation on an aromatic ring or as complex as a rearrangement depicted in the formation of glutathione adducts. NMR provides a vast and continually expanding combination of techniques applicable to the analysis of metabolite structures. The judicious choice of NMR experiments based on the particulars of the system and the nature of the metabolites can be combined with mass spectrometry and liquid chromatography to successfully analyze a variety of biological metabolites to benefit drug discovery. 

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