Preface

Increasing interest in topics related to health and quality of life in recent years has led to a growing need in food, environmental and bioanalytical research for high-throughput separation techniques able to cope with the qualitative/quantitative determination of a large number of compounds in very complex matrices. High-performance liquid chromatography (HPLC) is a well-established separation technique widely employed in many fields. The versatility of chromatographic separation modes, coupled with low-resolution and high-resolution mass spectrometry, makes HPLC among the best options to solve emerging analytical problems.

This book provides an overview of new advances in high-performance liquid chromatography and its applications in different fields. The first of the book's two sections is devoted to principles and new advances in HPLC. In Chapter 1, "Principles and Applications of Ultra-High-Performance Liquid Chromatography", Ahmed et al. describe the fundamentals of UHPLC techniques (solvent delivery systems, columns, sample injection, and detection), and review the role of UHPLC in different fields such as the analysis of herbal medicines, drugs in human plasma, pharmacokinetics and bioavailability studies, identification of metabolites (metabolomics), detection of impurities, analysis of dosage formulations, food safety and agricultural applications.

The higher separation capacity of 2D-LC techniques can be especially useful. A commercial application, the TurboFlow technology developed by Thermo Fisher Scientific, may enable the direct introduction of biological samples into an online automated extraction system without any pre-treatment. In Chapter 2, "Turbulent Flow Chromatography: A Unique Two-Dimensional Liquid Chromatography", Di Gaudio et al. explain the principles of turbulent flow chromatography, the different column chemistries available, the hardware employed, how to operate in multichannel systems, and how to develop a focus mode method to implement this technique. They also describe successful applications of the turbulent flow technique in different fields, including therapeutic drug monitoring and environmental analysis, and applied to different matrices such as urine, plasma, food commodities and water.

Monolithic media are excellent substitutes for conventional particle-packed columns. This is because monolithic columns show higher permeability and lower flow resistance than conventional liquid chromatography columns, providing high-throughput performance, resolution and separation in short run times. In Chapter 3, "Monoliths Media: Stationary Phases and Nanoparticles", Hernawy et al. address the general characteristics and properties of monolithic materials, the separation mechanism involved, and the different types of monoliths: organic polymer, silica and metal. Applications of monolithic materials in LC separations and nanoparticle-based monoliths are also described.

In Chapter 4, "Perspective Chapter: High-performance Liquid Chromatography Coupled to Mass Spectrometry – The Advance in Chemical Analysis", da Silva Bezerra presents the advantages and limitations of LC-MS techniques, addressing the principles of coupling, sample preparation and other analytical issues and describing relevant LC-MS(/MS) applications in different fields.

The second section is devoted to applications. Chapter 5 by Nakov et al., "Green Strategies toward Eco-Friendly HPLC Methods in Pharma Analysis", describes green chemistry strategies that can be easily applied to conventional liquid chromatography instruments to develop eco-friendly HPLC methods for pharma analysis. Several tools for the evaluation of the greenness of chromatographic methods are also described.

The next two chapters are devoted to the application of HPLC techniques in the identification and determination of polyphenolic compounds, important bioactive substances with antioxidant properties, in food products. Chapter 6, "Phenolic Compounds Profile of Brazilian Commercial Orange Juice", by Estevam et al., addresses the characterization of bioactive compounds such as flavonoids and phenolic acids in orange juice from Brazil using HPLC-DAD and UHPLC-ESI-MS, together with multivariate analysis. In Chapter 7, "HPLC-MS(n) Applications in the Analysis of Anthocyanins in Fruits", Yuzuak et al. review the application of HPLC-MS/MS in the identification and characterization of anthocyanins. These compounds are watersoluble pigments found abundantly in the flesh and skin of fruits, flowers, and roots of different varieties of plants. Correct identification of anthocyanins with similar structures and accurate estimation of their contents within fruit matrices remain challenging. LC-MS/MS-based metabolomic studies have been found to be an effective technology for distinguishing anthocyanins that are similarly structured.

In Chapter 8, "Current Trends in HPLC for Quality Control of Spices", Kumar Sahu et al. address the role of LC in the characterization and quality control of spices and condiments that have important antioxidant, antibacterial, anticancer and anti-inflammatory properties. Both aflatoxins secreted after fungal contamination and illegal dyes used to adulterate spices cause quality degradation. HPLC is a rapid and adaptable technique for the quality assessment of spices.

We hope this book will be useful to all in the scientific community dealing with the development of HPLC analytical methods and their applications in different fields.

> **Oscar Núñez, Sònia Sentellas, Mercè Granados and Javier Saurina** Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Barcelona, Spain

Section 1

Principles and New Advances

Section 1
