Retention Factors Research Articles

A singular chromatographic column breakthrough: Achieving full polarity range separations with the epoxy propanol molecular cage bonded silica stationary phase

The epoxy propanol molecular cage bonded silica stationary phase, RCC3-GLD@silica, synthesized through the ring-opening reaction of secondary amine with epoxy propanol using RCC3-R as the scaffold unit, was successfully prepared as confirmed by infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption characterization. This stationary phase demonstrated excellent separation performance in both reversed-phase and hydrophilic chromatography modes, effectively separating a wide variety of compounds including alkylbenzenes, polycyclic aromatic hydrocarbons, phenols, anilines, sulfonamides, nucleosides, amino acids, sugars, and acids. The development of RCC3-GLD@silica benefits from the synergistic effects of its hydrophobic and hydrophilic actions, as evidenced by the U-shaped characteristic of the retention factor for nucleoside compounds with changes in the aqueous content of the mobile phase, further confirming the simultaneous presence of reversed-phase and hydrophilic chromatography mechanisms. Not only did this stationary phase successfully separate 33 compounds in reversed-phase chromatography mode, but it also separated 54 compounds in hydrophilic interaction chromatography mode, showcasing its broad separation capability from weakly polar to strongly polar compounds on a single chromatographic column. This indicates a wide application prospect in the field of chromatographic analysis.

The Impact of the Retention Factors on Organizational Commitment: A case of High -Tech Employees in the Sudanese Telecommunications Sector

The Impact of the Retention Factors on Organizational Commitment: A case of High -Tech Employees in the Sudanese Telecommunications Sector

Continuous stationary phase gradient preparation on planar chromatographic media using vapor phase deposition of silane

A new, versatile, and straightforward vapor phase deposition (VPD) approach was used to prepare continuous stationary phase gradients (cSPGs) on silica thin-layer chromatography (TLC) plates using phenyldimethylchlorosilane (PDCS) as a precursor. A mixture of paraffin oil and PDCS was placed at the bottom of an open-ended rectangular chamber, allowing the reactive silanes to evaporate and freely diffuse under a controlled atmosphere. As the volatile silane diffused across the length of the TLC plate, it reacted with the surface silanol groups thus functionalizing the surface in a gradient fashion. Characterization of the gradient TLC plates was done through UV visualization and diffuse reflectance spectroscopy (DRS). Visualizing the fluorescent gradient plates under UV radiation shows the clear presence of a gradient with the side closest to the vapor source undergoing the most modification. More quantitative characterization of the shape of the gradient was provided by DRS. The DRS showed that the degree of modification and shape of the gradient was dependent on the concentration of silane, VPD time, and relative humidity. To evaluate the chromatographic performance, a mixture of three aromatic compounds (acetaminophen (A), aspirin (As), and 3-hydroxy-2-naphthoic acid (3H)) was spotted on the high (GHP) and low phenyl (GLP) ends of the gradient TLC plates and the results compared to the separations carried out on unmodified and uniformly modified plates. The GHP TLC plates showed retention factors (Rf) of 0.060 ± 0.006, 0.391 ± 0.006, and 0.544 ± 0.006, whereas the unmodified plate displayed Rf values of 0.059 ± 0.006, 0.092 ± 0.003, and 0.037 ± 0.002 for the analytes A, As, and 3H, respectively. From the Rf values, it was observed that each modified plate exhibited different selectivity for the analytes. The GHP TLC plates exhibited better separation performance, and improved resolution compared to the GLP, unmodified, and uniformly modified plates. Overall, VPD is a new, cost-effective method for creating a gradient on the stationary phase which has the potential to advance chromatographic separation capabilities.

A logarithmic law for the velocity- and retention-dependency of the eddy dispersion in chromatographic columns

Applying the recently introduced patchwork model for porous media, we present a new step forward in the modelling of eddy dispersion in chromatographic columns. The logarithmic law describing the velocity dependency emerging from this patchwork model is supplemented with a retention factor dependency via first principles modelling of the variations in flow resistance and retention capacity caused by the packing disorder. Furthermore, it is shown the derived expression is also able to fit the eddy dispersion originating from the wall effect on the packing. When applied to literature data of eddy dispersion, the newly introduced logarithmic law has a goodness of fit that is at least equal to that of Knox’ empirical power law (R2>0.98). The main difference is that, whereas Knox’ power law requires a separate fit for each component due to the retention factor dependency, the present model simultaneously fits all plate height curves measured on one chromatographic column, using only two parameters with a clear physical meaning.

PFAS transport under lower water-saturation conditions characterized with instrumented-column systems

The transport of PFOS and PFOA in well-characterized sand was investigated for relatively low water saturations. An instrumented column was used for some experiments to provide real-time in-situ monitoring of water saturation and matric potential. The results showed that water saturations and matric potentials varied minimally during the experiments. Flow rates were monitored continuously and were essentially constant. These results demonstrate that surfactant-induced flow and other nonideal hydraulic processes did not materially impact PFAS transport for the experiment conditions. Air-water interfacial adsorption was demonstrated to provide the great majority of retention for PFOS and PFOA. Retention was significantly greater at the lower water saturations (0.35–0.45) compared to the higher saturations (∼0.66) for both PFAS, due to the larger extant air-water interfacial areas. Retardation factors were 5 and 3-times greater at the lower water saturations for PFOS and PFOA, respectively. Early breakthrough was observed for the PFAS but not for the non-reactive tracers at the lower water saturations, indicating the possibility that air-water interfacial adsorption was rate-limited to some degree. Independently determined retention parameters were used to predict retardation factors for PFOS and PFOA, which were similar to the measured values in all cases. The consistency between the predicted and measured values indicates that PFAS retention was accurately represented. In addition, air-water interfacial adsorption coefficients measured from the transport experiments were consistent with independently measured equilibrium-based values. Based on these results, it appears that the air-water interfacial adsorption processes mediating the magnitude of PFOS and PFOA retention under lower water-saturation conditions are consistent with those for higher water saturations. This provides some confidence that our understanding of PFAS retention obtained from work conducted at higher water saturations is applicable to lower water saturations.

WhatsApp groups: the Nexus between retention, reciprocity, and user satisfaction

High dropout rates in higher education pose a significant challenge, prompting a need for effective retention strategies. Research shows promoting students’ engagement as key factor in retention. This is most effectively nurtured through regular activities that explicitly connect to academic goals and involve all students. This study proposes to investigate the role of reciprocity which involves the exchange of knowledge and resources on the basis of mutual benefits, and considers WhatsApp groups as an interactive medium for connecting and sharing. Data from an online questionnaire of 309 university students was used to test the research model. Data analysis was performed using the partial least squares method. The findings revealed that that information quality (IQ) and service quality (SERQ) exert a positive influence on satisfaction (SAT), while system quality (SQ) does not. Similarly, reciprocity has a positive influence on both SAT and intention to stay (INTENT). Moreover, our study reaffirmed the established positive relationship between SAT and INTENT. Online platforms like WhatsApp groups, supported by reciprocity and a higher quality of contents and services, can promote satisfaction and knowledge sharing among students, ultimately addressing the challenge of student retention in higher education.

Proper retention factor for Avanafil and Dapoxetine Hydrochloride Separation and Validation with RP-HPLC in Bulk, Dosage Form and Rat Plasma; Validation, Degradation, and Pharmacokinetic Application

Proper retention factor for Avanafil and Dapoxetine Hydrochloride Separation and Validation with RP-HPLC in Bulk, Dosage Form and Rat Plasma; Validation, Degradation, and Pharmacokinetic Application

Why did I participate in an HIV vaccine study? Experiences of participation in the first phase II HIV vaccine trial in Mozambique: An ancillary study using a mixed-method approach

IntroductionThis study recognized the lack of information regarding recruitment and retention factors associated with implementing HIV vaccine trials from the perspective of de facto participants. It aimed to describe the motives and experiences of 31 young adults who participated in a phase II HIV vaccine clinical trial conducted in Maputo, Mozambique. MethodsThis was an ancillary study with a mixed-method approach that employed a convergent design, combining both quantitative and qualitative methodologies. Data collection involved questionnaire surveys, in-depth interviews, and focus group discussions. Participants were assessed before and after learning whether they received the experimental vaccine or placebo. Thematic analysis was used for qualitative data, while descriptive analysis and statistical tests such as Fischer’s test and McNemar’s exact test were applied to quantitative data. The study also utilized the Health Belief Model to understand the decision-making process of participating in an HIV vaccine study. ResultsMost of our participants were young females, single, with limited financial resources. Participants joined the trial with the belief that they had a unique opportunity to help the fight against HIV and contribute to the research for the discovery of an HIV vaccine. Positive experiences related to trial participation include gaining knowledge about HIV and personal health and receiving risk reduction counseling. Participants reported blood collection as a negative experience and that they suffered social harm because of trial participation. Participants felt abandoned after the trial ended. ConclusionPreventive HIV vaccine trials should integrate a social-behavioral component to assess reasons for participation and refusal in real-time. Providing ongoing personal attention is crucial for young individuals who have committed 1–2 years to trial participation, extending beyond the trial period. Implementing tailored strategies for HIV risk assessment and reduction during and after the trial is essential. Addressing these factors can enhance preventive HIV vaccine trial implementation.

The Effect of Different Ethanol Concentrations as The Extraction Solvent on Total Flavonoid Content of White Mulberry Leaves Extracts (Morus alba L.)

White mulberry leaves (Morus alba L.) contain flavonoid which empirically have many health benefits, such as reducing fever, relieving headaches and throats, coughs, dysentery, digestive disorders, flu, and according to research it has antioxidant activity. Many factors effect the total flavonoid content, one of which is the concentration of the extraction solvent. The purpose of the research was to determine the effect of different ethanol concentrations as the extraction solvent on total flavonoid content of white mulberry (Morus alba L.) leaves extract. White mulberry leaves (Morus alba L.) were extracted using the maceration method, the extract was tested for phytochemical screening and thin layer chromatography using chloroform: ethyl acetate (6: 4) as the eluent. The resulting spots were observed visually and with λ 254 nm and λ 366 nm UV light. Determination of flavonoid content by UV-Vis spectrophotometry using the AlCl3 colorimetric method at a maximum wavelength of 415 nm. The research results showed that the yield of 50% and 96% ethanol extract of white mulberry leaves (Morus alba L.) was 17.42 % and 11.04 %. Phytochemical screening showed that both extracts positively contained flavonoids. The presence of flavonoids was confirmed using a thin layer chromatography test, resulting in an average Rf value for 50% and 96% ethanol extracts are 0.71 and 0.70, close to quercetin Rf standard is 0,73 as comparison. The total flavonoid content obtained from the 50% ethanol extract was 36.0902 mgQE/g and the 96% ethanol extract was 56.4699 mgQE/g. The conclusions are the concentration of the extraction solvent effect the yield and total flavonoid content.

Risk factors for postoperative urinary retention in fragility hip fracture patients: a prospective study

BackgroundPostoperative urinary retention (POUR) among older patients with hip fractures is common and may result in delayed ambulation, prolonged hospital stays, and urinary tract infections. Although preoperative urinary catheter indwelling and early postoperative removal can prevent perioperative urinary retention, this condition may occur in some patients after catheter removal, which requires urinary catheter re-indwelling or intermittent catheterization. Therefore, this study aims to identify risk factors and develop a screening tool for postoperative urinary retention in patients who have undergone operative treatment for fragility hip fractures subsequent to urinary catheter removal.MethodsA prospective cohort study of 145 fragility hip fracture in older patients who were operatively treated between September 2020 and May 2022 was conducted. All patients were evaluated for urine retention after urinary catheter removal using a bladder scan. In addition, factors related to urinary retention were collected and utilized for screening tool development.ResultsOf the included patients, 22 (15.2%) were diagnosed with POUR. A multivariable logistic regression model using a stepwise backward elimination algorithm identified the current use of drugs with anticholinergic effect (OR = 11.9, p = 0.012), international prostate symptom score (IPSS) ≥ 8 (OR = 9.3, p < 0.001), and inability to independently get out of bed within 24 h postoperatively (OR = 6.5, p = 0.051) as risk factors of POUR. The screening tool that has been developed revealed an excellent performance (AuROC = 0.85, 95%CI 0.75 to 0.91) with good calibration and minimal optimism.ConclusionsCurrent use of drugs with anticholinergic effects, IPSS ≥ 8, and inability to independently get out of bed within 24 h postoperatively are significant variables of POUR. For additional external validation, a proposed scoring system for POUR screening was developed.Trial registrationThe study protocol was retrospectively registered in The Thai Clinical Trials Registry (TCTR20220502001: 2 May 2022).

Extraction and Purification of Squalene from Virgin Olive Oil via Catalytic Transesterification and Molecular Distillation

Squalene, a highly valuable compound abundant in various natural sources, shows great potential in pharmaceutical, cosmetic, and nutraceutical applications. This research article outlines a comprehensive methodology for extracting and purifying squalene from virgin olive oil, a rich source of the compound. The extraction process begins with degumming, which involves heating the olive oil to 60-70°C to reduce viscosity, followed by the addition of 2-3% warm water to hydrate phospholipids. Food-grade phosphoric acid is then added to react with the phospholipids, forming precipitates. The mixture is stirred for 20-30 minutes and allowed to rest for an additional 20-30 minutes, enabling impurities to settle. The upper layer of degummed oil is separated via decantation or centrifugation and washed with warm water for pH adjustment. Next, transesterification is performed by mixing 100 ml of virgin olive oil with 25% methanol (w/w) and a catalyst (0.5% sodium methoxide or PTSA), and heating the mixture to 80-90°C under reflux for 1-2 hours. Following transesterification, the solvent and acetone are distilled out, and acetone precipitation is repeated 2-3 times to remove unsaponified matter, which is then filtered and evaporated. The concentrated oil undergoes molecular distillation at 180°C and 0.0033 bar pressure for 1 hour, yielding the distillate and residue for further analysis. Qualitative analysis using Thin Layer Chromatography (TLC) involves Merck TLC plates with silica gel 60 F254 and a hexane: chloroform (9:1) mobile phase. Spots are developed with a 10% HCl solution, confirming the presence of squalene with an RF value of 0.93. Quantitative analysis via High-Performance Thin-Layer Chromatography (HPTLC) employs Merck TLC plates with cyclohexane as the mobile phase and CAMAG at 254 nm and 366 nm wavelengths, revealing a squalene purity of 67% and a recovery rate of 69.8%. The initial purification through transesterification facilitated the conversion of ester groups, yielding squalene-rich fractions, while acetone precipitation effectively removed saponified matter. Molecular distillation further enhanced squalene purity. TLC analysis confirmed the qualitative presence of squalene, and HPTLC provided precise quantitative measurements. The obtained squalene purity of 67% significantly enriches the initial content in virgin olive oil, though further optimization could enhance purity and yield. Complementary techniques like GC-MS or HPLC could validate the purification process. This study presents an efficient, replicable procedure for extracting and purifying squalene from virgin olive oil, with significant implications for pharmaceutical, cosmetic, and nutraceutical industries. The findings support a sustainable and ethical shift towards vegetable-derived squalene, meeting market demands while ensuring high-quality production.

Determination of physicochemical parameters of (bio)molecules and (bio)particles by capillary electromigration methods.

The review provides an overview of recent developments and applications of capillary electromigration (CE) methods for the determination of important physicochemical parameters of various (bio)molecules and (bio)particles. These parameters include actual and limiting (absolute) ionic mobilities, effective electrophoretic mobilities, effective charges, isoelectric points, electrokinetic potentials, hydrodynamic radii, diffusion coefficients, relative molecular masses, acidity (ionization) constants, binding constants and stoichiometry of (bio)molecular complexes, changes of Gibbs free energy, enthalpy and entropy and rate constants of chemical reactions and interactions, retention factors and partition and distribution coefficients. For the determination of these parameters, the following CE methods are employed: zone electrophoresis in a free solution or in sieving media, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography. In the individual sections, the procedures for the determination of the above parameters by the particular CE methods are described.

Comprehensive in vitro evaluation of Indigofera hochstetteri Baker extract: Effect of chemicals in antimicrobial, anticancer, anti-inflammatory, and anti-diabetic activities

The study aimed to analyze the pharmacological properties of medicinal plant Indigofera hochstetteri Baker extracts. Preliminary phytochemical analysis revealed a diverse range of secondary metabolites present in it. TLC analysis detected numerous phytochemicals with varying Rf values, aiding in different solvent systems. GC-MS analysis revealed the presence of 29 bioactive compounds with diverse pharmacological activities, including anti-inflammatory, antioxidant, analgesic and antimicrobial properties. Antimicrobial effect of I. hochstetteri Baker methanolic extract showed significant inhibitory effects against E. coli, E. aerogenes, S. flexneri, P. aeruginosa, S. aureus, E. faecalis, B. cereus, and fungal strain C. albicans. The methanol extract also showed significant antifungal activity by inhibiting the growth of Sclerotium rolfsii in food poisoning method. MTT assays revealed significant cytotoxic activity of methanolic extract against human leukemia HL-60 cancer cells with IC50 of 116.01 μg/mL. In apoptotic study, I. hochstetteri Baker methanolic extract showed 28.84% viable cells, 30.2% early apoptosis, 35.54% late apoptosis, and 5.86% necrosis comparatively similar with standard used. The extract showed significant anti-inflammatory effect on HRBC stabilization, and protein denaturation of BSA and egg albumin denaturation with IC50 of 193.62 μg/mL, 113.94 μg/mL respectively. In anti-diabetic assays like α-amylase, α-glucosidase, and Glucose uptake assay, I. hochstetteri extract showed good anti-diabetic effect with IC50 of 60.64 μg/mL, 169.34 μg/mL, and 205.63 μg/mL respectively. In conclusion I. hochstetteri Baker have promising bioactive metabolites with significant biological activities, it can be good substitute for the chemical drugs after successful clinical studies.

Preparation of carboxyl-functionalized silica core-shell microspheres and their applications in weak cation exchange chromatography, heavy metal removal, and lysozyme enrichment.

Chromatography is a technique of separation based on adsorption and/or interaction of target molecules with stationary phases. Herein, we report the design and fabrication of BTDA@SiO2 core-shell microspheres as a new class of stationary phase and demonstrate its impressive performance for chromatographic separations. The silica microspheres of BTDA@SiO2 were synthesized by in situ method with 1,3,5-benzenetricarboxaldehyde and 3,5-diaminobenzoic to separate peptides and proteins on high-performance liquid chromatography. The BTDA@SiO2 core-shell structure has a high specific surface area and retention factor of 4.27 and 8.31 for anionic and cationic peptides, respectively. The separation factor and resolution were high as well. A typical chromatogram illustrated nearly baseline resolution of the two peptides in less than 3 min. The BTDA@SiO2 was also highly stable in the pH range of 1 to 14. Furthermore, the prepared BTDA@SiO2 core-shell material not only be used for chromatographic separation but also as heavy metal removal from water. Using a BTDA@SiO2, we also achieved a lysozyme enrichment with a maximum saturated adsorption capacity reaching 714mg/g. In summary, BTDA@SiO2 has great application prospects and significance in separation and purification systems.

A microchip gas chromatography column assembly with a 3D metal printing micro column oven and a flexible stainless-steel column

In this work, a microchip gas chromatography (GC) column assembly utilizing a three-dimensional (3D) printed micro oven and a flexible stainless steel capillary column was developed. The assembly's performance and separation capabilities were characterized. The key components include a 3D printed aluminum plate (7.50 × 7.50 × 0.16 cm) with a 3-meter-long circular spiral channel, serving as the oven, and the column coiled on the channel with an inner diameter of 320 μm and a stationary phase of OV-1. A heating ceramic plate was affixed on the opposite side of the plate. The assembly weighed 40.3 g. The design allows for easy disassembly, or stacking of heating devices and columns, enabling flexibility in adjusting column length. When using n-C13 as the test analyte at 140 °C, a retention factor (k) was 8.5, and 7797 plates (2599 plates/m) were obtained. The assembly, employing resistance heating, demonstrated effective separation performance for samples containing alkanes, aromatics, alcohols and ketones, with good reproducibility. The reduction in theoretical plates compared to oven heating was only 2.95 %. In the boiling point range of C6 to C18, rapid temperature programming (120 °C/min) was achieved with a power consumption of 119.512 W. The assembly was successfully employed to separate benzene series compounds, gasoline and volatile organic compounds (VOCs), demonstrating excellent separation performance. This innovative design addresses the challenges of the complexity and low repeatability of the fabrication process and the high cost associated with microchip columns. Furthermore, its versatility makes it suitable for outdoor analysis applications.

Guidelines for descriptor assignments for the solvation parameter model by separation techniques

The solvation parameter model uses six compound descriptors to model equilibrium properties in biphasic systems formally defined as excess molar refraction, E, dipolarity/polarizability, S, overall hydrogen-bond acidity, A, overall hydrogen-bond basicity, B, McGowan's characteristic volume, V, and the gas-liquid partition constant on hexadecane at 25 °C, L. The V descriptor can be assigned from structure and the E descriptor for compounds liquid at 20 °C can be calculated from its refractive index and characteristic volume. The E descriptor for compounds solid at 20 °C and the S, A, B, and L descriptors are assigned from experimental properties traditionally obtained by chromatographic, liquid-liquid partition, and solubility measurements. Here I report an efficient experimental design using the Solver method for the accurate assignment of descriptors for neutral compounds that simultaneously minimizes laboratory resources. This multi-technique approach requires 3 retention factor measurements in a 60 °C temperature range per compound on four columns by gas chromatography, 3 retention factor measurements in a 30 % (v/v) acetonitrile composition range per compound on two columns by reversed-phase liquid chromatography, and eight partition constant measurements by liquid-liquid partition in totally organic and aqueous biphasic systems for a total of 26 experimental measurements. The accuracy of the descriptor assignments was validated by comparison with the values in the Wayne State University (WSU) descriptor database taken as the best estimate of the true descriptor values. The E, S, A, B and L descriptors were assigned simultaneously by the Solver method using the above approach without significant bias and with an average absolute deviation (AAD) of 0.054, 0.018, 0.015, 0.013, and 0.040, respectively, compared with the WSU database values, corresponding to a relative absolute average deviation in percent (RAAD) of 7.2, 1.9, 3.6, 5.1, and 0.84 %, respectively, for 32 varied compounds. This streamlined approach represents a significant improvement on earlier single-technique approaches used as the starting point for the development of the multi-technique approach. For compounds of variable hydrogen-bond basicity modifications to the multi-technique approach were implemented while maintaining the same number of experimental measurements. Acceptable descriptor assignments for B/B° were obtained for compounds liquid at 20 °C for which the E descriptor was available by calculation. For solid compounds at 20 °C the E and B/B° descriptors are restricted to qualitative application where approximate values may be acceptable.

Thin layer chromatography of methylated derivatives of sodium alkylbenzenesulfonates in water analysis by GC-MS

Sodium alkylbenzene sulfonates or linear alkyl benzene sulfonates (LAS) are the most common synthetic anionic surfactants and water pollutants. They can cause both acute and chronic toxic effects on water organisms. Selective determination of sodium alkylbenzene sulfonates as a separate class of anionic surfactants is possible using gas chromatography coupled with mass spectrometry (GC-MS) in the form of linear alkylbenzenesulfonic acid methyl esters (LABSA ME). In order to purify the extracts and concentrate the analytes, we studied the behaviour of these compounds by ascending high-performance thin-layer chromatography using Kieselgel 60 F254 and Sorbfil plates. A mixture of n-hexane and methanol solvents in a ratio of 23:1 (by volume) was used as the mobile phase. Under these conditions, sodium alkylbenzenesulphonates remain on the start line, while their derivatives (ME ABSC), obtained by methylation with trimethyl orthoformate in the presence of trifluoroacetic acid (with a yield of η=98%), form zones characterised by retention coefficient values of Rf = 0.62 and Rf = 0.71 on Kieselgel 60 F254 and Sorbfil plates, respectively. The repeatability of the Rf values was characterised by a standard deviation of 6.1 and 5.9 %, respectively (n=16). The completeness of extraction (95.0–100.0 %) of analytes from the plates by descending TLC with acetonitrile was noted. The applicability of the TLC method for the concentration of analytes and pretreatment of extracts on the example of real water samples was shown. Using GC-MS with electron impact ionisation, we determined the concentrations of sodium alkylbenzenesulphonates in water sampled in the southern basin of Lake Baikal from a depth of 400 m (0.24±0.02 µg/dm3) and in snowmelt water from the ice of the Krestovka River where it flows into Lake Baikal near the village of Listvyanka (31.1 ± 1.0 µg/dm3).

Optimization of Culturing Conditions for the Production of Antimicrobial Metabolite by Bacillus Carotarum

Forest soil antagonistic bacteria Bacillus carotarum was isolated and tested for optimum antimicrobial metabolite production. Maximum antimicrobial metabolite production was found at temperature 30°C and pH 7.0 and on Ist day of incubation at stationary condition. The medium consisting of beef extract - 0.3%, peptone - 0.5% and NaCl - 0.05%, was screened out as a suitable medium for maximum antimicrobial production supplemented individually with four carbon sources of which starch was found as the best carbon source. The active agent was best extracted with petroleum ether. Homogeneity of the crude bioactive metabolites were also tested by paper chromatographic analysis where a single type of bioactive metabolite was found with a Rf value of 0.94 in the solvent system n- butanol: acetic acid : water = 4 : 1 : 5 . The antimicrobial spectrum of the metabolite was wide and showed activity against Shigella dysenteriae (AE14612), Salmonella typhi(AE14296), Vibrio cholerae (A214748), Pseudomonas aeruginosa (CRL, ICDDR’ B), Bacillus cereus (BTCC19), and Bacillus subtilis (BTTC17). The Chittagong Univ. J. B. Sci. 8(1&amp;2): 01-10, 2013

Chiral Hydroxy Metabolite of Mebendazole: Analytical and Semi-Preparative High-Performance Liquid Chromatography Resolution and Chiroptical Properties.

Mebendazole (MBZ) is a benzimidazole carbamate anthelmintic used worldwide for the treatment and prevention of parasitic disorders in animals and humans. A large number of in vivo and in vitro studies have demonstrated that MBZ also has anticancer activity in multiple types of cancers. After oral administration, the phenylketone moiety of MBZ is rapidly reduced to the hydroxyl group to form the chiral hydroxy metabolite (MBZ-OH). To the best of our knowledge, there is no information in the literature on the stereochemical course of transformation and the anthelmintic and antitumor activity of individual enantiomers of MBZ-OH. In the present study, we describe in detail the direct HPLC resolution of MBZ-OH on a 100 mm × 4.6 mm Chirapak IG-3 column packed with 3 μm silica particles containing amylose (3-chloro-5-methylphenylcarbamate) as a selector. At 25 °C and using pure methanol as the mobile phase, the enantioseparation and resolution factors were 2.38 and 6.13, respectively. These conditions were scaled up at a semi-preparative scale using a 250 mm × 10 mm Chiralpak IG column to isolate multi-milligram amounts of both enantiomeric forms of the chiral metabolite. The chiroptical properties of the collected enantiomers were determined and, through a theoretical study, were related to the more stable conformations of MBZ-OH. The first and second eluted enantiomers were dextrorotatory and levorotatory, respectively, in dimethylformamide solution. Finally, by recording the retention factors of the enantiomers as the water content in the water-acetonitrile mobile phases was progressively varied, U-shaped retention maps were generated, indicating a dual and competitive hydrophilic interaction liquid chromatography and reversed-phase liquid chromatography retention mechanism on the Chirapak IG-3 chiral stationary phase.

Dynamic changes in dissolved organic matter during transport of landfill leachate in porous medium.

The dynamic changes in dissolved organic matter (DOM) during the transport of landfill leachate (LL) in porous medium should be explored, considering the high levels of DOM in the LL of municipal solid waste. Column experiments were carried out at 25°C at a Darcy's flux of 0.29cm/h for 2722h to compare the transport of Cl-, ultraviolet absorbance at 254nm (UV254), chemical oxygen demand (COD), and dissolved organic carbon (DOC) in the simulated porous medium by using the CXTFIT2.1 code. Results showed that the convection-dispersion equation (CDE) could describe Cl- transport well. The high levels of λ and D could be highly correlated with the physicochemical properties of the porous medium. The transport of the studied DOM with evident aromatic character could be described appropriately by the CDE model with the first-order reaction assumption, considering the similar variation trends of UV254, COD, and DOC in the effluent during experiments. Specifically, the values of retardation factor (R) were in the following order: DOC > UV254 > COD, whereas the low values of the first-order decay coefficient (k1) for DOC and COD were still higher than that for UV254. High contents of humic-like substances in the DOM with complex toxic components resulted in the natural low removal efficiencies of COD, DOC, and UV254 (≤ 23%), which could be confirmed by the variations of fluorescence index (FI) and humification index (HIX) in the effluent. The results should be helpful in evaluating the environmental risk induced by the LL leakage in a landfill site.