Green, fast and simple dispersive liquid-liquid microextraction method by using hydrophobic deep eutectic solvent for analysis of folic acid in fortified flour samples before liquid chromatography determination

An efficient deep eutectic magnetic nano gel for rapid ultrasound-assisted dispersive µ-solid phase extraction of residue of tetracyclines in food samples

In the present study, a magnetic nano gel as the sorbent which is the combination of octatonic acid: cumarin as eutectic solvent and Fe3O4@SiO2 was introduced as the sorbent in ultrasound-assisted dispersive µ-solid phase extraction process coupled with high performance liquid chromatography with photo diode array detector for simultaneous separation and determination of tetracyclines residues in food samples. FT-IR, SEM, VSM were used for the characterization of the synthetized magnetic nano gel. Under obtained optimum conditions, the obtained linear ranges were 1.5-500 (µg L-1), 2.5-750 (µg L-1), 2-750 (µg L-1), and 2.5-500 (µg L-1) for tetracycline, oxytetracycline, chlortetracycline, and doxycycline, respectively. Moreover, the below level of quantification (BLQ) (based on S/N = 3) of 0.47 µg L-1, 0.11 µg L-1, 0.85 µg L-1, 0.66 µg L-1, 0.81 µg L-1 and the limit of quantification (based on S/N = 10) of 1.61, 2.74, 2.23 (µg L-1), and 2.66 were achieved for tetracycline, oxytetracycline, chlortetracycline, and doxycycline, respectively. The intra-day and inter-day precision (%) of the procedure were less than 3.2 and 3.8, respectively. The recoveries over 95% confirmed high sufficiency of the proposed method for application in complex matrices such as honey, milk, and egg.

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Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05798-w.

Quantitative determination of bromochloroacetamide in mice urine by gas chromatography combined with salting-out assisted dispersive liquid-liquid microextraction

Bromochloroacetamide (BCAcAm) is the main haloacetamide (HAcAm) detected in drinking water in different regions and exhibits strong cytotoxicity and genotoxicity. However, there is no appropriate method for detecting BCAcAm in urine or other biological samples, and thus, the internal exposure level in the population cannot be accurately assessed. In this study, a gas chromatography-electron capture detector (GC-ECD) was combined with salting-out assisted dispersive liquid-liquid microextraction (SA-DLLME) to develop a rapid and robust method for BCAcAm detection in urine of mice continuously exposed to BCAcAm. The factors influencing the pre-treatment procedure, including the type and volume of extraction and disperser solvents, extraction and standing time, and the amount of salt, were evaluated systematically. Under the optimised conditions, the analyte achieved good linearity in the spiked concentration range of 1.00-400.00 μg L^-1, and the correlation coefficient was higher than 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 μg L^-1 and 0.50 μg L^-1, respectively. The recoveries ranged from 84.20% to 92.17%. The detection of BCAcAm at three different calibration levels using this method afforded an intra-day precision of 1.95-4.29%, while the inter-day precision range was 5.54-9.82% (n = 6). This method has been successfully applied to monitor the concentration of BCAcAm in mouse urine in toxicity experiments and can provide technical support for assessing human internal exposure levels and health risks in later studies.

A simple synthesis method of microsphere immunochromatographic test strip for time-resolved luminescence detection of folic acid

Folic acid (FA) is an ingredient that must be added to infant milk powder to avoid potential defects. Rapid, sensitive and reliable detection methods are needed to determined FA addition levels. Thus, this study established a microsphere immunochromatographic test strip for time-resolved luminescence detection (TRLM-ICTS) based on carboxyl-functionalized time-resolved luminescent microspheres (Eu-TRLMs) prepared by a one-step method as fluorescent markers for the immediate quantitative detection of FA in milk powder. Eu-TRLMs prepared by the one-step method showed good dispersion, high stability and strong fluorescence intensity, which is improving the sensitivity of TRLM-ICTS. In the performance evaluation of TRLM-ICTS, the detection limit was 0.487 ng mL^-1, the recovery rate was 97.3-105 %, and the actual sample detection results were in line with those of UPLC-MS/MS. TRLM-ICTS has the advantages of rapid, high sensitivity and strong specificity and could as a practical quantitative detection method for the detection of FA in milk powder.

Hydrophobic Deep Eutectic Solvents as Greener Substitutes for Conventional Extraction Media: Examples and Techniques

Deep eutectic solvents (DESs) are multicomponent designer solvents that exist as stable liquids over a wide range of temperatures. Over the last two decades, research has been dedicated to developing noncytotoxic, biodegradable, and biocompatible DESs to replace commercially available toxic organic solvents. However, most of the DESs formulated until now are hydrophilic and disintegrate via dissolution on coming in contact with the aqueous phase. To expand the repertoire of DESs as green solvents, hydrophobic DESs (HDESs) were prepared as an alternative. The hydrophobicity is a consequence of the constituents and can be modified according to the nature of the application. Due to their immiscibility, HDESs induce phase segregation in an aqueous solution and thus can be utilized as an extracting medium for a multitude of compounds. Here, we review literature reporting the usage of HDESs for the extraction of various organic compounds and metal ions from aqueous solutions and absorption of gases like CO₂. We also discuss the techniques currently employed in the extraction processes. We have delineated the limitations that might reduce the applicability of these solvents and also discussed examples of how DESs behave as reaction media. Our review presents the possibility of HDESs being used as substitutes for conventional organic solvents.

Synergetic effects of Mo2C sphere/SCN nanocatalysts interface for nanomolar detection of uric acid and folic acid in presence of interferences

Till to date, the application of sulfur-doped graphitic carbon nitride supported transition metal carbide interface for electrochemical sensor fabrication was less explored. In this work, we designed a simple synthesis of molybdenum carbide sphere embedded sulfur doped graphitic carbon nitride (Mo₂C/SCN) catalyst for the nanomolar electrochemical sensor application. The synthesized Mo₂C/SCN nanocatalyst was systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with elemental mapping. The SEM images show that the porous SCN network adhered uniformly on Mo₂C, causing a loss of crystallinity in the diffractogram. The corresponding elemental mapping of Mo₂C/SCN shows distinct peaks for carbon (41.47%), nitrogen (32.54%), sulfur (1.37%), and molybdenum (24.62%) with no additional impurity peaks, reflecting the successful synthesis. Later, the glassy carbon electrode (GCE) was modified by Mo₂C/SCN nanocatalyst for simultaneous sensing of uric acid (UA) and folic acid (FA). The fabricated Mo₂C/SCN/GCE is capable of simultaneous and interference free electrochemical detection of UA and FA in a binary mixture. The limit of detection (LOD) calculated at Mo₂C/SCN/GCE for UA and FA was 21.5 nM (0.09 - 47.0 μM) and 14.7 nM (0.09 - 167.25 μM) respectively by differential pulse voltammetric (DPV) technique. The presence of interferons has no significant effect on the sensor's performance, making it suitable for real sample analysis. The present method can be extended to fabricate an electrochemical sensor for various molecules.

Determination of quinolone antibiotics in honey by pH-induced natural deep eutectic solvent combined with vortex-assisted dispersive liquid-liquid microextraction

A green, fast, and efficient pH-induced natural deep eutectic solvent combined with vortex-assisted dispersive liquid-liquid microextraction method (pH-NADES-VA-DLLME) followed by HPLC was established for determination of ofloxacin (OFL), ciprofloxacin (CIP) and enrofloxacin (ENR) in honey. In this method, NaOH, as an emulsifier, can increase the contact area between the NADES and the sample solution, which can efficiently improve the extraction efficiency of the analytes. Moreover, HCl acts as the phase separation agent without centrifugation in the process, which can greatly enhance the efficiency of the sample analysis process. In addition, the main factors affecting the extraction effect were optimized by single factor experiments. Under the optimal conditions, the limits of detection (LODs), the limits of quantification (LOQs) and recoveries were in the range of 0.004-0.015 μg mL^-1, 0.012-0.050 μg mL^-1, and 98.0-112.5%, respectively. The RSD values of intra-day and inter-day precisions were no more than 5.5% and 6.0%, respectively. The developed method was successfully applied to determine the three quinolone antibiotics in honey.

Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Using Deep Eutectic Solvents (DESs) for Neutral Red Dye Spectrophotometric Determination

Deep eutectic solvents (DES), which have low toxicity and are low cost, biodegradable, and easily synthesized, were used for the extraction of neutral red (NR) dye before its spectrophotometric analysis. DES, containing choline chloride as a hydrogen bond acceptor and phenol as a hydrogen bond donor with a molar ratio of 1:2, was used for the extraction of NR dye from aqueous media. The possible interaction of different DESs with NR was studied using density functional theory (DFT) calculations. Experimentally, a UV-visible spectrophotometer was used for the quantitative analysis. The most important parameters affecting method performance, such as pH, extraction temperature, DES type, its volume, THF volume, sonication time, and centrifugation time, were optimized. The developed method provides exceptional sensitivity in terms of LOD and LOQ, which were 2.2 and 7.3 µg/L respectively. The relative standard deviation was 1.35−1.5% (n = 10), and the pre-concentration factor was 40. The method was found to be linear in the range of 2−300 µg/L (R2 = 0.9967). The method was successfully used for the determination of NR in wastewater samples. Finally, the DES-based method presents operational simplicity, high sensitivity, and rapid determination (<5 min) compared with other analytical procedures.

Nitrogen-doped carbon dots as a fluorescent probe for folic acid detection and live cell imaging

The folic acid (FA) level in human body can be used as an indicator for body's normal physiological activities and offer insight into the growth and reproduction of the body's cells. But the abnormal level of FA can cause some diseases. Herein, we designed a simple and convenient approach to prepare fluorescent N-doped carbon dots (N-CDs) for the FA detection. These N-CDs have excellent hydrophilicity, high photostability, and outstanding biocompatibility, as well as excitation-independent emission behavior with typical excitation/emission peaks at 295 nm/412 nm. Upon the existence of FA, the fluorescence emission spectrum of N-CDs was significantly quenched through the synergy of static quenching mechanism and internal filtering effect (IFE). Under optimal conditions, the limit of detection was 28.0 nM (S/N = 3) within the FA concentration range of 0-200.0 μM. In addition, N-CDs were successfully employed to detect FA in real samples such as urine and fetal bovine serum (FBS), with a recovery rate of 99.6%-100.7% for quantitative addition. Furthermore, cell experiments confirmed the low toxicity and the cell imaging performance of these N-CDs, indicating that the obtained N-CDs could be served as a credible quantitative probe for FA analysis in the field of biosensing.

Vortex-assisted dispersive liquid-liquid microextraction based on the solidification of sedimentary deep eutectic solvents for the determination of triazine and phenylurea herbicides in milk samples

Vortex-assisted dispersive liquid-liquid microextraction based on the solidification of sedimentary deep eutectic solvents was developed and applied to the extraction of triazine and phenylurea herbicides in milk samples. In this study, a series of novel hydrophobic deep eutectic solvents were prepared using tetrabutylammonium chloride as the hydrogen bond acceptor and perfluorooctanol as the hydrogen bond donor, and their structures, viscosities, densities and melting points were determined. The deep eutectic solvent was used as the extraction solvent and dispersed in the sample solution with the assistance of vortex. After extraction, through centrifugation and subsequent cooling in an ice bath, the deep eutectic solvent was solidified and deposited on the bottom of the centrifuge tube. Subsequently, the deep eutectic solvent combined with the target analytes was diluted and used for chromatographic analysis. Some parameters, including the extraction temperature, type and volume of the deep eutectic solvent, amount of NaCl, vortex time and pH of the sample solution, were optimized by the single-factor experiment, Plackett-Burman design and Box-Behnken design. The limits of detection and quantification were in the range of 0.41-0.59 μg L^-1 and 1.37-1.95 μg L^-1, respectively. The intra-day precision and inter-day precision were in the range of 0.28-2.14% and 2.02-7.99%, respectively. The present method was successfully applied to the determination of triazine and phenylurea herbicides in milk samples.

Deep Eutectic Solvents Application in Food Analysis

Current trends in Analytical Chemistry are focused on the development of more sustainable and environmentally friendly procedures. However, and despite technological advances at the instrumental level having played a very important role in the greenness of the new methods, there is still work to be done regarding the sample preparation stage. In this sense, the implementation of new materials and solvents has been a great step towards the development of "greener" analytical methodologies. In particular, the application of deep eutectic solvents (DESs) has aroused great interest in recent years in this regard, as a consequence of their excellent physicochemical properties, general low toxicity, and high biodegradability if they are compared with classical organic solvents. Furthermore, the inclusion of DESs based on natural products (natural DESs, NADESs) has led to a notable increase in the popularity of this new generation of solvents in extraction techniques. This review article focuses on providing an overview of the applications and limitations of DESs in solvent-based extraction techniques for food analysis, paying especial attention to their hydrophobic or hydrophilic nature, which is one of the main factors affecting the extraction procedure, becoming even more important when such complex matrices are studied.

Deep Eutectic Solvents for the Extraction of Bioactive Compounds from Natural Sources and Agricultural By-Products

In this work, a review about the applicability of eutectic solvents, mainly deep eutectic solvents (DES) and natural deep eutectic solvents (NADES), for the extraction of bioactive compounds from natural products has been carried out. These alternative solvents have shown not only to have high extraction yields but also to be environmentally friendly, exhibiting very low or almost no toxicity, compared to conventional organic solvents. The last trends and main extraction methods that have been most widely used in studies using these emerging solvents have been reviewed, as well as the varied natural sources in which they have been used, including agro-food by-products. Besides the toxicity, biodegradability of these solvents is reviewed. Likewise, different reported bioactivity tests have been included, in which extracts obtained with these ecological solvents have been tested from antioxidant activity analysis to in vivo studies with rats, through in vitro cytotoxicity tests.