Publication List for Department of Chemistry

Publication statistics for Department of Chemistry

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  • 20

    Journal Article

  • 1

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    PhD Thesis

  • 1

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    Document

The Use of Fourier-Transform Infrared Spectroscopy to Assess Libyan Virgin Olive Oil Adulteration with Corn and Sun Flower Oils

Modern improvements in Fourier transform infrared spectroscopy instrumentation spread out the application of this technique to the field of food research. This study is focused to evaluate the efficiency of FT-IR spectroscopy in order to assess the Libyan virgin olive oil adulteration with cheaper vegetable oils: sunflower oil and corn oil. Taking a closer inspection to different regions of recorded IR spectra of both pure oil sample (virgin olive oil, sun flower oil, corn oil) and their mixture: It is noticed that an absorbance shift was identified at about 3000 cm-1 due to the C-H stretching vibration of the cis-double bond proved to be reliable index for assessing of virgin olive oil adulteration by vegetable oil addition. Also, the absorbance at about 3008 cm-1, characteristic to the oils with a high saturated fatty acids content and short carbohydrate chain, recorded appreciable changes by increasing of vegetable oil percent added in virgin olive oil. Based on the calibration curve (absorbance versus percent of vegetable oil added in virgin olive oil), it is possible to determine the degree of virgin olive oil adulteration. A significant positive correlation for both adulterant oils (R2 > 0.97) at wavenumber 3008.3 cm-1 was observed in our study. Our data demonstrated that FT-IR spectroscopy proved to be a valuable tool to identify the differences recorded in oil samples spectra and finally, to appreciate the degree of virgin olive oil adulteration
Ragiab Ali Mokhtar Issa(1-2018)
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Determination of Lead in human blood and serium and the relationship among its exposures, Zawia, Libya

In this study, six residents of Zawia City who had no history record of occupational lead exposure were investigated. One sample of venous blood was collected from each. Sample preparation consisted of a simple dilution (twenty-fold) with 0.15N HNO3. The was centrifuged to separate serum, which was then isolated and analyzed for lead content by Flame Atomic Absorption Spectroscopy (FAAS). The residue of the sample was also analyzed by the same technique for blood level. The blood lead level in the residue was higher than that in serum lead level. Mean lead concentrations were 4.48mg/L in serum and 60.23 mg/L in residual blood respectively. Blood lead level was quietly correlated with serum lead and accounted for 95% of the variability of serum lead concentration. The bivariate regression coefficient of serum lead was 0.221 (p. 0.001). In a multivariate regression model of serum lead levels that include blood and serum lead level remained an independent predictor of lead plasma level (p. 0.007, p
Ragiab Ali Mokhtar Issa(2-2018)
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Reversibility in radionuclide/bentonite bulk and colloidal ternary systems

Ternary systems of 152Eu(III), bulk bentonite and ethylenediaminetetraacetic acid (EDTA) ([Eu] = 7.9 × 10−10 M; pH = 6.0–7.0) have been studied. Without EDTA, there was slow uptake in a two-stage process, with initial rapid sorption of Eu(III) (96%), followed by slower uptake of a much smaller fraction (3.0% over a period of one month). The reversibility of Eu(III) binding was tested by allowing Eu(III) to sorb to bentonite for 1–322 days. EDTA was added to the pre-equilibrated Eu bentonite systems at 0.01 M, a concentration that was sufficient to suppress sorption in a system where EDTA was present prior to the contact of Eu(III) with bentonite. A fraction of the Eu was released instantaneously (30‒50%), but a significant amount remained bound. With time, the amount of Eu(III) retained by the bentonite reduced, with a slow fraction dissociation rate constant of approximately 4.3 × 10−8 s−1 (values in the range 2.2 × 10−8 – 1.0 × 10−7 s−1) for pre-equilibration times ≥7 days. Eventually, the amount of Eu(III) remaining bound to the bentonite was within error of that when EDTA was present prior to contact (4.5% ± 0.6), although in systems with pre-equilibration times >100 days, full release took up to 500 days. Europium interactions with colloidal bentonitewere also studied, and the dissociation rate constant measured by a resin competition method. For the colloids, more Eu was found in the slowly dissociating fraction (60–70%), but the first-order dissociation rate constant was faster, with an average rate constant of 8.8 × 10−7 s−1 and a range of 7.7 × 10−7–9.5 × 10−7 s−1. For both bulk and colloidal bentonite, although slow dissociation was observed for Eu(III), there was no convincing evidence for ‘irreversible’ binding.
RAGIAB ISSA(1-2021)
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An investigation on Libyan olive oil in the western region

Thirteen Olive oil samples were collected from five different places in the western Libyan region with different cultivation periods. The physical and chemical properties of samples were investigated and classified whether they comply with the Libyan standard specification number 8/2002 or not. The density and refractive index of almost all samples were found within the normal range (0.908-0.919) and (1.4688-1.4705) respectively whereas the chemical properties showed a range of fluctuated values such as peroxide number (11.20-60.40), acidity value (0.737-17.94), saponification number (185.34-199.65), esterification number (173.84-194.36) and iodine number (71.00-94.10). A third of the investigated samples are considered to be of good quality mainly the newer samples
Ragiab A. M. Issa(9-2017)
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MATERIALS CHARACTERIZATION BY COMBINED THERMOVOLTAIC DETECTION (TVD) AND THERMAL ANALYSIS (DTA) TECHNIQUES

The thermovoltaic detection (TVD) technique is based on measurement of the EMF generated by two dissimilar metal electrodes in contact with the specimen. This technique has recently been applied when investigating different types of materials involving thermal decomposition reactions which have more normally been studied by conventional thermal analysis techniques, such as DTA, TG, etc. This paper reports the application of the combined TVD and DTA techniques for thermal characterization of materials. The Harrop DTA system has been modified such that measurements by the two techniques can be made simultaneously in the same environment. Data have been obtained on different types of materials, e.g., NiSO,.6H,O and CoSO,.7H,O, etc., at a programmed heating rate of 10” C rnin- ‘. Results obtained by these techniques are discussed and compared with the corresponding values in the literature.
Ragiab Ali Mokhtar(5-1990)
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Lipophilicity of some guaianolides isolated from two endemic subspecies of Amphoricarpos neumayeri (Asteraceae) from Montenegro

In this study 10 guaianolide-type sesquiterpene g-lactones named amphoricarpolides, isolated from the aerial parts of two endemic subspecies of Amphoricarpos neumayeri (ssp. neumayeri and ssp. murbeckii Bošnjak), were investigated by means of reversed-phase thin-layer chromatography. Methanol–water and tetrahydrofuran–water binary mixtures were used as mobile phase in order to determine lipophilicity parameters RM0 and C0. Some of the investigated compounds were screened for their cytotoxic activity against HeLa and B16 cells. Chromatographically obtained lipophilicity parameters were correlated with calculated logP values and IC50 values. Principal component analysis identified the dominant pattern in the chromatographically obtained data.
ABUBAKER A BASHIR ATRROG(9-2008)
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تقدير تركيز فيتامين C في عينات من أصناف الليمون والبرتقال بالطريقة الحجمية

أجري هذا البحث لتقدير فيتامين C في العصائر الطازجة لبعض عينات الليمون والبرتقال المحلي. وتم تقدير تركيزالفيتامين بطريقة المعايرة باستخدام محلول اليود القياسي وأظهرنتائج هذا البحث أن كمية الفيتامين تختلف باختلاف العينة وحتى في عينات نفس النوع، حيث وجد أن تركيز فيتامين C بوحدة ملغ\100مل لعينتين من نفس النوعللبرتقال الدمي (37 و 76) وبرتقال أبو سرة (33 و 64) وللبرتقال الحلو (28 و 40) ولليوسفي (17 و 28) وللبرتقال المر (24.7 و 48) وللبرتقال الحامض (31 و 58) ولليمون (21 و 41) وأعلى تركيز كان لعينة البرتقال الدمي وأقل تركيز كان لعينة الليمون.
رجب علي المختار عيسى(1-2021)

Spectrophotometric determination of iron in dietary supplements in Libyan market

In most cases dietary supplements especially in Libya are consumed without prescriptions and the public has very limited any awareness of their health risk. The lack of quality control on numerous brands of dietary supplements in pharmacies of Libya today may result in a serious health problem. The aim of this study is to determine the iron content using a fast and accurate method for quality control of some imported dietary supplements, based on spectrophotometric measurement of iron after complexation with 1, 10-phenanthroline in an acidic medium. Eight types of vitamin supplementary tablets were randomly collected from the Libyan market and analyzed for the iron content. The analysis showed an average value of 61mg Fe/pill for the range of 40.07-112.63 mg Fe/pill. Results showed that 75% of the samples were lower in iron content than that recorded on the dietary products.
Ragiab A. M. Issa(4-2020)