Solid-Phase Extraction

Colin F. Poole

• Publisher: Elsevier
• Year: 2019
• ISBN:
  9780128169070
• Topic: Sciences physiques
• Subtopic: Chimie analytique

Solid Phase Extraction thoroughly presents both new and historic techniques for dealing with solid phase extraction. It provides all information laboratory scientists need for choosing and utilizing suitable sample preparation procedures for any kind of sample. In addition, the book showcases the contemporary uses of sample preparation techniques in the most important industrial and academic project environments, including solid-phase Microextraction, molecularly imprinted polymers, magnetic nanoparticles, and more. Written by recognized experts in their respective fields, this one-stop reference is ideal for those who need to know which technique to choose for solid phase extraction.

Used in conjunction with a similar release, Liquid Phase Extraction, this book allows users to master this crucial aspect of sample preparation.

• Defines the current state-of-the-art in extraction techniques and the methods and procedures for implementing them in laboratory practice
• Includes extensive referencing that facilitates the identification of key information
• Aimed at both entry-level scientists and those who want to explore new techniques and methods

1

Core concepts and milestones in the development of solid-phase extraction

Colin F. Poole Department of Chemistry, Wayne State University, Detroit, MI, United States

Abstract

The evolution of materials, apparatus, and techniques for the solid-phase extraction of gas and liquid samples is described and their virtues placed in a modern context of the requirement for streamlined, efficient, low-cost, and automated sample preparation methods. For gas-solid extraction methods include cartridge- and needle-based packed beds with thermal desorption to recover target compounds and typically gas chromatography for analysis. For liquid-solid extraction cartridge-based, membrane-based (disk), and thin-film based sorbents are used with a wide range of inorganic oxide, low-specificity, and high-specificity sorbents. Second generation formats include microextraction by packed sorbent, solid-phase microextraction, in-tube solid-phase extraction, stir bar sorptive extraction, coated magnetic nanoparticles, nanofibers, and monoliths. Low-specificity sorbent chemistries include silica-based chemically bonded sorbents, macroreticular porous polymers, carbon (activated, graphitized, and carbon nanotubes). High-specificity sorbents include mixed-mode, immunosorbents, aptamers, molecularly printed polymers, metal-organic frameworks, and restricted access media. A general theory of sample processing for cartridge and disk devices is presented for the estimation of breakthrough volumes, rinse solvent conditions, and recovery of target compounds by solvent or thermal desorption.

Keywords

Breakthrough volumes; Extraction devices; Gas-solid extraction; Liquid-solid extraction; Solid-phase extraction; Solid-phase microextraction; Solvation parameter model; Sorbent characteristics

1.1. Introduction

The origins of solid-phase extraction are as old as chromatography, which in its early days was exploited for the isolation of compounds from mixtures by their selective interaction with a solid stationary phase and subsequent recovery by elution in a mobile phase. Chromatography and extraction have since diverged in their general function in chemical analysis and are regarded as complementary techniques today. Extraction is typically employed for isolation, preconcentration, matrix simplification, or solvent exchange ahead of the separation and identification of compounds by chromatographic-based (and other) techniques. The key to understanding the relationship between these common laboratory techniques is to consider extraction as an enabling technique that modifies sample properties to facilitate a successful separation and detection of target compounds by the most appropriate technique. In the absence of an extraction step the sample would appear to be too complex, too dilute or incompatible with sustaining instrument performance rendering the analysis unsuccessful. Overtime the scale, speed, material costs, and level of automation for the extraction step have adapted to changing laboratory needs. Thus, solid-phase extraction, one variant of extraction methods, is a dynamic field, and while old, it is still heavily researched with the flux of advances far from concluded. At the time of writing, it is reasonable to identify miniaturization, advances in material science, ease of automation, and compatibility with the goals of green analytical chemistry as the primary driving forces maintaining the general interest in advancing the techniques of solid-phase extraction [1–3].

1.2. First generation formats

Solid-phase extraction is based on the transfer of target compounds in a gas, liquid, or supercritical fluid matrix to a solid sorbent [4]. Typically, the sample containing the target compounds flows over the solid sorbent which retains the compounds by their favorable interactions with the sorbent. The sorbent is subsequently separated from the sample and the target compounds recovered by solvent displacement or thermal desorption into the gas phase. An early application of solid-phase extraction in the 1950s was the use of activated carbon-filled columns to isolate organic contaminants from surface waters for toxicity evaluation [5]. The low concentration of contaminants and the poor capability of instrumental methods to identify compounds and assess their toxicity at that time resulted in large-scale operations in which thousands of liters of water were sampled over several days. The introduction of macroreticular porous polymers in the early 1970s was responsible for redirecting interest in solid-phase extraction for both field and laboratory applications as well as extending its scope to air sampling and the isolation of drugs from biological fluids. These sorbents had reasonable mechanical strength, a large surface area, a large sample capacity, low water retention, and provided high recovery of target compounds by solvent or thermal desorption. Compared with activated carbon the overall recovery of target compounds was generally better and irreversible adsorption and catalytic activity greatly diminished. These properties together with further improvements in instrumental methods facilitated a general downsizing of sorbent beds, a reduction in sample size, and increasing use of solid-phase extraction as a general laboratory technique for a wider range of applications than was previously the case [6,7]. Porous polymers of high thermal stability and low water retention were responsible for revolutionizing the analysis of volatile organic compounds in air and purge gas samples from dynamic stripping of volatile organic compounds from aqueous solution. Compounds trapped on the sorbent bed were thermally desorbed directly into a gas chromatograph for analysis eventually leading to fully automated sampling and analysis systems for routine use [8,9]. The general acceptance of solid-phase extraction for sampling liquids, however, occurred later in the early 1980s with the introduction of disposable cartridge devices containing silica-based chemically bonded sorbents of a suitable particle size for sample processing by gently suction [10–14]. Within a few years cartridge-based solid-phase extraction was considered a suitable alternative to liquid-liquid extraction for many applications and entered a period of evolutionary change. Typical cartridge devices consist of short columns (generally an open syringe barrel) containing sorbent with a nominal particle size between 20 and 60 μm, preferably with a narrow particle size range, packed between porous plastic or metal frits, Fig. 1.1. A wide range of sorbent chemistries (silica-based chemically bonded, mixed mode, porous polymer, restricted access media, molecularly imprinted polymers, immunosorbent, bonded cryptands, etc.) are available today providing for the diverse application base of modern cartridge-based solid-phase extraction [12–14]. Low-volume cartridges or precolumn devices soon appeared as the basis of online integrated systems for automation of the sampling and separation processes, in for example, solid-phase extraction (SPE)-liquid chromatography (LC), SPE-gas chromatography (GC), SPE-capillary electrophoresis (CE), SPE inductively coupled plasma spectroscopy (ICP) and LC-SPE-nuclear magnetic resonance spectroscopy (NMR). By the mid-1990s these systems had matured into robust practical systems in use in many laboratories with a high sample workload and little variation in sample matrix, for example, drugs in biological fluids, contaminants in surface waters, target compounds in food extracts, etc. [15–18]. Standard solid-phase extraction procedures lend themselves to automation using robotic platforms or special purpose processing units that simultaneously extract and prepare samples for separation [12,19]. M...