Critical evaluation of microextraction pretreatment techniques – Part 1: Single drop and sorbent‐based techniques

Sample pretreatment techniques or preconcentration constitute a very important step before the analysis of environmental, clinical, pharmaceutical, and other complex samples. Thanks to extraction techniques it is possible to achieve higher method sensitivities and selectivities. Miniaturization microextraction methods make them more environmentally friendly and only small amounts of samples are required. In the past 30 years, a number of microextraction methods have been developed and used and are documented in thousands of articles. Many reviews have been written focusing on their use in specified professional fields or on the latest trends. Unfortunately, no uniform nomenclature has been introduced for these methods. Therefore, this review attempts to classify all the essential microextraction techniques and describes their advantages, disadvantages, and the latest innovations. The methods are divided into two main groups: single drop and sorbent‐based techniques according to the type of extraction phase.     

Recent advances and trends in miniaturized sample preparation techniques

Advances in the area of sample preparation are significant and have been growing significantly in recent years. This initial step of the analysis is essential and must be carried out properly, consisting of a complicated procedure with multiple stages. Consequently, it corresponds to a potential source of errors and will determine, at the end of the process, either a satisfactory result or a fail. One of the advances in this field includes the miniaturization of extraction techniques based on the conventional sample preparation procedures such as liquid‐liquid extraction and solid‐phase extraction. These modern techniques have gained prominence in the face of traditional methods since they minimize the consumption of organic solvents and the sample volume. As another feature, it is possible to reuse the sorbents, and its coupling to chromatographic systems might be automated. The review will emphasize the main techniques based on liquid‐phase microextraction, as well as those based upon the use of sorbents. The first group includes currently popular techniques such as single drop microextraction, hollow fiber liquid‐phase microextraction, and dispersive liquid‐liquid microextraction. In the second group, solid‐phase microextraction techniques such as in‐tube solid‐phase microextraction, stir bar sorptive extraction, dispersive solid‐phase extraction, dispersive micro solid‐phase microextraction, and microextraction by packed sorbent are highlighted. These approaches, in common, aim the determination of analytes at low concentrations in complex matrices. This article describes some characteristics, recent advances, and trends on miniaturized sample preparation techniques, as well as their current applications in food, environmental, and bioanalysis fields.     

New developments in microextraction techniques in bioanalysis. A review

In recent years, the interest in new extraction methods with lower sample volume requirements, simpler equipment and handling, and lower reagent consumption, has led to the development of a series of microextraction methods based on extraction phases in the microliter order. Nowadays, many references can be found for several of these methods, which imply a wide range of applications referred to both the analyte and the sample nature. In this paper, recent developments in both well-established microextraction techniques (solid phase microextraction, hollow-fiber liquid phase microextraction, dispersive liquid–liquid microextraction, etc.) and recently appeared microextraction procedures (nanoextraction systems, microchip devices, etc.) for the clinical analysis of biological samples will be reviewed and discussed.     

Recent Advances in Sample Preparation for Cosmetics and Personal Care Products Analysis

The use of cosmetics and personal care products is increasing worldwide. Their high matrix complexity, together with the wide range of products currently marketed under different forms imply a challenge for their analysis, most of them requiring a sample pre-treatment step before analysis. Classical sample preparation methodologies involve large amounts of organic solvents as well as multiple steps resulting in large time consumption. Therefore, in recent years, the trends have been moved towards the development of simple, sustainable, and environmentally friendly methodologies in two ways: (i) the miniaturization of conventional procedures allowing a reduction in the consumption of solvents and reagents; and (ii) the development and application of sorbent- and liquid-based microextraction technologies to obtain a high analyte enrichment, avoiding or significantly reducing the use of organic solvents. This review provides an overview of analytical methodology during the last ten years, placing special emphasis on sample preparation to analyse cosmetics and personal care products. The use of liquid–liquid and solid–liquid extraction (LLE, SLE), ultrasound-assisted extraction (UAE), solid-phase extraction (SPE), pressurized liquid extraction (PLE), matrix solid-phase extraction (MSPD), and liquid- and sorbent-based microextraction techniques will be reviewed. The most recent advances and future trends including the development of new materials and green solvents will be also addressed.     

Recent advances of green pretreatment techniques for quality control of natural products

A few advancing technologies for natural product analysis have been widely proposed, which focus on decreasing energy consumption and developing an environmentally sustainable manner. These green sample pretreatment and analysis methods following the green Analytical Chemistry (GAC) criteria have the advantage of improving the strategy of chemical analyses, promoting sustainable development to analytical laboratories, and reducing the negative effects of analysis experiments on the environment. A few minimized extraction methodologies have been proposed for replacing the traditional methods in the quality evaluation of natural products, mainly including solid-phase microextraction (SPME) and liquid phase microextraction (LPME). These procedures not only have no need for large numbers of samples and toxic reagent, but also spend a small amount of extraction and analytical time. This overview aims to list out the main green strategies on the application of quality evaluation and control for natural products in the past 3 years.     

Basic principles,recent trends and future directions of microextraction techniques for the analysis of aqueous environmental samples

Microextraction-based sample preparation techniques have exhibited remarkable importance in analytical chemistry since they were first developed in the 1980s. The application of these techniques involves efficient and, at the same time, environmentally-friendly analytical methodologies. They are also generally faster when compared with classical sample preparation techniques, requiring low solvent and sample volumes, and also allowing for automated or semi-automated procedures. This paper provides an overview of the basic principles of sample preparation techniques and the important applications and developments that have taken place in this area over the past five years. These procedures include solid-phase microextraction (SPME), stir bar sorptive extraction (SBSE), bar adsorptive microextraction (BAμE), rotating disk sorptive extraction (RDSE), micro solid-phase extraction (μ-SPE) and liquid-phase microextraction (LPME). The main variations are discussed with a focus on recent applications in the analysis of environmental water samples. Lastly, some of the trends and perspectives associated with these outstanding microextraction sample preparation approaches are highlighted.     

用于化学毒剂检测的微萃取技术研究进展

对化学毒剂及其降解产物的分析检测是准确鉴别化学沾染的重要手段.由于化学毒剂及其降解产物的样品可能存在于各种基质中,且部分化学毒剂在水体等基质中降解速度过快,所以将痕量样品从复杂基质中快速高效的富集提取出来显得尤其重要.微萃取技术具有装置体积小、使用少量或不使用溶剂、绿色环保、易与色谱分析技术联用等突出优势受到广泛的关注...     

微萃取技术在环境分析中的应用

微萃取技术是近年来出现的绿色样品前处理技术。它具有操作简便、环境友好等优点,并且在环境、医药及食品等领域得到广泛的应用。本文仅就固相微萃取和液相微萃取在环境分析中的应用作一简要综述。     

液相微萃取研究与应用

液相微萃取是近年来新兴的一种微型化样品前处理技术。该技术集萃取、净化、浓缩于一体,具有溶剂耗量少、成本低廉、操作便捷、精确和灵敏度高的特点。本文全面深入地综述了液相微萃取的各种工作模式及其原理和特点,阐述了相关的联用分析技术和方法的适用性,归纳和分析了影响萃取的主要影响因素及优化的方法,突出了上述几方面中具有发展潜力的新进展,包括各种动态萃取模式与装置、 与其它技术联用的新策略、离子液体作为萃取溶剂等,详细总结了近年来液相微萃取技术在环境、药物和食品等分析领域中的应用情况。     

Microextraction sample preparation techniques in forensic analytical toxicology

Sample preparation is a critical step in forensic analytical toxicology. Different extraction techniques are employed with the goals of removing interferences from the biological samples, such as blood, tissues and hair, reducing matrix effects and concentrating the target analytes, among others. With the objective of developing faster and more ecological procedures, microextraction techniques have been expanding their applications in the recent years. This article reviews various microextraction methods, which include solid‐based microextraction, such as solid‐phase microextraction, microextraction by packed sorbent and stir‐bar sorptive extraction, and liquid‐based microextraction, such as single drop/hollow fiber‐based liquid‐phase microextraction and dispersive liquid–liquid microextraction, as well as their applications to forensic toxicology analysis. The development trend in future microextraction sample preparation is discussed.     

Strategies for the microextraction of polar organic contaminants in water samples

In this paper the most recent developments in the microextraction of polar analytes from aqueous environmental samples are critically reviewed. The particularities of different microextraction approaches, mainly solid-phase microextraction (SPME), stir-bar-sorptive extraction (SBSE), and liquid-phase microextraction (LPME), and their suitability for use in combination with chromatographic or electrically driven separation techniques for determination of polar species are discussed. The compatibility of microextraction techniques, especially SPME, with different derivatisation strategies enabling GC determination of polar analytes and improving their extractability is revised. In addition to the use of derivatisation reactions, the possibility of enhancing the yield of solid-phase microextraction methods for polar analytes by using new coatings and/or larger amounts of sorbent is also considered. Finally, attention is also focussed on describing the versatility of LPME in its different possible formats and its ability to improve selectivity in the extraction of polar analytes with acid-base properties by using separation membranes and buffer solutions, instead of organic solvents, as the acceptor solution.     

Membrane-based microextraction techniques in analytical chemistry: A review

The use of membrane-based sample preparation techniques in analytical chemistry has gained growing attention from the scientific community since the development of miniaturized sample preparation procedures in the 1990s. The use of membranes makes the microextraction procedures more stable, allowing the determination of analytes in complex and “dirty” samples. This review describes some characteristics of classical membrane-based microextraction techniques (membrane-protected solid-phase microextraction, hollow-fiber liquid-phase microextraction and hollow-fiber renewal liquid membrane) as well as some alternative configurations (thin film and electromembrane extraction) used successfully for the determination of different analytes in a large variety of matrices, some critical points regarding each technique are highlighted.     

Solid‐phase microextraction for the human biomonitoring of environmental chemicals: Current applications and future perspectives

Sample preparation is one of the crucial steps in the analytical chemistry including human biomonitoring studies. Although there are several traditional approaches available, solid‐phase microextraction is emerged as one of the pioneering techniques due to its simplicity, rapidness, wide applicability, and miniaturization of traditional sample preparation (e.g., use of less or no organic solvents). There are few earlier review articles available on the advancements in solid‐phase microextraction and its use for the measurement of environmental chemicals in various types of environmental samples. However, a collective information on applicability and current usage of solid‐phase microextraction for the human biomonitoring of environmental chemicals are scarce, nonetheless, rising demands on innovative analytical approaches for human biomonitoring studies. Hence, in this review article, we covered the application of solid‐phase microextraction as extraction/purification methods for more than 15 classes of environmental chemicals to assess their respective exposure levels and associated health outcomes in various human population reported across the globe. Further, a detailed discussion on various types of matrix used, nature of coupled analytical instrumentations, and limitations and future perspectives of solid‐phase microextraction for human biomonitoring studies is presented in this review.     

Recent advances in applications of single-drop microextraction: a review

During the past fifteen years since its introduction, single-drop microextraction has witnessed incessant growth in the range of applications of samples preparation for trace organic and inorganic analysis. This was mainly due to the array of modes that are available to accomplish extraction in harmony with the nature of analytes, and to use the extract directly for analysis by diverse instrumental methods. Whilst engineering of novel sorbent materials has expanded the sample capabilities of rival method of solid-phase microextraction, the single-drop microextraction – irrespective of the mode of extraction – uses common equipment found in analytical laboratories sans any modification, and in a much economic way. The recent innovations made in the field, as highlighted in this review article in the backdrop of historical developments, are due to the freedom in operational conditions and practicability to exploit chemical principals for optimum extraction and sensitive determination of analytes. Literature published till July 2011 has been covered.     

Recent development in liquid phase microextraction for determination of trace level concentration of metals—A review

As the drive towards green extraction methods has gained momentum in recent years, it has not always been possible to eliminate organic solvents completely. However, the volumes employed have been reduced remarkably, so that a single microdrop is sufficient in some cases. This effort has led to the development of various liquid phase microextractions namely single drop microextraction (SDME), hollow fiber liquid phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME) and solidified floating organic drop microextraction (SFODME). In this review, the historical development and overview of these miniaturized liquid phase extraction methodologies have briefly been discussed and a comprehensive collection of application of the these methods in combination with different analytical techniques for preconcentration and determination of ultra trace amounts of metals and organometal ions in various matrices have been summarized.     

Determination of pesticides and their degradation products in soil: critical review and comparison of methods

Pesticides are applied widely to protect plants from disease, weeds and insect damage, and usually come into contact with soil, where they undergo a variety of transformations that provide a complex pattern of metabolites. This article reviews the most relevant analytical methods for determining pesticides and their transformation products in soils. We address some recent advances in sampling and sample-preparation technologies for soil analysis. We discuss and critically evaluate procedures, such as liquid extraction methods (pressurized liquid extraction or microwave-assisted extraction) and solid-phase based methods (headspace solid-phase microextraction, solid-phase microextraction or matrix-solid-phase dispersion). Analysis of pesticides is generally carried out by gas chromatography (GC) or liquid chromatography (LC) coupled to different detectors, especially to mass spectrometers (MSs). However, alternative and/or complementary methods, using capillary electrophoresis (CE), biosensors and bioassays have emerged recently. We also consider the advantages and the disadvantages of the various methodologies.     

离子液体在微萃取方面的应用进展

离子液体具有蒸汽压低、热稳定性好、溶解性能高、可设计性和多样性等特性,使其在萃取尤其是微萃取方面得到迅速发展和应用.而在单滴微萃取、分散液相微萃取、液-液-液微萃取和固相微萃取中,离子液体更以其较大的粘度、密度及非挥发性等特性,使得微萃取技术更容易操作,无有机溶剂污染,方法的灵敏度更高,且扩展了微萃取的应用范围.文章综述了近年来离子液体在液相微萃取和固相微萃取方面的应用进展,并对其发展趋势进行了展望.     

Green Extraction Techniques as Advanced Sample Preparation Approaches in Biological,Food, and Environmental Matrices: A Review

Green extraction techniques (GreETs) emerged in the last decade as greener and sustainable alternatives to classical sample preparation procedures aiming to improve the selectivity and sensitivity of analytical methods, simultaneously reducing the deleterious side effects of classical extraction techniques (CETs) for both the operator and the environment. The implementation of improved processes that overcome the main constraints of classical methods in terms of efficiency and ability to minimize or eliminate the use and generation of harmful substances will promote more efficient use of energy and resources in close association with the principles supporting the concept of green chemistry. The current review aims to update the state of the art of some cutting-edge GreETs developed and implemented in recent years focusing on the improvement of the main analytical features, practical aspects, and relevant applications in the biological, food, and environmental fields. Approaches to improve and accelerate the extraction efficiency and to lower solvent consumption, including sorbent-based techniques, such as solid-phase microextraction (SPME) and fabric-phase sorbent extraction (FPSE), and solvent-based techniques (μQuEChERS; micro quick, easy, cheap, effective, rugged, and safe), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), in addition to supercritical fluid extraction (SFE) and pressurized solvent extraction (PSE), are highlighted.     

Wooden-based materials: Eco-friendly materials for direct mass spectrometric analysis and microextraction

Lignocellulosic materials have arisen as a sustainable alternative in microextraction techniques during the last 10 years. As they are natural materials, their use fits into some of the principles of Green Analytical Chemistry. Their inherent porosity, narrow shape, and rigidity permit their use in ambient ionization mass spectrometry techniques. In particular, the combination of wooden-based materials and direct analysis gives birth to the so-called wooden-tip electrospray ionization mass spectrometry technique. This approach has been used for the direct analysis of complex samples, and as a streamlined tool for fingerprint quality analysis. Also, wooden-based materials can be superficially modified to boost the interaction with target compounds, allowing their isolation from complex samples. This review describes the potential and applicability of direct analysis using lignocellulosic materials, as well as other alternatives related to their use in microextraction.     

A review of modern sample-preparation techniques for the extraction and analysis of medicinal plants

Sample preparation is the crucial first step in the analysis of herbs. In recent years there has been increasing interest worldwide in the use of alternative/herbal medicine for the prevention and treatment of various illnesses. Currently, however, quality-related problems (lack of consistency, safety, and efficacy) seem to be overshadowing the potential genuine health benefits of various herbal products. Thus, the development of "modern" sample-preparation techniques with significant advantages over conventional methods for the extraction and analysis of medicinal plants is likely to play an important role in the overall effort of ensuring and providing high-quality herbal products to consumers worldwide. In this article, recent developments and applications of modern sample-preparation techniques for the extraction, clean-up, and concentration of analytes from medicinal plants or herbal materials are reviewed. These modern techniques include solid-phase microextraction, supercritical-fluid extraction, pressurized-liquid extraction, microwave-assisted extraction, solid-phase extraction, and surfactant-mediated extraction.