Ranjith Mahanama

University of Colombo · Department of Chemistry

Accumulation of water treatment sludge is a major environment problem in the water purification process. Recovery of waste constituents or reuse of sludge is a cost-effective method in handling this environmental dilemma. The present study investigates the suitability of sludge in the production of bricks and recovery of aluminum from the sludge ac...

Being the dietary staple in most Asian countries, the concentrations of toxic and essential element content in rice is an important aspect in terms of both toxicological and nutritional standpoints. This study aimed to analyse trace elements (As, Cd, Pb, Hg, Cr, Ni, Zn, Cu, Mn, Fe, and Mo) in improved, traditional, and imported rice varieties consu...

Two novel compounds, dicarbonyl ester (2) and artolankanin A (3) were isolated from the sequential ethyl acetate and ethanol extracts of stem bark of A. nobilis along with the known compounds, artonin E (1) and artobiloxanthone (4) by bioassay-guided fractionation using a combination of normal phase and size exclusion column chromatography. Their s...

Study presents the variation in free amino acids (FAAs) and total AAs in rice upon different milling degrees. Two rice cultivars; Pachchaperumal and Bg 406 were subjected to three (4%, 7%, 12%) degrees of milling and the variations in AA composition of milled rice and resulting bran were studied. Milling caused significant (p<0.05) reduction (5.7%...

This study evaluated fatty acid profiles (FAPs) of fifteen pigmented and non-pigmented traditional and new improved rice varieties (RVs) of Sri Lanka. Fat was extracted from rice flour, derivatized to methyl esters and analyzed by gas chromatography (n=3 each). Results showed significant (P < 0.05) differences in FAPs among the tested RVs. Total fa...

Cooking accounted for significant (p<0.01) loss in free and total amino acids (AAs) in rice. Fully milled raw rice reported relatively the lowest loss in total AAs (TAAs) over majority of cooking techniques. Cooking rice with draining excess water, cooking after discarding the soaked water and cooking with higher water to rice ratios accounted for...

With the aim of assessing the feasibility of utilization of amino acid (AA) profiles in characterization of rice varieties grown under distinct influential conditions, the impact of seasonal, geographical and varietal variations on AA and organic acid profiles in rice was investigated. Seven traditional rice varieties with diverse grain and agronom...

Rice (Oryza sativa L.) is the backbone of Sri Lankan agriculture with the accomplishment of the daily nutritional requirements of humans. This study is intended to explore the cultivation seasonal variation on minerals in selected rice varieties and to examine the possible health risks due to toxic heavy metal contamination. Twenty-six different ri...

Parboiling imparts significant changes to nutritional composition of rice. The study presents the variations in amino acid (AA) composition of rice observed during parboiling process, observed in selected Sri Lankan rice cultivars. Upon parboiling, the change in levels of free and protein bound amino acids inconsistently varied across the rice cult...

Cellulose and its forms are widely used in biomedical applications due to their biocompatibility, biodegradability and lack of cytotoxicity. It provides ample opportunities for the functionalization of supported magnetic nanohybrids (CSMNs). Because of the abundance of surface hydroxyl groups, they are surface tunable in either homogeneous or heter...

Investigation made on the variation in amino acid compositions among selected traditional and newly improved rice varieties cultivated in Sri Lanka is presented. The free amino acid (FAA) composition including gamma-amino butyric acid (GABA) and protein bound total amino acids (TAAs) of eleven traditional and seven improved rice cultivars grown at...

Chemical kinetics or reaction kinetics is renowned as a division of physical chemistry which includes with understanding the rates of chemical reactions. As physical chemistry lessons play a vital role in secondary level chemistry syllabus in Sri Lanka, in order to understand the concepts of chemical kinetics the use of only traditional chalk and b...

This study investigated the amino acid composition of eight local and three imported rice varieties frequently consumed by consumers in the capital of Sri Lanka. Investigation included twenty free amino acids (FAAs) analysed using liquid chromatography-tandem mass spectrometry (LCMS/MS) and sixteen protein bound amino acids analysed using high perf...

Coconut oil is the commonly used edible oil in Sri Lanka. Due to similar chemical and physical characteristics, palm oil is a good candidate to adulterate coconut oil targeting profit gains while ignoring the health impacts. In this study a gas chromatographic method was developed to investigate the levels of adulteration. The developed method reve...

The purity of coconut oil is important in assuring the benefits to the consumers as well as to the food industry. In the study, palm olein adulteration in copra coconut oil (CCO) and Virgin coconut oil (VCO) was respectively quantified by Fourier Transform near Infrared (FT-NIR) Spectroscopy combine with partial least square (PLS) model. NIR spectr...

Adaptable to any routine laboratory, the study presents the validation results of a simple, accurate and reliable method developed for the analysis of total amino acids (TAAs) in rice using reversed-phase high-performance liquid chromatography-diode array detection (RP-HPLC-DAD). Exhibiting excellent selectivity with resolution (Rs) ≥ 2 for sevente...

The study presents the variation in free amino acids (FAAs) and total amino acid; (TAAs) in rice upon different degrees of milling. With the use of 0.2 g of the sample, amino acid levels in two rice cultivars resulting from three degrees of milling (DOM) (4%, 7%, well milled) and the resulting bran collected, each in three replicates were studied....

A simple, sensitive, quick, cost effective, and reliable fluorimetric method for the determination of paracetamol has been developed. The method was based on oxidation of paracetamol by potassium chlorate in the presence of sulphuric acid followed by monitoring of the fluorescence quenching of quinine sulphate by chloride ions at the excitation wav...

In Press, Corrected Proof Development and validation of a method for direct, underivatized analysis of free amino acids in rice using liquid chromatography-tandem mass spectrometry Author links open overlay panel G. rights and content Highlights • A method was developed and validated for analysis of free amino acids(FAAs) in rice. • The method enab...

Inspired by the apparent relationship of free amino acids (FAAs) which are present in minute quantities with the organoleptic characteristics of food, there is an increased demand for analytical methods sensitive in trace level detection. This study presents the validation results of a simple and rapid method developed for direct, underivatized ana...

The search for natural cosmeceuticals has gained an increasing demand due to its fewer side effects and become more prevalent in cosmetic formulations. Plant sources contain numerous natural compounds which can be used as whitening, anti-aging anti-wrinkle ingredients and also for the treatment of dermatological disorders. Ethanol extracts of 15 Sr...

Humans are prone to get exposed to heavy metals, a well-known potential health hazard, through common consumer products such as leather. Hazardous hexavalent chromium or Cr (VI), along with other heavy metals, gets added into the leather products during tannery operations. Leather products with improper hazard screening can enter the market in the...

The dissolved oxygen (DO) of a water body (WB) is dynamically equilibrated between the two films such as gas and liquid phases. Urban drainage system (UDS) containing waste disposals and other related waste materials may alter this equilibrium; as a result, aquatic organisms can suffocate. Therefore, an investigation is necessary to analyse the imp...

The dissolved oxygen (DO) of a water body (WB) is dynamically equilibrated between the two films such as gas and liquid phases. Urban drainage system (UDS) containing waste disposals and other related waste materials may alter this equilibrium; as a result, aquatic organisms can suffocate. Therefore, an investigation is necessary to analyse the imp...

Effect of metal additives on carbon formation during volatile organic compound oxidation over Ni/Al2O3 catalysts has been investigated. Cyclohexane is used as the model volatile organic compound. Reaction is carried out under oxygen limited conditions with just sufficient oxygen to convert similar to 10% of cyclohexane into carbon dioxide and water...

Nowadays, the Inland agricultural water sources are contaminated by a number of different types of pollutants such as domestic, municipal and industrial effluents. These pollutants are subjected to the degradation of these water sources and made by the urbanization after colonization altering the quality of agricultural land through changing its ch...

Agricultural runoff is a leading source that degrades the quality of stagnant water bodies (SWB) through its substances. The contribution of agricultural runoff and other improper waste disposals (such as hospital discharges, domestic effluent, and farm discharges) to the SWB’s were considered over a period of six months for three of different SWB’...

The dissolved oxygen (DO) of a water body (WB) is dynamically equilibrated between the two films such as gas and liquid phases. Urban drainage system (UDS) containing waste disposals and other related waste materials may alter this equilibrium; as a result, aquatic organisms can suffocate. Therefore, an investigation is necessary to analyse the imp...

The dissolved oxygen (DO) of a water body (WB) is dynamically equilibrated between the two films such as gas and liquid phases. Domestic and other related waste materials may alter this equilibrium as a result aquatic organism can suffocate. Therefore, an investigation is necessary to analyse the Contribution of Organic Contaminations and Nutrient...

Domestic and other related waste disposals lead to degrading the rate of equilibrium of dissolved oxygen (DO) in the water bodies. The aim of this study is to investigate the contributions of the organic contamination throughout the measured parameters of dissolved sulfide, chemical oxygen demand (COD), nutrient level and salinity in the dynamic eq...

Adulteration of petrol (gasoline) and diesel using petrochemical based products has often been reported in developing countries. This leads to the degradation of engine performances and fugitive emissions. Having similar chemical properties, the fuel and the adulterant cannot be distinguished easily leading to complications in identification and qu...

The chemical stuff containing domestic and industrial waste effluents are principal sources to degrade the quality of agricultural land through water supplying practices from its related inland water bodies. The contribution of domestic and other improper waste disposal to the inland water bodies were monitored over a period of six months for three...

The dissolved oxygen (DO) of a water body (WB) is dynamically equilibrated between the two films such as gas and liquid phases. Domestic and other related waste materials may alter this equilibrium as a result aquatic organism can suffocate. Therefore, an investigation is necessary to analyse the Contribution of Organic Contaminations and Nutrient...

The dissolved oxygen (DO) of a water body (WB) is dynamically equilibrated between the two films such as gas and liquid phases. Domestic and other related waste materials may alter this equilibrium as a result aquatic organism can suffocate. Therefore, an investigation is necessary to analyse the Contribution of Organic Contaminations and Nutrient...

Accumulation of sulfur-containing compounds and their bacterial mediated reductions have led to the emission of pungent odors from stagnant water bodies. This study is focused on the contribution of inorganic sulfur compounds in the emission of hydrogen sulfide. The measured dissolved oxygen levels have demonstrated good negative correlations with...

Catalytic activity of V, Mn, Ni, Cu, Zn, Mo, Zr and Ce oxides over an alpha-alumina support was evaluated for cyclohexane oxidation under oxygen deficient conditions in order to understand the relation between carbon deposition and catalytic activity/selectivity. Carbon formation over the catalysts during the oxidation reaction was measured by mean...

Effect of metal additives on carbon formation during volatile organic compound oxidation over Ni/Al2O3 catalysts has been investigated. Cyclohexane is used as the model volatile organic compound. Reaction is carried out under oxygen limited conditions with just sufficient oxygen to convert ~10% of cyclohexane to carbon dioxide and water. Presence o...

Environmental tobacco smoke (ETS) is suspected to be a major source of exposure to many of the compounds identified as toxic air contaminants. However, we lack emission factors for many of the ETS air toxics for the brands of cigarettes which currently dominate the market and therefore cannot adequately estimate contributions of ETS to such exposur...

Most environmental tobacco smoke (ETS) issues from the tips of smoldering cigarettes between puffs. Smokeless ashtrays are designed to reduce ETS exposure by removing particulate and/or gas-phase contaminants from this plume. This paper describes an experimental investigation of the effectiveness of four smokeless ashtrays: two commercial devices a...

Studies of phase distributions and emission factors for polycyclic aromatic hydrocarbons (PAH) in environmental tobacco smoke (ETS) require collection and analysis of very small samples. To achieve the necessary selectivity and sensitivity, a method has been devised and tested for extraction and cleanup of gas- and particulate-phase ETS samples. Ga...

A more convenient sampling and analysis method for the volatile N-nitrosamines (VNA) in ETS, using commercially available TherrnosorbIN cartridges, was developed and validated. Using the method, emission factors for the two major VNA in environmental tobacco smoke (ETS) were determined in a room-sized environmental chamber for six commercial cigare...

Three volatile nitrogen-containing compounds, 3-ethenylpyridine (3-EP), pyridine and pyrrole, were investigated as potential tracers for determining the contribution of environmental tobacco smoke (ETS) to concentrations of volatile organic compounds (VOCs) in indoor environments with smoking. The source emission rates of the three tracers and ten...

A mg-scale fractionation method has been developed for polar organic matter in airborne particles. The method gives reproducibly good recoveries ofmass while avoiding the use ofwater or sa1ts. Cyanopropyl-bonded silica solid-phase extraction (SPE) columns were used to fractionate a mixture of standard compounds and acetone-soluble extracts from par...

An analytical method is described for the simultaneous quantitation of polycyclic aromatic hydrocarbons [PAHs] and alkyl-derivatives [alkyl-PAHs] in “real world” samples using microbore reversed-phase high performance liquid chromatography in conjunction with two programmable fluorescence detectors. Sensitivity and selectivity were enhanced by anal...

An annular denuder-based sampler, here called the integrated organic vapor/particle sampler (IOVPS), has been developed for direct determination of both gaseous and particulate semi-volatile organic species. The IOVPS uses a cyclone inlet for removal of particles greater than 2.5 μm (D50) from the airstream, followed by two or three sandblasted gla...

The primary objective of this study was to measure emission factors for selected toxic air contaminants in environmental tobacco smoke (ETS) using a room-sized environmental chamber. The emissions of 23 volatile organic compounds (VOCs), including, 1,3-butadiene, three aldehydes and two vapor-phase N-nitrosamines were determined for six commercial...

A mg-scale fractionation method has been developed for polar organic matter in airborne particles. The method give reproducibly good recoveries of mass while avoiding the use of water or salts. Cyanopropyl-bonded silica solid-phase extraction (SPE) columns were used to fractionate a mixture of standard compounds and acetone-soluble extracts from pa...

Vitamin K1 (phylloquinone) is extracted from commercial soy protein-based and milk-based powdered infant formulas by using supercritical fluid extraction with CO2 at 8000 psi and 60 degrees C. Quantitative extraction requires only 15 min, and does not suffer from the problems associated with conventional solvent extraction of lipophilic materials f...

To avoid sampling artifacts, an integrated organic vapor-particle sampler (IOVPS) has been developed for polycyclic aromatic hydrocarbons (PAH). The ICIVPS is based on an XAD-4-coated annular denuder which strips gas phase species from the air stream before collection of particles on a filter. A second denuder downstream of the filter collects spec...