Silica-alumina Gels Research Articles

Combination of Hollow Capsule Structure and Zn Uniform Load for the Conversion of Methanol to Aromatics over Zn/ZSM-5 Zeolites.

As an important nonoil route for acquiring aromatics, the highly efficient conversion of methanol to aromatics over Zn/ZSM-5 zeolites remains an ongoing challenge. In this work, we developed a uniform loading approach of zinc and further combined it with a hollow capsule structure to design the high-performance Zn/ZSM-5 catalyst. The electrostatic assembly among EDTA3-, n-butylamine+ and negative silica-alumina gel gave rise to an "Inorganic-Organic Hybrid Sphere" in form of Na(l+m+n+3x)-(y+z)·{[(SiO)4Al-]l/(SiO-)m(n-butylamine+)y(EDTA3-)x(n-butylamine+)z(SiO-)n, which further transformed into mesoporous aluminosilicates sphere (MASS) through calcination. The characteristic of abundant mesopore guaranteed MASS fantastic ability to evenly incorporate Zn ingredient inside, and the resultant Zn/MASS further served as a "hard template" for the direct synthesis of Hollow Zn/ZSM-5 capsules, rather than after impregnation. When tested in the methanol-to-aromatics (MTA) process, the direct synthesis method not only facilitated the homogeneous dispersion of the Zn ingredient, but also benefited for the generation of more (ZnOH)+ sites and strengthened their synergism with zeolite acid for the superior aromatics selectivity (50.63%). Meanwhile, the hollow capsule structure increased the contact time of MTA intermediate products with the Zn/ZSM-5 shell, and it increased the coke-admitting capacity and suppressed the coke rate, which maintained quite an excellent stability (131 h). Therefore, the above combination of hollow capsule structure and uniform load of Zn ingredient brings forward a wide prospect to develop zeolite materials with excellent properties in catalysis.

An eco-friendly and cost-effective HPTLC method for quantification of COVID-19 antiviral drug and co-administered medications in spiked human plasma

The coronavirus-2 has led to a global pandemic of COVID-19 with an outbreak of severe acute respiratory syndrome leading to worldwide quarantine measures and a rise in death rates. The objective of this study is to propose a green, sensitive, and selective densitometric method to simultaneously quantify remdesivir (REM) in the presence of the co-administered drug linezolid (LNZ) and rivaroxaban (RIV) in spiked human plasma. TLC silica gel aluminum plates 60 F254 were used as the stationary phase, and the mobile phase was composed of dichloromethane (DCM): acetone (8.5:1.5, v/v) with densitometric detection at 254 nm. Well-resolved peaks have been observed with retardation factors (Rf) of 0.23, 0.53, and 0.72 for REM, LNZ, and RIV, respectively. A validation study was conducted according to ICH Q2 (R1) Guidelines. The method was rectilinear over the concentration ranges of 0.2–5.5 μg/band, 0.2–4.5 μg/band and 0.1–3.0 μg/band for REM, LNZ and RIV, respectively. The sensitivities of REM, LIN, and RIV were outstanding, with quantitation limits of 128.8, 50.5, and 55.8 ng/band, respectively. The approach has shown outstanding recoveries ranging from 98.3 to 101.2% when applied to pharmaceutical formulations and spiked human plasma. The method’s greenness was assessed using Analytical Eco-scale, GAPI, and AGREE metrics.

Development and Validation of High-Performance Thin Layer Chromatographic Method for Simultaneous Estimation of Curcumin and Artemisinin

Curcumin and Artemisinin are proposed to be formulated as combination therapy to expand the antimalarial effect in resistant and liable isolates. The present research work was to develop and validate a simple, accurate, precise, high-performance thin layer chromatographic method for simultaneous determination of Curcumin and Artemisinin. The chromatographic separation was carried out on a precoated silica gel aluminum plate, 20 × 20 cm, 100μm thickness, with a mixture of Hexane, Toluene and Ethyl acetate (6:1:3) as mobile phase UV detection was performed at 496nm. The Rf were 0.23 and 0.76 for Curcumin and Artemisinin, respectively. Calibration plots were linear over the concentration range 200-1000ng/band for both Curcumin and Artemisinin. The method was validated in accordance with ICH Q2(R1) guidelines for linearity, sensitivity accuracy, precision, and robustness. The percent recoveries in terms of accuracy for the synthetic mixture were found to be 99.8% to 100.0% and 99.94% to 100.4%, and the pooled percent relative standard deviation for repeatability and intermediate precision studies was found to be 0.015-0.042% and 0.008-0.070% for Curcumin and Artemisinin, respectively. A factorial design was used to optimize the chromatographic conditions for the robustness study. In conclusion, a novel, simple, accurate and reproducible HPTLC method was developed and could be applied for quality control testing of Curcumin and Artemisinin in synthetic mixture.

Desitometric Development and Validation for Simultaneous Determination of Antiretroviral Drugs Lamivudine, Zidovudine and Nevirapine in Fixed-Dose Combination Tablets

A cutting-edge high-performance thin layer chromatography (HPTLC) approach designed for simultaneous measurement of tablets containing drugs like lamivudine, nevirapine, and zidovudine. Chromatograms were performed employing chloroform and methanol (8:2 v/v) on pre-coated silica gel aluminum thin-layer chromatography (TLC) plates. The data was quantified using the optical density absorbance mode at 271 nm. The Rf values for lamivudine, zidovudine, and nevirapine were 0.140, 0.523, and 0.678, respectively. Linearity was found for lamivudine, zidovudine and nevirapine at concentrations of 150 to 900 ng band-1, 300 to 1800 and 200 to 1200 ng band-1, respectively. Lamivudine had a lower limit of detection (LLoD) of 27.36 ng band-1 and a lower limit of quantitation (LLoQ) of 82.91 ng band-1, whereas zidovudine had LoQs of 64.13 ng band-1 and 194.34 ng band-1. For nevirapine, the values were 35.52 and 107.64 ng band-1, respectively. Lamivudine had a lower LoD of 27.36 ng band-1 and a lower LoQ of 82.91 ng band-1, whereas zidovudine had LoQs of 64.13 and 194.34 ng band-1. For nevirapine, the values were 35.52 and 107.64 ng band-1, respectively. The recovery, specificity, and accuracy of this device have been demonstrated. This new formulation evaluated market tablet formulations of the above drugs (Duovir, Cipla Ltd.). The developed method demonstrated the ability to simultaneously identify these drugs from quantitative data without interference.

Levels of polycyclic aromatic hydrocarbon in the soil around typical automobile repair workshops in Nigeria.

This study determined the levels of polycyclic aromatic hydrocarbons (PAHs) in the soil around typical automobile repair workshops in Nigeria. Risk assessment associated with human contact with the soil was carried out using hazard quotient (HQ) and incremental life cancer risk (ILCR) from human unconscious ingestion and dermal contact with the soil. Soil samples were obtained at different automobile workshops in Ado-Ekiti, Western Nigeria. The PAHS in the samples were extracted using dichloromethane and extracts were cleaned up using silica-alumina gel open column chromatography. Analysis of PAHs in the soil was done using a gas chromatograph coupled to a mass selective detector operated on electron ionization mode. The results showed the mean PAHs concentration at the sampling locations ranged from 5.58 - 6.4 μg/g and the mean ∑ carcinogenic PAHs was 58.4 μg/g, equivalent to 59.39 % of total PAHs observed. The mean Toxicity equivalence (TEQs) ranged from 0.02 - 6.680 μg/g. Benzo (a) pyrene and dibenzo(a,h)anthracene have the highest toxicity equivalent. The total ILCRs from accidental ingestion and dermal contact in adults were 1 ×10^(-3) and 9.8 ×10^(-5), for adults and children respectively; both are higher than the permissible limit stipulated by the World Health Organization.The HQs obtained are several folds higher than 1. This implies high carcinogenic and non-carcinogenic risks for children and adults. The study revealed the levels of PAHs and also revealed the risks associated with human contact with the soil around automobile repair workshops.

Structural and energetic characterization of silica-alumina gels for adsorption processes

The surface chemistry of silica-alumina gels is largely determined by number and type of silanol groups present. However, until now the influence of different silanol groups on adsorption processes is largely unknown. The aim of this study is to develop a method for an energetic characterization of silica-alumina gels by combining data measured by nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and adsorption calorimetry. The silica-alumina gels used for the studies are systematically modified by pretreating at temperatures between 200 °C and 1000 °C. To quantify number and distribution of silanol groups, complementary data from 29Si-NMR and 1H NMR and thermogravimetric measurements is combined. Adsorption measurements with the adsorptives cyclopentane (nonpolar) and pyrrolidine (polar molecule capable of hydrogen bonding) provide further information. Based on the adsorption isotherms and load-dependent heats of adsorption, it is shown that number and distribution of silanol groups have little effect on the adsorption of cyclopentane. In contrast, different energy levels are found for the heat of adsorption of pyrrolidine at ∼106 kJ mol−1, ∼95 kJ mol−1, ∼87 kJ mol−1, and ∼80 kJ mol−1 depending on pretreatment temperature. Based on the combination of all data, a model is proposed to assign the identified energy levels of adsorption to different silanol groups.

Levels of polycyclic aromatic hydrocarbon in the soil around typical automobile repair workshops in Nigeria

Background: This study determined the levels of polycyclic aromatic hydrocarbons (PAHs) in the soil around typical automobile repair workshops in Nigeria. Risk assessment associated with human contact with the soil was carried out using hazard quotient (HQ) and incremental life cancer risk (ILCR) from human unconscious ingestion and dermal contact with the soil. Methods: Soil samples were obtained at different automobile workshops in Ado-Ekiti, Western Nigeria. The PAHS in the samples were extracted using dichloromethane and extracts were cleaned up using silica-alumina gel open column chromatography. Analysis of PAHs in the soil was done using a gas chromatograph coupled to a mass selective detector operated on electron ionization mode. Results: The results showed the mean PAHs concentration at the sampling locations ranged from 5.58 – 6.4 μg/g and the mean ∑ carcinogenic PAHs was 58.4 μg/g, equivalent to 59.39 % of total PAHs observed. The mean Toxicity equivalence (TEQs) ranged from 0.02 - 6.680 μg/g. Benzo (a) pyrene and dibenzo(a,h)anthracene have the highest toxicity equivalent. The total ILCRs from accidental ingestion and dermal contact in adults were 1 ×10^(-3) and 9.8 ×10^(-5) , for adults and children respectively; both are higher than the permissible limit stipulated by the World Health Organization.The HQs obtained are several folds higher than 1. This implies high carcinogenic and non-carcinogenic risks for children and adults. Conclusions: The study revealed the levels of PAHs and also revealed the risks associated with human contact with the soil around automobile repair workshops.

High early pozzolanic reactivity of alumina-silica gel: A study of the hydration of composite cements with carbonated recycled concrete paste

Carbonated recycled concrete paste (cRCP) is a unique supplementary cementitious material with pozzolanic properties stemming from the alumina-silica gel. This study reveals that the high early strength of composite cements with cRCP is attributed to its rapid pozzolanic reactivity. 27Al and 29Si NMR investigations show that the alumina-silica gel is consumed after only 7 days of hydration. The rapid gel reaction results in the formation of a C-(A)-S-H phase with a low Ca/Si ratio. After 7 days, belite and remains of alite react further and increases the Ca/Si ratio of the C-(A)-S-H phase to a level typical for blended cements. As a result, a lower porosity forms already at early age, resulting in high strength. The reactivity of cRCP is influenced by its origin and carbonation conditions. Carbonation in sulfate-rich solutions enhances the gel surface area and accelerates the reaction. Slag remnants in cRCP react aiding to microstructure and strength development.

Performance and hydration of ternary cements based on Portland clinker, carbonated recycled concrete paste (cRCP) and calcined clay

This study explored composite cements consisting of Portland clinker, two pozzolans (alumina-silica gel in carbonated Recycled Concrete Paste (cRCP) and metakaolin), and calcium carbonate. The rapid reactivity of alumina-silica gel resulted in full reaction within 28 days, while metakaolin exhibited slower reactivity. cRCP played a significant role in strength development between 1 and 7 days, with metakaolin becoming prominent thereafter. The combination of materials preserved their distinct characteristics. Early hydration was mainly influenced by clinker and cRCP, leading to high early compressive strength. After alumina-silica gel dissolved, metakaolin forms a microstructure, reducing porosity and allowing for continued strength improvement over time. The pozzolans did not hinder their respective reactions, and calcium carbonate from cRCP stabilized ettringite content, similar to limestone-calcined clay systems. This study’s findings offer insights for developing multi-component cement with cRCP and calcined clays, resulting in higher strength and reduced CO2 footprint compared to calcined clay-limestone cements.

Composite cements with aqueous and semi-dry carbonated recycled concrete pastes

Carbonation of recycled concrete paste (RCP) may reduce cement industry’s CO2 emissions by sequestering CO2 and by using the carbonated material in new composite cements enabling a decrease in the clinker content. This study examines effects of wet and semi-dry carbonation of RCP on the hydration reactions and performance for composite cements incorporating the carbonated material. The two carbonation methods lead to differences in composition and morphology of the carbonated RCP’s. Semi-dry conditions produce CaCO3 as aragonite instead of calcite and results in a lower carbonation degree and denser particles. Despite these differences, the effects on the hydration and performance of the two types of carbonated RCP in composite cements are similar. For both methods, the fast reaction of the alumina-silica gel results initially in a C-(A)-S-H phase with a low Ca/Si ratio, resulting in early-age microstructure densification and higher early strengths. The Ca/Si ratio of the C-(A)-S-H phase increases again when all alumina-silica gel has reacted after a few days of hydration. It is found that the differences in cement performance are associated with different carbonation degrees of the two RCP’s rather than morphological changes between the carbonated pastes.

Mechanism underlying early hydration kinetics of carbonated recycled concrete fines-ordinary portland cement (CRCF-OPC) paste

Aiming to promote applications of carbonated recycled concrete fines (CRCF) as a low-carbon alternative to ordinary Portland cement (OPC), this study explored the effect of CRCF on the early hydration kinetics of OPC paste. The results show that CRCF is not only a highly active pozzolanic material but also an effective accelerator affecting the early hydration kinetics of OPC paste, thereby leading to an increased early compressive strength and a comparable 28-d compressive strength, even at a replacement ratio of 20%. Although the rheological properties and workability are negatively affected due to the high surface area and fine particle size of CRCF, the amorphous silica and silica-alumina gels and calcite present in CRCF facilitate initial ions dissolution and provide additional active nucleation sites for hydrates. As a result, the microstructure is densified due to the formation of additional C–S–H gels with high Si/Ca and Al/Ca ratios and carboaluminate phases, along with the inert filler effect of unreacted calcite particles. The incorporation of 20% CRCF to replace OPC can achieve a CO2 emissions reduction up to 25%. These indicate that the CRCF has a promising application scenario in transforming wasted concrete into high-value industrial products by CO2 activation.

Chromatographic separation to determine doxycycline monohydrate and ornidazole

AbstractHigh‐performance thin‐layer chromatography offers a variety of benefits that may assist you to save time and money, notably the capacity to run multiple samples at once and its reduced solvent usage. In alignment with the needs of molecular chemistry, it was also employed to modify and derivatize the stationary phase. Using a precise, accurate, as well as affordable high‐performance thin‐layer chromatography approach, the simultaneous measurement method for Doxycycline monohydrate and Ornidazole in the formulation has been developed and validated. Methanol: Iso‐propyl alcohol: Triethylamine (8:1.5:0.5, v/v/v) was used as the mobile phase during the separation, which took place on a stationary phase of pre‐treated derivatized silica gel aluminum plate 60 F254. At 285 nm, separated components were densitometrically measured. The method was validated for Linearity and range, precision, reproducibility, accuracy, the limit of detection, the limit of quantification, and robustness as per the International Council for Harmonization Q2(R1) guideline. Doxycycline monohydrate and Ornidazole regression coefficients (R2) were found to be 0.9967 and 0.9964, accordingly. Doxycycline monohydrate and Ornidazole percentage recoveries were measured to be 99.74 ± 0.65 and 100.8 ± 1.17, respectively. The analytical findings demonstrate that the proposed approach could be used to quantify Doxycycline monohydrate and Ornidazole simultaneously in pharmaceutical formulation.

Simultaneous Analysis of Flumethasone Pivalate and Clioquinol in the Presence of Phenoxyethanol Preservative in Their Pharmaceuticals Using TLC and UHPLC Methods

Two novel separation methods have been presented for the concurrent assessment of flumethasone pivalate (FP) and clioquinol (CL) in their combinations in ear drop formulations or in the presence of phenoxyethanol preservative (PEP) in their cream formulations. The first method is an innovative thin-layer chromatographic (TLC) method. The optimal separation was accomplished via silica gel aluminum plates F254, with a mixture of benzene, ethyl acetate and formic acid (5:5:0.2, in volumes) as the mobile system. In Method II, a new ultra-high-performance liquid chromatographic method (UHPLC) with a photodiode array detector (PDA) was presented. A reversed-phase inertsil ODS 5 µm C 18 packed column (100 Å, 4.6 mm internal diameter (I.D.) × 50 mm) at 30 °C was employed. Elution was completed in 3 min. Unfortunately, greener solvents were tested as a mobile phase, but an asymmetric peak for CL was noted. In addition, the new UHPLC method has a priority over the old HPLC one by Sayed et al., 2014, in terms of quickness and avoiding interference from the PEP preservative. Concerning the TLC method, the novel TLC method has the advantage of preventing the interference of PEP. This paper represents the first analytical approach for the concurrent assay of FP and CL in the presence of the preservative phenoxyethanol in the cream formulation.

Simultaneous quantification of Fluticasone propionate and Olopatadine hydrochloride by High‐performance thin‐layer chromatography

AbstractHigh‐performance thin‐layer chromatography has the capacity to run many samples simultaneously and reduced solvent usage. It offers a number of advantages that can save both time and money. The simultaneous quantification of fluticasone propionate and olopatadine hydrochloride in nasal spray has been developed and validated using a specific, precise, accurate, and economical high‐performance thin‐layer chromatography technique. Methanol:water:glacial acetic acid (8:2:0.05, v/v/v) was used as the mobile phase during the separation, which took place on a stationary phase of pre‐coated silica gel aluminum plate 60 F254. At 232 nm, separated components were densitometrically measured. The method was validated for linearity and range, precision, reproducibility, specificity, accuracy, the limit of detection, and the limit of quantification as per the International Council for Harmonization Q2(R1) guideline. Fluticasone propionate and olopatadine hydrochloride regression coefficients (R2) were found to be 0.9996 and 0.9991, accordingly. Fluticasone propionate and olopatadine hydrochloride percentage recoveries were measured to be 101.6 ± 0.69 and 99.62 ± 0.54, respectively. The analytical findings demonstrate that the proposed approach could be used to quantify Fluticasone propionate and olopatadine hydrochloride simultaneously in Pharmaceutical formulations.

Carbonation and related behaviors of hardened cement pastes under different hydration degrees

This paper develops a kind of molded disc samples to investigate the carbonation and related behaviors of hardened cement pastes under different previous hydration degrees. Weight and length changes of cement pastes over time are monitored during a multistep process including carbonation, drying, rewetting, and redrying. The combination of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) is used to identify and quantify the mineral compositions of carbonated cement pastes. An exponential function between CO2 uptake capacity and hydration time of cement pastes is established, which shows that the CO2 uptake capacity of cement pastes decreases dramatically at the very beginning days of hydration and then remaining relatively stable as hydration time is prolonged. Two reasons for this finding are revealed: i) the equilibrium between the carbonation and the post-carbonation reaction of carbonation product, i.e., silica-alumina gel; ii) refining of pore structures by hydration products which hinders carbonation. A clearer zonation of carbonation areas is proposed, and the spatial distribution equations of CO2 absorption are initially established. By monitoring carbonation and drying behavior of cement pastes with different hydration ages, it is revealed that carbonation reduces drying shrinkage of cement pastes especially for early-age samples, whereas drying increases carbonation shrinkage. By investigating the water changes during the multistep process, it is found that water is little released during the carbonation of C–S–H gels. New insight into mechanism of carbonation shrinkage is provided by a newly proposed model.

A specific high‐performance thin‐layer chromatography method validated for estimation of mometasone furoate and olopatadine hydrochloride

AbstractHigh‐performance thin‐layer chromatography has the capacity to run many samples simultaneously and reduced solvent usage, It offers a number of advantages that can save both time and money. The simultaneous quantification of mometasone furoate and olopatadine hydrochloride in a combined dose has been developed and validated using a specific, precise, accurate, and economical high‐performance thin‐layer chromatography technique. Methanol: Water (8: 2, v/v) was used as the mobile phase during the separation, which took place on a stationary phase of pre‐coated silica gel aluminum plate 60 F254. At 248 nm, separated components were densitometrically measured. The method was validated for Linearity and range, precision, reproducibility, specificity, accuracy, the limit of detection, and the limit of quantification as per the International Council for Harmonization Q2(R1) guideline. mometasone furoate and olopatadine hydrochloride regression coefficients (R2) were found to be 0.9995 and 0.9991, accordingly. Mometasone furoate and olopatadine hydrochloride percentage recoveries were measured to be 98.99 ± 0.39 and 99.15 ± 0.95, respectively. The analytical findings demonstrate that the proposed approach could be used to quantify mometasone furoate and olopatadine HCl simultaneously in a combined dose.

Development of thin layer chromatographic densitometric method for simultaneous quantification of Ivabradine HCl and Bisoprolol fumarate

AbstractThe literature review reveals that no thin‐layer chromatographic method has been developed for the simultaneous estimation of Bisoprolol fumarate and Ivabradine HCl in the combined dosage form. A sensitive, precise, accurate, and robust thin‐layer chromatographic method was developed and validated for the simultaneous quantification of a newer combination of Bisoprolol fumarate and Ivabradine HCl used in the treatment of angina, according to the International Council for Harmonization Q2 (R1) guideline. The stationary phase was pre‐coated silica gel aluminum plate 60 F254 and toluene‒methanol‐triethylamine (9:1:0.1, v/v/v) was used as the mobile phase. A common detection wavelength of 279 nm was selected for the simultaneous quantification of Bisoprolol fumarate and Ivabradine HCl. The method was validated for different parameters like linearity, precision, accuracy, robustness, the limit of detection, and the limit of quantification as per the International Council for Harmonization guidelines. The correlation coefficients (r2) for Bisoprolol fumarate and Ivabradine HCl were found to be 0.9976 and 0.9965, respectively. The mean percentage recoveries for Bisoprolol fumarate and Ivabradine HCl were found to be 99.19%–101.70% and 98.71%–101.86%, respectively. As per the International Council for Harmonization Q2 (R1) guideline, the proposed TLC method was repeatable and selective as per statistical analysis and it can be used for simultaneous estimation of Bisoprolol fumarate and Ivabradine HCl in bulk and formulation.

Effect of temperature on carbon dioxide mineralisation in recycled cement paste

In this work, an approach towards a carbon-neutral cement industry using carbon dioxide mineralisation of recycled concrete paste is investigated. It focuses on the effect of temperature on the enforced carbonation of cement paste. The enforced carbonation is a rapid process at ambient temperature, which is further accelerated at elevated temperatures. Moreover, the extent of the reaction is increased when the temperature rises. The carbonation reaction is divided into two kinetic stages. During the first stage, the carbonation kinetics is controlled by the availability of carbon dioxide that increases at higher temperatures. During the second stage, the reaction kinetics is controlled by the dissolution of the hydrates. Increased temperature accelerates this process by increasing the undersaturation level of the dissolving phases. The main carbonation products are calcium carbonate and an alumina–silica gel. The increasing temperature has a limited impact on these phases, and the differences come mainly from the different degrees of carbonation.

Assessment of seasonal variation in distribution, source identification, and risk of polycyclic aromatic hydrocarbon (PAH)-contaminated sediment of Ikpoba River, South-South Nigeria.

The study aims to assess the seasonal variation in distribution, source identification, and risk of 20 polycyclic aromatic hydrocarbons (20 PAHs) in the sediment of the Ikpoba River, south-south Nigeria. The PAHs were extracted in an ultrasonic bath with a mixture of n-hexane and dichloromethane (1:1 v/v). The extract was cleaned by silica-alumina gel mixed with anhydrous Na2SO4 in a chromatography column, eluted by n-hexane, and analysed by gas chromatography-mass spectrometry. The range of the average PAHs in mg.kg-dw was 0.15 (Nap)-0.54 (Acy) and 0.13 (D.al.P)-0.99 (Acy) in wet and dry periods correspondingly, indicating an increase in concentration from wet to dry period. However, the rings of the average concentration of the PAHs show 6 and 3 rings to be the highest values during the wet and dry seasons, respectively. Based on the human health risk analysis, the hazard quotient (HQ) and hazard index (HI), and carcinogenic risk indices showed low non-carcinogenic and carcinogenic risk for both seasons. The ecological risk analysis showed the mean effect range median quotient (mERMQ) recorded a medium-low effect on the biota of the locations, except in AS3 during the wet season and also in WS8 and WS9 during the dry season. The minimum value of the toxic equivalent quotient (TEQ) was > 0.2mg/kg, which indicated a recommendation for the clean-up of the Ikpoba River. The isomer ratio and the principal component analysis (PCA) revealed the sources of the PAHs to be majorly combustion, followed by pyrolytic and petrogenic sources for both seasons.

IDENTIFICATION AND CHARACTERIZATION OF D-LIMONENE AND ROSMARINIC ACID BY HPTLC ANALYSIS OF BLACK CARAWAY OIL WITH ANTIOXIDANT AND ANTIBACTERIAL ACTIVITIES

Due to their enticing citrus scent, the phenolic chemicals D-limonene (DL) and Rosmarinic (RA) acid have been widely employed in food flavoring, soaps, and perfumes in addition to the treatment of many disorders. Using the essential oils extracted from Black caraway oil, a simple and straightforward high-performance thin-layer chromatography (HPTLC) method was created for the simultaneous detection of d-limonene and rosmarinic acid. Hexane, ethyl acetate, and formic acid, in the ratio of 20:19:1, v/v/v, were used as the mobile phase to generate the chromatogram on a silica gel aluminum plate 60 F254 (20 x 10 cm). The concurrent detection of DL and RA in commercial essential oils was successfully accomplished using the devised HPTLC approach. Infrared spectroscopy (IR) and mass spectrometry (MS) experiments were conducted on samples of d-limonene and rosmarinic acid in order to obtain the functional group and mass spectral information. The study data from the mass study were used to pattern the entire mass fragmentation process of DL and RA. The best and most effective molecular formula was used to suggest structures for each fragment. The antibacterial activity was studied with gram-positive bacteria; Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. coccus), and antioxidant activity with that of methanol.