Screening determination of food additives using capillary electrophoresis coupled with contactless conductivity detection: A case study in Vietnam

Efficient separation of organic anions in beverages using aminosilane-functionalized capillary electrophoresis with contactless conductivity detection

BACKGROUND

Capillary electrophoresis (CE) has the advantage of rapid anion analysis, when employing a reverse electroosmotic flow (EOF). The conventional CE method utilizes dynamic coatings with surfactants like cetyltrimethylammonium bromide (CTAB) in the run buffer to reverse the EOF. However, this method suffers from very slow equilibration leading to drifting effective migration times of the analyte anions, which adversely affects the identification and quantification of peaks. Permanent coating of the capillary surface may obviate this problem but has been relatively little explored. Thus, permanent capillary surface modification by the covalent binding of 3-aminopropyltriethoxysilane (APTES) was studied as an alternative.

RESULTS

This study investigates the effect of APTES concentration for surface functionalization on EOF mobility, separation efficiency, and reproducibility of anion separation. The performance data was complemented by X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The XPS measurements showed that the coverage with APTES was dependent on its concentration in the coating solution. The XPS measurements correlated well with the EOF values determined for the capillaries tested. A standard mixture of 21 anions could be baseline separated within 10 min in the capillaries with lower EOF, but not in the capillary with the highest EOF as the residence time of the analytes was too short in this case. Compared to conventional dynamic coating with CTAB, APTES-functionalized capillaries provide faster equilibration and long-term EOF stability. The application of APTES-functionalized capillaries in analyzing different beverages demonstrates the precision, reliability, and specificity in determining organic anions, providing valuable insights of their compositions.

SIGNIFICANCE

APTES coating on capillaries provides a facile approach to achieve a permanent reversal of the stable EOF to determine anions. The control of the coverage via the concentration of the reagent solution allows the tailoring of the EOF to different needs, a faster EOF for less complex samples where resolution is not challenging, while a lower EOF for higher complex samples where the focus is on separation efficiency. This enhancement in efficiency and sensitivity has been applied to analyzing organic acids in several beverages.

Green Analytical Method for Simultaneous Determination of Glucosamine and Calcium in Dietary Supplements by Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection

The need for analytical methods that are fast, affordable, and ecologically friendly is expanding. Because of its low solvent consumption, minimal waste production, and speedy analysis, capillary electrophoresis is considered a "green" choice among analytical separation methods. With these "green" features, we have utilized the capillary electrophoresis method with capacitively coupled contactless conductivity detection (CE-C⁴D) to simultaneously determine glucosamine and Ca²⁺ in dietary supplements. The CE analysis was performed in fused silica capillaries (50 μm inner diameter, 40 cm total length, 30 cm effective length), and the analytical time was around 5 min. After optimization, the CE conditions for selective determination of glucosamine and Ca²⁺ were obtained, including a 10 mM tris (hydroxymethyl) aminomethane/acetic acid (Tris/Ace) buffer of pH 5.0 as the background electrolyte; separation voltage of 20 kV; and hydrodynamic injection (siphoning) at 25 cm height for 30 s. The method illustrated good linearity over the concentration range of 5.00 to 200 mg/L of for glucosamine (R ² = 0.9994) and 1.00 to 100 mg/L for Ca²⁺ (R ² = 0.9994). Under the optimum conditions, the detection limit of glucosamine was 1.00 mg/L, while that of Ca²⁺ was 0.05 mg/L. The validated method successfully analyzed glucosamine and Ca²⁺ in seven dietary supplement samples. The measured concentrations were generally in line with the values of label claims and with cross-checking data from reference methods (HPLC and ICP-OES).

Ultrahigh-Sensitivity Capillary Electrophoresis Analysis of Trace Amounts of Nitrate and Nitrite in Environmental Water Samples

The role of nitrite (NO2−) and nitrate (NO3−) is essential in the global nitrogen cycle. Monitoring their concentration in environmental and industrial aqueous samples, surface water, soil, food and agricultural products are of high importance. Especially, the effect of anthropogenic emission, i.e., intensified agriculture is essential due to the overuse of nitrogen, phosphorus and potassium fertilizers. The most widely utilized methods for nitrate and nitrite determination are colorimetry, potentiometry, UV absorption and liquid chromatography. Among them, UV spectroscopy is the most frequently used technique due to the fact of its versatility and simplicity. However, there are industrial and academic needs to develop new methods to overcome some drawbacks of the currently used techniques such as an inadequate limit of detection and potential interferences with organic compounds in the sample. In this paper, we report on the development of a new analytical method based on capillary electrophoresis separation with high-sensitivity UV detection, capable of measuring trace concentrations of nitrite and nitrate well below the current limits of UV spectroscopy methods. During the development process special attention was paid to practical aspects, i.e., the method was tested to quantify nitrate and nitrite in various surface water samples.

Simultaneous determination of vitamin B6 and magnesium using capillary electrophoresis coupled with contactless conductivity detection: Method development, validation, and application to pharmaceutical and nutraceutical samples

Vitamins and minerals are usually incorporated in pharmaceutical and nutraceutical products, but a simple, rapid, and inexpensive analytical method for their simultaneous determination is still lacking. In this study, we developed a quantification method for pyridoxine (vitamin B₆) and magnesium (Mg) by using purpose-made capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D) instrument. Main analytical conditions include: fused silica capillary (total length 55 cm, effective length 40 cm, inner diameter 50 μm); background electrolyte consisted of 10 mM L-arginine/acetic acid (pH 5) with 20% acetonitrile; separation voltage + 20 kV; hydrodynamic injection (siphoning at 20 cm in 25 s). Detection limits of vitamin B₆ and Mg were 1 and 0.1 mg/L, respectively. Good linearity (R² > 0.999) was observed for vitamin B₆ and Mg calibration curves over concentration ranges of 3-100 and 0.3-200 mg/L, respectively. The method was applied to analyze vitamin B₆ and Mg in several pharmaceutical and nutraceutical samples. The analytical results obtained by our method were in good agreement with reference methods (i.e., HPLC for vitamin B₆ and ICP-OES for Mg). High-efficient and low-cost CE-C⁴D method can accordingly serve as a promising tool for concurrent analysis of inorganic and organic species in pharmaceutical and nutraceutical analysis.

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.

Capillary and microchip electrophoresis with contactless conductivity detection for analysis of foodstuffs and beverages

The paper provides a comprehensive survey of the use of capillary and microchip electrophoresis in combination with contactless conductivity detection (C⁴D) for the analysis of drinking water, beverages and foodstuffs. The introduction sets forth the fundamentals of conductivity detection anddescribes an axialC⁴Dversion. There is also a detailed discussion of the determination of inorganic ions, organic acids, fatty acids, amino acids, amines, carbohydrates, foreign substances and poisons from the standpoint of separation conditions, sample treatment and detection limits. Special attention is paid to the analysis of foodstuffs at microchips with emphasis on the employed material and connection of the microchip with the C⁴D. The review attempts to draw attention to modern trends, such as dual-opposite injection, field-enhanced sample injection, electromembrane extraction and on-line combination of microdialysis with CE. CE/C⁴D is characterised by high universality, high speed of analysis, simple sample preparation, small consumption of sample and other chemicals.

Analytical Methods for Determination of Non-Nutritive Sweeteners in Foodstuffs

Sweeteners have been used in food for centuries to increase both taste and appearance. However, the consumption of sweeteners, mainly sugars, has an adverse effect on human health when consumed in excessive doses for a certain period, including alteration in gut microbiota, obesity, and diabetes. Therefore, the application of non-nutritive sweeteners in foodstuffs has risen dramatically in the last decade to substitute sugars. These sweeteners are commonly recognized as high-intensity sweeteners because, in a lower amount, they could achieve the same sweetness of sugar. Regulatory authorities and supervisory agencies around the globe have established the maximum amount of these high-intensity sweeteners used in food products. While the regulation is getting tighter on the market to ensure food safety, reliable analytical methods are required to assist the surveillance in monitoring the use of high-intensity sweeteners. Hence, it is also necessary to comprehend the most appropriate method for rapid and effective analyses applied for quality control in food industries, surveillance and monitoring on the market, etc. Apart from various analytical methods discussed here, extraction techniques, as an essential step of sample preparation, are also highlighted. The proper procedure, efficiency, and the use of solvents are discussed in this review to assist in selecting a suitable extraction method for a food matrix. Single- and multianalyte analyses of sweeteners are also described, employing various regular techniques, such as HPLC, and advanced techniques. Furthermore, to support on-site surveillance of sweeteners’ usage in food products on the market, non-destructive analytical methods that provide practical, fast, and relatively low-cost analysis are widely implemented.

Intelligent evaluation of taste constituents and polyphenols-to-amino acids ratio in matcha tea powder using near infrared spectroscopy

Matcha tea is rich in taste and bioactive constituents, quality evaluation of matcha tea is important to ensure flavor and efficacy. Near-infrared spectroscopy (NIR) in combination with variable selection algorithms was proposed as a fast and non-destructive method for the quality evaluation of matcha tea. Total polyphenols (TP), free amino acids (FAA), and polyphenols-to-amino acids ratio (TP/FAA) were assessed as the taste quality indicators. Successive projections algorithm (SPA), genetic algorithm (GA), and simulated annealing (SA) were subsequently developed from the synergy interval partial least squares (SiPLS). The overall results revealed that SiPLS-SPA and SiPLS-SA models combined with NIR exhibited higher predictive capabilities for the effective determination of TP, FAA and TP/FAA with correlation coefficient in the prediction set (R_p) of R_p > 0.97, R_p > 0.98 and R_p > 0.98 respectively. Therefore, this simple and efficient technique could be practically exploited for tea quality control assessment.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Research of mechanisms of transformation and removal of antibiotics from wine by sorbents of different nature

On the basis of own research, the authors experimentally confirmed the reliability of the hypothesis expressed in the scientific literature about the possibility of effective removal of nisin and natamycin from wines and wine materials. New knowledge has been obtained about the possible mechanisms of sorption of nisin and natamycin through the use of sorbents of various nature. Comparative experimental data on the interaction of sorbents with antibiotics in wines are presented. In this work, experimental data are presented that indicate different efficiency of antibiotic removal during wine processing, which is due to the structure and properties of sorbents. It has been shown that the sorption capacity of sorbents for natamycin and nisin decreases in the series: activated carbon, bentonite, and colloidal silicon dioxide. Mathematical models have been obtained for decontamination of antibiotics from wine production using sorbents of various nature.

Detection of food spoilage and adulteration by novel nanomaterial-based sensors

Food industry is always looking for more innovative and accurate ways to monitor the food safety and quality control of final products. Current detection techniques of analytes are costly and time-consuming, and occasionally require professional experts and specialized tools. The usage of nanomaterials in sensory systems has eliminated not only these drawbacks but also has advantages such as higher sensitivity and selectivity. This article first presents a general overview of the current studies conducted on the detection of spoilage and adulteration in foods from 2015 to 2020. Then, the sensory properties of nanomaterials including metal and magnetic nanoparticles, carbon nanostructures (nanotubes, graphene and its derivatives, and nanofibers), nanowires, and electrospun nanofibers are presented. The latest investigations and advancements in the application of nanomaterial-based sensors in detecting spoilage (food spoilage pathogens, toxins, pH changes, and gases) and adulterants (food additives, glucose, melamine, and urea) have also been discussed in the following sections. To conclude, these sensors can be applied in the smart packaging of food products to meet the demand of consumers in the new era.

Modular instrumentation for capillary electrophoresis with laser induced fluorescence detection using plug-and-play microfluidic, electrophoretic and optic modules

This study reports on the development of a novel instrument for capillary electrophoresis (CE) coupled with laser induced fluorescence (LIF) detection that is inspired by the Lego-toy concept. The Lego CE-LIF design is an evolution of purpose-made CE instrumentation, allowing the users to construct their own analytical device with a high degree of standardization (i.e. a "standard" setup) without requirement of mechanical and electronic workshop facilities. To allow instrument reproduction outside the original fabrication laboratory, which is not trivial for in-house-built CE systems, the new design is based on unprecedent 'plugging' hyphenation of various off-the-shelf parts available for microfluidics, optics and electrophoresis. To render the operation with Lego CE-LIF optimal, we developed a new background electrolyte (BGE), using for the first time extremely high concentrations of zwitterionic and large weakly charged species for much improvement of detection sensitivity. The Lego CE-LIF was demonstrated for separation and detection of oligosaccharides labelled with 8-aminopyrene-1,3,6-trisulfonic acid (APTS). The new gel-free BGE for oligosaccharide analysis also allowed simplification of the conventional CE-LIF protocol used with commercial instruments while keeping satisfactory separation performances. Furthermore, the new BGE is fully compatible with a non-thermostatted Lego CE instrument thanks to low current and therefore low heat generation under application of a high voltage.

Application of Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection (CE-C4D): 2017-2020

Capacitively coupled contactless conductivity detection (C⁴D) has emerged as influential to detect analytes that do not have chromogenic or fluorogenic functional group. Since our last review several new capillary electrophoresis (CE) methods coupled with (CE-C⁴D) have been communicated. The aim of this review is to give an update of the almost all the new applications of CE-C⁴D in the field of pharmaceutical, food and biomedical analysis covering the period from 2017 to April 2020. The utilization of CE with C⁴D in the areas of pharmaceutical, food and biomedical analysis is presented. Finally, concluding remarks and outlooks are discussed.

A simple and highly sensitive masking fluorescence detection system for capillary array electrophoresis and its application to food and medicine analysis

A high sampling rate, good stability, high throughput masking fluorescence detection system with easy positioning of each channel for capillary array electrophoresis was prepared and studied. A special mask combined with convex lenses was designed to modulate signals, without using any extra device to position each channel. The signal of each channel was detected by a photomultiplier tube, classified and saved by software. The design was used to evidently reduce the rotational vibration of optical components and to stabilize the system, so a high sampling rate was obtained by increasing the DC motor speed. To improve the optical system, optical fibers instead of conventional bulky optical components were used to transmit optical signal and to collect fluorescences in multiple directions, which greatly raised the sensitivity. Other important parameters including sampling rate, rotating speed and driven voltage laser diode (LDs) have also been investigated. Under optimal conditions, the performance of the detection system was evaluated. This novel system had a well-designed structure, and allowed independent multiple capillary operations and easy microanalysis. Its limit of detection for rhodamine 6G was 2.0 × 10^-2 µg/mL.

Recent Advances and Perspectives of Molecularly Imprinted Polymer-Based Fluorescent Sensors in Food and Environment Analysis

Molecular imprinting technology (MIT), also known as molecular template technology, is a new technology involving material chemistry, polymer chemistry, biochemistry, and other multi-disciplinary approaches. This technology is used to realize the unique recognition ability of three-dimensional crosslinked polymers, called the molecularly imprinted polymers (MIPs). MIPs demonstrate a wide range of applicability, good plasticity, stability, and high selectivity, and their internal recognition sites can be selectively combined with template molecules to achieve selective recognition. A molecularly imprinted fluorescence sensor (MIFs) incorporates fluorescent materials (fluorescein or fluorescent nanoparticles) into a molecularly imprinted polymer synthesis system and transforms the binding sites between target molecules and molecularly imprinted materials into readable fluorescence signals. This sensor demonstrates the advantages of high sensitivity and selectivity of fluorescence detection. Molecularly imprinted materials demonstrate considerable research significance and broad application prospects. They are a research hotspot in the field of food and environment safety sensing analysis. In this study, the progress in the construction and application of MIFs was reviewed with emphasis on the preparation principle, detection methods, and molecular recognition mechanism. The applications of MIFs in food and environment safety detection in recent years were summarized, and the research trends and development prospects of MIFs were discussed.

Greenwash and Green Purchase Intention: The Mediating Role of Green Skepticism

Along with the acceleration of green marketing in recent years, greenwash has been utilized by firms to get ahead of their rivals. Underpinned by the cognition–affect–behavior (C-A-B) paradigm, this study examines a model linking greenwash and green skepticism with green purchase intentions. It also investigates the moderating role of information and knowledge on the relationship between greenwash and green purchase intentions. Data were obtained from 419 Vietnamese consumers who had been involved in purchasing green vegetables using an online survey. Multivariate data analysis demonstrated that greenwash was negatively associated with green purchase intentions and that green skepticism mediated this negative association. In addition, the moderating effect of information and knowledge was confirmed. These findings enrich the extant knowledge on the relationship between greenwash and green purchase intentions. They also have important implications for firms that aim to reduce consumers’ skepticism and increase their intentions to purchase green food.

Dual-channeled capillary electrophoresis coupled with contactless conductivity detection for rapid determination of choline and taurine in energy drinks and dietary supplements

In this study is reported a simple and inexpensive method for concurrent determination of taurine and choline in different supplementary nutrient samples using dual-channeled capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C⁴D). The objective of the work is to propose a tool for food control activities that allows screening of different target compounds (having different characteristics) in a single run for high throughput and can be realizable even with modest infrastructure. Taurine was analyzed in the first CE channel using the background electrolyte (BGE) composed of 150 mM tris(hydroxymethyl)aminomethane/lactic acid (pH 8.96) whereas choline was simultaneously separated in the second CE channel using a BGE containing 150 mM tris(hydroxymethyl)aminomethane/acetic acid (pH 9.5). The best achieved detection limit was 0.27 mg/L and 0.45 mg/L for taurine and choline, respectively, using the developed CE-C⁴D method. Good agreement between results obtained from CE-C⁴D and those with the standard confirmation methods (HPLC-DAD for taurine and LC/MS for choline) was achieved, with the result deviation for the two pairs of data being less than 12%.

Contactless conductivity detection for analytical techniques: Developments from 2016 to 2018

The publications concerning capacitively coupled contactless conductivity detection for the 2-year period from mid-2016 to mid-2018 are covered in this update to the earlier reviews of the series. Relatively few reports on fundamental investigations or new designs have appeared in the literature in this time interval, but the development of new applications with the detection method has continued strongly. Most often, contactless conductivity measurements have been employed for the detection of inorganic or small organic ions in conventional capillary electrophoresis, less often in microchip electrophoresis. A number of other uses, such as detection in chromatography or the gauging of bubbles in streams have also been reported.

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high-voltage

An improved method for the concurrent determination and separation of cations and anions by microchip electrophoresis with capacitively coupled contactless conductivity detection (ME-C4 D) is described. Two kinds of microchip structures were designed. The first microchip has a long bent separation channel. And for the defects of the first microchip, the second microchip with a Y-type separation channel has been proposed. The background electrolyte (BGE) composed of 20 mm His/MES and 0.01 mm CTAB was optimized for inhibiting the electroosmotic flow (EOF). Due to the low electroosmotic flow, the cations and anions migrate in opposite directions and can be separated from each other. With the precisely controlled high-voltage, cations and anions can be migrated in microchannels according to our requirements and sequentially detected by a C4 D detector built in-house. Samples containing K+ , Na+ , Li+ , Cl- , F- and PO43- were analyzed simultaneously in a single run (within 140 s) by both methods. The reproducibility obtained by both methods remained below 5% for migration time and within 3.5-9.1% for peak areas. The proposed concurrent determination methods are inexpensive, simple, fast, ease of operation, high degree of integration.

Recent advances in the application of capillary electromigration methods for food analysis and Foodomics

This review work presents and discusses the main applications of capillary electromigration methods in food analysis and Foodomics. Papers that were published during the period February 2015-February 2017 are included following the previous review by Acunha et al. (Electrophoresis 2016, 37, 111-141). The paper shows the large variety of food related molecules that have been analyzed by CE including amino acids, biogenic amines, carbohydrates, chiral compounds, contaminants, DNAs, food additives, heterocyclic amines, lipids, peptides, pesticides, phenols, pigments, polyphenols, proteins, residues, toxins, vitamins, small organic and inorganic compounds, as well as other minor compounds. This work describes the last results on food quality and safety, nutritional value, storage, bioactivity, as well as uses of CE for monitoring food interactions and food processing including recent microchips developments and new applications of CE in Foodomics.