Automation of dispersive liquid–liquid microextraction and related techniques. Approaches based on flow, batch, flow-batch and in-syringe modes

Determination of aconitum alkaloids in acute poisoning case by electromembrane extraction

In this work, electromembrane extraction (EME) was used for the first time to separate aconitine (AC), mesaconitine (Mes-AC) and hypaconitine (Hyp-AC) from biological samples and Chinese herbal medicines. Efficient EME of polar and high molecular weight aconitine alkaloids from different sample matrices was achieved with the solvent of 1-ethyl-2-nitrobenzene (ENB). Under the optimal EME conditions, EME provided recoveries for all targets in the range of 72%-74 %, 85%-103 % and 92%-94 % for whole blood, urine and aqueous samples. The proposed EME systems combined with LC-MS/MS and HPLC-UV were evaluated using different sample matrices, and the methods displayed satisfactory analytical characteristic including negligible matrix effect. The LOD and LOQ of AC, Mes-AC, and Hyp-AC by EME-LC-MS/MS were in the range of 0.002-0.068 ng/mL and 0.005-0.228 ng/mL respectively. The LOD and LOQ of AC, Mes-AC, and Hyp-AC by EME-HPLC-UV were in the range of 0.06-0.26 μg/mL and 0.20-0.86 μg/mL, respectively. The coefficient of determination, R2-value was ≥0.9926 for all cases, and the accuracy in the linear ranges was in the range of 91%-111 %. Finally, the method was successfully applied for the qualitative and quantitative analysis of AC and Mes-AC in the whole blood and herbal medicine dreg samples from an actual forensic case, and poisoning by aconitum alkaloids was identified as the cause of death. Therefore, we believe that EME could be a powerful tool to identify poisoning, and EME has great potential for efficient separation of polar and high molecular weight substances. These are of great importance in the fields of but not limited to forensic science, Traditional Chinese Medicine and clinics.

Relevant insights and concepts overlooked throughout the development of flow analysis. A tutorial

The conceptual expansion, fast development, and general acceptance of flow analysis are consequence of its adherence to the principles of green and white analytical chemistry, and chemical derivatization plays an essential role in this context. Through the flow analysis development, however, some of its potentialities and limitations have been overlooked. This is more evident when the involved modifications in flow rates, timing and/or manifold architecture deteriorate the analytical signals. These aspects have not always been systematically investigated, and are addressed here in relation to flow analyzers with UV-Vis spectrophotometric detection. Novel strategies for solution handling, guidance for dealing with the aforementioned analytical signal deterioration, and an alternative possibility for exploiting differential aspiration are presented. The concept of blank reagent carrier stream is proposed.

Nitrophenols in the environment: An update on pretreatment and analysis techniques since 2017

Nitrophenols, a versatile intermediate, have been widely used in leather, medicine, chemical synthesis, and other fields. Because these components are widely applied, they can enter the environment through various routes, leading to many hazards and toxicities. There has been a recent surge in the development of simple, rapid, environmentally friendly, and effective techniques for determining these environmental pollutants. This review provides a comprehensive overview of the latest research progress on the pretreatment and analysis methods of nitrophenols since 2017, with a focus on environmental samples. Pretreatment methods include liquid-liquid extraction, solid-phase extraction, dispersive extraction, and microextraction methods. Analysis methods mainly include liquid chromatography-based methods, gas chromatography-based methods, supercritical fluid chromatography. In addition, this review also discusses and compares the advantages/disadvantages and development prospects of different pretreatment and analysis methods to provide a reference for further research.

Deep eutectic solvents in sample preparation and determination methods of pesticides: Recent advances and future prospects

This review summarizes recent advances of deep eutectic solvents (DESs) in sample preparation and determination methods of pesticides in food, environmental, and biological matrices since 2019. Emphasis is placed on new DES categories and emerging microextraction techniques. The former incorporate hydrophobic deep eutectic solvents, magnetic deep eutectic solvents, and responsive switchable deep eutectic solvents, while the latter mainly include dispersive liquid-liquid microextraction, liquid-liquid microextraction based on in-situ formation/decomposition of DESs, single drop microextraction, hollow fiber-liquid phase microextraction, and solid-phase microextraction. The principles, applications, advantages, and limitations of these microextraction techniques are presented. Besides, the use of DESs in chromatographic separation, electrochemical biosensors, fluorescent sensors, and surface-enhanced Raman spectroscopy are discussed. This review is expected to provide a valuable reference for extracting and detecting pesticides or other hazardous contaminants in the future.

Improving greenness and sustainability of standard analytical methods by microextraction techniques: A critical review

Since environmental awareness has increased in analytical chemistry, the demand for green sample preparation methods continues to grow. Microextractions such as solid-phase microextraction (SPME) and liquid-phase microextraction (LPME) miniaturize the pre-concentration step and are a more sustainable alternative to conventional large-scale extractions. However, the integration of microextractions in standard and routine analysis methods is rare, although these applications are used most frequently and have a role model function. Therefore, it is important to highlight that microextractions are capable to replace large-scale extractions in standard and routine methods. This review discusses the greenness, benefits, and drawbacks of the most common LPME and SPME variants compatible with gas chromatography based on the following key evaluation principles: Automation, solvent consumption, hazards, reusability, energy consumption, time efficiency, and handling. Furthermore, the need to integrate microextractions into standard and routine analytical methods is presented by using method greenness evaluation metrics AGREE, AGREEprep, and GAPI applied to USEPA methods and their replacements.

An integrated automatic lab-in-syringe sol-gel coated foam microextraction platform as a front-end to high performance liquid chromatography for the migration studies of bisphenol A

The proof-of-concept of an integrated automatic foam microextraction lab-in-syringe (FME-LIS) platform coupled to high performance liquid chromatography is presented. Three different sol-gel coated foams were synthesized, characterized, and conveniently packed inside the glass barrel of the LIS syringe pump, as an alternative approach for sample preparation, preconcentration and separation. The proposed system efficiently combines the inherent benefits of lab-in-syringe technique, the good features of sol-gel sorbents, the versatile nature of foams/sponges, as well as the advantages of automatic systems. Bisphenol A (BPA) was used as model analyte, due to the increasing concern for the migration of this compound from household containers. The main parameters that affect the extraction performance of the system were optimized and the proposed method was validated. The limit of detection for BPA were 0.5 and 2.9 μg L^-1, for a sample volume of 50 mL and 10 mL, respectively. The intra-day precision was <4.7% and the inter-day precision was <5.1% in all cases. The performance of the proposed methodology was evaluated for the migration studies of BPA using different food simulants, as well as for the analysis of drinking water. Good method applicability was observed based on the relative recovery studies (93-103%).

Modern automated microextraction procedures for bioanalytical, environmental, and food analyses

Sample preparation frequently is considered the most critical stage of the analytical workflow. It affects the analytical throughput and costs; moreover, it is the primary source of error and possible sample contamination. To increase efficiency, productivity, and reliability, while minimizing costs and environmental impacts, miniaturization and automation of sample preparation are necessary. Nowadays, several types of liquid-phase and solid-phase microextractions are available, as well as different automatization strategies. Thus, this review summarizes recent developments in automated microextractions coupled with liquid chromatography, from 2016 to 2022. Therefore, outstanding technologies and their main outcomes, as well as miniaturization and automation of sample preparation, are critically analyzed. Focus is given to main microextraction automation strategies, such as flow techniques, robotic systems, and column-switching approaches, reviewing their applications to the determination of small organic molecules in biological, environmental, and food/beverage samples.

Flow-based determination of lead exploiting in-syringe dispersive liquid-liquid micro-extraction in xylene and integrated spectrophotometric detection

A lab-in-syringe flow system exploiting dispersive liquid-liquid micro-extraction in a solvent lighter than water is proposed for the spectrophotometric determination of lead in industrial residual waters. The steps inherent to both liquid-liquid extraction and monitoring of the formed compound are in-syringe carried out. The classical carbon tetrachloride is not used as the extracting solvent, as it does not present the friendly characteristics inherent to the Green Analytical Chemistry. Aiming at a cleaner alternative for this determination, xylene is selected. Enrichment factor, linear dynamic range, detection limit, sample throughput and residue volume inherent to the proposed procedure were estimated as 36, 50.0-250 μg L^-1, 9.0 μg L^-1, 13 h^-1, and 2.0 mL, respectively.

Lab-In-Syringe automation of deep eutectic solvent-based direct immersion single drop microextraction coupled online to high-performance liquid chromatography for the determination of fluoroquinolones

Lab-In-Syringe direct immersion single drop microextraction is proposed as an automated sample pretreatment methodology and coupled online to HPLC with fluorescence detection for the determination of fluoroquinolones in environmental waters. For the first time, a drop of a natural deep eutectic solvent (NADES), synthesized from hexanoic acid and thymol, has been used as an extractant in automated single-drop microextraction. The extraction procedure was carried out within the 5 mL void of an automatic syringe pump. A 9-position head valve served the aspiration of all required solutions, air, waste disposal, and hyphenation with the HPLC instrument. Sample mixing during extraction was done by a magnetic stirring bar placed inside the syringe. Only 60 μL of NADES were required omitting toxic classical solvents and improving the greenness of the proposed methodology. By direct injection, linear working ranges between 0.1 and 5 μg L^-1 were achieved for all fluoroquinolones. The limit of quantification values and enrichment factors ranged from 20 ng L^-1 to 30 ng L^-1 and 35 to 45, respectively. Accuracies obtained from the analysis of spiked surface water and wastewater treatment plant effluent analysis at two concentration levels (0.5 and 4 μg L^-1) ranged from 84.6% to 119.7%, with RSD values typically <3%.

Chemical Derivatization in Flow Analysis

Chemical derivatization for improving selectivity and/or sensitivity is a common practice in analytical chemistry. It is particularly attractive in flow analysis in view of its highly reproducible reagent addition(s) and controlled timing. Then, measurements without attaining the steady state, kinetic discrimination, exploitation of unstable reagents and/or products, as well as strategies compliant with Green Analytical Chemistry, have been efficiently exploited. Flow-based chemical derivatization has been accomplished by different approaches, most involving flow and manifold programming. Solid-phase reagents, novel strategies for sample insertion and reagent addition, as well as to increase sample residence time have been also exploited. However, the required alterations in flow rates and/or manifold geometry may lead to spurious signals (e.g., Schlieren effect) resulting in distorted peaks and a noisy/drifty baseline. These anomalies can be circumvented by a proper flow system design. In this review, these aspects are critically discussed mostly in relation to spectrophotometric and luminometric detection.

Screen-Printed Technologies Combined with Flow Analysis Techniques: Moving from Benchtop to Everywhere

Screen-printed electrodes (SPEs) coupled with flow systems have been reported in recent decades for an ever-growing number of applications in modern electroanalysis, aiming for portable methodologies. The information acquired through this combination can be attractive for future users with basic knowledge, especially due to the increased measurement throughput, reduction in reagent consumption and minimal waste generation. The trends and possibilities of this set rely on the synergistic behavior that maximizes both SPE and flow analyses characteristics, allowing mass production and automation. This overview addresses an in-depth update about the scope of samples, target analytes, and analytical throughput (injections per hour, limits of detection, linear range, etc.) obtained by coupling injection techniques (FIA, SIA, and BIA) with SPE-based electrochemical detection.

Towards a comprehensive characterisation of the human internal chemical exposome: Challenges and perspectives

The holistic characterisation of the human internal chemical exposome using high-resolution mass spectrometry (HRMS) would be a step forward to investigate the environmental ætiology of chronic diseases with an unprecedented precision. HRMS-based methods are currently operational to reproducibly profile thousands of endogenous metabolites as well as externally-derived chemicals and their biotransformation products in a large number of biological samples from human cohorts. These approaches provide a solid ground for the discovery of unrecognised biomarkers of exposure and metabolic effects associated with many chronic diseases. Nevertheless, some limitations remain and have to be overcome so that chemical exposomics can provide unbiased detection of chemical exposures affecting disease susceptibility in epidemiological studies. Some of these limitations include (i) the lack of versatility of analytical techniques to capture the wide diversity of chemicals; (ii) the lack of analytical sensitivity that prevents the detection of exogenous (and endogenous) chemicals occurring at (ultra) trace levels from restricted sample amounts, and (iii) the lack of automation of the annotation/identification process. In this article, we discuss a number of technological and methodological limitations hindering applications of HRMS-based methods and propose initial steps to push towards a more comprehensive characterisation of the internal chemical exposome. We also discuss other challenges including the need for harmonisation and the difficulty inherent in assessing the dynamic nature of the internal chemical exposome, as well as the need for establishing a strong international collaboration, high level networking, and sustainable research infrastructure. A great amount of research, technological development and innovative bio-informatics tools are still needed to profile and characterise the "invisible" (not profiled), "hidden" (not detected) and "dark" (not annotated) components of the internal chemical exposome and concerted efforts across numerous research fields are paramount.

Lab-In-Syringe with Bead Injection Coupled Online to High-Performance Liquid Chromatography as Versatile Tool for Determination of Nonsteroidal Anti-Inflammatory Drugs in Surface Waters

We report on the hyphenation of the modern flow techniques Lab-In-Syringe and Lab-On-Valve for automated sample preparation coupled online with high-performance liquid chromatography. Adopting the bead injection concept on the Lab-On-Valve platform, the on-demand, renewable, solid-phase extraction of five nonsteroidal anti-inflammatory drugs, namely ketoprofen, naproxen, flurbiprofen, diclofenac, and ibuprofen, was carried out as a proof-of-concept. In-syringe mixing of the sample with buffer and standards allowed straightforward pre-load sample modification for the preconcentration of large sample volumes. Packing of ca. 4.4 mg microSPE columns from Oasis HLB^® sorbent slurry was performed for each sample analysis using a simple microcolumn adapted to the Lab-On-Valve manifold to achieve low backpressure during loading. Eluted analytes were injected into online coupled HPLC with subsequent separation on a Symmetry C18 column in isocratic mode. The optimized method was highly reproducible, with RSD values of 3.2% to 7.6% on 20 µg L^-1 level. Linearity was confirmed up to 200 µg L^-1 and LOD values were between 0.06 and 1.98 µg L^-1. Recovery factors between 91 and 109% were obtained in the analysis of spiked surface water samples.

Determination of long-chain fatty acids in anaerobic digester supernatant and olive mill wastewater exploiting an in-syringe dispersive liquid-liquid microextraction and derivatization-free GC-MS method

Long-chain fatty acids (LCFA) are commonly found in lipid-rich wastewaters and are a key factor to monitor the anaerobic digesters. A new simple, fast, precise, and suitable method for routine analysis of LCFA is proposed. The system involves in-syringe-magnetic stirring-assisted dispersive liquid-liquid microextraction (DLLME) prior to gas chromatography-mass spectrometry (GC-MS) without a derivatization process. Calibration curves were prepared in an ethanol solution (R² ≥ 0.996), which was also useful as disperser solvent. Hexane was chosen as the extraction solvent. Several parameters (pH, ionic strength, extraction solvent volume, stirring time) were optimized in multivariate and univariate studies. Limits of detection (LODs) were found in the range 0.01-0.05 mg L^-1 and good precision inter-day (RSDs≤7.9%) and intra-day (RSDs≤4.4%) were obtained. The method was applied to quantify LCFA in supernatants of anaerobic digesters and olive mill wastewaters (OMW). Palmitic, stearic, and oleic acids were the most abundant fatty acid in the analyzed samples and the relative recoveries for all of them were between 81 and 113%.

Automated method for volatile fatty acids determination in anaerobic processes using in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction and gas chromatography with flame ionization detector

Volatile fatty acids (VFAs) are key parameters to monitor anaerobic digestion processes. Thus, a fast, simple and precise determination of these analytes is necessary for a timely characterization of the biological processes present in municipal solid waste and wastewater treatment plants. In this work, an automated method for the extraction and preconcentration of VFAs, based on dispersive liquid-liquid microextraction with magnetic stirring in syringe, and gas chromatography with flame ionization detector for the separation and detection, is described. The effect of parameters such as the type and volume of extraction solvent, pH, salting out effect and stirring time, was studied using a multivariate and univariate experimental design. Extraction and preconcentration were performed simultaneously using tert-butyl methyl ether (TBME) as the extraction solvent, after stirring 100 s at a constant rate. The detection limits were in the range of 0.1 - 1.3 mg L^-1 and a good linearity was observed up to 1000 mg L^-1 of the studied VFAs, with a range of R² between 0.9997 and 0.9999. The intra and interday precision expressed as relative standard deviation (n= 5) varied between 0.7 and 2.4% and between 1.7 and 7.0%, respectively. Subsequently, the developed method was successfully applied to evaluate the presence of VFAs in wastewater samples from anaerobic treatments and an average relative recovery of 102% was obtained.

Microscale extraction versus conventional approaches for handling gastrointestinal extracts in oral bioaccessibility assays of endocrine disrupting compounds from microplastic contaminated beach sand

The unified bioaccessibility method (UBM) was harnessed to assess in vitro oral bioaccessibility pools of dialkyl phthalate congeners (with methyl, -ethyl, -butylbenzyl, -n-butyl, -2-ethylhexyl, and -n-octyl moieties) and bisphenol A at the 17 μg g^-1 level in beach sand contaminated with polyethylene microplastics. A variety of sample preparation approaches prior to the analysis of the UBM gastrointestinal extracts, including traditional methods (protein precipitation, liquid-liquid extraction, and solid-phase extraction) and dispersive liquid-liquid microextraction (DLLME) were comprehensively evaluated for clean-up and analyte enrichment. DLLME was chosen among all tested approaches on account of the high extraction efficiency (73-95%, excluding bis(2-ethylhexyl)phthalate and di-n-octyl phthalate), high sample throughput (∼7 min per set of samples), and environmental friendliness as demonstrated by the analytical eco-scale score of 83, and the green analytical procedure index pictogram with green/yellow labeling. The release of the less hydrophobic plastic-laden compounds (dimethyl phthalate, diethyl phthalate and bisphenol A) from the contaminated sample into the body fluids was significant, with bioaccessibility values ranging from 30 to 70%, and from 43 to 74% in gastric and gastrointestinal fluids, respectively, and with relative standard deviation < 17% in all cases. The majority of the compounds were leached during gastric digestion, likely as the combined action of the low pH and the gastric enzymes. The risk exposure analysis revealed that accumulation/concentration in the body fluids is potentially relevant for dimethyl phthalate, diethyl phthalate and bisphenol A, with relative accumulation ratios ranging from 1.1 ± 0.1 to 2.6 ± 0.4. The average daily intake values for the suite of compounds, corrected with the bioaccessibility fraction, ranged from 60 to 430 ng kg of body weight^-1·day^-1, in all cases, far below the tolerable daily intakes, thus indicating the lack of children health risk by ingestion of microplastic-laden sand with elevated concentrations of plasticizers.

In-a-syringe surfactant-assisted dispersive liquid-liquid microextraction of polycyclic aromatic hydrocarbons in supramolecular solvent from tea infusion

In this work, an automated surfactant-assisted dispersive liquid-liquid microextraction approach based on in-a-syringe concept was developed for the first time. The procedure assumed mixing aqueous sample phase and hydrophilic emulsion containing hexanoic acid and sodium hexanoate in a syringe of flow system. Sodium hexanoate acted as an emulsifier in dispersive liquid-liquid microextraction process and it was required for the formation of supramolecular solvent phase. After spontaneous separation of phases in the syringe, the upper supramolecular solvent phase containing target analytes was withdrawn and analyzed. The procedure was applied to the determination of 13 polycyclic aromatic hydrocarbons in tea infusion by high performance liquid chromatography with fluorescence detection. It was shown that the supramolecular solvent provided effective extraction of polycyclic aromatic hydrocarbons and fast phase separation in the syringe without centrifugation. The enrichment factors were in the range of 38-46. The automated microextraction procedure lasted 4 min including syringe cleaning. Under optimal experimental conditions the linear detection ranges were found to be 0.05-50.00 μg L^-1 with limits of detection calculated from a blank test, based on 3σ, 0.02-0.04 μg L^-1. Recovery values in the range of 85-105% were achieved for tea infusion with a reproducibility expressed as RSD less than 4.1%.

Ouzo Column under Impact: Formation of Emulsion Jet and Oil-Lubricated Droplet

We investigated the dynamics of a liquid column consisting of ouzo emulsion under the impact generated when the liquid container lands on a hard ground. At a cavitation number of 0.36, where cavitation is expected to occur, our high-speed videography captured the traveling jet and cavitation bubbles while the oil microdroplets in ouzo after different runs of impact were visualized by an optical microscope. Importantly, the impact on an ouzo column can eject a focused jet of the emulsion and deposit a small volume of emulsion on a solid substrate. As revealed by our still photography, the deposited emulsion formed an oil-lubricated drop immediately. Our findings have implications for jetting applications such as inkjet printing of emulsions or fast deposition of self-lubricating drops for assembling supraparticles. We also discuss the jet formation mechanism in terms of the existence of oil microdroplets.

Application of microextraction techniques in alternative biological matrices with focus on forensic toxicology: a review

The interest in alternative biological matrices (e.g., hair and saliva) for forensic toxicology analysis has increased, and recent developments in sample preparation have targeted rapid, cheap, efficient and eco-friendly methods, including microextraction techniques. For this review, we have gathered information about these two hot topics. We discuss the composition, incorporation of analytes and advantages and disadvantages of different biological matrices, and also present the operation principles of the most reported microextraction procedures and their application in forensic toxicology. The outcome of this review may encourage future forensic researches into alternative samples and microextraction techniques.

Dispersive liquid-liquid microextraction followed by green high-performance liquid chromatography for fluconazole determination in cerebrospinal fluid with the aid of chemometric tools

A new method, simple and fast, for fluconazole (FLU) quantification in cerebrospinal fluid (CSF) samples using dispersive liquid-liquid microextraction (DLLME) and an eco-friendly mobile phase for HPLC-PDA was developed. The study of DLLME extraction condition covered the investigation of 12 combinations of extraction and disperser solvents followed by a fractional factorial design 2(7-3) to determine the influence of seven factors. After this stage, a central composite design was performed for three factors and a response surface was obtained. Aiming a compromise between a good recovery and a low organic solvent use it was established an extraction condition that consists of: 100 μL of chloroform, 100 μL of isopropyl alcohol, 200 μL of CSF, 200 μL of 50 mM phosphate buffer pH 7.3 and centrifugation for 5 min at 2200g and 4 °C. The HPLC analysis used an Ascentis® Express C18 column (100 mm × 4.6 mm, 2.7 μm) and an Ascentis® Express C18 guard column (3 mm × 4.6 mm, 2.7 μm), ethanol : water (15 : 85, v/v) as mobile phase, temperature of 45 °C, flow rate of 0.8 mL min-1 and phenacetin as internal standard. The method validation was performed according to European Agency's Guideline on Bioanalytical Validation Methodology and a linear range was obtained from 0.25 to 62.5 μg mL-1, with precision and accuracy within the recommended limits and recovery of 70% for FLU and 81% for phenacetin. Samples were stable in the studies performed and the method showed to be selective and with no carryover effect. The feasibility of the obtained method was confirmed by FLU determination at a CSF from a patient who was treated for neuromycosis. Therefore, here is described a method that meets many principles of green analytical chemistry and is useful for FLU therapeutic monitoring.

Liquid phase microextraction techniques combined with chromatography analysis: a review

Sample pretreatment is the first and the most important step of an analytical procedure. In routine analysis, liquid–liquid microextraction (LLE) is the most widely used sample pre-treatment technique, whose goal is to isolate the target analytes, provide enrichment, with cleanup to lower the chemical noise, and enhance the signal. The use of extensive volumes of hazardous organic solvents and production of large amounts of waste make LLE procedures unsuitable for modern, highly automated laboratories, expensive, and environmentally unfriendly. In the past two decades, liquid-phase microextraction (LPME) was introduced to overcome these drawbacks. Thanks to the need of only a few microliters of extraction solvent, LPME techniques have been widely adopted by the scientific community. The aim of this review is to report on the state-of-the-art LPME techniques used in gas and liquid chromatography. Attention was paid to the classification of the LPME operating modes, to the historical contextualization of LPME applications, and to the advantages of microextraction in methods respecting the value of green analytical chemistry. Technical aspects such as description of methodology selected in method development for routine use, specific variants of LPME developed for complex matrices, derivatization, and enrichment techniques are also discussed.

The Automation Technique Lab-In-Syringe: A Practical Guide

About eight years ago, a new automation approach and flow technique called "Lab-In-Syringe" was proposed. It was derived from previous flow techniques, all based on handling reagent and sample solutions in a flow manifold. To date Lab-In-Syringe has evidently gained the interest of researchers in many countries, with new modifications, operation modes, and technical improvements still popping up. It has proven to be a versatile tool for the automation of sample preparation, particularly, liquid-phase microextraction approaches. This article aims to assist newcomers to this technique in system planning and setup by overviewing the different options for configurations, limitations, and feasible operations. This includes syringe orientation, in-syringe stirring modes, in-syringe detection, additional inlets, and addable features. The authors give also a chronological overview of technical milestones and a critical explanation on the potentials and shortcomings of this technique, calculations of characteristics, and tips and tricks on method development. Moreover, a comprehensive overview of the different operation modes of Lab-In-Syringe automated sample pretreatment is given focusing on the technical aspects and challenges of the related operations. We further deal with possibilities on how to fabricate required or useful system components, in particular by 3D printing technology, with over 20 different elements exemplarily shown. Finally, a short discussion on shortcomings and required improvements is given.

3D Printing in analytical sample preparation

In the last 5 years, additive manufacturing (three-dimensional printing) has emerged as a highly valuable technology to advance the field of analytical sample preparation. Three-dimensional printing enabled the cost-effective and rapid fabrication of devices for sample preparation, especially in flow-based mode, opening new possibilities for the development of automated analytical methods. Recent advances involve membrane-based three-dimensional printed separation devices fabricated by print-pause-print and multi-material three-dimensional printing, or improved three-dimensional printed holders for solid-phase extraction containing sorbent bead packings, extraction disks, fibers, and magnetic particles. Other recent developments rely on the direct three-dimensional printing of extraction sorbents, the functionalization of commercial three-dimensional printable resins, or the coating of three-dimensional printed devices with functional micro/nanomaterials. In addition, improved devices for liquid-liquid extraction such as extraction chambers, or phase separators are opening new possibilities for analytical method development combined with high-performance liquid chromatography. The present review outlines the current state-of-the-art of three-dimensional printing in analytical sample preparation.

Applications of Mass Spectrometry for Clinical Diagnostics: The Influence of Turnaround Time

This critical review discusses how the need for reduced clinical turnaround times has influenced chemical instrumentation. We focus on the development of modern mass spectrometry (MS) and its application in clinical diagnosis. With increased functionality that takes advantage of novel front-end modifications and computational capabilities, MS can now be used for non-traditional clinical analyses, including applications in clinical microbiology for bacteria differentiation and in surgical operation rooms. We summarize here recent developments in the field that have enabled such capabilities, which include miniaturization for point-of-care testing, direct complex mixture analysis via ambient ionization, chemical imaging and profiling, and systems integration.

Automated on-line liquid-liquid extraction in a multisyringe flow injection analysis manifold for migration studies in food-contact materials: analysis of 4,4´-dihydroxybiphenyl

Packaging may represent a source of food contamination, as different organic compounds and degradation compounds may migrate from packaging to foodstuff. For fatty foods, rectified olive oil is the common simulant, which implies time-consuming and laborious liquid-liquid extraction (LLE) procedures to isolate the contaminant(s) from the oil. Here we propose a Multisyringe Flow Injection Analysis manifold to automate this sample treatment, using the monomer 4,4´-dihydroxybiphenyl as the contaminant. The LLE procedure, using water as extractant, was fully automated. After the on-line LLE, the resulting extract was pumped through a fluorescence detector, inside which a flow-cell filled with C₁₈ silica gel solid support was placed. The analyte was pre-concentrated on the solid support (in which the analytical signal was directly recorded), so improving the sensitivity of the system. Under optimum conditions, the method detection limit is 0.05 mg kg^-1, well within the specific migration limit of 6 mg kg^-1. The method developed was compared with the standard CEN test method (off-line LLE and HPLC determination) observing savings in sample and reagents of 90% and a 7-fold increase in sample throughput.

Robotic-assisted dynamic large drop microextraction

By proper design of an innovative extraction device, a lab-made multipurpose autosampler was exploited in the automated performance of the dynamic large drops based microextraction. The pluses of this new analytical strategy were demonstrated in the determination of sulfonamides and fluoroquinolones in surface water samples, by direct immersion single drop microextraction (SDME) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis. Operational autosampler features and critical experimental factors influencing SDME, including the extraction mode (static or dynamic), extraction, stirring rate, salt addition, drop size, number of cycles and drop exposition time, were comprehensively investigated using both univariate and multivariate optimization. The lab-made autosampler allowed to performance challenging dynamic and static large drop based SDMEs in an automated and effortless way and with minimal requirements of hardware and software. Large stable drops provided high surface area, enhancing the phase ratio and in consequence increasing the analytes uptake. The best extraction efficiencies were obtained as a result of the synergic interaction between the use of large drops and the automated dynamic mode of extraction. The developed method proved to be a reliable, sensitive, and robust analytical tool, with intraday RSDs ranging between 4.0 and 7.6% (n = 6), and interday RSDs between 4.8 and 9.3% (n = 6), and, LOD and LOQ in the range of 15-50 and 35-100 ng L^-1, respectively.

State-of-the-art on the technique of dispersive liquid-liquid microextraction

Dispersive liquid-liquid microextraction is a new sample pretreatment technology based on traditional liquid liquid extraction. In this paper, the application of low-toxicity extractants such as low-density extractants, auxiliary extractants, stripping agents and ionic liquids in this technology and the extraction modes such as solvent de-emulsification, suspension extractant curing, auxiliary extraction, back extraction, and ionic liquid-dispersion liquid microextraction, are summarized. In addition, the synergism of this technique with other sample preparation techniques, such as liquid-liquid extraction, solid-phase extraction, solid-phase microextraction, dispersive solid phase extraction, matrix solid-phase dispersion extraction, supercritical fluid extraction and ultrasound-assisted dispersive liquid-liquid microextraction is discussed.

Miniaturized sample preparation methods for saliva analysis

Saliva, as the first body fluid encountering with the exogenous materials, has good correlation with blood and plays an important role in bioanalysis. However, saliva has not been studied as much as the other biological fluids mainly due to restricted access to its large volumes. In recent years, there is a growing interest for saliva analysis owing to the emergence of miniaturized sample preparation methods. The purpose of this paper is to review all microextraction methods and their principles of operation. In the following, we examine the methods used to analyze saliva up to now and discuss the potential of the other microextraction methods for saliva analysis to encourage research groups for more focus on this important subject area.

Functional Femtoliter Droplets for Ultrafast Nanoextraction and Supersensitive Online Microanalysis

A universal femtoliter surface droplet-based platform for direct quantification of trace of hydrophobic compounds in aqueous solutions is presented. Formation and functionalization of femtoliter droplets, concentrating the analyte in the solution, are integrated into a simple fluidic chamber, taking advantage of the long-term stability, large surface-to-volume ratio, and tunable chemical composition of these droplets. In situ quantification of the extracted analytes is achieved by surface-enhanced Raman scattering (SERS) spectroscopy by nanoparticles on the functionalized droplets. Optimized extraction efficiency and SERS enhancement by tuning droplet composition enable quantitative determination of hydrophobic model compounds of rhodamine 6G, methylene blue, and malachite green with the detection limit of 10^-9 to 10^-11 m and a large linear range of SERS signal from 10^-9 to 10^-6 m of the analytes. The approach addresses the current challenges of reproducibility and the lifetime of the substrate in SERS measurements. This novel surface droplet platform combines liquid-liquid extraction and highly sensitive and reproducible SERS detection, providing a promising technique in current chemical analysis related to environment monitoring, biomedical diagnosis, and national security monitoring.

Microwave-assisted dispersive liquid-liquid microextraction coupling to solidification of floating organic droplet for colorants analysis in selected cosmetics by liquid chromatography

A convenient and rapid method was developed for determination of fourteen colorants in selected cosmetics based on microwave-assisted dispersive liquid-liquid microextraction (MA-DLLME) using solidification of the floating organic droplet (SFOD) as a clean-up step followed by high-performance liquid chromatography diode array detection (HPLC-DAD). DLLME was performed in a microwave device for reducing manual operations and facilitating rapid extraction equilibrium, resulting in high sample throughput and good extraction efficiency. Matrix effects could be effectively eliminated by SFOD technique. Various parameters affecting the extraction efficiency were optimized by multi-response surface methodology. The limits of detection and quantification were 0.25-3.2 mg kg^-1 and 0.85-11.0 mg kg^-1, respectively. The recoveries ranged from 90.2% to 106.1% with relative standard deviations of 0.30-3.1%. The method was successfully applied to the analysis of cosmetics, in which all the colorants could be quantified, and their median values ranged from 4.94 to 591 mg kg^-1 for seventy-two lipsticks, and from 7.70 to 1.73 × 10³ mg kg^-1 for fifty eye shadows, respectively. The proposed protocol could achieve batch preparation of samples and avoid measurement errors from the obvious volume reduction of the recovered extract, and it could serve as a powerful tool for high-throughput analysis of multiple colorants in complex samples.