An Efficient Disinfectant, Composite Material {SLS@[Zn3(CitH)2]} as Ingredient for Development of Sterilized and Non Infectious Contact Lens.

The [Zn3(CitH)2] (1) (CitH4= citric acid), was dispersed in sodium lauryl sulphate (SLS) to form the micelle of SLS@[Zn3(CitH)2] (2). This material 2 was incorporated in hydrogel made by hydroxyethyl-methacrylate (HEMA), an ingredient of contact lenses, toward the formation of pHEMA@(SLS@[Zn3(CitH)2]) (3). Samples of 1 and 2 were characterized by UV-Vis, 1H-NMR, FT-IR, FT-Raman, single crystal X-ray crystallography, X-ray fluorescence analysis, atomic absorption and TG/DTA/DSC. The antibacterial activity of 1-3 as well as of SLS against Gram-positive (Staphylococcus epidermidis (St. epidermidis) and Staphylococcus aureus (St. aureus)) and Gram-negative (Pseudomonas aeruginosa (PAO1), and Escherichia coli (E. coli)) bacteria was evaluated by the means of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and inhibitory zone (IZ). 2 showed 10 to 20-fold higher activity than 1 against the bacteria tested. Moreover the 3 decreases the abundance of Gram-positive microbes up to 30% (St. aureus) and up to 20% (PAO1) the Gram-negative ones. The noteworthy antimicrobial activity of the obtained composite 3 suggests an effective antimicrobial additive for infection-free contact lenses.

Selective microextraction of mononucleotides from milk using alumina and stannia hollow fibers prior to their determination by hydrophilic interaction liquid chromatography-diode array detection.

Alumina- and stannia-based hollow fibers were synthesized via simple sol-gel procedures and characterized with respect to morphology, crystalline phase and specific surface area. Then, an optimization study was undertaken for the preconcentration of five 5'-mononucleotides using the hollow fibers. The separation and quantification of the analytes were carried out by HILIC with diode array detection, after proper optimization of the chromatographic conditions. The method demonstrated satisfactory linearities over a concentration range of 0.09-50 µg mL(-1) with regression coefficients to range from 0.9993 to 0.9997. A range of commercially available 5'-mononucleotide supplemented infant formulas and three human breast milk samples were used to apply alumina hollow fibers, as a proof of concept. Recoveries ranged from 84% to 104%, while the calculated RSDs were from 3.6% to 4.3%. The proposed preconcentration-clean-up method is environmentally friendly and convenient, indicating that alumina and stannia are suitable for the applications by immersing them into milk samples, after removal of proteins.

In situ trapping of As, Sb and Se hydrides on nanometer-sized ceria-coated iron oxide-silica and slurry suspension introduction to ICP-OES.

A procedure is developed for the analysis of sub-µg L(-1) levels of arsenic, antimony and selenium after preconcentration of their hydrides. The study highlights the capability of an aqueous suspension of a nanometer-sized magnetic ceria, in the presence of iodide, to function as a sorbent for the in situ trapping and preconcentration of the hydrides of certain metalloids. After extraction, the material is magnetically separated from the trapping solution and analyzed. A slurry suspension sampling approach with inductively coupled plasma-optical emission spectrometry (ICP-OES) is employed for measurements, as the quantitative elution of the adsorbed metalloids is not feasible. The whole analytical procedure consists of five steps: (i) pre-reduction of As, Sb and Se, (ii) generation of the hydrides AsH3, SbH3 and SeH2, (iii) in situ collection in the trapping suspension of magnetic ceria, (iv) isolation of the particles by applying a magnetic field, and (v) measurement of As, Sb and Se concentrations using ICP-OES. Under the established experimental conditions, the efficiency of trapping accounted for 94 ± 2%, 89 ± 2% and 98 ± 3% for As, Sb and Se, respectively, signifying the effective implementation of the overall procedure. The applicability of the procedure has been demonstrated by analyzing tap and lake water and a reference material (soft drinking water). The obtained analytical figures of merit were satisfactory for the analysis of the above metalloids in natural waters by ICP-OES.

Nanometer-sized ceria-coated silica-iron oxide for the reagentless microextraction/preconcentration of heavy metals in environmental and biological samples followed by slurry introduction to ICP-OES.

A slurry suspension sampling technique is developed and optimized for the rapid microextraction of heavy metals and analysis using nanometer-sized ceria-coated silica-iron oxide particles and inductively coupled plasma optical emission spectrometry (ICP-OES). Magnetic-silica material is synthesized by a co-precipitation and sol-gel method followed by ceria coating through a precipitation. The large particles are removed using a sedimentation-fractionation procedure and a magnetic homogeneous colloidal suspension of ceria-modified iron oxide-silica is produced for microextraction. The nanometer-sized particles are separated from the sample solution magnetically and analyzed with ICP-OES using a slurry suspension sampling approach. The ceria-modified iron oxide-silica does not contain any organic matter and this probably justifies the absence of matrix effect on plasma atomization capacity, when increased concentrations of slurries are aspirated. The As, Be, Mo, Cr, Cu, Pb, Hg, Sb, Se and V can be preconcentrated by the proposed method at pH 6.0 while Mn, Cd, Co and Ni require a pH ≥ 8.0. Satisfactory values are obtained for the relative standard deviations (2-6%), recoveries (88-102%), enrichment factors (14-19) and regression correlation coefficients as well as detectability, at sub-µg L(-1) levels. The applicability of magnetic ceria for the microextraction of metal ions in combination with the slurry introduction technique using ICP is substantiated by the analysis of environmental water and urine samples.

Chemical and physicochemical profile of wastewaters produced from the different stages of Spanish-style green olives processing.

The main purpose of the processing of table olives is the removal, at least partially, of the natural bitterness of the fruit in order to render it edible. The preparation of Spanish-style green olives after harvesting involves cleaning followed by debittering using NaOH solution, washing with water, a lactic acid fermentation step and finally canning. Wastewaters originating from table olives processing industries pose an important environmental threat, as they are characterized by a very high organic load and high concentration of phenolic compounds, which are toxic to living organisms. In this communication, the chemical and physicochemical profile of wastewaters produced from the different stages of Spanish-Style green olives processing was investigated. Phenolic compounds, organic acids, amino acids and total sugars along with common physicochemical parameters were determined in order to appraise the specific features of each individually produced wastewater.

Photophysical properties of Hypericum perforatum L. extracts--novel photosensitizers for PDT.

We report the preparation of the methanolic extract (ME), and polar methanolic fraction (PMF) from the plant Hypericum perforatum L. The extracts contain various photosensitizing constituents such as naphthodianthrone derivatives (in 1.37% w/w), and chlorophylls (in 0.08% w/w). Upon light emission these constituents can be activated, providing photodynamic properties to the extracts, and making them a potent, new class, natural photosensitizers for use in photodynamic therapy (PDT), and photodynamic diagnosis (PDD). The absorbance spectra of the extracts are similar to the spectrum of hypericin, the main naphthodianthrone identified within, with two major bands at 548 and 590 nm. The fluorescence spectra in ethanol exhibit two main bands around 595 and 640 nm, in accordance with the spectrum of pure hypericin. The fluorescence intensity of PMF at 595 nm is only eight times less than the intensity of pure hypericin at the same wavelength, even though its hypericin concentration is only 0.57% w/w. The dependence of the PMF fluorescence signal on the pH of the medium, alone and in comparison with the signal of hypericin, has been investigated. PMF signal fades steadily, and smoothly both in acidic, and basic environment.

An optimised single-reagent method for the speciation of chromium by flame atomic absorption spectrometry based on surfactant micelle-mediated methodology.

The toxicity of chromium in the environment is dependent on the species in which it exists. This paper outlines a method for the analysis of the oxidation states of Cr employing a suitable chelating agent and the cloud point phenomenon for Cr(VI) and total Cr analysis. The method involves preconcentration of metal chelates followed by air-acetylene flame atomic absorption spectrometric analysis. The chelating agent chosen for this task is the ammonium pyrrolidinedithiocarbamate, which reacts with either Cr(VI) or total Cr under specific experimental conditions. The condensed surfactant phase with the metal chelate(s) is introduced into a flame atomic absorption spectrometer, whereby discrimination of Cr species is feasible by calculating the Cr(III) concentration from the difference between total Cr and Cr(VI). A multivariate design was employed to study the variables affecting the overall analytical performance for total Cr assay. The analytical curves are rectilinear up to 100 micrograms l-1 for both oxidation states of the metal. The limits of detection are 0.6 microgram l-1 and the relative standard deviation (n = 5) at a concentration of 30 micrograms l-1 for both species is around 2.0%. The method was validated by analysing BCR 544 reference material certified for both Cr species. High recoveries in the range 96-107% were attained for the environmental and biological samples tested.

Analysis of malondialdehyde in biological matrices by capillary gas chromatography with electron-capture detection and mass spectrometry.

A gas chromatographic method is described for the quantification of free and total malondialdehyde (MDA) in biological materials. The procedure involves derivatization of the analyte with 2,4,6-trichlorophenylhydrazine, extraction with n-hexane, and separation of the cyclic derivatization product on a OV-5 gas chromatographic column. Concentration of the derivatization reagent, pH, reaction time, and temperature were investigated to determine the optimal derivatization conditions. Under these conditions, the method allows for the selective detection of free and total MDA at femtomole levels in several biological materials without any interferences. The procedure yields relative standard deviation values for the intra- and interassays in the range 3.3 and 3.9%, respectively, for the electron-capture and mass-selective (SIM mode) detection systems. Recoveries of MDA from spiked matrices reached 96%. The present method offers the advantage of the alternative use of either electron-capture or mass-selective detection. Furthermore it avoids overestimation of MDA since it employs mild conditions for sample processing and there is no need for preventing protein separation for the assessment of free MDA.

Analytical methods to determine phosphonic and amino acid group-containing pesticides.

A comprehensive view on the possibilities of the most recently developed chromatographic methods and emerging techniques in the analysis of pesticides glyphosate, glufosinate, bialaphos and their metabolites is presented. The state-of-the-art of the individual pre-treatment steps (extraction, pre-concentration, clean-up, separation, quantification) of the employed analytical methods for this group of chemicals is reviewed. The advantages and drawbacks of the described analytical methods are discussed and the present status and future trends are outlined.

Degradation of medical x-ray film developing wastewaters by advanced oxidation processes.

Effluents from X-ray film developing processes feature high contaminant load (COD about 200 g/l). Identification of the main organics present in these wastewaters was performed by using liquid chromatography-mass spectrometry in electron impact mode, LC-(EI)MS. Both, unconsumed ingredients and sulphonated/hydroxylated derivatives and dimers yielded from the developing agents hydroquinone and phenidone were found to be the main organics contributing to the contaminant load of these effluents. Their potential degradation by oxidation with both photo- and thermal-Fenton reactions was investigated and the optimal degradation conditions were determined. Under these conditions the initial COD was reduced by about 97% within 6 h of treatment. The intermediates detected by LC-(EI)MS in the oxidation of hydroquinone and phenidone during the treatment were essentially hydroxylated derivatives and dimers and the residual organic matter was mainly made up of carboxylic acids. Reaction pathways for the oxidation of the developing agents hydroquinone and phenidone were proposed. The presence of many organic and inorganic components in the wastewaters did not affected the favoured oxidation route of these developers. The results obtained allow to assess the reduction of costs permitted in the treatment of X-ray effluents with the photo- and thermal-Fenton reaction without affecting the degradation degree and quality of the discharge.

Bioremediation of olive oil mill wastewater: chemical alterations induced by Azotobacter vinelandii.

An environmentally friendly bioremediation system of olive oil mill wastewater (OMWW) is studied with respect to its physicochemical characteristics and degradation efficiency on major characteristic constituents. The method exploits the biochemical versatility of the dinitrogen fixing bacterium Azotobacter vinelandii (strain A) to grow in OMWW at the expense of its constituents and to transform it into an organic liquid fertilizer. The system eliminates the phytotoxic principles from OMWW and concomitantly enriches it with an agriculturally beneficial microbial consortium along with useful metabolites of the latter. The end product, branded "biofertilizer", is used as soil conditioner and liquid organic fertilizer. Growth of A. vinelandii in OMWW results in the decline of content of most of the compounds associated with phytotoxicity, and this is confirmed by the assessment of degradation yields. In parallel, during the process several other compounds noncommittally undergo degradation and biotransformation. More specifically, the biofertilization system is capable of achieving removal yields as high as 90 and 96% after 3 and 7 days of treatment, respectively. Statistical analysis of the results showed that between the periods of operation no significant difference occurs with respect to the degradation yield. Moreover, the degradation yield from 3 to 7 days of continuous operation of the system remains almost unaltered during 2 consecutive years.

Development of a method for the simultaneous determination of phosphoric and amino acid group containing pesticides by gas chromatography with mass-selective detection optimization of the derivatization procedure using an experimental design approach.

An integrated gas chromatographic-mass-selective detection method for the analysis of the phosphoric and amino acid group containing pesticides is presented. The analytes are derivatized using a single-step procedure for the simultaneous esterification and acetylation of the active groups of analytes (-OH, -COOH, -NH2) by means of acetic acid and trimethyl orthoacetate. An experimental design approach based on the central composite design is used to investigate the dependence of the derivatization variables with the total yield of derivatization of pesticides. The variables selected for study were: the amount of reagents, the temperature and the reaction time. When considering the total pesticide derivatization yield, the amount of acetic acid, the reaction temperature and the reaction time are found to be statistically significant. The electron impact ionization mass spectra of the resulting derivatives are acquired and properly interpreted. Under the chromatographic conditions employed, acceptable peak separation is attained. When the selective ion monitoring mode is used for quantitation purposes, low detection limits in the range 0.05 to 14 microg/l are achieved. Recoveries of spiked water samples range from 96 to 103% and the mean RSD of the method do not exceed 3.5%.

Multielement concentrations in vegetable species grown in two typical agricultural areas of Greece.

The multielement (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, V, Zn) levels in various common vegetables and surface soils collected from two typical growing areas of north-western Greece are presented. The results are representative and indicate metal concentration levels in vegetables grown in Greek areas under similar conditions. The content of the metals is generally at the same levels or even lower than that reported for vegetables consumed in several countries and species grown in other agricultural and industrial Greek areas. Enhanced levels of metals observed in certain vegetable species could be related to their concentration in the corresponding soils. The results of the present study indicate that the mean intake of heavy metals (As, Cd, Pb and Se) by adults due to consumption of vegetables from the two sites, for an average consumption, pattern, generally is well below the allowable daily intakes. On the other hand, the contribution of the vegetables to the recommended amounts of the essential elements (Cu, Fe, Mn and Zn) is satisfactory and higher than previously reported.

Simultaneous spectrofluorimetric determination of selenium (IV) and (VI) by flow injection analysis.

A simple, sensitive, highly selective, automatic spectrofluorimetric method for the simultaneous determination of selenium (IV) and (VI) as selenite-selenate by flow injection analysis (FIA) has been developed. The method is based on the selective oxidation of the non-fluorescent reagent 2-(alpha-pyridyl)thioquinaldinamide (PTQA) in acidic solution (1.5-3.0 M H2SO4) by SeIV to give an intensely fluorescent oxidation product (lambda ex =350 nm; lambda em = 500nm). Selenium (VI) is reduced on-line to SeIV, in a reduction coil installed in a photo-reactor, which is then treated with PTQA and the fluorescene due to the sum of SeIV and SeVI is measured; SeVi is determined from the difference in fluorescence values. Various analytical parameters, such as effect of acidity, flow rate, sample size, dispersion coefficient, temperature, reagent concentration and interfering species were studied. The photo-reduction conditions were optimized, with an FIA procedure, for SeVI on the basis of its reduction efficiency. The calibration graphs were rectilinear for 0.1-2.4 micrograms ml-1 of SeVI and 10 ng ml-1-2.2 micrograms ml-1 of SeIV, respectively. The method was applied to the determination of Se in several Standard Reference Materials (alloy, sediments and tea), as well as in some environmental waters (tap and surface water), food samples (flour and egg), a biological sample (human hair), soil sample and in synthetic mixtures. Up to 25 samples per hour can be analysed with an RSD approximately 0.1-2%.

Simultaneous spectrophotometric determination of nitrite and nitrate by flow-injection analysis.

An automatic direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow-injection analysis has been developed. Nitrite reacts with 3-nitroaniline in the presence of hydrochloric acid (0.96-1.8 M HCl or pH 0.5-0.7) to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)-ethylenediamine dihydrochloride to form a stable purple azo dye, the absorbance of which is measured at 535 nm. Nitrate is reduced on-line to nitrite in a copper-coated cadmium column which is then treated with azo dye reagent and the absorbance due to the sum of nitrite and nitrate is measured; nitrate is determined from the difference in absorbance values. A copper column incorporated into the reaction manifold before the copperised cadmium column not only improves the long-term accuracy, but also extends the life time of the copperised cadmium column. Various analytical parameters, such as effect of acidity (pH), flow rate, sample size, dispersion coefficient, time, temperature, reagent concentration and interfering species, were studied. The calibration graphs were rectilinear for 0.1-3.5 mug ml(-1) of NO(3) and 10 ng ml(-1)-2.2mug ml(-1) of NO(2). The method is successfully applied to some food samples (meat, flour and cheese), environmental waters (inland and surface), beer and soil samples. Up to 30 samples can be analysed per hour with a relative precision of approximately 0.1-2%.

Determination of glycerol in alcoholic beverages using packed bed reactors with immobilized glycerol dehydrogenase and an amperometric FIA system.

A flow injection analysis system incorporating amperometric detection and enzyme reactor for glycerol determination in alcoholic beverages is described. The reactor is based on the glycerol dehydrogenase system, and the enzyme was immobilized through chemical modification on several supporting materials such as aminopropyl and isothiocyanate controlled pore glass, aminopolystyrene resin and m-aminobenzyloxymethyl cellulose. NADH, the product of the enzymatic reaction, was monitored amperometrically with a three-electrode wall-jet type flow through cell, at + 0.5 V vs. Ag/AgCl. The method was evaluated in the presence or absence of potassium and the following linear dynamic ranges were found: 2 x 10(-5) -2 x 10(-4) mol l(-1) and 4 x 10(-5) -4 x 10(-4) mol l(-1), respectively. The interference effects of various compounds were also studied. The relative standard deviation was found to be better than 1.0% (n = 6). The reactors are stable for over a period of 3 months and after about 2500 injections. Under optimum working conditions the sampling frequency was 30 samples h(-1). The successive application of the method was confirmed by comparison with a reference method. The mean relative error is 2.2% and the recovery 95-102%.

Flow injection determination of glutamate in human serum and rat brain samples with immobilized glutamate oxidase and glutamate dehydrogenase reactors.

Two methods are proposed for the determination of regional concentrations of glutamate in the rat brain as well as in human serum. Glutamate oxidase was immobilized on non-porous glass beads and glutamate dehydrogenase was immobilized on glass derivatives. These supports were employed for the construction of Single Bead String Reactors and Packed Bed Reactors, respectively, which in turn were linked to Flow Injection Analysis systems with either photometric or fluorometric detection. Analytical working curves are linear in the range 1-200 mumol/l for packed bed reactors and 10-500 mmol/l for single bead string reactors. The samples were pretreated depending on their origin and the applied measuring system. Optimal dilution factors were established for the two techniques. Optimal dilution ratios were established and the influence of several added substances was investigated. Recovery and method comparison studies including high performance liquid chromatography verified the accuracy of the proposed methods. Results from within-day and between-day measurements gave relative standard deviations of 4.7 and 5.9% for serum samples and 2.5 and 4.0% for brain samples, respectively.

Spectrophotometric kinetic determination of copper(II) trace amounts based on its catalytic effect on the reaction of the reduced 2,6-dichlorophenolindophenol and hydrogen peroxide.

A catalytic spectrophotometric method is presented for the determination of Cu(II), based on the oxidation of the leucocompound of the 2.6-dichlorophenolindophenol (DCPI)(r), in the presence of hydrogen peroxide and the catalytic effect of Cu(II) on this reaction in ammonia-ammonium chloride buffer solution of pH 10.5. The above reaction is followed spectrophotometrically at 562 nm. The study was carried out with a filter spectrophotometer equipped with a fiber optic and an immersed type optical cell of 1 cm. The optimum operating conditions regarding concentration of the reagents involved, pH and temperature were established. The interference effect of several metallic species was also investigated. It was found that the proposed method shows fairly good selectivity and sensitivity, simplicity and rapidity compared to other kinetic methods. The working curve of the recommended reaction-rate method is linear in the concentration range 5-300 ng/ml. The relative standard deviation for a standard solution of 30 ng/ml Cu(II) is better than 2.5%. The method was applied successfully on the determination of Cu(II) in a wide variety of real samples such as alloys, pharmaceuticals, foodstuffs and environmental samples. The results were compared to those received with official methods. Good agreement was attained.

Immobilization of glutamate dehydrogenase on glass derivatives. A method for the assay of glutamates in real samples with simplex optimized automated FIA-system.

An enzymatic method for the determination of glutamic acid in food samples and pharmaceuticals is described. l-Glutamate dehydrogenase (GLDH) from beef liver was immobilized on isothiocyanate modified Controlled Pore Glass for the construction of a packed bed reactor. The NADH produced from the enzymic reaction was monitored fluorimetrically. The working curve is linear up to 200 mumol/l glutamate for an injection volume of 58 mul. The detection limit of the method is 0.3 mumol/l. The composite modified simplex was employed for the selection of the proper experimental conditions using an in-house flow injection manifold. Many interfering species and several amino acids were tested to verify the specificity of the enzyme reactor. The system works selectively for glutamic acid. The method is ideally suited to the assay of glutamic acid in a large number of samples because of its simplicity, stability and low cost. Forty-five samples per hour can be analyzed with a relative standard deviation better than 2%. The reactor is stable for a period of more than four months under specified storage conditions. The accuracy of the proposed method is tested by comparison of the results with those obtained by the official methods and the manufacturer's specifications for the analyzed samples. Good correlation was attained. Recovery experiments showed results between 97 and 104%.