On-chip ion pair-based dispersive liquid-liquid extraction for quantitative determination of histamine H2 receptor antagonist drugs in human urine

Recent Advances in Dispersive Liquid-Liquid Microextraction for Pharmaceutical Analysis

Sample clean-up and pre-concentration are critical components of pharmaceutical analysis. The dispersive liquid-liquid microextraction (DLLME) technique is widely recognized as the most effective approach for enhancing overall detection sensitivity. While various DLLME modes have been advanced in pharmaceutical analysis, there need to be more discussions on pre-concentration techniques specifically developed for this field. This review presents a comprehensive overview of the different DLLME modes used in pharmaceutical analysis from 2017 to May 2023. The review covers the principles of DLLME, the factors affecting microextraction, the selected applications of different DLLME modes, and their advantages and disadvantages. Additionally, it focuses on multi-extraction strategies employed for pharmaceutical analysis.

Electrochemical biosensors in healthcare services: bibliometric analysis and recent developments

Biosensors are nowadays being used in various fields including disease diagnosis and clinical analysis. The ability to detect biomolecules associated with disease is vital not only for accurate diagnosis of disease but also for drug discovery and development. Among the different types of biosensors, electrochemical biosensor is most widely used in clinical and health care services especially in multiplex assays due to its high susceptibility, low cost and small in size. This article includes comprehensive review of biosensors in medical field with special emphasis on electrochemical biosensors for multiplex assays and in healthcare services. Also, the publications on electrochemical biosensors are increasing rapidly; therefore, it is crucial to be aware of any latest developments or trends in this field of research. We used bibliometric analyses to summarize the progress of this research area. The study includes global publication counts on electrochemical biosensors for healthcare along with various bibliometric data analyses by VOSviewer software. The study also recognizes the top authors and journals in the related area, and determines proposal for monitoring research.

Magnetic Torus Microreactor as a Novel Device for Sample Treatment via Solid-Phase Microextraction Coupled to Graphite Furnace Atomic Absorption Spectroscopy: A Route for Arsenic Pre-Concentration

This work studied the feasibility of using a novel microreactor based on torus geometry to carry out a sample pretreatment before its analysis by graphite furnace atomic absorption. The miniaturized retention of total arsenic was performed on the surface of a magnetic sorbent material consisting of 6 mg of magnetite (Fe₃O₄) confined in a very small space inside (20.1 µL) a polyacrylate device filling an internal lumen (inside space). Using this geometric design, a simulation theoretical study demonstrated a notable improvement in the analyte adsorption process on the solid extractant surface. Compared to single-layer geometries, the torus microreactor geometry brought on flow turbulence within the liquid along the curvatures inside the device channels, improving the efficiency of analyte–extractant contact and therefore leading to a high preconcentration factor. According to this design, the magnetic solid phase was held internally as a surface bed with the use of an 8 mm-diameter cylindric neodymium magnet, allowing the pass of a fixed volume of an arsenic aqueous standard solution. A preconcentration factor of up to 60 was found to reduce the typical “characteristic mass” (as sensitivity parameter) determined by direct measurement from 53.66 pg to 0.88 pg, showing an essential improvement in the arsenic signal sensitivity by absorption atomic spectrometry. This methodology emulates a miniaturized micro-solid-phase extraction system for flow-through water pretreatment samples in chemical analysis before coupling to techniques that employ reduced sample volumes, such as graphite furnace atomic absorption spectroscopy.

Microfluidic Chip-Based Induced Phase Separation Extraction as a Fast and Efficient Miniaturized Sample Preparation Method

Induced phase separation extraction (IPSE) is an efficient sample clean-up technique that can replace liquid-liquid extraction (LLE). The purpose of this study was to miniaturize IPSE by carrying it out in a microfluidic chip. An IPSE chip was designed and evaluated for its ability to separate and purify samples on a microscale. The 5 × 2 cm chip was fed with a solution of polar to non-polar model compounds in acetonitrile-water (1:1). In the 100 µm wide and 40 µm deep microchannels, the sample solution was efficiently separated into two immiscible phases by adding a hydrophobic solvent as inducer. Analytes present in the sample solution each migrated to their own favorable phase upon phase separation. After optimization, extraction and fractionation were easily and efficiently achieved. The behavior of analytes with a pH-dependent partitioning could be influenced by adjusting the pH of the sample solution. Scutellaria baicalensis extract, used in Traditional Chinese Medicine (TCM), was successfully separated in aglycones and glycosides. In this microscale system, the sample and solvent consumption is reduced to microliters, while the time needed for the sample pretreatment is less than one minute. Additionally, the extraction efficiency can reach up to 98.8%, and emulsion formation is avoided.

Direct immersion single-drop microextraction of semi-volatile organic compounds in environmental samples: A review

Single-drop microextraction (SDME) techniques are efficient approaches to pretreatment of aqueous samples. The main advantage of SDME lies in the miniaturization of the solvent extraction process, minimizing the hazards associated with the use of toxic organic solvents. Thus, SDME techniques are cost-effective, and represent less harm to the environment, subscribing to green analytical chemistry principles. In practice, two main approaches can be used to perform SDME - direct immersion (DI)-SDME and headspace (HS)-SDME. Even though the DI-SDME has been shown to be quite effective for extraction and enrichment of various organic compounds, applications of DI-SDME are normally more suitable for moderately polar and non-polar semi-volatile organic compounds (SVOCs) using organic solvents which are immiscible with water. In this review, we present a historical overview and current advances in DI-SDME, including the common analytical tools which are usually coupled with DI-SDME. The review also focuses on applications concerning SVOCs in environmental samples. Currents trends in DI-SDME and possible future direction of the procedure are discussed.

High-Throughput Liquid-Liquid Extractions with Nanoliter Volumes

Current methods for liquid-liquid extractions generally require microliter to milliliter volumes of solvents and sample, long equilibration times, and manual procedures. Extraction methods for samples in microfluidic systems have been limited as this tool is difficult to implement on the nanoliter or smaller scale. We have developed slug-flow nanoextraction (SFNE), a method based on droplet microfluidics that allows multiple liquid-liquid extractions to be performed simultaneously in a capillary tube, using only 5 nL of sample and extraction solvent per extraction. Each two-phase slug is segmented from the others by immiscible carrier fluid. We found rapid extractions (<5 s), partition coefficients matching those achieved at larger scale extractions, and potential to preconcentrate samples through volume manipulation. This method was used to accurately and rapidly determine octanol-water partition coefficients (Kow), determining identical Kow as the shake-flask method for acetaminophen, Kow = 2.48 ± 0.02. The measurement, along with calibration and 12 replicates, was complete within 5 min, consuming under 150 nL of solvent and sample. The method was also applied to extract analytes from complex biological samples prior to electrospray ionization-tandem mass spectrometry (ESI-MS/MS) at a rate of 6 s per sample, allowing for simultaneous determination of five different drugs spiked into human plasma, synthetic urine (SU), and artificial cerebral spinal fluid (aCSF) using ethyl acetate as the extraction phase. The signal-to-noise (S/N) for analytes improved up to 19-fold compared to direct ESI-MS of single-phase droplets (aqueous plugs segmented by carrier fluid), with limits of detection down to 7 nM (35 amol).