Retention and lipophilicity of newly synthesized 3-benzyloxy steroid derivatives in normal- and reversed-phase HPLC

The retention behaviour and separation ability of nine newly synthesized 3-benzyloxy estrone derivatives were studied by FIPLC on silica and C-18 commercially available columns. The mobile phases used were: benzene-ethyl acetate, benzene-tetrahydrofuran, benzene-acetonitrile, methanolwaler and acetonitrilc-water in various proportions. The results are discussed in terms of nature of the solute, eluent and stationary phase. The correlation between the retention constants of nine 3- benzyloxy estrone derivatives obtained on C-18 column and calculated log P was examined too

Normal and reversed phase high performance liquid chromatography of some new 1, 2, 4-triazole derivatives

The retention behaviour and separation ability of normal and reversed phase HPLC with one non-polar and two polar mobile phases, have been studied by measuring the retention constants of a series of newly synthesized 1,2,4-triazole derivatives. The results are discussed in terms of the nature of the solute, eluent and stationary phase

Characterisation of colloidal gold systems by photometry, spectrophotometry and chronopotentiometric stripping analysis

Colloidal systems of different metals attract lot of attention in scientific research due to their specific physico-chemical properties and possible application routes. In this respect particularly interesting is colloidal gold that has very broad application in different fields, including catalysis, biological and cancer research, electronics etc. Colloidal gold was generated by electric arc discharge method in a home-made generator. The generator consisted of a control system which maintained a constant distance between the electrodes (2 mm), a power supply system and amperometer which controlled the arc discharge parameters, halogen bulbs used as resistors, a glass container with deionized water and a magnetic stirrer. Generation technique consisted in adding 10 l of 35% hydrochloric acid to 500 ml of distilled water, submerging gold (99.9999%) electrodes (d=1 mm) in the solution and initiating electric arc discharge. Initial voltage was set to 20-70 V and the current was maintained at 205 A during entire generation process (30 min) by adjusting electrode distance. The influence of the initial voltage on optical characteristic of colloidal systems was examined by photometry and spectrophotometry, whereas the concentration of free gold ions was determined by chronopotentiometric stripping analysis at glassy carbon electrode. Photometric and spectrophotometric analyses were performed to characterise indirectly particle size distribution, since light absorption, reflection and transmission are highly affected by particle size. The size of gold nanoparticles, in return, affects strongly their properties and behavior in biological systems. By using both yellow-green and blue optical filters in photometric analysis, absorption increased almost linearly in the entire voltage range. Spectrophotometric analysis revealed absorption maximum in the range of 470-590 nm, depending on the initial voltage. Absorption maximum increased with initial voltage, indicating increase in the concentration of colloidal gold. Initial voltage also affected dominant particle size. Particle size distribution was determined by Zetasiyer Nano ZS90. Dominant particle size was in the range from 5 nm (at 50 V) to 19 nm (at 30 V). The influence of generation potential on the concentration of free gold was evaluated by chronopotentiometric stripping analysis at glassy carbon electrode. As a supporting electrolyte 0.1 HCl was used. Electrolysis potential was -0.6 V. After 600 s of electrolysis dissolution current of 8.3 A was applied to reach final potential of +1.25V. The concentration of free gold increased linearly with initial voltage (y=0.0 1x+0.73; r2=0.9849) from 0.95 mg/l (at 20 V) to 1.3 mg/l (at 70 V)

Thermo-Acid pretreatment of starch based kitchen waste for ethanol production

Recently, research on the alcoholic fermentation of kitchen waste has been accelerating for both ecological and economical reasons, primarily for ethanol use as renewable biofuel. Present work deals with the fermentative production of ethanol from different starch based kitchen waste. Kitchen waste from local students restaurant was separated by basic component as: peas, green beans, beans, rice, potato, wheat bread and corn. Thermo-acidic pretreatment of these raw materials was conducted by the addition of HCl up to pH of 1, and by autoclaving at 120 oC for 30 min. From the experimental result, maximum ethanol yield was obtained from wheat bread (0.11 g/g). The highest ethanol yield per starch of 0.36 g/g, which equals to 64% of the theoretical value, was obtained for peas. From the overall analysis, the examined thermo-acid pretreatment was the most efficient for hydrolysis of wheat bread, while it was least efficient for green beans. In order to enhance the efficiency of conversion of starch from kitchen waste into ethanol, pH lower than 1 is highly recommended. The results demonstrated the potential of different food waste as a promising biomass resource for the production of ethanol

Thermo-acid pretreatment of starch based kitchen waste for ethanol production

Recently, research on the alcoholic fermentation of kitchen waste has been accelerating for both ecological and economical reasons, primarily for ethanol use as renewable biofuel. Present work deals with the fermentative production of ethanol from different starch based kitchen waste. Kitchen waste from local students restaurant was separated by basic component as: peas, green beans, beans, rice, potato, wheat bread and corn. Thermo-acidic pretreatment of these raw materials was conducted by the addition of HCl up to pH of 1, and by autoclaving at 120oC for 30 min. From the experimental result, maximum ethanol yield was obtained from wheat bread (0.11 g/g). The highest ethanol yield per starch of 0.36 g/g, which equals to 64% of the theoretical value, was obtained for peas. From the overall analysis, the examined thermo-acid pretreatment was the most efficient for hydrolysis of wheat bread, while it was least efficient for green beans. In order to enhance the efficiency of conversion of starch from kitchen waste into ethanol, pH lower than 1 is highly recommended. The results demonstrated the potential of different food waste as a promising biomass resource for the production of ethanol

Comparation of fundamental analytical methods for quantitative determination of copper(II)ion

Copper is a ductile metal with excellent electrical conductivity, and finds extensive use as an electrical conductor, heat conductor, as a building material, and as a component of various alloys. In this work accuracy of methods for quantitative determination (gravimetric and titrimetric methods of analysis) of copper(II) ion was studied. Gravimetric methods do not require a calibration or standardization step (as all other analytical procedures except coulometry do) because the results are calculated directly from the experimental data and molar masses. Thus, when only one or two samples are to be analyzed, a gravimetric procedure may be the method of choice because it involves less time and effort than a procedure that requires preparation of standards and calibration. In this work in gravimetric analysis the concentration of copper(II) ion is established through the measurement of a mass of CuSCN and CuO. Titrimetric methods is a process in which a standard reagent is added to a solution of an analyze until the reaction between the analyze and reagent is judged to be complete. In this work in titrimetric analysis the concentration of copper(II) ion is established through the measurement of a volume of different standard reagents: Km, Na2S2O3 and AgNO3. Results were discussed individually and mutually with the aspect of exactility, reproductivity and rapidity. Relative error was calculated for all methods

Correlation between retention constants obtained in reversed-phase liquid chromatography and partition coefficients of some benzimidazole derivatives

Several calculation procedures for log P values based on the fragmental and atomic contributions are compared with experimental reversed-phase liquid chromatography (RPLC) retention constants of benzimidazole derivatives. The RPLC experiments were performed on HPLC comerrcially available LiChrosorb RP(-18 column with binary solvent mixtures of methanol-phosphate buffer (pH 7) as mobile phase. Retention constant log k0 was determined by the extrapolation method. Good correlaton was found between the retention constants log k0 and log P, as well as m and log P of the compounds investigated

Determination of carbonyl compounds (acetaldehyde and formaldehyde) in polyethylene terephthalate containers designated for water conservation

Polyethylene terephthalate (PET) has in the last several years become the main packaging material for many food products, particularly carbonated beverages and bottled water, as well as for products of chemical industry (packaging of various hygiene maintenance agents, pesticides, solvents, etc.). The strength and permeability properties of PET are very good for packaging of beverages, its resistance to chemicals is high and it has a high degree of transparency. Acetaldehyde and formaldehyde are formed during the thermoforming of PET containers. After cooling, acetaldehyde and formaldehyde remain trapped in the walls of a PET bottle and may migrate into the water after filling and storage. Since there are no migration tests in Serbia prescribed for the determination of acetaldehyde and formaldehyde, the purpose of the paper is to test the quantitative contents of carbonyl compounds (acetaldehyde and formaldehyde) in PET containers of different volumes, made by various manufacturers of bottled mineral carbonated and noncarbonated water, and exposed to different temperatures. In this study, the migration of acetaldehyde and formaldehyde from PET bottles into mineral carbonated and noncarbonated water was determined by high performance liquid chromatography. Taking into consideration that formaldehyde and acetaldehyde have no UV active or fluorescent group, the chromatography shall be preceded by derivatization in a closed system (due to a low boiling point of acetaldehyde and formaldehyde), which shall transform carbonyl compounds into UV active compounds

Qualitative analysis of hexane flour extract of spelt

Gas chromatography with mass spectrometry (GC-MS) was used for performing a qualitative analysis of the hexane flour extract of three samples of spelt. All the three samples were first treated with hexane and the obtained extracts were used for the analysis of the fatty acid lipid components. The transesterification reaction was performed using TMSH (trimethylsulfonium hydroxide, 0.2M in methanol), and the fatty acids were esterified from acylglycerol to methyl-esters. In all analyzed extracts, the predominant component was methyl linoleate, followed by methyl oleate and methyl palmitate. The subsequent tests, performed by cluster analysis, were used to compare the hexane flour extracts of different types of spelt. [Projekat Ministarstva nauke Republike Srbije, br. III46005 i br. TR 31066