Hanna Chebib

Chemical Composition of Lebanese Rosemary (Rosmarinus officinalis L.) Essential Oil as a Function of the Geographical Region and the Harvest Time

Abstract The essential oils of rosemary (Rosmarinus officinalis L.) from three locations in Lebanon were extracted by steam distillation and their chemical composition was determined by GC/MS. The plants were collected during two years at either flowering stage or after. The oils obtained did not show appreciable differences in their composition in relation to geographical region. The three oil samples were found to be rich in α-pinene (18.8–38.5%) and 1,8-cineole (19.1–25.1%). The Lebanese oils had particularly high levels of α-terpineol (2.9–11.2%) and geraniol (1.8–9.3%). Although the results obtained did not indicate a large variation of oil composition in relation to harvest time (flowering and after flowering), some reproducible differences were noticeable. A parallel study on rosemary leaves and flowers from one of the three locations showed that their oils had the same chemical composition.

Characterization of different diamond-like carbon electrodes for biosensor design.

Diamond-like carbon (DLC) films are gaining big interest in electrochemistry research area. DLC electrodes made with different ratio of sp(3)/sp(2) carbon hybridization or doped with different percentages of nickel were characterized electrochemically by cyclic voltammetry and by amperometric measurements towards hydrogen peroxide. SiCAr1 and SiCNi5% were chosen as sensitive transducers for the elaboration of amperometric glucose biosensors. Immobilization of glucose oxidase was carried out by cross-linking with glutaraldehyde. Measurements were made at a fixed potential+1.0V in 40mM phosphate buffer pH 7.4. SiCAr1 seems to be more sensitive for glucose, 0.6875muA/mM, than SiCNi5%, 0.3654muA/mM. Detections limits were 20muM and 30muM, respectively. Apparent Michaelis-Menten constants were found around 3mM. Forty-eight percent and 79% of the original response for 0.5mM glucose remained after 10 days for both biosensors, respectively.

Rapid discrimination of plastic packaging materials using MIR spectroscopy coupled with independent components analysis (ICA).

Plastic packaging wastes increased considerably in recent decades, raising a major and serious public concern on political, economical and environmental levels. Dealing with this kind of problems is generally done by landfilling and energy recovery. However, these two methods are becoming more and more expensive, hazardous to the public health and the environment. Therefore, recycling is gaining worldwide consideration as a solution to decrease the growing volume of plastic packaging wastes and simultaneously reduce the consumption of oil required to produce virgin resin. Nevertheless, a major shortage is encountered in recycling which is related to the sorting of plastic wastes. In this paper, a feasibility study was performed in order to test the potential of an innovative approach combining mid infrared (MIR) spectroscopy with independent components analysis (ICA), as a simple and fast approach which could achieve high separation rates. This approach (MIR-ICA) gave 100% discrimination rates in the separation of all studied plastics: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS) and polylactide (PLA). In addition, some more specific discriminations were obtained separating plastic materials belonging to the same polymer family e.g. high density polyethylene (HDPE) from low density polyethylene (LDPE). High discrimination rates were obtained despite the heterogeneity among samples especially differences in colors, thicknesses and surface textures. The reproducibility of the proposed approach was also tested using two spectrometers with considerable differences in their sensitivities. Discrimination rates were not affected proving that the developed approach could be extrapolated to different spectrometers. MIR combined with ICA is a promising tool for plastic waste separation that can help improve performance in this field; however further technological improvements and developments are required before it can be applied at an industrial level given that all tests presented here were performed under laboratory conditions.

Chemometric tools to highlight non-intentionally added substances (NIAS) in polyethylene terephthalate (PET).

In an effort to identify non-intentionally added substances (NIAS), which is still a challenging task for analytical chemists, PET pellets, preforms and bottles were analyzed by an optimized headspace solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME/GC-MS). Fingerprints obtained by the proposed method were analyzed by three chemometric tools: Principal Components Analysis (PCA), Independent Components Analysis (ICA) and a multi-block method (Common Components and Specific Weights Analysis CCSWA) in order to extract pertinent variations in NIAS concentrations. Total ion current (TIC) chromatograms were used for PCA and ICA while extracted ion chromatograms (EIC) were used for CCSWA, each ion corresponding to a block. PCA managed to discriminate pellets and preforms from bottles due to several NIAS. Volatiles like 2-methyl-1,3-dioxolane, ethylene glycol, ethylbenzene and xylene were responsible for the discrimination of pellets and preforms. Less volatile compounds like linear aldehydes and phthalates were responsible for the discrimination of bottles. ICA showed more specific discriminations especially for bottles and pellets while CCSWA managed to discriminate preforms. The proposed methodology, combining HS-SPME/GC-MS with chemometric tools proved its efficiency in highlighting NIAS in PET samples in a relatively simple and fast approach compared to classical techniques.

Independent components analysis coupled with 3D-front-face fluorescence spectroscopy to study the interaction between plastic food packaging and olive oil.

Olive oil is one of the most valued sources of fats in the Mediterranean diet. Its storage was generally done using glass or metallic packaging materials. Nowadays, plastic packaging has gained worldwide spread for the storage of olive oil. However, plastics are not inert and interaction phenomena may occur between packaging materials and olive oil. In this study, extra virgin olive oil samples were submitted to accelerated interaction conditions, in contact with polypropylene (PP) and polylactide (PLA) plastic packaging materials. 3D-front-face fluorescence spectroscopy, being a simple, fast and non destructive analytical technique, was used to study this interaction. Independent components analysis (ICA) was used to analyze raw 3D-front-face fluorescence spectra of olive oil. ICA was able to highlight a probable effect of a migration of substances with antioxidant activity. The signals extracted by ICA corresponded to natural olive oil fluorophores (tocopherols and polyphenols) as well as newly formed ones which were tentatively identified as fluorescent oxidation products. Based on the extracted fluorescent signals, olive oil in contact with plastics had slower aging rates in comparison with reference oils. Peroxide and free acidity values validated the results obtained by ICA, related to olive oil oxidation rates. Sorbed olive oil in plastic was also quantified given that this sorption could induce a swelling of the polymer thus promoting migration.

Attenuated total reflectance-mid infrared spectroscopy (ATR-MIR) coupled with independent components analysis (ICA): A fast method to determine plasticizers in polylactide (PLA)

Compliance of plastic food contact materials (FCMs) with regulatory specifications in force, requires a better knowledge of their interaction phenomena with food or food simulants in contact. However these migration tests could be very complex, expensive and time-consuming. Therefore, alternative procedures were introduced based on the determination of potential migrants in the initial material, allowing the use of mathematical modeling, worst case scenarios and other alternative approaches, for simple and fast compliance testing. In this work, polylactide (PLA), plasticized with four different plasticizers, was considered as a model plastic formulation. An innovative analytical approach was developed, based on the extraction of qualitative and quantitative information from attenuated total reflectance (ATR) mid-infrared (MIR) spectral fingerprints, using independent components analysis (ICA). Two novel chemometric methods, Random_ICA and ICA_corr_y, were used to determine the optimal number of independent components (ICs). Both qualitative and quantitative information, related to the identity and the quantity of plasticizers in PLA, were retrieved through a direct and fast analytical method, without any prior sample preparations. Through a single qualitative model with 11 ICs, a clear and clean classification of PLA samples was obtained, according to the identity of plasticizers incorporated in their formulations. Moreover, a quantitative model was established for each formulation, correlating proportions estimated by ICA and known concentrations of plasticizers in PLA. High coefficients of determination (higher than 0.96) and recoveries (higher than 95%) proved the good predictability of the proposed models.

Chemical Composition of the Essential Oil of Micromeria libanotica Boiss., an Endemic Species of Lebanon

Abstract The essential oil obtained by steam distillation from Micromeria libanotica growing wild in the cedar mountains of Lebanon, was examined by GC and GC/MS. Twenty-five components, representing about 83% of the oil were identified. The major constituents of the oil were found to be the monoterpene ketones isomenthone (44.5%), pulegone (13.5%) and isopulegone (6.5%).

Migration of iron, lead, cadmium and tin from tinplate-coated cans into chickpeas

Migration studies of trace metals were carried out on coated chickpea cans marketed in Lebanon. Four elements – iron (Fe), tin (Sn), lead (Pb) and cadmium (Cd) – were analysed by atomic absorption spectrometry (AAS) after microwave digestion. Over 3 months, three different storage temperatures (5°C, room temperature and 40°C) were tested. In all cases, the migration of Fe reached a plateau after around 50 days of storage, while the migration of Pb was slow till 50 days, then it increased rapidly. Cd and Sn levels did not increase. Moreover, no effect of temperature was observed in the case of Fe, whereas Pb levels showed slower migration in cans stored at 5°C. Comparing cans from different chickpea brands (Lebanese and foreign) showed that the characteristics of the container have an effect on metal release.

Phenolic Compounds from Diluted Acid Hydrolysates of Olive Stones: Effect of Overliming

Annually, important quantities of olive residue are produced and may be the source of ecological damages. Like agricultural residues, which are abundant, renewable, low cost raw materials, olive stones are mainly subjected to biotechnological or chemical modifications in order to be transformed into valuable products (biofuels, biofertilizers, animal feed and chemical feed-stock). In aim to valorize olive stones, we are trying to identify the presence of different phenolic compounds in their dilute-acid hydrolysate (DAH). Phenolic compounds (PC) are considered as toxic material for fermentation process, therefore, their behavior are studied under overliming treatment with distinct pH levels (10 and 12), temperature (25 and 60°C) and detoxification time (15,30 and 60 min). Identification and quantification of phenolic compounds were performed by two chromatographic methods: Gas Chromatography mass spectrometry (GC-MS) and High-Performance Liquid Chromatography (HPLC). A liquid-liquid microextraction procedure is used in conjunction with silylation prior to the analysis of the compounds by GC-MS. Derivatives of benzoic acid, cinnamic acid, simple phenols, and aldehydes were identified. For all treatments combinations, pH 12 was more effective in reducing the total amount of phenolic compounds. Treatment of the hydrolysate with alkali at pH 12, 60°C and 60 min resulted in up to 29% decrease in the concentration of total phenolic compounds. Tyrosol, which was the main phenolic compound decreased by 73% under the same treatment. Chromatographic methods contributed to an accurate quantification and better understanding of the behavior of each PC, solely.

Effect of sterilisation and storage conditions on the migration of bisphenol A from tinplate cans of the Lebanese market

ABSTRACT The use of bisphenol A (BPA) in lacquer coating of food cans has been restricted by different authorities in many countries, such as in Europe. However, such regulation does not exist in many other countries including Lebanon. Due to the lack of data on the quality of Lebanese can production; this study investigates the migration of BPA from two types of tinplate cans manufactured in Lebanon, before and after sterilisation. Cans were analysed under different storage conditions (time and temperature) and filled with an aqueous simulant. The determination of BPA was carried out using UPLC with fluorescence detection, and further confirmed by MS detection. After sterilisation BPA levels drastically increased from an average of 0.15 to 109 µg/kg, giving a BPA migration around 10.5 µg/dm2 for both types of cans. Storage temperature and time had no significant influence on BPA levels in sterilised cans (p-value > 0.05); however, these factors significantly affected BPA levels in non-sterilised cans.