Ayenew Ashenef

By Esayas Tesfaye, Tadele Eticha, Ariaya Hymete and Ayenew Ashenef

Many complex mixtures usually constitute hundreds or even thousands of individual components of interest. Such mixtures are much too complicated to be separated for analytical duties in a reasonable period of time using only a single-dimensional chromatographic method. However, if a complex mixture is separated by an initial dimension using multi-dimensional liquid chromatography, a simpler portion of that separation is collected and goes to the second dimension. Each of these fractions will be analyzed separately, allowing exceedingly complex mixtures to be resolved in a short period of time. This chapter explains the fundamental principles, theoretical discussions as well as various applications with typical examples of multi-dimensional liquid chromatography in different fields.

Part of the book: Analytical Liquid Chromatography

By Feruza Ahmed, Tadele Eticha, Ariaya Hymete and Ayenew Ashenef

The science of separation had advanced significantly with the development of ultra-high-performance liquid chromatography (UHPLC), a brand-new type of liquid chromatography. The need for the evolution of HPLC into UHPLC has been driven by the continuously evolving of packing material modifications that affect the separation of mixtures. The separation process of analytes is completed in a substantially decreased amount of time due to the lower particle sizes, which increases surface area of interaction allowing reduction of column length to one-third; thus, shorter columns are employed in UHPLC, which consequently causes the flow rate to be three times higher and subsequently reducing analysis time. Although UHPLC shares the same fundamental idea and instrument layout as HPLC, it differs from HPLC in that it produces narrow peaks and has high spectral quality, allowing for simple compound identification in a variety of analytical applications such as impurity profiling, product formulation, and improved analytical technique and method development. However, high back pressure in UHPLC might lead to decreased column life, and the instrument’s higher price compared to HPLC are the disadvantages.

Part of the book: High Performance Liquid Chromatography