Methods of Therapeutic Drug Monitoring Including Pharmacogenetics

Georg Hempel, Georg Hempel

• Publisher: Elsevier Science
• Year: 2019
• ISBN:
  9780444640673
• Edition: 2
• Topic: Biowissenschaften
• Subtopic: Biochemie

Methods of Therapeutic Drug Monitoring Including Pharmacogenetics, Second Edition, Volume Seven in the Handbook of Analytical Separations series, covers all aspects of drug monitoring, including laboratory work, pharmacokinetic analysis and clinical aspects, thus enabling readers from different fields to understand the whole process of therapeutic drug monitoring and how to avoid common pitfalls. The book contains analytical techniques for the quantification of drugs, along with pharmacogenetic and pharmacogenomic methods. Also included are updates on sample preparation, including dried blood spot technology and microextraction methods. In addition, the book includes new drugs, such as tyrosine kinase inhibitors and the monitoring of immunosuppressant drugs.

• Presents a unique, interdisciplinary approach that appeals to a wide range of users
• Written by authors from international labs, providing a global perspective that can be applied in various regulatory environments
• Features additional therapeutic drugs to reflect the rising number of immunocompromised patients
• Includes a new mass spectroscopic methods chapter to capture the frequent use in TDM and the improved availability of LC-MS across laboratories

Chapter 1

Sample preparation for the analysis of drugs in biological fluids

Yoshihiro Saito ^∗ and Koki Nakagami Department of Applied Chemistry and Life Science, Toyohashi University of Technology, Toyohashi, Japan
^∗ Corresponding author.

Abstract

Sample preparation techniques for the analysis of therapeutic drug in biological sample matrices have been overviewed. On the basis of the recent requirements for analytical separations, any undesirable compounds that may affect the performance in the subsequent analysis must be eliminated in advance. In addition a satisfactory sensitivity can be obtained with an appropriate choice of the sample preparation method for each sample matrix. High throughput processing of the sample pre-treatment is also required for real sample analysis in clinical situations. As well as conventional liquid-liquid extraction (LLE) technique, solid-phase extraction (SPE) using particulate packing materials, solid-phase micro extraction (SPME) and the techniques derived from it, and other modern miniaturized sample preparation methods were briefly summarized. The coupling and/or combination of the sample preparation methods with separation instruments such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) is described as well.

Keywords

Capillary electrophoresis; High performance liquid chromatography; High-throughput analysis; Liquid-liquid extraction; Liquid-phase microextraction; Miniaturization; Sample preconcentration; Sample preparation; Solid-phase extraction; Solid-phase microextraction

1.1. Introduction

In order to effectively analyze therapeutic drug in various biological sample matrices, an appropriate choice of suitable sample preparation technique has been regarded as the most important step in the entire analytical process [1–5]. Because of the complexity of typical biological sample matrices, any undesirable compounds must be eliminated, and also the preconcentration of the target analyte(s) is necessary to make sure the precise identification and the reproducible quantification with a desirable sensitivity. A suitable combination of the sample preparation techniques and the subsequent high performance separation and determination methods must be considered in advance of the real analytical situations. The features of high throughput and cost-effective analyses are often required to effectively process a number of samples in hospitals, and also the processing time of total analysis must be strongly considered especially for the drug analysis in the emergency clinical situations.

As a traditional sample preparation technique for the analysis of biological fluids, liquid–liquid extraction (LLE) has been widely employed as shown in Fig. 1.1 [5,6]. This conventional method is based on quite a simple phenomenon; however, the consumption of a large amount of organic solvent is typically needed along with a relatively long processing time. In addition, possible interferences from the sample matrix and the emulsion formation must be taken into account for the analysis of biological fluids [6,7]. For the analysis of biological fluids, protein removal must be often carried out before the preconcentration of the target analytes, where a centrifuge process of the sample, with an addition of small amount of organic solvents and an appropriate buffer solution into the sample matrix, is also employed.

Solid-phase extraction (SPE) is an alternative sample preparation method for the analysis of various complex biological sample matrices and a wide variety of applications have been reported including the combination with high performance separation systems, such as high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) [8–10]. Introducing a sample preparation with the SPE method, several advantages can be obtained: more purified samples, rapid and high throughput processing with an automated instrument, a good repeatability, and no emulsion formation. A reduced organic solvent disposal is another attractive feature of the SPE method, when compared with a conventional LLE procedure.

As the extension of the downsizing of the sample preparation process, the SPE method has been further miniaturized as solid-phase microextraction (SPME). Although the SPME was originally developed for the analysis of volatile target analytes in gas chromatography (GC) [11,12], the online coupling with HPLC has been reported for various types of biological sample matrices [12,13]. One of the online coupling was established by using a section of GC open tubular capillary column as the extraction medium [14–16]. This in-tube SPME method is based on the extraction with the polymeric coating materials in the capillary, where the sample solution was repeatedly passed through the capillary in the extraction process for an effective extraction. Further enhancement of the extraction efficiency during the extraction process was also established by several other specially designed extraction media such as fine fiber-packed capillary [17–19], porous hollow fiber [20,21], and polymeric resin disk [10,22].

Figure 1.1 Drug screening process on the basis of multistep liquid–liquid extraction.

In this chapter, various types of sample preparation methods for the analysis of therapeutic drug in biological fluids will be overviewed along with brief descriptions for the combination of the sample preparation techniques with the subsequent separation methods such as HPLC and CE. The analysis of therapeutic drugs in biological fluids by various chromatographic separation methods will be described in the following chapter.

1.2. Conventional sample preparation for therapeutic drug analysis in biological samples

1.2.1. Protein removal and liquid–liquid extraction

Deproteinization from the biological sample matrix is normally carried out by the addition of an organic solvent and/or an appropriate buffer solution [23,24]. The deproteinization process could be simultaneously conducted with the LLE process of the analytes of interest [25]. A wide variety of centrifuge tubes with membrane filter [26] have been commercialized to effectively remove the protein and/or other insoluble constituents in the biological samples as typically shown in Fig. 1.2. In order to solve the clogging problem, the sample preconcentration by typical SPE cartridges sometimes requires a protein removal process [7], although a satisfactory recovery of the target analyt...