Amberlite XAD-2 Resin Research Articles

Engineering Streptomyces albus B4 for Enhanced Production of (R)-Mellein: A High-Titer Heterologous Biosynthesis Approach.

The natural compound (R)-(-)-mellein exhibits antiseptic and fungicidal activities. We investigated its biosynthesis using the polyketide synthase encoded by SACE_5532 (pks8) from Saccharopolyspora erythraea heterologously expressed in Streptomyces albus B4, a chassis chosen for its fast growth, genetic manipulability, and ample large short-chain acyl-CoA precursor supply. High-level heterologous (R)-(-)-mellein yield was achieved by pks8 overexpression and duplication. The precursor supply pathways were strengthened by overexpression of SACE_0028 (encoding acetyl-CoA carboxylase) and four genes involved in β-oxidation (fadD, fadE, fadB, and fadA). Cell growth inhibition by (R)-(-)-mellein production at high concentration was relieved by in situ adsorption using Amberlite XAD16 resin. The final strain, B4mel12, produced (R)-(-)-mellein at 6395.2 mg/L in shake-flask fermentation. Overall, this is the first report of heterologous (R)-(-)-mellein synthesis in microorganism with a high titer. (R)-(-)-mellein prototype in this study opens a possibility for the overproduction of valuable melleins in S. albus B4.

Quercetin as the primary xanthine oxidase inhibitor compound in Maclura tricuspidata leaf

Maclura tricuspidata (MT) leaf demonstrated various health benefits, notably the inhibition of xanthine oxidase (XOD) activity, which is crucial in the management of hyperuricaemia and many diseases related to oxidative stress. This study aimed to identify the primary compound responsible for this inhibitory effect. Through a systematic investigation, MT leaf extracts were subjected to solvent-solvent partitioning using ethyl acetate, n-hexane, n-butanol, and dichloromethane. Further purification involved adsorption and desorption using Amberlite XAD-2 resin, followed by column chromatography on Silica Gel and Sephadex LH-20. The purified compounds were analysed using UPLC-QTOF-MS coupled with NMR spectroscopy. Our findings identified quercetin, a phenolic compound, as the most significant inhibitor of XOD activity in MT leaf, with an IC50 value of 212.92 μg/ml. This is the first report of purifying and identifying a single compound responsible for XOD inhibition in MT.

Native Mexican black bean purified anthocyanins fractionated by high-performance counter-current chromatography modulate inflammatory pathways

In addition to their pigment properties, the potential health benefits of anthocyanins have made them a subject of interest in recent years. This study aimed to obtain purified anthocyanin fractions from native Mexican black bean cultivars using Amberlite XAD-7 resin column and HPCCC and evaluate their anti-inflammatory properties using RAW 264.7 cells. The major anthocyanins in the purified anthocyanin fractions were delphinidin 3-glucoside (61.8%), petunidin 3-glucoside (25.2%), and malvidin 3-glucoside (12.2%). Purified anthocyanin fractions at 12.5 μg/mL effectively prevented LPS-induced ERK1/ERK2 phosphorylation and reduced the protein expression of COX-2 and mRNA expression of iNOS. Results showed that purified anthocyanin fractions have the potential to modulate the inflammatory response by inhibiting the production of pro-inflammatory mediators through the ERK1/ERK2 and NF-κB pathways. This study suggests that anthocyanins from black beans could be used as a natural strategy to help modulate inflammation-associated diseases.

Anticandidal Activity of a Siderophore from Marine Endophyte Pseudomonas aeruginosa Mgrv7.

An endophytic symbiont P. aeruginosa-producing anticandidal siderophore was recovered from mangrove leaves for the first time. Production was optimal in a succinate medium supplemented with 0.4% citric acid and 15 µM iron at pH 7 and 35 °C after 60 h of fermentation. UV spectra of the acidic preparation after purification with Amberlite XAD-4 resin gave a peak at 400 nm, while the neutralized form gave a peak at 360 nm. A prominent peak with RP-HPLC was obtained at RT 18.95 min, confirming its homogeneity. It was pH stable at 5.0-9.5 and thermally stable at elevated temperatures, which encourages the possibility of its application in extreme environments. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against Candida spp. Were in the range of 128 µg/mL and lower. It enhanced the intracellular iron accumulation with 3.2-4.2-fold (as judged by atomic absorption spectrometry) with a subsequent increase in the intracellular antioxidative enzymes SOD and CAT. Furthermore, the malondialdehyde (MDA) concentration due to cellular lipid peroxidation increased to 3.8-fold and 7.3-fold in C. albicans and C. tropicalis, respectively. The scanning electron microscope (SEM) confirmed cellular damage in the form of roughness, malformation, and production of defensive exopolysaccharides and/or proteins after exposure to siderophore. In conclusion, this anticandidal siderophore may be a promising biocontrol, nonpolluting agent against waterborne pathogens and pathogens of the skin. It indirectly kills Candida spp. by ferroptosis and mediation of hyperaccumulation of iron rather than directly attacking the cell targets, which triggers the activation of antioxidative enzymes.

Isolation of Polyphenols from Aqueous Extract of the Halophyte Salicornia ramosissima.

Polyphenols from residual non-food grade Salicornia ramosissima have health-promoting effects in feed, food, or nutraceutical applications. Therefore, the isolation of polyphenols is of interest from a series of environmentally friendly isolation methods with recyclable solvents. The isolation of polyphenols from non-food grade S. ramosissima was investigated using sequential membrane filtration with and without acid pretreatment, liquid-liquid extraction, resin adsorption, and centrifugal partition chromatography (CPC); analyzed by the Folin-Ciocalteu assay for total polyphenols; and finally analyzed using UPLC-TQMS in negative ion-spray mode for detection of 14 polyphenols. Sequential membrane filtration and acid hydrolysis indicated the polyphenols forming complexes with other compounds, retaining the polyphenols in the retentate fraction of large molecular weight cut-off membrane sizes. Conventional liquid-liquid extraction using sequential ethyl acetate and n-butanol showed most polyphenols were extracted, apart from chlorogenic acids, indicating a low isolation efficiency of higher polarity polyphenols. Analysis of the extract after resin adsorption by Amberlite XAD-4 resin showed high efficiency for separation, with 100% of polyphenols adsorbed to the resin after 13 bed volumes and 96.7% eluted from the resin using ethanol. CPC fractionations were performed to fractionate the concentrated extract after resin adsorption. CPC fractionations of the 14 polyphenols were performed using an organic or aqueous phase as a mobile phase. Depending on the mobile phase, different compounds were isolated in a high concentration. Using these easily scalable methods, it was possible to comprehensively study the polyphenols of interest from S. ramosissima and their isolation mechanics. This study will potentially lead the way for the large-scale isolation of polyphenols from S. ramosissima and other complex halophytes. The compounds of the highest concentration after CPC fractionation were isoquercitrin and hyperoside (155.27 mg/g), chlorogenic acid (85.54 mg/g), cryptochlorogenic acid (101.50 mg/g), and protocatechuic acid (398.67 mg/g), and further isolation using CPC could potentially yield novel polyphenol nutraceuticals.

Preconcentration and determination of Cu(II) and Cd(II) ions from wastewaters by using hazelnut shell biosorbent immobilized on Amberlite XAD-4 resin

Hazelnut shell biosorbent immobilized on Amberlite XAD-4 polymer resin as solid phase extraction method was developed and used for preconcentration of Cu(II) and Cd(II) ions from aqueous solutions. Concentrations of analytes in solutions were determined by Flame Atomic Absorption Spectrometry after extraction with column technique. Functional groups of nutshell biosorbent immobilized on resin were characterized by Fourier transform infrared spectrometry. Optimized critical parameters for preconcentration of Cu2+ and Cd2+ ions from sample solutions with nutshell immobilized on the resin were the pH value of solution, type of eluent solutions, the flow rate of sample solution, quantities of nutshell biosorbent, Amberlite XAD-4 resin, and enrichment factors, respectively. Detection limits of Cu2+ and Cd2+ ions found were 0.29 μg L-1 and 0.25 μg L-1, respectively. The method proposed was applied for determinations of Cu2+ and Cd2+ ions in standard reference material (BCR-670 aquatic plant sample) for accuracy and applied to real water samples such as wastewater and Van lake water. At the 95% confidence level, relative standard deviations (RSDs) were found as 1.44% for Cd2+ and 1.21% for Cu2+ ions with three replicate measurements.

Biotechnological strategies for controlled accumulation of flavones in hairy root culture of Scutellaria lateriflora L.

Accumulation of medicinally important flavones and acteoside was evaluated in Scutellaria lateriflora hairy root cultures subjected to different experimental strategies – feeding with precursors of phenolics biosynthesis (phenylalanine, cinnamic acid, and sodium cinnamate), addition of elicitors (chitosan, jasmonic acid) and Amberlite XAD-4 and XAD-7 resins and permeabilization with dimethyl sulfoxide (DMSO) and methanol. The production profile of S. lateriflora cultures changed under the influence of the applied strategies. Hairy roots of S. lateriflora were found to be a rich source of wogonoside or wogonin, depending on the treatment used. The addition of sodium cinnamate (1.0 mg/L) was the most effective approach to provide high production of flavonoids, especially wogonoside (4.41% dry weight /DW/; 566.78 mg/L). Permeabilization with DMSO (2 µg/ml for 12 h) or methanol (30% for 12 h) resulted in high biosynthesis of wogonin (299.77 mg/L and 274.03 mg/L, respectively). The obtained results provide new insight into the selection of the optimal growth conditions for the production of in vitro biomass with a significant level of flavone accumulation. The data may be valuable for designing large-scale cultivation systems of hairy roots of S. lateriflora with high productivity of bioactive compounds – wogonin or wogonoside.

Highly efficient and selective adsorption of palladium(II) from simulated nuclear waste solution using Amberlite XAD-7 resin impregnated with a phenanthroline-derived diamide

The increasing demand and limited natural resources for rare precious metal palladium render its separation and recovery from secondary sources such as acidic nuclear liquid waste greatly interesting. Herein, a novel Et-Tol-DAPhen extraction resin was prepared by impregnating Amberlite XAD-7 resin with a phenanthroline-derived diamide extractant N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), and the adsorption behavior of this new extraction resin towards Pd2+ in HNO3 solution was investigated through the batch and column experiments. The Et-Tol-DAPhen extraction resin exhibited strong adsorbability, high adsorption capacity, excellent selectivity and good reusability for Pd2+ in highly acidic HNO3 solution. In addition, the pseudo-second-order and Langmuir models were applied to understand the adsorption process of Pd2+ on Et-Tol-DAPhen extraction resin, respectively. It demonstrated the characteristics of a uniform single-layer chemisorption. The maximum uptake capacity could reach as high as 74.6 mg g−1 for Pd2+ in 3.0 mol/L HNO3 solution which is much higher than most adsorbent materials of palladium reported before. Furthermore, Et-Tol-DAPhen extraction resin could selectively uptake Pd2+ from a simulated acidic nuclear waste solution containing 20 different kinds of ions with the separation factor SFPd/M values as high as 100 to 10,000. Moreover, although the adsorption efficiency had a slight decrease after 5 times of adsorption-desorption process, it still remained at a high level. This new extraction resin displayed a potential application prospect in the field of separation and recovery of Pd2+ from acidic nuclear liquid waste.

Fungal biodegradation of ellagitannins extracted from rambutan peel

The rambutan peel is a by-product with a high quantity of ellagitannins. When ellagitannins are biodegraded, they produce ellagic acid. This work aimed to extract ellagitannins from rambutan peel and make a solid-state fermentation (SSF) to identify which enzymes are involved in the biodegradation of ellagitannins. Extraction of rambutan ellagitannins (RE) was done by microwave/ultrasound technology, isolated by column chromatography with Amberlite XAD-16 resin, and characterized by HPLC-MS. The SSF was done using RE as substrate at three different concentrations (7.5, 15, and 22.5 g/L), Aspergillus niger GH1, polyurethane foam as support and Czapeck-dox medium in tray reactors. Enzymatic activities cellulase, xylanase, polyphenol oxidase, ellagitannase, tannase, β-glucosidase and α-L-arabinofuranosidase were tested, and ellagic acid was quantified. The microwave/ultrasound allowed the extraction of seven ellagitannins where the major compound was geraniin. SSF allows the biodegradation of geraniin into ellagic acid, and ellagitannase was the enzyme with the highest value (25.49 U/L) at the times of maximum accumulation of ellagic acid (6–12 h of fermentation), indicating that this enzyme is directly associated to the process of biodegradation. Finally, the maximum titles of this enzymatic activity (353.27 U/L) were found at fermentation time of 42 h and RE concentration of 22.5 g/L.

Ce(III) and La(III) ions adsorption using Amberlite XAD-7 resin impregnated with DEHPA extractant: response surface methodology, isotherm and kinetic study

In this paper, the removal efficiency of Cerium (Ce(ΙΙΙ)) and lanthanum (La(ΙΙΙ)) ions from aqueous solution using Amberlite XAD-7 resin impregnated with DEHPA(XAD7-DEHPA) was studied in the batch system. The adsorbent ( XAD7–DEHPA) was characterized by SEM–EDX, FTIR and BET analysis Techniques. The response surface methodology based on the central composite design was applied to model and optimize the removal process and evaluate operating parameters like adsorbent dose (0.05–0.065), initial pH (2–6) and temperature (15–55). Variance analysis showed that the adsorbent dose, pH and temperature were the most effective parameters in the adsorption of Ce(ΙIΙ)and La(IΙI) respectively. The results showed that the optimum adsorption condition was achieved at pH = 6, the optimum amount of absorbent and the equilibrium time equal to 0.6 gr and 180 min, respectively. According to the results, the adsorption percentage of Ce(ΙIΙ) and La(ΙΙΙ) ions onto the aforementioned resin were 99.99% and 78.76% respectively. Langmuir, Freundlich, Temkin and sips isotherm models were applied to describe the equilibrium data. From the results, Langmuir isotherm (R2 (Ce) = 0.999, R2 (La) = 0.998) was found to better correlate the experimental rate data. The maximum adsorption capacity of the adsorbent ( XAD7–DEHPA) for both Ce(IΙI) and La(III) was found to be 8.28 and 5.52 mg g−1 respectively. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and Intra particle diffusion models. Based on the results, the pseudo-first-order model and Intra particle diffusion model described the experimental data as well. In general, the results showed that ( XAD7–DEHPA) resin is an effective adsorbent for the removal of Ce(IΙI) and La(III) ions from aqueous solutions due to its high ability to selectively remove these metals as well as its reusability.

Ce(ΙΙΙ) and La(ΙΙΙ) ions adsorption through Amberlite XAD-7 resin impregnated via CYANEX-272 extractant

The goal of this paper is to investigate the ability of Amberlite XAD-7 (AXAD-7) resin impregnated with CYANEX-272 (di-2,4,4-trimethylpentyl phosphonic acid) to remove cerium (Ce(ΙΙΙ)) and lanthanum (La(ΙΙΙ)) ions from aqueous solutions in the batch scheme. The prepared adsorbent material was determined utilizing FTIR, SEM–EDX, and BET methods. The impact of three individual process variable factors involving feed solution pH (2–6), adsorbent dose (0.05–0.65), and process temperature (15–55 °C) on the simultaneous removal of Ce(ΙΙΙ) and La(ΙΙΙ) ions was evaluated via response surface methodology (RSM) according to the central composite design (CCD). The modeling of Ce(ΙΙΙ) and La(ΙΙΙ) ions adsorption was performed using the quadratic model and was evaluated using a coefficient of determination for both ions. The optimization data revealed that the adsorption amount of Ce(ΙΙΙ) and La(ΙΙΙ) ions removal under optimal conditions were 99.75% and 69.98%, respectively. Equilibrium and kinetic investigations were also conducted to define the removal performance of the calculated adsorbent for Ce(ΙΙΙ) and La(ΙΙΙ) ions removal. Various isotherms models such as Langmuir, Freundlich, Temkin, and Sips were examined at 25 °C to analyze the equilibrium isotherm data. The data revealed that the Sips approach is compatible with the experimental data. The highest adsorption capacity of the resin for Ce(ΙΙΙ) and La(ΙΙΙ) ions were 11.873 mg g−1 and 7.324 mg g−1, correspondingly. The kinetic study of the Ce(ΙΙΙ) and La(ΙΙΙ) adsorption process was conducted via pseudo-first-order, pseudo-second-order, and intraparticle diffusion models(IDMs). Based on the data obtained, kinetic data were fitted well to a pseudo-second-order rate correlation. According to the obtained results, the (AXAD-7) resin impregnated with CYANEX-272 performed well in removing both Ce(ΙΙΙ) and La(ΙΙΙ) ions from aqueous solutions with well stability during several adsorption–desorption cycles and well regeneration and excellent metallic ions recovery.

The efficiency of the hard wood origin biochar addition on the PAHs bioavailability and stability in sediment

Polluted sediments with organic pollutants like PAHs represent a potential danger to environment, human health and potential obstacle to water management. Removal of polluted sediment provides the potential for reuse of nutrients from sediment, for crop production or for materials in building industry. The purpose of this study was to determine the efficacy of using hard wood biochar for the immobilization of bioaccessible polycyclic aromatic hydrocarbons (PAHs) in historically polluted sediment. The main question is would carbon materials' presence (in this case biochar) have influence on PAH bioavailability and their stability in sediment. This is important because the world trend is to go for sediment reuse in agriculture purposes, and biochar is proven to be good amendment for increasing soil organic carbon (SOC) stabilization and increasing soil carbon stock. The manuscript provides a detailed consideration of the supersorption performance of the biochar and PAH sequestration in different types of PAHs with aging period up to 6 months in ex situ treatment. The efficiency of biochar to sequester the PAHs was evaluated by assessing the bioavailable fraction (Frap) using desorption method with Amberlite XAD4 resin assistance. In untreated sediment, Frap ranged from 22% up to 42% for 2–4 rings, and around 9% for 5–6 rings PAHs. 180-days amendment of biochar led to a further decrease in the bioavailable portion of PAHs. The results of this laboratory study shown that biochar produced from hard wood gave promising results for binding and further stabilizing PAH in historically polluted sediments.

Iridoid- and flavonoid-enriched fractions of Cornus sanguinea and Cornus mas exert antioxidant and anti-inflammatory effects and inhibit key enzymes in the treatment of metabolic disorders.

Background: Berry fruits are recognized as a "superfood" due to their high content of bioactive compounds and health benefits. Scope and approach: Herein, extracts of Cornus sanguinea and Cornus mas fresh and dried fruits obtained by different extraction procedures (ethanolic and hydroalcoholic maceration, ultrasound-assisted extraction, and Soxhlet apparatus) were analysed using liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (LC-ESI-QTOF-MS) and compared to identify the main healthy compounds and their impact on the inhibition of key enzymes (pancreatic lipase, α-glucosidase, and α-amylase) associated with metabolic disorders. The antioxidant activity and inhibition of nitric oxide (NO) and NF-κB pathway were also investigated. Key findings and conclusions: Flavonoids, iridoids, and phenolic acids were the main classes of identified compounds. Herein, kaempferol 3-O-galactoside, kaempferol 3-O-glucoside, quercetin, quercetin 3-O-xyloside, and myricetin 3-O-galactoside were detected for the first time in C. sanguinea. Remarkable antioxidant effects and promising α-glucosidase and lipase inhibitory activity were observed with extracts obtained by hydroalcoholic maceration of both Cornus dried fruits. Consequently, these extracts were subjected to fractionation using Amberlite XAD-16 resin. The most promising biological activities, which are attributed to the presence of some flavonoids and iridoids, were detected with the C. sanguinea fractions, in particular SD2(II). The results of this study offer new insights into the potential development of functional foods, nutraceuticals, and food supplements using the Cornus species.

Temperature Dependence of Electrical Conductivity and XRD Studies of Hydroquinone Modified Amberlite XAD-4 Resin

Temperature Dependence of Electrical Conductivity and XRD Studies of Hydroquinone Modified Amberlite XAD-4 Resin

Evaluation of scandium sorption using modified Amberlite XAD-4 resin

Evaluation of scandium sorption using modified Amberlite XAD-4 resin

Improved sono-assisted adsorption of a binary dye mixture using bis(2-ethylhexyl) phosphate modified Amberlite XAD-2 resin and response optimization

Methylene blue (MB) and crystal violet (CV) was simultaneously adsorbed ultrasonically on bis (2-ethylhexyl) phosphate (D2EHPA) modified Amberlite XAD-2 resin. The prepared resin was characterized by FESEM, SEM with EDS, FTIR, and point of zero charge. Preliminary studies for the removal of MB and CV dye in the mixture was done by using different ratio of D2EHPA impregnated XAD-2 resin and at different pH. Central Composite Design (CCD) of response surface methodology (RSM) was used to design and optimize the removal process. The effective parameters chosen for this study were: ultrasonication time (tus: 3–15 min), adsorbent dosage (m: 0.3–1.5 g), and initial concentration of MB (Cmbin) and CV (Ccvin) dye in solution (5–25 mg L−1). At optimized condition (tus = 10.5 min, m = 1.16 g, and concentration of Cmbin = 16 mg.L−1and Ccvin = 16 mg L−1), the maximum percentage removal for MB and CV dye was 93.38% (Qt = 1.29 mg g−1) and 97.80% (Qt = 1.32 mg g−1), respectively. pH study was performed at optimized condition by varying the pH of the dye solution from 3 to 12. At optimized condition, kinetic and equilibrium studies were performed. For single dye adsorption study, Freundlich model and for binary dye adsorption study extended Freundlich model was best fitted. The pseudo-second-order model best fitted the kinetic data for both the dyes with R2 = 0.998 for MB dye and R2 = 0.999 for CV dye which indicated the chemisorption nature of adsorbent. The possible interaction mechanism between D2EHPA and MB/CV dye was proposed. The continuous study was performed by varying flow rates using a recirculating flow vessel and found to be 12.5% more energy efficient than the batch mode. Regeneration of the adsorbent was done successfully using ethanol-water solution up to five cycles.

Determination of some heavy metals from aqueous solutions using modified Amberlite XAD-4 resin by selective solid-phase extraction

The adsorption efficiency of Pb(II) and Cd(II) from aqueous solutions on m-phenylenediamine-modified Amberlite XAD-4 resin was investigated. The effects of pH, adsorbent amount, initial metal concentration, eluent type and volume and flow rate on the retention of the metal ions have been studied on column studies. The optimum parameters were determined as pH 5, concentration 10 mg/L, stirring time 30 min and 0.2 g adsorbent amount and flow rate 2.5 mL/min for a quantitative adsorption. Sorption data were interpreted in terms of Langmuir and Freundlich equations, and both models were found to be fully appropriate. Each column can be used up to 10 sequential analyses without considerable change. The results indicate high metal adsorption capacity and satisfactory recovery of Pb(II) and Cd(II).

Efficient and selective lanthanide recovery from highly acidic solutions by using a porous pillar[5]arene-based diglycolamide impregnated resin

The recovery of lanthanides from high level liquid waste (HLLW) is of great significance for both environmental protection and sustainable development of resources. Traditional methods for this purpose are often plagued by poor selectivity, low capacity, and limited acid tolerance. Here we report a new material prepared by impregnating P[5]A-DGA onto porous Amberlite XAD-7 resin for efficient and selective lanthanide adsorption from highly acidic solutions. The as-prepared composite material (PDA resin) shows outstanding sorption efficiency for lanthanides in a wide range of acidities (0.01–3 M HNO3) and exhibits good selectivity towards lanthanides over different kinds of competing metal ions in simulated nuclear wastewater. Adsorption equilibrium can be achieved within 60 min and the pseudo-second-order model shows better correlation with the kinetic data, indicating that chemical adsorption is the rate determining step. Adsorption isotherm data can be well fitted by Langmuir model, giving a Eu(III) sorption capacity of 33.3 mg/g at 1 M HNO3, which is superior to other materials employed for the similar purpose. Importantly, the adsorption capacity can be regenerated by using a mixture of 1 M guanidine carbonate and 0.05 M EDTA-2Na solution as the eluent, and the lanthanide adsorption efficiency from simulated nuclear wastewater remains at the initial level after three desorption-adsorption cycles. Finally, the possible configurations of the ligand-Ln(III) complexes were optimized by DFT calculations, which suggest that each Ln(III) tends to bind to three DGA arms via a nine coordination mode. This research advances the development of pillar[5]arenes for lanthanide recovery by demonstrating a simple and generally applicable method to convert P[5]A-DGA extractant into an efficient adsorbent.

A voltammetric approach to the quantification of tungsten in environmental waters using a solid bismuth microelectrode

In this paper, a novel eco-friendly solid bismuth microelectrode for direct tungsten quantification by cathodic stripping voltammetry (CSV) is discussed. The novelty of the proposed sensor results from the fact that the used microelectrode (Ø = 25 µm) exhibits perfect long-term persistence. Moreover, on account of spherical diffusion and insensitivity to the presence of oxygen in the solution the analysis could be performed at the point of sampling. The instrumental and chemical factors influencing the sensitivity of the sensor were thoroughly investigated and their most favorable values were selected (pH = 2.88, acetic acid concentration: 0.1 M; activation potential/time: −1.8 V/1 s; accumulation potential/time: −0.5 V/20 s). Under selected conditions, the method exhibits linearity in the range of 1 × 10−8 to 5 × 10−6 M, while the detection boundary was calculated to be 1.3 × 10−9 M. This method has been shown to be highly selective and insensitive to the presence of even 10 mg L−1 of humic substances due to the addition of the adsorptive Amberlite XAD-7 resin to the test solution. In keeping with the outlined procedure, the certified reference materials (SPS-SW1, SPS-WW1, NAAS-5), tap and well water samples were analyzed without any pretreatment and recovery values from 90.4 to 108.5% were obtained.

Attempt to Develop an Effective Method for the Separation of Gamma-Decalactone from Biotransformation Medium

Gamma-decalactone (GDL) is a fragrance compound obtained in the process of β-oxidation of ricinoleic acid, which is derived from the hydrolysis of castor oil. The biotechnological method of the synthesis of this lactone has been improved for over two decades, but the vast majority of research results have been based only on determining the concentration of the lactone by chromatographic methods without separating it from the biotransformation medium. In this study, we attempted to separate GDL from the medium in which the lactone was synthesized by Yarrowia lipolytica from castor oil. The effectiveness of liquid–liquid extraction, hydrodistillation, and adsorption on the porous materials (zeolite, vermiculite and resin Amberlite XAD-4) was compared. The influence of the solvent on the efficiency of GDL extraction, the influence of the acidity of the medium on the amount of GDL in the distillate, and the level of lactone adsorption on the above-mentioned adsorbents were compared by calculating the initial adsorption rate. The adsorption isotherm was determined for the most effective adsorbent. Among the five solvents tested, the most effective was diethyl ether, used at the ratio of 1:1. The extraction was characterized by higher efficiency than hydrodistillation; the difference in GDL determinations by these two methods ranged from 12.8 to 22%. The purity of the distillates was much higher than that of the extracts at 88.0 ± 3.4% compared to 53.0 ± 1.8%. The acidification of the biotransformation medium increased the concentration of the lactone in both the reaction mixture and the distillate. GDL was most efficiently adsorbed on Amberlite XAD-4 resin, for which the lactone isotherm adsorption was linear. The amount of lactone adsorbed on Amberlite XAD-4 within 1 h was approx. 80% (2.45 g), of which 1.96 g was then desorbed with ethanol. In the context of industrial applications, adsorption of GDL on Amberlite XAD-4 seems to be the most appropriate method due to material costs, the ease of the process, and low environmental burden.