Practical sample pretreatment techniques coupled with capillary electrophoresis for real samples in complex matrices

Recent advances in microscale separation techniques for glycome analysis

The glycomic analysis holds significant appeal due to the diverse roles that glycans and glycoconjugates play, acting as modulators and mediators in cellular interactions, cell/organism structure, drugs, energy sources, glyconanomaterials, and more. The glycomic analysis relies on liquid-phase separation technologies for molecular purification, separation, and identification. As a miniaturized form of liquid-phase separation technology, microscale separation technologies offer various advantages such as environmental friendliness, high resolution, sensitivity, fast speed, and integration capabilities. For glycan analysis, microscale separation technologies are continuously evolving to address the increasing challenges in their unique manners. This review discusses the fundamentals and applications of microscale separation technologies for glycomic analysis. It covers liquid-phase separation technologies operating at scales generally less than 100 µm, including capillary electrophoresis, nanoflow liquid chromatography, and microchip electrophoresis. We will provide a brief overview of glycomic analysis and describe new strategies in microscale separation and their applications in glycan analysis from 2014 to 2023.

A new coaxial flow-through probe for electromembrane extraction of methadone from clinical samples on-line coupled to capillary electrophoresis

BACKGROUND

A new design of a flow-through coaxial electromembrane extraction (EME) probe that can be on-line coupled with CE instrument is described and tested. The supporting base of the probe is a PDMS microchip with T-shaped channels into which two coaxially arranged capillaries for inlet and outlet solutions are inserted. The extraction part of the probe is a porous polypropylene hollow fiber, sealed at one end and modified with nitrophenyloctyl ether (NPOE) extraction fluid. The internal volume of the extraction probe is 1.1 μL.

RESULTS

The EME probe was tested on laboratory samples and methadone was extracted into 3.0 M AcOH as acceptor. The concentration dependence was linear in the range of 0.1-1.0 μg mL-1 at EME 300 s/150 V and in the range of 0.5-10.0 μg mL-1 at EME 100 s/150 V. The enrichment factor was greater than 30 and the LOD was 0.21 μg mL-1. The EME of methadone in clinical samples showed a linear concentration dependence in human urine and a nonlinear concentration dependence in serum. The distribution of methadone in each phase of the extraction system and the effect of extraction membrane thickness on the enrichment factor were studied. The EME probe can be applied repeatedly.

SIGNIFICANCE

The supporting base of EME probe and flow gating interface (FGI) are realized by a microfluidic PDMS microchips cast in the laboratory without the use of lithography. A supporting PDMS chip with coaxially arranged capillaries and extraction membrane forms a compact analytical instrument. The entire EME/CE analysis process is performed on a laboratory-made instrument and automated by LabView.

Fast and sensitive smartphone colorimetric detection of whole blood samples on a paper-based analytical device

BACKGROUND

Methods based on paper-based analytical devices (PAD) and smartphone photographic colorimetric detection have become representative instrument-independent point-of-care testing (POCT) platforms due to their low cost and simplicity. However, the detection of target components from whole blood sample still presents challenges in terms of field preparation of small amounts of blood sample and detection sensitivity. This paper presents a rapid online processing method for whole blood samples on PAD based on plasma separation membrane (PSM), and combined with electrokinetic stacking and selective chromatic reaction. Real-time smartphone-based colorimetric detection of free hemoglobin (FHb) and human serum albumin (HSA) was successfully demonstrated.

RESULTS

With the proposed method, both detections for low and high concentration analytes could be implemented. The limits of detection of 16.6 mg L-1 for FHb and 0.67 g L-1 for HSA were obtained, respectively, with RSD below 8 %. The reliability of the method was verified by the recovery test and desktop spectrophotometric method. The detection results for real blood samples were in agreement with that by clinical methods.

SIGNIFICANCE AND NOVELTY

The PAD method is inexpensive, simple and fast, and detection of a whole blood sample of 5 μL can be finished in 5 min. This work shows that POCT of biomarkers from whole blood with PAD is possible without using any desktop facilities.

Transient isotachophoresis-Capillary zone electrophoresis-Mass spectrometry method with off-line microscale solid phase extraction pretreatment for quantitation of intact low molecular mass proteins in various biological fluids

Quantification of proteins is still predominantly done by the traditional bottom-up approach. Targeting of intact proteins in complex biological matrices is connected with multiple challenges during the sample pretreatment, separation, and detection step of the analytical workflow. In this work, we focused on the development of an on-line hyphenated capillary zone electrophoresis-mass spectrometry method employing off-line microscale solid-phase extraction based on hydrophilic lipophilic balance (HLB) sorbent as a sample pretreatment step for the analysis of low molecular mass intact proteins (<20 kDa) spiked in various biological fluids (human serum, plasma, urine, and saliva). A detailed optimization process involved the selection of a suitable capillary surface, background electrolyte (BGE), and comparison of two in-capillary preconcentration methods, namely transient isotachophoresis (tITP) and dynamic pH junction (DPJ), to enhance the sensitivity of the method. Optimum separation of the analytes was achieved using uncoated bare fused silica capillary employing 500 mM formic acid (pH 1.96) + 5 % (v/v) acetonitrile as BGE. tITP was utilized as an optimum preconcentration technique, achieving a 19- to 127-fold increase in the signal intensity when using 200 mM ammonium formate (adjusted to pH 4.00) as the leading electrolyte and BGE as the terminating electrolyte. Off-line microscale solid-phase extraction with various eluate treatment procedures was evaluated to ensure the compatibility of the sample pretreatment method with the selected in-capillary preconcentration, separation, and detection process. Achieved extraction recoveries of spiked proteins were in the range of 76-100 % for urine, 12-54 % for serum, 21-106 % for plasma, and 25-98 % for saliva when the eluate was evaporated and reconstituted in the solution of the leading electrolyte to achieve the tITP process. The optimum method was validated across different biological matrices, offering good linearity, accuracy, and precision, and making it suitable for proteomic studies (e.g., therapeutic drug monitoring, biomarker research) in different biological samples.

A review on hyphenation of droplet microfluidics to separation techniques: From instrumental conception to analytical applications for limited sample volumes

In this study, we review various strategies to couple sample processing in microfluidic droplets with different separation techniques, including liquid chromatography, mass spectrometry, and capillary electrophoresis. Separation techniques interfaced with droplet microfluidics represent an emerging trend in analytical chemistry, in which micro to femtoliter droplets serve as microreactors, a bridge between analytical modules, as well as carriers of target analytes between sample treatment and separation/detection steps. This allows to overcome the hurdles encountered in separation science, notably the low degree of module integration, working volume incompatibility, and cross contamination between different operational stages. For this droplet-separation interfacing purpose, this review covers different instrumental designs from all works on this topic up to May 2023, together with our viewpoints on respective advantages and considerations. Demonstration and performance of droplet-interfaced separation strategies for limited sample volumes are also discussed.

Steady state microdialysis of microliter volumes of body fluids for monitoring of amino acids by capillary electrophoresis with contactless conductivity detection

BACKGROUND

The availability of dialysis membranes in the form of hollow fibres with diameters compatible with the fused silica capillaries used in capillary electrophoresis is very limited. However, haemodialysis bicarbonate cartridges commonly used in human medicine containing polysulfone hollow fibres are available on the market and are used for the fabrication of coaxial microdialysis probes. The miniature probe design ensures that steady-state conditions are achieved during microdialysis of minimal volumes of body fluids.

RESULTS

A coaxial microdialysis probe with a length of 5 cm and an inner diameter of 200 μm is used for microdialysis of 10 μL of body fluid collected into a sampling fused silica capillary with an inner diameter 430 μm. Microdialysis is performed into 0.01 M HCl as a perfusate at stopped flow and 2 μL of the resulting microdialysate are subjected to analysis by capillary electrophoresis with contactless conductivity detection. Microdialysis pre-treatment is verified by analysis of 11 common amino acids at a 100 μM concentration level, resulting in recoveries of 98.3-102.5%. The electrophoretic separation of amino acids is performed in 8.5 M acetic acid at pH 1.37 as a background electrolyte with analysis time up to 4.5 min and LOD in the range of 0.12-0.28 μM. The reproducibility of the developed technique determined for the peak area ranges from 1.2 to 4.5%. Applicability is tested in the quantification of valine and leucine in plasma during fasting and subsequent reconvalescence.

SIGNIFICANCE

The fabrication of a coaxial microdialysis probe for the laboratory preparation of microliter volumes of various types of clinical samples is described, which is coupled off-line with capillary electrophoretic monitoring of amino acids in 2 μL volumes of microdialysate. The developed methodology is suitable for quantification of 20 amino acids in whole human blood, plasma, tears and has potential for analysis of dry blood spots captured on hollow fibre.

Design of a Facile Antifouling Sensor Based on the Synergy between an Antibody and Phase-Transited BSA

Nonspecific adsorption has always been a critical challenge for sensor detection; thus, an efficient and facile approach for fabricating antifouling sensors is highly desirable. Here, we developed an antifouling coating on sensor surfaces, conveniently made with a simple drip of phase-transited BSA (PTB) followed by a modification with a peanut allergen antibody, which unexpectedly provides synergistic antifouling properties in sensors. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface evenness. Optimizations in terms of PTB modification time and concentrations were performed using surface plasmon resonance by measuring protein resistance capabilities. Compared to bare Au surfaces, the PTB-modified surfaces exhibited low adsorption against BSA (<10 ng/cm2) and good resistance against lysozyme (Lyz). After immobilizing antibodies, the antifouling performance of the sensor coatings had an obvious enhancement, with almost no BSA adsorption and low lysozyme adsorption. The target recognition was also analyzed to verify the good sensing performance of the antifouling sensor. This understanding of antibody synergy provides suggestions for the development of antifouling sensors.

Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications-Updated and completely revised edition

This review is in support of the development of selective, precise, fast, and validated capillary electrophoresis (CE) methods. It follows up a similar article from 1998, Wätzig H, Degenhardt M, Kunkel A. "Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications," pointing out which fundamentals are still valid and at the same time showing the enormous achievements in the last 25 years. The structures of both reviews are widely similar, in order to facilitate their simultaneous use. Focusing on pharmaceutical and biological applications, the successful use of CE is now demonstrated by more than 600 carefully selected references. Many of those are recent reviews; therefore, a significant overview about the field is provided. There are extra sections about sample pretreatment related to CE and microchip CE, and a completely revised section about method development for protein analytes and biomolecules in general. The general strategies for method development are summed up with regard to selectivity, efficiency, precision, analysis time, limit of detection, sample pretreatment requirements, and validation.

Progress in on-line, at-line, and in-line coupling of sample treatment with capillary and microchip electrophoresis over the past 10 years: A review

The review presents an evaluation of the development of on-line, at-line and in-line sample treatment coupled with capillary and microchip electrophoresis over the last 10 years. In the first part, it describes different types of flow-gating interfaces (FGI) such as cross-FGI, coaxial-FGI, sheet-flow-FGI, and air-assisted-FGI and their fabrication using molding into polydimethylsiloxane and commercially available fittings. The second part deals with the coupling of capillary and microchip electrophoresis with microdialysis, solid-phase, liquid-phase, and membrane based extraction techniques. It mainly focuses on modern techniques such as extraction across supported liquid membrane, electroextraction, single drop microextraction, head space microextraction, and microdialysis with high spatial and temporal resolution. Finally, the design of sequential electrophoretic analysers and fabrication of SPE microcartridges with monolithic and molecularly imprinted polymeric sorbents are discussed. Applications include the monitoring of metabolites, neurotransmitters, peptides and proteins in body fluids and tissues to study processes in living organisms, as well as the monitoring of nutrients, minerals and waste compounds in food, natural and wastewater.

On-line dual-stage enrichment via magneto-extraction and electrokinetic preconcentration: A new concept and instrumentation for capillary electrophoresis

This study reports on the development of a new concept of on-line dual preconcentration stages for capillary electrophoresis (CE), in which two completely different preconcentration approaches can be realized in the same capillary. In the first stage, a dynamic magneto-extraction of target analytes on circulating magnetic beads is implemented within the capillary. In the second one, electrokinetic preconcentration of eluted analytes via large volume sample stacking is carried out to focus them into a nano band, prior to CE separation of enriched analytes. To implement the dual-stage preconcentration operation, a purpose-made instrument was designed, combining electrophoretic and microfluidic modules to allow precise control of the movement of magnetic beads and analyte's flow. The potential of this new enrichment principle and its associated instrument was demonstrated for CE separation with light-emitting-diode-induced fluorescent (LEDIF) detection of target double-stranded DNA (ds-DNA). The workflow consists of purification and preconcentration of a target DNA fragment (300 bp) on negatively charged magnetic beads, followed by in-capillary elution and fluorescent labelling of the enriched DNA. Large volume sample stacking of the DNA eluent was then triggered to further preconcentrate the labelled DNA before its analysis by CE-LEDIF. An enrichment factor of 125 was achieved for the target DNA fragment. With our new approach, dual-stage sample pretreatment and CE separation can now be performed in-capillary without any mismatch of working volumes, nor any waste of pretreated samples.

Determination of aflatoxin B1 by novel nanofiber-packed solid-phase extraction coupled with a high performance liquid chromatography-fluorescence detector

A novel analytical proposal based on nanofiber-packed solid-phase extraction coupled with high performance liquid chromatography-fluorescence detector (HPLC-FLD) has been successfully developed for determining aflatoxin B1 (AFB1) in foods. Four types of nanofibers, including polystyrene (PS) nanofibers, polypyrrole (PPY) nanofibers, polystyrene-acrylic resin (PS-AR) nanofibers, and polystyrene-polyvinyl pyrrolidone (PS-PVP) nanofibers, were fabricated by electrospinning and utilized to prepare a home-made extraction device. In this study, the factors of different fibers, namely, fiber dosage, pH of extraction solution, type of salt ion, concentration of salt ion, and volume of the eluent were optimized. Under optimized conditions, the method showed good linearity in the range of 0.1-40 ng mL^-1 with a correlation coefficient greater than 0.999 and good inter-day accuracy (90.8-112.7% recovery) and precision (1.8-3.6% intra-day RSDs, 2.6% inter-day RSD), and the limit of detection (LOD) was 0.05 ng mL^-1. Due to its cost-effective, time-saving, environmentally friendly, and simple performance, it has the potential to be utilized to determine aflatoxins in complicated matrices.

Aptamer affinity-based microextraction in-line coupled to capillary electrophoresis mass spectrometry using a porous layer/nanoparticle -modified open tubular column

An aptamer affinity based microextraction column is developed to be directly in-line coupled to capillary electrophoresis-mass spectrometry (CE-MS) for analyzing mycotoxins in food samples. Single-stranded DNA aptamers for selective recognition of aflatoxin B1 (AFB1) and ochratoxin A (OTA) targets are co-immobilized via covalent bonds on the surface of the inlet end of a capillary, which is pre-modified with three-dimensional porous layer and gold nanoparticles to enhance the specific surface area and loading capacity. The outlet of the capillary is designed as a porous tip to serve as the spray source for injection to the mass spectrometry. All the necessary processes for pretreatment and analysis of a sample are accomplished in one injection, including aptamer affinity-based microextraction, CE separation and MS detection of analytes. AFB1 and OTA are simultaneously determined in a wide linear range with sample consumption of only 1 μL and the limit-of-detection as low as 1 pg/mL. The microextraction column exhibits excellent repeatability and stability, which can be used over 45 runs within a month with CE separation efficiency and only MS intensity slightly decreased. Mycotoxins in three kinds of cereal based infant foods are accurately analyzed using the proposed method. The study provides a robust and universal approach that would have potential applications in a variety of analytical fields based on selective molecular recognition coupling to CE-MS analysis.

In capillary labeling and online electrophoretic separation of N-glycans from glycoproteins

In this study, we present a new approach for in-capillary fluorescent labeling of N-glycans prior to their analysis with CE coupled with laser-induced fluorescent detection. This integrated approach allows using a CE capillary as a microreactor to perform several steps required for labeling glycans with 8-aminopyrene-1,3,6 trisulfonic acid and at the same time as a separation channel for CE of fluorescently labeled glycans. This could be achieved through careful optimization of all different steps, including sequential injections of fluorescent dye and glycan plugs, mixing by transverse diffusion of laminar flow profiles, incubation in a thermostatic zone, and finally separation and detection with CE. Such a complex sample treatment protocol for glycan labeling that is feasible thus far only in batchwise mode can now be converted into an automated and integrated protocol. Our approach was applied successfully to analyze fluorescently labeled N-linked oligosaccharides released from human immunoglobulin G and rituximab, a monoclonal antibody used for cancer treatment. We demonstrated the superiority of this in-capillary approach over the conventional in-tube protocol, with fourfold less reagent consumption and full automation without remarkable degradation of the glycan separation profile obtained by capillary electrophoresis.

Deep Eutectic Solvents for Extraction and Preconcentration of Organic and Inorganic Species in Water and Food Samples: A Review

Deep eutectic solvents (DESs) have been developed as green solvents and these are capable as alternatives to conventional solvents used for the extraction of organic and inorganic species from food and water samples. The continuous generation of contaminated waste and increasing concern for the human health and environment have compelled the scientific community to investigate more ecological schemes. In this concern, the use of DESs have developed in one of the chief approach in the field of chemistry. These solvents have appeared as a capable substitute to conventional hazardous solvents and ionic liquids. The DESs has distinctive properties, easy preparation and components availability. It is not only used in scienctific fields but also used in quotidian life. There are many advantages of DESs in analytical chemistry, they are largely used for extraction and determination of inorganic and organic compounds from different samples. In previous a few years, several advanced researches have been focused on the separation and preconcentration of low level of pollutants using DESs as the extractants. This review summarizes the use of DESs in the separation and preconcentration of organic and inorganic species from water and food samples using various microextraction processes.

Ethanol-ammonium sulfate system based modified quick, easy, cheap, effective, rugged and safe method for the determination of four neonicotinoid pesticide and metabolite residues in two canned fruits

As the pesticide and its metabolite residues in processed fruits could become a significant route of human exposure. The work presented herein focuses on developing a feasible quick, easy, cheap, effective, rugged and safe method with improved extraction and cleanup system for the determination of imidacloprid, acetamiprid, thiamethoxam and clothianidin (metabolite of thiamethoxam) in canned fruits. The low toxic solvent ethanol was used to extract the analytes, and ammonium sulfate was used to promote the phase separation. Moreover, the carboxylated multi walled carbon nanotube was acted as the clean-up sorbent for removal of high solubility impurities. The proposed method was validated with fortified real samples at different concentration levels (20∼200 μg kg^-1 ). Recoveries obtained from three spiked levels (20, 50, 200 μg kg^-1 ) were ranged from 74.9% to 86.4% with relative standard deviations of the intra-day and inter-day in the range of 0.8 to 5.5% and 2.0 to 7.1%, respectively. Limit of detections were ranged from 0.2 to 0.5 μg kg^-1 and 0.2 to 0.6 μg kg^-1 for orange and peach, respectively. The results demonstrated that the proposed method could be considered appropriate, comparatively lower toxic for the analysis of neonicotinoid pesticide residues in canned fruit. This article is protected by copyright. All rights reserved.

Applications of capillary electrophoresis in the fields of environmental, pharmaceutical, clinical and food analysis (2019-2021)

So far, the potential of capillary electrophoresis (CE) in the application fields has been increasingly excavated due to the advantages of simple operation, short analysis time, high-resolution, less sample consumption and low cost. This review examines the implementations and advancements of CE in different application fields (environmental, pharmaceutical, clinical and food analysis) covering the literature from 2019 to 2021. In addition, ultrasmall sample injection volume (nanoliter range) and short optical path lead to relatively low concentration sensitivity of the most frequently used UV-absorption spectrophotometric detection, so the pretreatment technology being developed has been gradually utilized to overcome this problem. Despite the review is focused on the development of CE in the fields of environmental, pharmaceutical, clinical and food analysis, the new sample pretreatment techniques of microextraction and enrichment which fit excellently to CE in recent three years are also described briefly. This article is protected by copyright. All rights reserved.

Establishment and validation of an SIL-IS LC-MS/MS method for the determination of ibuprofen in human plasma and its pharmacokinetic study

In this work, we developed and validated a highly sensitive, rapid and stable LC-MS/MS method for the determination of ibuprofen in human plasma with ibuprofen-d3 as a stable isotopically labeled internal standard (SIL-IS). Human plasma samples were prepared by one-step protein precipitation. The chromatographic separation was achieved on a Poroshell 120 EC-C₁₈ (2.1 × 50 mm, 2.7 μm). Aqueous solution (containing 0.05% acetic acid and 5 mm NH₄ Ac) and methanol were selected as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in negative ion mode. Multiple reaction monitoring mode was used for quantification using target fragment ions m/z 205.0 → 161.1 for ibuprofen and m/z 208.0 → 164.0 for SIL-IS, respectively. This method exhibited a linear range of 0.05-36 μg/ml for ibuprofen with correlation coefficient >0.99. Mean recoveries of ibuprofen in human plasma ranged from 78.4 to 80.9%. The RSD of intra- and inter-day precision were both < 5%. The accuracy was between 88.2 and 103.67%. The matrix effect was negligible in human plasma, including lipidemia and hemolytic plasma. A simple, efficient and accurate LC-MS/MS method was successfully established and applied to a pharmacokinetic study in healthy Chinese volunteers after a single oral administration of ibuprofen granules.

Recent developments in capillary and microchip electroseparations of peptides (2019-mid 2021)

The review provides a comprehensive overview of developments and applications of high performance capillary and microchip electroseparation methods (zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography) for analysis, microscale isolation, and physicochemical characterization of peptides from 2019 up to approximately the middle of 2021. Advances in the investigation of electromigration properties of peptides and in the methodology of their analysis, such as sample preparation, sorption suppression, EOF control, and detection, are presented. New developments in the individual CE and CEC methods are demonstrated and several types of their applications are shown. They include qualitative and quantitative analysis, determination in complex biomatrices, monitoring of chemical and enzymatic reactions and physicochemical changes, amino acid, sequence, and chiral analyses, and peptide mapping of proteins. In addition, micropreparative separations and determination of significant physicochemical parameters of peptides by CE and CEC methods are described.

Facile and highly efficient three-phase single drop microextraction in-line coupled with capillary electrophoresis

A high-performance version of in-line, three-phase direct immersion-single drop microextraction (DI-SDME) coupled with capillary electrophoresis (CE) was demonstrated using a commercial CE instrument, and all the major and minor details were described to provide an easy-to-follow and user-friendly protocol. The excellent sample cleanup and enrichment power of this method was demonstrated with nonsteroidal anti-inflammatory drugs (NSAIDs) in human urine. The only preparation of urine samples was the addition of HCl to acidify the urine sample to pH 2. The acidic NSAIDs in the acidified urine sample were extracted into a basic acceptor drop covered with a thin organic layer attached to the inlet tip of a capillary immersed in the sample. A simple but powerful DI-SDME-CE method could be carried out automatically without any modification of the existing CE instrument. For improved performance, sample agitation and heating were employed by installing a microstirrer and a thermostating jacket in the sample tray. With 10 min of DI-SDME at 35°C with stirring, NSAIDs such as ketoprofen, ibuprofen, and naproxen in urine were enriched 340-970-fold with intraday and interday RSDs of 0.8-2.4% and 1.1-3.6%, respectively. The LODs obtained with in-line coupled CE/UV were 10-50 nM (2-10 µg/L). The performance of DI-SDME-CE/UV was also demonstrated by determining the naproxen level in human urine collected 24 h after taking a single oral dose of the drug. The spike recovery of naproxen from a single-point standard addition to the urine sample was 80%. Our high-performance three-phase DI-SDME-CE method is quite promising for the analysis of ionizable trace analytes in a complex sample matrix.

An ionic covalent organic framework for rapid extraction of polar organic acids from environmental waters

An ionic covalent organic framework (Fe₃O₄@EB-TFB-iCOF) as a polar adsorbent was synthesized and characterized. It was applied in the magnetic solid phase extraction (MSPE) of four polar organic acids, namely, 2-(2,4,5-trichlorophenoxy)propionic acid, 2-methyl-4-chlorophenoxy acetic acid, naphthyloxyacetic acid, and naphthylacetic acid. The organic acids were detected by high performance liquid chromatography-ultraviolet analysis (HPLC-UV). A method for the determination of organic acids based on MSPE-HPLC-UV was established. The method shows good linear regression (R²≥ 0.9950), high precision (1.53-3.80%, n = 6), and low detection limit (0.10-0.49 ng mL^-1). The recovery rate of environmental water samples ranges from 73.3% to 101.0%. This method provides a possibility for high sensitivity analysis of polar organic acids.

Recent Applications of Capillary Electrophoresis in the Determination of Active Compounds in Medicinal Plants and Pharmaceutical Formulations

The present review summarizes scientific reports from between 2010 and 2019 on the use of capillary electrophoresis to quantify active constituents (i.e., phenolic compounds, coumarins, protoberberines, curcuminoids, iridoid glycosides, alkaloids, triterpene acids) in medicinal plants and herbal formulations. The present literature review is founded on PRISMA guidelines and selection criteria were formulated on the basis of PICOS (Population, Intervention, Comparison, Outcome, Study type). The scrutiny reveals capillary electrophoresis with ultraviolet detection as the most frequently used capillary electromigration technique for the selective separation and quantification of bioactive compounds. For the purpose of improvement of resolution and sensitivity, other detection methods are used (including mass spectrometry), modifiers to the background electrolyte are introduced and different extraction as well as pre-concentration techniques are employed. In conclusion, capillary electrophoresis is a powerful tool and for given applications it is comparable to high performance liquid chromatography. Short time of execution, high efficiency, versatility in separation modes and low consumption of solvents and sample make capillary electrophoresis an attractive and eco-friendly alternative to more expensive methods for the quality control of drugs or raw plant material without any relevant decrease in sensitivity.

A Review of Analytical Methods for Codeine Determination

Codeine is derived from morphine, an opioid analgesic, and has weaker analgesic and sedative effects than the parent molecule. This weak opioid is commonly used in combination with other drugs for over-the-counter cough relief medication. Due to the psychoactive properties of opioid drugs, the easily obtained codeine often becomes subject to misuse. Codeine misuse has emerged as a concerning public health issue due to its associated adverse effects such as headache, nausea, vomiting, and hemorrhage. Thus, it is very important to develop reliable analytical techniques to detect codeine for both quality control of pharmaceutical formulations and identifying drug misuse in the community. This review aims to provide critical outlooks on analytical methods applicable to the determination of codeine.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Droplet-interfacing strategies in microscale electrophoresis for sample treatment, separation and quantification: A review

In this study, for the first time we report on a comprehensive overview of different strategies to hyphenate droplet-based sample handling and preparation with electrophoretic separation in different formats (i.e. microchip and capillary electrophoresis). Droplet-interfaced electrophoresis is an emerging technique in which micro/nanometric droplets are used as a bridge and carrier of target analytes between sample treatment and electrokinetic separation steps, thus being expected to overcome the challenges of working dimension mismatch and low degree of module integration. This review covers all works on this topic from 2006 (the year of the first communication) up to 2020, with focus being given to three principal interfacing strategies, including droplets in immiscible phases, digital microfluidics with electrowetting-on-dielectric principle and inkjet droplet generation. Different instrumental developments for such purpose, the viewpoints on pros and cons of these designs as well as application demonstrations of droplet-interfaced electrokinetic strategies are discussed.

Digital image colorimetry detection of carbaryl in food samples based on liquid phase microextraction coupled with a microfluidic thread-based analytical device

This research used a digital image colorimetry (DIC) method to detect carbaryl in food samples using effervescence-assisted liquid phase microextraction based on solidification of switchable hydrophilicity solvent combined with a microfluidic thread-based analytical device (EA-LPME-SSHS-μTAD). 1-naphthol, the hydrolysate of carbaryl, was extracted into octanoic acid by the adjustment of pH values of the sample solution and separated through solidification in an ice bath. Then 1-naphthol contained in the extracted solution was coupled with 4-methoxybenzenediazonlum tetrafluoroborate (MBDF) fixed on the μTAD to produce tangerine compounds. The inherent colour variation was captured by a smartphone and processed to calculate the intensity (I). Under the optimal conditions, the limit of quantification was within 0.020-0.027 mg kg^-1. The recovery was varied in the range from 92.3% to 105.9% with a relative standard deviation (RSD) below 5%. The developed method provides an alternative strategy to extract and detect pesticides for food samples.

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.