Sensitive determination of seven triazine herbicide in honey, tomato and environmental water samples by hollow fiber based liquid-liquid-liquid microextraction combined with sweeping micellar electrokinetic capillary chromatography

Insights into interaction of triazine herbicides with three kinds of different alkyl groups (simetryne, ametryn and terbutryn) with human serum albumin via multi-spectral analysis

In this study, the interaction of triazine herbicides with three kinds of different alkyl groups (simetryne, ametryn and terbutryn) with human serum albumin (HSA) are investigated through UV-vis, fluorescence, and circular dichroism (CD) spectra. The mechanisms on the fluorescence quenching of HSA initiated by triazine herbicides are obtained using Stern-Volmer, Lineweaver-Burk and Double logarithm equations. The quenching rate constant (Kq), Stern-Volmer quenching constant (Ksv), binding constant (KA), thermodynamic parameters such as enthalpy change (∆H), entropy change (∆S) and Gibbs free energy (∆G) and number of binding site (n) are calculated and compared. The variations in the microenvironment of amino acid residues are studied by synchronous fluorescence spectroscopy. The binding sites and subdomains are identified using warfarin and ibuprofen as site probes. The conformational changes of HSA are measured using CD spectra. The results reveal that the triazine herbicides with different alkyl groups can interact with HSA by static quenching. The combination of the three herbicides and HSA are equally proportional, and the binding processes are spontaneous. Hydrophobic interaction forces play important roles in simetryne-HSA and ametryn-HSA, while the interaction of terbutryn-HSA is Van der Waals forces and hydrogen bonding. Moreover, the three herbicides can bind to HSA at site I (sub-domain IIA) more than site II (subdomain IIIA), and combine with tryptophan (Trp) more easily than tyrosine (Tyr) residues, respectively. By comparison, the order of interaction strength is terbutryn-HSA > ametryn-HSA > simetryne-HSA. Terbutryn can destroy the secondary structure of HSA more than simetryne and ametryn, and the potential toxicity of terbutryn is higher. It is expected that the interactions of triazine herbicides with HSA via multi-spectral analysis can offer some valuable information for studying the toxicity and the harm of triazine herbicides on human health at molecular level in life science.

Two-step pressure injection-assisted online enrichment of herbicides from foods with affinity micelle sweeping by micellar electrokinetic chromatography

A novel online two-step pressure injection-assisted stacking preconcentration method, which involves sweeping and affinity micelles in micellar electrokinetic chromatography was developed to simultaneously measure various organic anions. The micellar solution was a mixed solution that contained 0.3 mM didodecyldimethylammonium bromide and 20 mM borax. After the micellar solution was injected for 60 s, the tested analytes prepared in 20 mM borax were introduced into the capillary for 150 s. The key experimental factors that influenced the separation and sensitivity were investigated and optimized, including the concentration and injection time of the micellar solution, the concentration of borax in the sample solution, the concentration of sodium dodecyl sulfate and borax in the background electrolyte (BGE), the content of acetonitrile in the BGE and the injection time of the sample solution. Compared with typical injection methods, this method achieved sensitivity enhancement factors ranging from 85 to 97 under optimized conditions. Good linearity for matrix-matched calibration was established for all analytes with R2 values of 0.9986-0.9996. The intraday (n = 6) and interday (n = 6) precisions of the method were less than 2.85% when expressed as relative standard deviations. When the method was applied to analyze rice and dried ginger samples, analyte recoveries ranged from 85.81% to 106.59%. Through sweeping and affinity micelles, stacking preconcentration method was successfully employed to analyze trace amounts of fenoprop and 2,4-dichlorophenoxyacetic acid in rice and dried ginger samples.

Simultaneous microextraction of pesticides from wastewater using optimized μSPEed and μQuEChERS techniques for food contamination analysis

Food contamination with pesticides poses significant risks to consumer safety and undermines confidence in food supply chains. Detecting pesticides in food samples is a challenging task that requires efficient extraction techniques. This study aims to compare and validate two microextraction techniques, μSPEed and μQuEChERS-dSPE, for the simultaneous extraction of eight pesticides (paraquat, thiabendazole, asulam, picloram, ametryn, atrazine, linuron, and cymoxanil) from wastewater samples. A good analytical performance was obtained for both methodologies, with selectivity, linearity in the range 0.5-150 mg L^-1 with coefficients of determination up to 0.9979, limits of detection (LODs) and limits of quantification (LOQs) ranging from 0.02 to 0.05 mg L^-1 and from 0.06 to 0.17 mg L^-1, respectively, precision below 14.7 mg L^-1, and recoveries from wastewater samples in the range of 66.1-99.9%. The developed methodologies are simpler, faster, and require less sample and solvent volumes than conventional methodologies, having a lower impact on the environment. Nevertheless, the μSPEed approach was found to be more efficient, easier to perform, and with a higher greener profile. This study highlights the potential of microextraction techniques for the analysis of pesticide residues in food and environmental samples. Overall, it presents a fast and efficient method for the analysis of pesticides in wastewater samples, which can be useful for monitoring and controlling pesticide contamination in the environment.

New Approaches in Electroanalytical Determination of Triazines-Based Pesticides in Natural Waters

This study describes the preparation and use of a dental amalgam electrode for the voltammetric determination of triazine-based pesticides ametryn, atrazine, and simazine in natural waters, using square wave voltammetry. The experimental and voltammetric parameters were previously optimized, and analytical curves were constructed to calculate analytical parameters. The detection limits presented values that were lower than the maximum limits of residues permitted in natural water by the Brazilian Environmental Agency, 100 µg L−1 (100 ppb), and around the values obtained using other electrodic surfaces or high-performance liquid chromatography, traditionally used in triazine levels determination. Furthermore, the recovery percentages in pure electrolyte and natural waters were around 100%, demonstrating that the methodology proposed is suitable for determining triazines contamination in natural water samples, based on an environmentally friendly procedure.

Pseudophase microextraction for in-line sample concentration in micellar electrokinetic chromatography

Pseudophase microextraction (PPME) as a simple in-line sample concentration technique in micellar electrokinetic chromatography (MEKC) is presented. In contrast to popular electric-field driven stacking techniques in MEKC such as sweeping, PPME is pressure-driven. The technique afforded up to 403-2968x improvements in peak heights for fenoprop, dichlorprop, 1- and 2-naphthol compared to typical injection. Under the same MEKC conditions, the improvements in PPME were up to 23-59x better compared to sweeping. Briefly in PPME, the entire capillary was loaded (up to 20 capillary volumes) with the sample prepared in a dilute solution of cetyltrimethylammonium bromide ([CTAB] > critical surface aggregation concentration). The CTAB formed aggregates at the inner capillary walls and these aggregates acted as a stationary chromatographic pseudophase. After clean-up via flushing the capillary with purified water, the MEKC background solution (BGS) with sodium dodecyl sulfate was then introduced by pressure from the outlet end to elute the retained analytes. The analytes concentrate at front of the BGS and the front was moved to the inlet end of the capillary prior to MEKC. Optimization strategies and current limitations in PPME-MEKC are described. The linear ranges using a 4 capillary volume sample load obtained for fenoprop, dichlorprop, 1- and 2-naphthol were between 1 and 160 ng/mL (r²s ≥ 0.996), LOQs = 1-2.5 ng/mL and repeatability %RSDs (n = 6) were ≤5% (intra-day) and ≤7% (inter-day) (using low analyte concentrations 1-5x LOQ). PPME-MEKC with simple dilution of fortified real samples (no off-line sample concentration) was also able to detect low levels of dichlorprop (10 ng/mL, limit set in Australia) and 1- and 2-naphthol (7.5-15 ng/mL) in a drinking water and natural water sample, respectively (% recovery = 84-108%). The concept of PPME may find use in other modes of capillary electrophoresis and other nano-microscale separations.

In-syringe temperature-controlled liquid-liquid microextraction based on solidified floating ionic liquid for the simultaneous determination of triazine and phenylurea pesticide in vegetable protein drinks

A novel in-syringe temperature-controlled liquid-liquid microextraction based on solidified floating ionic liquid (in-syringe TC-LLME-SFIL) combined with high performance liquid chromatography was developed for the simultaneous determination of monuron, chlorotoluron, atrazine, monolinuron, propazine and prometryn in commercial vegetable protein drinks. The samples were deproteinized by trichloroacetic acid and further cleaned up by solid phase extraction column. The ionic liquid tributyldodecylphosphonium tetrafluoroborate ([P_{4 4 4 12}]BF₄) was used as extraction solvent and dispersed into the depurated sample solution to form fine droplets with the assistance of heating and vortex. With the help of an ice bath, the ionic liquid phase solidified and floated on the surface of aqueous phase. After separation from the aqueous phase, the solidified ionic liquids were dissolved with acetonitrile and the resulting solution was analyzed by high performance liquid chromatography. Some extraction parameters, including type and amount of adsorbent, type and amount of ionic liquids, amount of NaCl, melting temperature and time of ionic liquid, vortex time, pH of sample solution, ice bath temperature and time, were investigated and optimized by single-factor experiment, Plackett-Burman design and Box-Behnken design. The results showed that good linearities (r ≥ 0.9994) were obtained in the concentration range of 7.8-1000.0 μg/L. The limits of detection and quantification were in the range of 0.25-2.59 μg/L and 0.82-8.63 μg/L, respectively. The spiked recoveries were 81.26-118.42% with the relative standard deviation (RSD, n = 3) lower than 8.17%. The present method was successfully applied to the simultaneous determination of triazine and phenylurea herbicides in vegetable protein drinks.

New Trend in the Extraction of Pesticides from the Environmental and Food Samples Applying Microextraction Based Green Chemistry Scenario: A Review

This review focused on the green microextraction methods used for the extraction of pesticides from the environmental and food samples. Microextraction techniques have been explored and applied in various fields of analytical chemistry since its beginning, as evinced by the numerous reviews published. The success of any technique in science and technology is measured by the simplicity, environmentally friendly, and its applications; and the microextraction technique is highly successive. Deliberations were attentive to studies where efforts have been made to validate the methods through the inter-laboratory comparison study to assess the analytical performance of microextraction techniques against conventional methods. Succinctly, developed microextraction methods are shown to impart significant benefits over conventional techniques. Provided that the analytical community continues to put forward attention and resources into the growth and validation of the microextraction technique, a promising future for microextraction is forecasted.

Supramolecular solvent-based micro-extraction of pesticides in food and environmental samples

Supramolecular solvent-based micro-extraction is a very important green technique for the isolation and pre-concentration of pesticide residues in food and environmental samples prior to their chromatographic analysis. The attractive features of supramolecular solvent-based micro-extraction include its simplicity, high pre-concentration factor, fastness, accuracy, low cost, less consumption of chemical reagents and environmental friendliness. The supramolecular solvent is generated from a ternary mixture of amphiphiles, water and a water miscible dispersion and coacervating solvent. Tehydrofuran is one of the solvents commonly used as both a dispersion solvent and a coacervating agent. This paper gives a recent comprehensive review on the application of alkanols as amphiphiles during supramolecular solvent-based micro-extraction of pesticide residues in food and environmental samples. Other researchers used long chain fatty acids as amphiphiles during pesticide analysis in food and environmental samples using supramolecular solvent-based micro-extraction, and this is discussed in this paper. The incorporation of ferrofluids in supramolecular solvents enables phase separation using a magnet instead of the time-consuming centrifugation technique. This paper also gives a detailed review of the application of ferrofluid-based supramolecular solvent micro-extraction of pesticide residues in food and environmental samples.

Miniaturized sample preparation techniques and ambient mass spectrometry as approaches for food residue analysis

Analytical methods such as liquid chromatography (LC) and mass spectrometry (MS) are widely used techniques for the analyses of different classes of compounds. This is due to their highlighted capacity for separating and identifying components in complex matrices such food samples. However, in most cases, effective analysis of the target analyte becomes challenging due to the complexity of the sample, especially for quantification of trace concentrations. In this case, miniaturized sample preparation methods have been used as a strategy for analysis of complex matrices. This involves removing the interferents and concentrating the analytes in a sample. These methods combine simplicity and effectiveness and given their miniaturized scale, they are in accordance with green chemistry precepts. Besides, ambient mass spectrometry represents a new trend in fast and rapid analyses, especially for qualitative and screening analysis. However, for complex matrix analyses, sample preparation is still a difficult step and the miniaturized sample preparation techniques show great potential for an improved and widespread use of ambient mass spectrometry techniques. . This review aims to contribute as an overview of current miniaturized sample preparation techniques and ambient mass spectrometry methods as different approaches for selective and sensitive analysis of residues in food samples.

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - A review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.

Titanium dioxide nanotubes with triazine-methacrylate monomer to improve physicochemical and biological properties of adhesives

OBJECTIVE

Formulate experimental adhesives containing titanium dioxide nanotubes (nt-TiO₂) or titanium dioxide nanotubes with a triazine-methacrylate monomer (nt-TiO₂:TAT) and evaluate the effect of these fillers on the physical, chemical, and biological properties of the adhesives.

METHODS

First, nt-TiO₂ were synthesized via a hydrothermal method. The nt-TiO₂ were mixed with a triazine-methacrylate monomer (TAT) to formulate nt-TiO₂:TAT, which were characterized by transmission electron microscopy (TEM). The nt-TiO₂, TAT, and nt-TiO₂:TAT were evaluated via Fourier Transform Infrared, Ultraviolet-visible, and micro-Raman spectroscopies. An experimental adhesive resin was formulated with bisphenol A glycerolate dimethacrylates, 2-hydroxyethyl methacrylate, and photoinitiator/co-initiator system. nt-TiO₂ or nt-TiO₂:TAT were incorporated at 2.5 wt.% and 5 wt.% in the adhesive. The base resin without nt-TiO₂ or nt-TiO₂:TAT was used as a control group. The adhesives were evaluated for antibacterial activity, cytotoxicity, polymerization kinetics, degree of conversion (DC), Knoop hardness, softening in solvent (ΔKHN%), ultimate tensile strength (UTS), 24 h- and 1 year- microtensile bond strength (μ-TBS).

RESULTS

TEM confirmed the nanotubular morphology of TiO₂. FTIR, UV-vis, and micro-Raman analyses showed the characteristic peaks of each material, indicating the impregnation of TAT in the nt-TiO₂. Adhesives with nt-TiO₂:TAT showed antimicrobial activity against biofilm formation compared to control (p < 0.05), without differences in the viability of planktonic bacteria (p > 0.05). All groups showed high percentages of pulp cell viability. The polymerization kinetics varied among groups, but all presented DC above 50%. The addition of 5 wt.% of nt-TiO₂ and both groups containing nt-TiO₂:TAT showed higher values ​​of Knoop hardness compared to the control (p < 0.05). The groups with nt-TiO₂:TAT presented lower ΔKHN% (p < 0.05) and higher UTS (p < 0.05) than the control group. After one year, the group with 5 wt.% of nt-TiO₂, as well as both groups containing nt-TiO₂:TAT, showed higher μ-TBS than the control (p < 0.05).

SIGNIFICANCE

The mixing of a triazine-methacrylate monomer with the nt-TiO₂ generated a filler that improved the physicochemical properties of the adhesive resins and provided antibacterial activity, which could assist in preventing carious lesions around tooth-resin interfaces. The set of physical, chemical, and biological properties of the formulated polymer, together with the greater stability of the bond strength over time, make nt-TiO₂:TAT a promising filler for dental adhesive resins.

Applications of Hollow-Fiber and Related Microextraction Techniques for the Determination of Pesticides in Environmental and Food Samples—A Mini Review

Pesticides represent one of the most important groups of analytes in environmental analysis. Moreover, their levels are very frequently determined in food and beverages due to the concern over their possible adverse health effects. Their concentration in samples is usually very low; thus, they have to be preconcentrated. Conventional solvent and solid-phase extractions are mainly used for this purpose, but miniaturized approaches are also being applied more and more often. The present review covers solvent microextractions that use a semi-permeable membrane barrier between the sample and the solvent. The main representatives of this approach are hollow-fiber microextraction (HFME), solvent bar microextraction (SBME), electromembrane extraction (EME), and different variations of those, such as combinations with other sorbent or solvent microextractions, electromigration, etc. The relevant research from the last decade, dealing with the application of these microextractions to the isolation of pesticides from various environmental and food samples, is critically discussed with emphasis on their strengths and weak points.

Analytical methods to analyze pesticides and herbicides

Presented in this paper is an annual review of literatures published in 2018 on topics relating to analytical methods for pesticides and herbicides. According to the different techniques, this review is divided into six sections, including extraction methods; chromatographic or mass spectrometric techniques; electrochemical techniques; spectrophotometric techniques; chemiluminescence and fluorescence methods; and biochemical assays. PRACTITIONER POINTS: Totally 134 relevant research articles are summarized. The review is divided into six parts according to the techniques. Chromatographic and mass spectrometric methods are the most widely used.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016-2018)

One of the most cited limitations of capillary and microchip electrophoresis is the poor sensitivity. This review continues to update this series of biannual reviews, first published in Electrophoresis in 2007, on developments in the field of online/in-line concentration methods in capillaries and microchips, covering the period July 2016-June 2018. It includes developments in the field of stacking, covering all methods from field-amplified sample stacking and large-volume sample stacking, through to isotachophoresis, dynamic pH junction, and sweeping. Attention is also given to online or in-line extraction methods that have been used for electrophoresis.