Recent advances of online coupling of sample preparation techniques with ultra high performance liquid chromatography and supercritical fluid chromatography

Ultra high performance liquid chromatography and supercritical fluid chromatography techniques are favored because of their high efficiency and fast analysis speed. Although many sample preparation techniques have been coupled with common liquid chromatography online, the online coupling of sample preparation with the two popular chromatography techniques have gained increasing attention owing to the increasing requirements of efficiency and sensitivity. In this review, we have discussed and summarized the recent advances of the online coupling of sample preparation with ultra high performance liquid chromatography and supercritical fluid chromatography techniques. The main sample preparation techniques that have been coupled with ultra high performance liquid chromatography online are solid‐phase extraction and in‐tube solid‐phase microextraction, while solid‐phase extraction and supercritical fluid extraction are the main techniques that have been coupled with supercritical fluid chromatography online. Especially, the strategies for online coupling of sample preparation with chromatography techniques were summarized. Typical applications and growing trends of the online coupling techniques were also discussed in detail. With the increasing demands of improving the efficiency, throughput, and analytical capability toward complex samples of the analysis methods, online coupling of sample preparation with chromatography techniques will acquire further development.     

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.     

固相微萃取-高效液相色谱联用技术的进展

固相微萃取（SPME）技术是近年来发展起来的一种无溶剂,集采样、萃取、浓缩、进样于一体的样品预处理新技术,它与同效液相色谱技术的联用已受到人们的瞩目;该文评述了SPME-HPLC联用技术的进展,并展望这一技术的应用前景。     

Analytical methods for the assessment of endocrine disrupting chemical exposure during human fetal and lactation stages: A review

In the present work, a review of the analytical methods developed in the last 15 years for the determination of endocrine disrupting chemicals (EDCs) in human samples related with children, including placenta, cord blood, amniotic fluid, maternal blood, maternal urine and breast milk, is proposed. Children are highly vulnerable to toxic chemicals in the environment. Among these environmental contaminants to which children are at risk of exposure are EDCs —substances able to alter the normal hormone function of wildlife and humans—. The work focuses mainly on sample preparation and instrumental techniques used for the detection and quantification of the analytes. The sample preparation techniques include, not only liquid–liquid extraction (LLE) and solid-phase extraction (SPE), but also modern microextraction techniques such as extraction with molecular imprinted polymers (MIPs), stir-bar sorptive extraction (SBSE), hollow-fiber liquid-phase microextraction (HF-LPME), dispersive liquid–liquid microextraction (DLLME), matrix solid phase dispersion (MSPD) or ultrasound-assisted extraction (UAE), which are becoming alternatives in the analysis of human samples. Most studies focus on minimizing the number of steps and using the lowest solvent amounts in the sample treatment. The usual instrumental techniques employed include liquid chromatography (LC), gas chromatography (GC) mainly coupled to tandem mass spectrometry. Multiresidue methods are being developed for the determination of several families of EDCs with one extraction step and limited sample preparation.     

样品前处理技术在气相色谱分析中的应用进展

气相色谱法是当前应用最广泛的分析技术之一。使用气相色谱对复杂基体进行分析时的样品前处理步骤往往繁琐耗时,易引起误差,已成为制约分析效率和准确度提升的关键环节。本文综述了2009-2013年几种主要的样品前处理技术,包括吹扫捕集、固相萃取、固相微萃取、液相微萃取技术以及微波辅助萃取、超声波辅助萃取等场辅助萃取技术在气相色谱分析中的应用研究进展。     

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.     

分子印迹微萃取技术的研究进展

微萃取技术是一种将分析物高效萃取富集于微体积的聚合物或有机溶剂中,集采样、萃取、浓缩、进样于一体的无(少)溶剂、易于与其他技术在线联用的样品前处理方法。分子印迹聚合物是一种具有强大分子识别功能的材料,具有高效的选择特异性,可从复杂样品中选择性分离富集目标分析物,在微萃取技术中得到了广泛的应用。本文综述了近年来分子印迹微萃取技术的研究进展,包括分子印迹固相微萃取、分子印迹搅拌棒吸附萃取、分子印迹磁性微球萃取等微萃取技术。共引用文献75篇。     

Recent advances in metal‐organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal‐organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF‐ or COF‐based solid‐phase extraction (SPE), solid‐phase microextraction (SPME), gas chromatography (GC), high‐performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.     

High‐throughput microscale extraction using ionic liquids and derivatives: A review

Ionic liquids and derivatives—mainly polymeric ionic liquids and magnetic ionic liquids—have been extensively used in microscale extraction over the past few years. Current trends in analytical sample preparation gear toward linking microextraction approaches with high‐throughput sample processing to comply with green analytical chemistry requirements. A variety of high sample throughput strategies that are coupled to both ionic‐liquid‐based solid‐phase microextraction and ionic liquid‐based liquid‐phase microextraction are herein reported. The review is focused on microscale extraction methods that use (i) custom‐made and dedicated extraction devices, (ii) parallel extraction, (iii) magnetic‐based separation, and (iv) miniaturized systems employing semi‐automatic or fully automatic flow injection methods, related micro/millifluidic devices, and robotic equipment.     

基于中空纤维的液相微萃取技术的研究进展

基于中空纤维的液相微萃取集采样、萃取、浓缩于一体,具有成本低,溶剂用量少,易与高效液相色谱、气相色谱、毛细管电泳联用等特点。该技术不仅可实现较高的回收率和富集效率,而且具有突出的样品净化功能,是一种环境友好的样品前处理新技术。该文对基于中空纤维的液相微萃取的装置、操作模式、基本原理及近年来应用研究的进展进行了综述。     

Determination of atenolol in human plasma using ionic‐liquid‐based ultrasound‐assisted in situ solvent formation microextraction followed by high‐performance liquid chromatography

An efficient analytical method called ionic‐liquid‐based ultrasound‐assisted in situ solvent formation microextraction followed by high‐performance liquid chromatography was developed for the determination of atenolol in human plasma. A hydrophobic ionic liquid (1‐butyl‐3‐methylimidazolium hexafluorophosphate) was formed by the addition of a hydrophilic ionic liquid (1‐butyl‐3‐methylimidazolium tetrafluoroborate) to a sample solution containing an ion‐pairing agent during microextraction. The analyte was extracted into the ionic liquid phase while the microextraction solvent was dispersed throughout the sample by utilizing ultrasound. The sample was then centrifuged, and the extracting phase retracted into the microsyringe and injected to liquid chromatography. After optimization, the calibration curve showed linearity in the range of 2–750 ng/mL with the regression coefficient corresponding to 0.998. The limits of detection (S/N = 3) and quantification (S/N = 10) were 0.5 and 2 ng/mL, respectively. A reasonable relative recovery range of 90–96.7% and satisfactory intra‐assay (4.8–5.1%, n = 6) and interassay (5.0–5.6%, n = 9) precision along with a substantial sample clean‐up demonstrated good performance of the procedure. It was applied for the determination of atenolol in human plasma after oral administration and some pharmacokinetic data were obtained.     

Solid-phase microextraction in pesticide residue analysis

The applications of solid-phase microextraction (SPME) for sample preparation in pesticide residue analysis are reviewed in this paper taking into account the different approaches of this technique coupled mainly to gas chromatography but also to high-performance liquid chromatography. A complete revision of the existing literature has been made considering the different applications divided according to the pesticide families (organochlorine, organophosphorus, triazines, thiocarbamates, substituted uracils, urea derivatives and dinitroanilines among others) and the sample matrices analysed which included environmental samples (water and soil), food samples and biological fluids. Details on the analytical characteristics of the procedures described in the reviewed papers are given, and new trends in the applications of SPME in this field are discussed.     

Supported liquid membrane microextraction with high-performance liquid chromatography-UV detection for monitoring trace haloacetic acids in water

Supported liquid membrane microextraction (SLMME) with high-performance liquid chromatography (HPLC)-UV detection has been developed for the extraction, preconcentration, and determination of all the nine haloacetic acids (HAAs) in water. The HAAs are extracted into a supported liquid membrane, and then back-extracted into few microliters of an acceptor solution. The extract was directly analyzed by HPLC-UV with a 15-min run. Enrichment factors in the range of 300-3000 were obtained in a 60-min extraction, and detection limits were at low to sub-microg/L level with R.S.D. values between 1.5 and 10.8%. The parameters that affected analyte enrichment were studied. This approach offers an attractive alternative to the current US Environmental Protection Agency standard methods for HAA analysis, which require complex sample preparation and derivatization prior to analysis by gas chromatography. SLMME can also be used in conjunction with other analytical schemes, such as, ion chromatography and capillary electrophoresis.     

Metabolic Profiling and Quantitative Analysis of Cerebrospinal Fluid Using Gas Chromatography–Mass Spectrometry: Current Methods and Future Perspectives

Cerebrospinal fluid is a key biological fluid for the investigation of new potential biomarkers of central nervous system diseases. Gas chromatography coupled to mass-selective detectors can be used for this investigation at the stages of metabolic profiling and method development. Different sample preparation conditions, including extraction and derivatization, can be applied for the analysis of the most of low-molecular-weight compounds of the cerebrospinal fluid, including metabolites of tryptophan, arachidonic acid, glucose; amino, polyunsaturated fatty and other organic acids; neuroactive steroids; drugs; and toxic metabolites. The literature data analysis revealed the absence of fully validated methods for cerebrospinal fluid analysis, and it presents opportunities for scientists to develop and validate analytical protocols using modern sample preparation techniques, such as microextraction by packed sorbent, dispersive liquid–liquid microextraction, and other potentially applicable techniques.     

Solid-phase microextraction: a powerful sample preparation tool prior to mass spectrometric analysis

Sample preparation is an essential step in analysis, greatly influencing the reliability and accuracy of resulted the time and cost of analysis. Solid-Phase Microextraction (SPME) is a very simple and efficient, solventless sample preparation method, invented by Pawliszyn in 1989. SPME has been widely used in different fields of analytical chemistry since its first applications to environmental and food analysis and is ideally suited for coupling with mass spectrometry (MS). All steps of the conventional liquid-liquid extraction (LLE) such as extraction, concentration, (derivatization) and transfer to the chromatograph are integrated into one step and one device, considerably simplifying the sample preparation procedure. It uses a fused-silica fibre that is coated on the outside with an appropriate stationary phase. The analytes in the sample are directly extracted to the fibre coating. The SPME technique can be routinely used in combination with gas chromatography, high-performance liquid chromatography and capillary electrophoresis and places no restriction on MS. SPME reduces the time necessary for sample preparation, decreases purchase and disposal costs of solvents and can improve detection limits. The SPME technique is ideally suited for MS applications, combining a simple and efficient sample preparation with versatile and sensitive detection. This review summarizes analytical characteristics and variants of the SPME technique and its applications in combination with MS.     

肉类食品中杂环胺检测的样品前处理及分析方法的研究进展

杂环胺是畜禽、鱼肉等食品在高温烹饪过程中生成的一类致癌、致突变化合物,高效、高选择性的样品前处理方法和高灵敏的分析方法是食品中痕量杂环胺分析检测的关键。本文综述了近年来溶剂萃取、固相萃取和固相微萃取等样品前处理方法,以及液相色谱、液相色谱-质谱等分析方法在食品中痕量杂环胺检测中的应用,结合现有研究对其发展趋势进行了展望。共引用文献51篇。     

Polytetrafluoroethylene physisorption‐assisted emulsification microextraction as a cleanup and preconcentration step in the gas chromatography determination of aliphatic hydrocarbons in marine sediment samples

For the first time, the application of polytetrafluoroethylene powder as an extractant phase collector or holder in liquid‐phase microextraction has been developed. For this purpose, the analytical performances of two different ways of applying polytetrafluoroethylene powder in microextraction methods including polytetrafluoroethylene physisorption‐assisted emulsification microextraction and dispersive liquid‐phase microextraction via polytetrafluoroethylene extractant phase holders have been compared for analysis of aliphatic hydrocarbons in aqueous phases. Under the same conditions, the former showed better extraction efficiencies over the latter and as a result, it was applied as preconcentration and cleanup step in the analysis of aliphatic hydrocarbons in sediment samples followed by gas chromatography analysis. The linearity of the polytetrafluoroethylene physisorption‐assisted emulsification microextraction method was obtained over a range of 3.7 and 2000 ng/g (R ² > 0.993). The relative standard deviations were less than 6.5% (n = 3). The limits of detection and quantification obtained by this method were 1.1–9.0 and 3.7–30 ng/g, respectively, indicating that satisfactory results were achieved by the procedure.     

Ionic‐liquid‐based dispersive liquid–liquid microextraction for high‐throughput multiple food contaminant screening

This paper describes an innovation of dispersive liquid–liquid microextraction enabling multiple‐component analysis of eight high‐priority food contaminants in two chemically distinctive families: Sudan dyes and phthalate plasticizers. To provide convenient sample handling for solid and solid‐containing matrices, a modified dispersive liquid–liquid microextraction procedure used an extractant precoated frit to perform simultaneous filtration, solvent mixing, and phase dispersion in one simple step. A binary ionic liquid extractant system was carefully tuned to deliver high quality analysis based only on affordable LC with diode array detector instrumentation. The method is comprehensively validated for robust quantification with good precision (6.9–9.8% RSD) in a linear 2–1000 μg/L range. Having accomplished enrichment factors up to 451, the treatment enables sensitive detection at 0.09–1.01 μg/L levels. Analysis of six high‐risk solid condiments and sauces further verified its practical applicability within a 70–120% recovery range. Compared to other approaches, the current dispersive liquid–liquid microextraction treatment offers major advantages in terms of minimal solvent (1.5 mL) and sample (0.1 g) consumption, ultra‐high analytical throughput (6 min), and the ability to handle complex solid matrices. The idea of performing simultaneous analysis for multiple contaminants presented here fosters a more effective mode of operation in food control routines.     

Simultaneous determination of six synthetic phenolic antioxidants in edible oils using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography with diode array detection

A simple, rapid, organic‐solvent‐ and sample‐saving pretreatment technique, called dispersive liquid–liquid microextraction, was developed for the determination of six synthetic phenolic antioxidants from edible oils before high‐performance liquid chromatography with diode array detection. The entire procedure was composed of a two‐step microextraction and a centrifugal process and could be finished in about 5 min, only consuming only 25 mg of sample and 1 mL of the organic solvent for each extraction. The influences of several important parameters on the microextraction efficiency were thoroughly investigated. Recovery assays for oil samples were spiked at three concentration levels, 50, 100 and 200 mg/kg, and provided recoveries in the 86.3–102.5% range with a relative standard deviation below 3.5%. The intra‐day and inter‐day precisions for the analysis were less than 3.8%. The proposed method was successfully applied for the determination of synthetic phenolic antioxidants in different oil samples, and satisfactory results were obtained. Thus, the developed method represents a viable alternative for the quality control of synthetic phenolic antioxidant concentrations in edible oils.     

Application of tandem dispersive liquid–liquid microextraction for the determination of doxepin,citalopram, and fluvoxamine in complicated samples

A new type of dispersive liquid–liquid microextraction is used for the determination of doxepin, citalopram, and fluvoxamine in aqueous matrices. This method is based upon the tandem utilization of dispersive liquid–liquid microextraction, and by providing a high sample clean‐up, it efficiently improves the applicability of the method in complicated matrices. For this purpose, in the first step, the analytes contained in an aqueous sample solution (8.0 mL) were extracted into an organic solvent, and then these analytes were simply back‐extracted into an aqueous acceptor phase (50 μL). The overall extraction time was 7 min, and very simple tools were required for this aim. Optimization of the variables affecting the method such as the type and volume of the organic solvent used and effect of ionic strength was carried out to achieve the best extraction efficiency. Under the optimized experimental conditions, tandem dispersive liquid–liquid microextraction with high‐performance liquid chromatography and UV detection showed a good linearity in the range of 10–5000 ng/mL. The limits of detection were in the range of 3–10 ng/mL. The Intra‐day precisions (relative standard deviation) were 9.2, 4.5, and 4.8, and the recoveries were 58.5, 52.9, and 39.3% for citalopram, doxepin, and fluvoxamine, respectively.