Raman spectroscopy is a label-free, non-destructive, non-invasive analytical tool that provides insight into the molecular composition of samples with minimum or no sample preparation. The increased ...availability of commercial portable Raman devices presents a potentially easy and convenient analytical solution for day-to-day analysis in laboratories and production lines. However, their performance for highly specific and sensitive analysis applications has not been extensively evaluated. This study performs a direct comparison of such a commercially available, portable Raman system, with a research grade Raman microscope system for the analysis of water content of Natural Deep Eutectic Solvents (NADES). NADES are renewable, biodegradable and easily tunable “green” solvents, outcompeting existing organic solvents for applications in extraction from biomass, biocatalysis, and nanoparticle synthesis. Water content in NADES is, however, a critical parameter, affecting their properties, optimal use and extraction efficiency. In the present study, portable Raman spectroscopy coupled with Partial Least Squares Regression (PLSR) is investigated for rapid determination of water content in NADES samples in situ, i.e., directly in glassware. Three NADES systems, namely Betaine Glycerol (BG), Choline Chloride Glycerol (CCG) and Glucose Glycerol (GG), containing a range of water concentrations between 0% (w/w) and 28.5% (w/w), were studied. The results are directly compared with previously published studies of the same systems, using a research grade Raman microscope. PLSR results demonstrate the reliability of the analysis, surrendering R2 values above 0.99. Root Mean Square Errors Prediction (RMSEP) of 0.6805%, 0.9859% and 1.2907% w/w were found for respectively unknown CCG, BG and GG samples using the portable device compared to 0.4715%, 0.3437% and 0.7409% w/w previously obtained by analysis in quartz cuvettes with a Raman confocal microscope. Despite the relatively higher values of RMSEP observed, the comparison of the percentage of relative errors in the predicted concentration highlights that, overall, the portable device delivers accuracy below 5%. Ultimately, it has been demonstrated that portable Raman spectroscopy enables accurate quantification of water in NADES directly through glass vials without the requirement for sample withdrawal. Such compact instruments provide solvent and consumable free analysis for rapid analysis directly in laboratories and for non-expert users. Portable Raman is a promising approach for high throughput monitoring of water content in NADES that can support the development of new analytical protocols in the field of green chemistry in research and development laboratories but also in the industry as a routine quality control tool.
The inclusion complexes of cucurbitnuril, CBn (n = 6-8), with poly aromatic hydrocarbon (PAH) Benzo(a)Pyrene (BaP), and fluoranthene (FLT) were investigated carefully in aqueous media. Fluorescence ...and
H NMR spectroscopy were used to characterize and investigate the inclusion complexes that were prepared in the aqueous media. The most predominant complexes of both guests with hosts were the 1:1 guest: host complexes. Stability constants of 2322 ± 547 M
, 7281 ± 689 M
, 3566 ± 473 M
were obtained for the complexes of BaP with CB6, CB7, and CB8, respectively. On the other hand, stability constants of 5900.270 ± 326 M
, 726.87 ± 78 M
, 3327.059 ± 153 M
were obtained for the complexes of FLT with CB6, CB7, and CB8, respectively. Molecular dynamic (MD) simulations were used to study the mode and mechanism of the inclusion process and to monitor the stability of these complexes in aqueous media at an atomistic level. Analysis of MD trajectories has shown that both BaP and FLT form stable inclusion complexes with CB7 and CB8 in aqueous media throughout the simulation time, subsequently corroborating the experimental results. Nevertheless, the small size of CB6 prohibited the encapsulation of the two PAHs inside the cavity, but stable exclusion complex was observed between them. The main driving forces for the stability of these complexes are the hydrophobic forces, van der Waals interactions, electrostatic effect, the π····π and C-H···π interaction. These results suggest that BaP and FLT can form stable complexes with CBn (n = 6-8) in solution.
In this study, a carboxylated carbon nanotube-grafted Ag3PO4@AgIO4 (CNT-COO−/Ag3PO4@AgIO4) composite was synthesized through an in situ electrostatic deposition method. The synthesized composite was ...characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and energy-dispersive X-ray spectroscopy (EDS). The electron transfer ability of the synthesized composite was studied using electrochemical impedance spectroscopy (EIS). The CNT-COO−/Ag3PO4@AgIO4 composite exhibited higher activity than CNT/Ag3PO4@AgIO4, Ag3PO4@AgIO4, and bare Ag3PO4. The material characterization and the detailed study of the various parameters thataffect the photocatalytic reaction revealed that the enhanced catalytic activity is related to the good interfacial interaction between CNT-COO and Ag3PO4. The energy band structure analysis is further considered as a reason for multi-electron reaction enhancement. The results and discussion in this study provide important information for the use of the functionalized CNT-COOH in the field of photocatalysis. Moreover, providinga new way to functionalize CNT viadifferent functional groups may lead to further development in the field of photocatalysis. This work could provide a new way to use natural sunlight to facilitate the practical application of photocatalysts toenvironmental issues.
In aqueous and solid media, 2-HP-β/γ-CD inclusion complexes with poly aromatic hydrocarbon (PAH) Phenanthrene (PHN), Anthracene (ANT), Benz(a)pyrene (BaP), and Fluoranthene (FLT) were investigated ...for the first time. The inclusion complexes were characterized and investigated using fluorescence and 1HNMR spectroscopy. The most prevalent complexes consisting of both guests and hosts were those with a 1:1 guest-to-host ratio. The stability constants for the complexes of PHN with 2-HP-β-CD and 2-HP-γ-CD were 85 ± 12 M−1 and 49 ± 29 M−1, respectively. Moreover, the stability constants were found to be 502 ± 46 M−1 and 289 ± 44 M−1 for the complexes of ANT with both hosts. The stability constants for the complexes of BaP with 2-HP-β-CD and 2-HP-γ-CD were (1.5 ± 0.02) × 103 M−1 and (9.41 ± 0.03) × 103 M−1, respectively. The stability constant for the complexes of FLT with 2-HP-β-CD was (1.06 ± 0.06) × 103 M−1. However, FLT was observed to form a weak complex with 2-HP-γ-CD. Molecular dynamic (MD) simulations were used to investigate the mechanism and mode of inclusion processes, and to monitor the atomic-level stability of these complexes. The analysis of MD trajectories demonstrated that all guests formed stable inclusion complexes with both hosts throughout the duration of the simulation time, confirming the experimental findings. However, the flexible Hydroxypropyl arms prevented the PAHs from being encapsulated within the cavity; however, a stable exclusion complex was observed. The main forces that influenced the complexation included van der Waals interactions, hydrophobic forces, and C–H⋯π interaction, which contribute to the stability of these complexes.
Absorbance spectra β-CD, Moxi and Moxi-β-CD Inclusion complex, concentration of Moxi 2μg/mL, β-CD2×10−4M, at room temperature, time15min, pH 8.0. Display omitted
•Inclusion complex between Moxi and ...β-cyclodextrin was prepared and characterized by specrotrsopic methods.•Formation of inclusion complex 1:1 was confirmed by Job’s method.•A novel spectrofluorometric method was established for determination of Moxi in pharmaceutical formulation.
The supramolecular interaction of Moxifloxacin (Moxi) and β-cyclodextrin (β-CD) has been examined by UV–VIS, FTIR, H1NMR, SEM and fluorescence spectroscopy. The formation of inclusion complex has been confirmed on the base of changes of spectroscopy properties. The results showed that β-CD reacted with Moxi to form an inclusion complex. The Moxi and β-CD complex formed a host–guest complex in 1:1 stoichiometry and inclusion constant (K=3.95×102Lmol−1) was ascertained by the typical double reciprocal plots. Furthermore, the thermodynamic parameters (ΔH°, ΔS° and ΔG°) associated with the inclusion process were also determined.
Based on the significant enhancement of the fluorescence intensity of Moxi produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of Moxi in pharmaceutical formulation was developed. The measurement of relative fluorescence intensity was carried out at 464nm with excitation at 289nm.
The factors affecting the inclusion complex formation were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.99973) were in the concentration range of 10–60ng/mL for spectrofluorimetry. The limit of detection (LOD) was found to be 1.6ng/mL. The proposed method was successfully applied to the analysis of Moxi in pharmaceutical preparation.
Vibrational spectroscopic techniques, i.e., attenuated total reflectance infrared (ATR-IR), near infrared spectroscopy (NIRS) and Raman spectroscopy (RS), coupled with Partial Least Squares ...Regression (PLSR), were evaluated as cost-effective label-free and reagent-free tools to monitor water content in Levulinic Acid/L-Proline (LALP) (2:1, mol/mol) Natural Deep Eutectic Solvent (NADES). ATR-IR delivered the best outcome of Root Mean Squared Error (RMSE) of Cross-Validation (CV) = 0.27% added water concentration, RMSE of Prediction (P) = 0.27% added water concentration and mean % relative error = 2.59%. Two NIRS instruments (benchtop and handheld) were also compared during the study, respectively yielding RMSECV = 0.35% added water concentration, RMSEP = 0.56% added water concentration and mean % relative error = 5.13% added water concentration, and RMECV = 0.36% added water concentration, RMSEP = 0.68% added water concentration and mean % relative error = 6.23%. RS analysis performed in quartz cuvettes enabled accurate water quantification with RMECV = 0.43% added water concentration, RMSEP = 0.67% added water concentration and mean % relative error = 6.75%. While the vibrational spectroscopic techniques studied have shown high performance in relation to reliable determination of water concentration, their accuracy is most likely related to their sensitivity to detect the LALP compounds in the NADES. For instance, whereas ATR-IR spectra display strong features from water, Levulinic Acid and L-Proline that contribute to the PLSR predictive models constructed, NIRS and RS spectra are respectively dominated by either water or LALP compounds, representing partial molecular information and moderate accuracy compared to ATR-IR. However, while ATR-IR instruments are common in chemistry and physics laboratories, making the technique readily transferable to water quantification in NADES, Raman spectroscopy offers promising potential for future development for in situ, sample withdrawal-free analysis for high throughput and online monitoring.
Natural deep eutectic solvents (NADES) are ionic solutions, of great interest for extraction from biomass, biocatalysis, and nanoparticle synthesis. They are easily synthesised and eco-friendly, have ...low volatility and high dissolution power, and are biodegradable. However, water content in NADES is a critical parameter, affecting their optimal use and extraction efficiency. Vibrational spectroscopic techniques are rapid, label-free, non-destructive, non-invasive, and cost-effective analytical tools that can probe the molecular composition of samples. A direct comparison between a previous study using attenuated total reflectance infrared (ATR-IR) spectroscopy for water quantification in NADES and the same investigation performed with Raman spectroscopy is presently reported. Three NADES systems, namely betaine-glycerol (BG), choline chloride-glycerol (CCG), and glucose-glycerol (GG), containing a range of water concentrations between 0% (w/w) and 40% (w/w), have been analysed with Raman spectroscopy coupled to partial least squares regression multivariate analysis. The values of root mean square error of cross-validation (RMSECV) obtained from analysis performed on the pre-processed spectra over the full spectral range (150–3750 cm
−1
) are respectively 0.2966% (w/w), 0.4703% (w/w), and 0.2351% (w/w) for BG, GG, and CCG. While the direct comparison to previous ATR-IR results shows essentially similar outcomes for BG, the RMSECV is 33.14% lower and 65.84% lower for CG and CCG. Furthermore, mean relative errors obtained with Raman spectroscopy, and calculated from a set of samples used as independent samples, were 1.452% (w/w), 1.175% (w/w), and 1.188% (w/w). Ultimately, Raman spectroscopy delivered performances for quantification of water in NADES with similar accuracy to ATR-IR. The present demonstration clearly highlights the potential of Raman spectroscopy to support the development of new analytical protocols in the field of green chemistry.
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•Eleven phenolic compounds were reported for the first time from Ficus sycomorus.•Leaf and stem bark extracts displayed antioxidant and enzyme inhibition properties.•Bioinformatics ...analysis showed selective advantage of quercetin in tumorigenesis.•F. sycomorus could be a beneficial source of natural of bioactive agents.
This study was aimed to determine the phenolic profile of the leaf and stem bark of Ficus sycomorus and to investigate their antioxidant and enzyme inhibition properties. Extracts were prepared by maceration with hexane and dichloromethane: ethanol (DE) (1:1) respectively. Phenolic content was quantitatively determined and their constituents were identified on the basis of co-chromatography with reference compounds. Results showed that the leaf displayed significant higher polyphenolic and flavonoid contents than the stem bark while the latter showed significant highest total tannin content.. The leaf DE extract exhibited significant higher antiradical activity and higher capacity to reduce Fe3+ than the stem bark DE extract. The leaf DE and stem bark hexane extracts significantly (p < 0.05) displayed the highest acetylcholinesterase and α-glucosidase inhibition while the former showed significantly (p < 0.05) the highest inhibition towards tyrosinase. Regarding the enzyme inhibition effects, the bioinformatics analysis suggested that the quercetin pool could be at the basis of the observed effects. Results obtained from this study suggested that, F. sycomorus could be a rich natural source of bioactive molecules with antioxidant and enzyme inhibition properties.
The coupling of capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) has become convenient analytical method for determination of small molecules that do ...not possess chromogenic or fluorogenic group. The implementations of CE with C4D in the determination of inorganic and organic ions and amino acids in biomedical field are demonstrated. Attention on background electrolyte composition, sample treatment procedures, and the utilize of multi‐detection systems are described. A number of tables summarizing highly developed CE‐C4D methods and the figures of merit attained are involved. Lastly, concluding remarks and perspectives are argued.
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