bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of bound water content in sludge: The use of differential scanning calorimetry (DSC)
Authors: Lee Duu‐Jong , Lee Sun F.
Published: May 2005

The bound water content of original and frozen activated sludge and an inorganic sludge were measured via differential scanning calorimetry (DSC) and drying tests. Original sludge contained a significant level of bound water which was reduced by about 50% after freeze/thaw treatment. A simple thermodynamic interpretation showed that liquid–solid binding strength played an important role in depression of the freezing point of bound water in a sludge. The choice of a threshold temperature in a DSC test was equivalent to definition of a threshold binding strength dividing bound/non‐bound water content. The possible close relationship between the bound water content measured via DSC and the drying test is discussed. The importance for sample uniformity was also examined.
Transferrin metalloprotein affinity metal chromatography
Authors: Spires Kevin , Vincent John B.
Published: May 2005

The metal transport protein transferrin, when immobilized to Sepharose, can serve as an affinity media for the selective removal and subsequent release of heavy metal ions from aqueous solution. The material is stable over the pH range of 2–10, is self‐indicating for the binding of certain metal ions, and maintains its integrity towards metal‐binding capacity for long periods of time. In one step heavy metal ion concentrations can be reduced by at least five orders of magnitude to, at most, part per billion levels. The findings here presented suggest a novel practical method for the decontamination and/or recovery of metals ions from very dilute solutions and represent the first efforts to extend the concept of affinity chromatography to metal ions.
Claisen–Schmidt reaction in a hydrotropic medium
Authors: Sadvilkar Vikas G. , Samant Srinivas D. , Gaikar Vilas G.
Published: May 2005

The Claisen–Schmidt condensation of benzaldehydes with acetophenones was carried out in an aqueous medium using sodium butylmonoglycolsulfate (NaBMGS) and sodium salts of aromatic sulfonic acids as hydrotropes. Substantial enhancement in the rate of the reaction was obtained, along with the easy recovery of the product. Recycling of the hydrotrope solutions has been tested without any loss in the rate of the reaction.
Development of a pilot‐scale microfiltration harvest for the isolation of physostigmine from Streptomyces griseofuscus broth
Authors: Russotti Gregory , Göklen Kent E. , Wilson James J.
Published: May 2005

A pilot‐scale microfiltration harvest was developed for the isolation of physostigmine from a mycelial fermentation broth. Complete permeation for this extracellular secondary metabolite was obtained during initial laboratory screening with a variety of crossflow filtration membranes but poor filtration flux made process feasibility uncertain. Modification of the fermentation medium improved fluxes from 10–20 dm3 m−2 h−1 to 60–80 dm3 m−2 h−1 which significantly reduced membrane area requirements, making the process feasible for larger scale implementation. A commercially‐available ceramic membrane with 0·2 μm pores was employed for the scale‐up of this step to the pilot plant; this membrane was found to provide flux similar to that of polymeric membranes and had superior regeneration characteristics. Optimum performance at bench scale was obtained using 70 kPa transmembrane pressure and 4·0 m s−1 crossflow velocity. The mycelial broth had a very high suspended solids concentration (30% (v/v)) which limited us to a two‐fold concentration before starting the diafiltration washes. The process was scaled‐up to the 200–400 dm3 scale, with good reproducibility and excellent membrane regenerability observed in a series of five experiments. An increase in membrane loading did result in a decreased average flux at the larger scale (47·6 dm3 m−2 h−1), which indicated the importance of this parameter. A centrifugal pump was substituted for a positive displacement pump upon scale‐up and performed well if provided with the appropriate suction head. Scale‐up in general was straightforward, provided proper attention was given to the hydraulic design of the system.
Color difference measurement and color removal from dye wastewaters using different adsorbents
Authors: Yeh Ruth Yu‐Li , Thomas Adrian
Published: May 2005

Pollution from textile mills is a problem of formidable dimensions and color removal is the most perplexing problem facing environmental engineers designing appropriate treatment facilities for textile wastewaters. The CIE colorimetric system has been used in this study to measure the color in the treatment of disperse‐red‐60 dye wastewater using different adsorbents. The color removal is determined by using the CIE 1976 L*a*b* (CIELAB) color difference equation. The effect of contact time and dosage on color and color removal has been investigated for various adsorbents, namely, powdered activated carbon, granular activated carbon, activated alumina, molecular sieves and diatomite.
Oxidative dehydrogenation of ethyl alcohol over vanadium pentoxide supported on magnesia
Authors: Said Abd El‐Aziz A. , Abd El‐Wahab Mohamed M. M.
Published: May 2005

The catalytic dehydrogenation of ethyl alcohol on vanadium pentoxide supported on magnesia was studied in a flow system. The catalysts were characterised by DTA, X‐ray, surface area and electrical conductivity measurements. The results revealed that the yield of acetaldehyde is strongly affected by the nature of compounds formed as a result of the interaction between MgO and V2O5. The Mg3V2O8 formed at a calcination temperature of 550°C is the most active and selective catalyst. The activity of this spinel was correlated with the creation holes and the position of the Fermi potential. On the other hand, the catalyst calcined at 650°C was accompanied by the formation of an MgV2O6 spinel, which exhibited low activity and low selectivity.
Enantioselective separation of basic amino acids on talc
Authors: Arrou Dominique , Baboulène Michel
Published: May 2005

Certain amino acid derivatives (ε‐basic, anilide group) can be readily adsorbed onto various types of talc (steopac, SS20, C300, C400). For instance, talc is capable of adsorbing the amino acid esters but not the equivalent free amino acids. The types of talc which have high hydrophobicity (00, 15M00) were poor adsorbents. Two applications of these findings are presented: enhancement of the sensitivity of enzymatic tests in the presence of chromogenic substrates and enantioselective separation of ε‐basic amino acids (arginine, lysine, ornithine).
Preparation of 4‐bromophthalic anhydride by oxidation of 4‐bromo‐ortho‐xylene
Authors: Glukhovskii Naum , Effenberger Reinhard
Published: May 2005

The preparation of 4‐bromophthalic anhydride is described. This compound, useful as raw material for production of dianhydride monomers such as bisphthalic dianhydride, oxy‐bisphthalic dianhydride and several bisphenol dianhydrides for the specialty polyimide sector, was prepared via gas phase oxidation of 4‐bromo‐ortho‐xylene with air over a V–Ti–P catalyst in a yield of 85%. Oxidation of 3‐bromo‐ortho‐xylene gave only a 45% yield of 3‐bromophthalic anhydride. Mixtures of 4‐ and 3‐bromo‐ortho‐xylene gave, as expected, mixtures of 4‐ and 3‐bromophthalic anhydride which were enriched in the 4‐isomer (in comparison with the starting bromoxylene isomeric composition).
A method for estimating the state variables and parameters of fermentation systems
Authors: Maher Mostafa , Roux Gilles , Dahhou Boutaib
Published: May 2005

A major difficulty in the monitoring and control of bioprocesses is the lack of reliable and simple sensors for following the evolution of the main state variables and parameters such as biomass, substrate, product and growth rate. An adaptive estimation algorithm is proposed to recover the state and parameters in bioprocesses. This estimator utilises the physical process model and the reference model approach. Experiments concerning estimation of biomass and product concentrations and specific growth rate, during batch, fed‐batch and continuous fermentation processes are presented. The results show the performance of this adaptive estimation approach.
Synthesis and evaluation of some fatty esters as plasticizers and fungicides for poly(vinyl acetate) emulsion
Authors: Sadek E. M. , Motawie A. M. , Hassan A. M. , Gad E. A.
Published: May 2005

n‐Fatty alcohols (average molecular weight 187), prepared from n‐paraffins, were treated with a series of dibasic acids such as malonic, succinic, glutaric, adipic and phthalic anhydride to give the corresponding fatty esters. The prepared fatty esters were formulated with poly(vinyl acetate) emulsion and used as films or textile coatings. Tests such as rate of drying, mechanical properties and resistance to micro‐organisms were carried out. Samples of poly(vinyl acetate) plasticized with dibutyl phthalate were also prepared and evaluated for the purpose of comparison. The antifungal activity of these compounds was studied. The results obtained indicate that the prepared fatty esters can be used not only as plasticizers but also as fungicides and in some respects they are better than the conventional dibutyl phthalate plasticizer.
Methacrylic acid–acrylamide‐g‐poly(ethyleneterephthalate) fibres for urea hydrolysis
Authors: Elçin Y. Murat , Saçak Mehmet
Published: May 2005

This paper presents the results of urease immobilization onto methacrylic acid–acrylamide grafted poly(ethyleneterephthalate) fibres. The graft yield strongly affected the maximum activity of the immobilized enzyme up to a value of 70·2%. Higher grafting caused a decline in urease activity and led to the degradation of the fibres. The minor changes observed in Km and Vmax demonstrated that the conformational changes existed during immobilization were not extensive. However, 70·2% methacrylic acid–acrylamide‐g‐fibres containing urease were more stable towards acidic and alkaline pH, high temperature and storage conditions compared with free enzyme. Apart from the increase in stability to heat inactivation, the initial enzymatic activity of the urease–fibre system remained almost unchanged even after 40 repeated assays corresponding to 10 h of operation in 4 months, indicating the excellent durability of the system.
Hydrolysis of lecithin by phospholipase A2 in mixed reversed micelles of lecithin and sodium dioctyl sulphosuccinate
Authors: Morgado M. A. P. , Cabral J. M. S. , Prazeres D. M. F.
Published: May 2005

The hydrolysis of egg yolk lecithin was studied as catalysed by porcine pancreatic phospholipase A2 (phosphatide 2‐acyl‐hydrolase, EC 3.1.1.4) entrapped in reversed micelles of lecithin and sodium dioctyl sulphosuccinate (AOT) in isooctane. The influence of relevant parameters such as temperature, pH, water content, and buffer, AOT, lecithin, calcium and enzyme concentrations was investigated. The order in which the reactants were mixed showed a strong influence on catalytic activity. Higher activities were obtained if the enzyme, water and calcium were first solubilized and pre‐equilibrated in plain AOT reversed micelles before the addition of the substrate. Maximum activity was obtained at 750 mmol dm−3 calcium in the water pool of the micelles, which is an extremely high concentration when compared with the values reported in the literature. This was related to the formation of divalent chelates of calcium with AOT that compete with the binding of the co‐factor to the enzyme. Accordingly, the optimum concentration of calcium in the inner core of the micelles decreased from 750 to 500 mmol dm−3 when the AOT concentration was lowered from 15 to 10 mmol dm−3.
Mean residence time of gas in mechanically agitated gas–liquid contactors
Authors: Murugesan Thanapalan , Rathnam G. S. Venkat , Rao S. Panduranga , Rao P. Gangadhar
Published: May 2005

In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold‐up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature.
Solid‐phase acylating reagents. Part III. The reactions of a macroreticular acetyl polystyrenesulphonate with aniline in aqueous, dichloromethane, dimethylformamide, dioxan and ethyl acetate solutions and with acetone in aqueous solutions
Authors: Laird Robert M. , Pandit Subash
Published: May 2005

The effectiveness of a macroreticular matrix in reducing side‐reactions in the reaction of acetyl polystyrenesulphonate with aqueous aniline has been investigated. Results were comparable with those for the 2% cross‐linked resins and the use of four non‐aqueous solvents gave neither any improvement in the acetanilide yield nor in its purity. The synthesis of isopropenyl acetates by reacting the reagent with acetone was explored.
Characterization of biomass from a pilot plant digester treating saline wastewater
Authors: Omil Francisco , Méndez Ramón J. , Lema Juan M.
Published: May 2005

The evolution of biomass contained in a pilot‐scale digester treating wastewater from a sea‐food processing factory (15–45 g Chemical Oxygen Demand (COD) dm−3 and high salinity) was studied for 2 years. During this period, different effluents have been treated and several operational conditions were followed. Laboratory‐scale experiments were carried out to determine the sludge methanogenic activity and the salinity adaptation of the biomass which developed in the digester. During the different periods, sludge concentration remained between 10 and 12 g Volatile Suspended Solids (VSS) dm−3, a value that seems to be characteristic for this reactor. A global Organic Loading Rate (OLR) balance showed no significant change of biomass concentration inside the reactor, although a quite important growth of biomass (11·5% of OLR fed) was observed. Methanogenic activity assays indicated a sludge with a good activity (0·5–0·75 g COD g−1 VSS day−1) in a saline medium could be obtained from a low activity sludge (0·047 g COD g−1 VSS day−1). Toxicity assays showed the importance of antagonistic effects of other cations on the toxicity exerted by sodium.
Synthesis of fatty esters by polyethylene glycol‐modified lipase
Authors: Basri Mahiran , Ampon Kamaruzaman , Yunus Wan Md. Zin Wan , Razak Che Nyonya A. , Salleh A. Bakar
Published: May 2005

Monomethoxypolyethylene glycols (PEG) of molecular masses 1900 and 5000 were activated using p‐nitrophenyl chloroformate to form PEG–nitrophenyl carbonates (activated PEG) with high yield (96–98%). The activated PEG was covalently attached to Candida rugosa lipase. Increasing the molar ratio of activated PEG to the enzyme increased the degree of lipase modification. These modified lipases exhibited specific ester synthesis activities on organic solvents compared with native lipase. The degree of activity enhancement depended on the size of activated PEG used and the degree of modification of the enzyme. Maximal activity was attained after exhaustive of modification. The effects of different solvents, reaction temperature, and fatty acids on the esterification activity and the stability of the modified enzyme were investigated. The optimum esterification temperature (40° C) and preference of fatty acids as acyl donors of the modified lipase were very similar to those of the native enzyme. The modified lipase exhibited higher activity non‐polar solvents than in polar solvents, and showed higher temperature, solvent and storage stability then the native lipase.
Determination of relative wettability of porous sandstones by imbibition studies
Authors: Grattoni Carlos A. , Chiotis Efstathios D. , Dawe Richard A.
Published: May 2005

The effective wettability of consolidated sandstone rocks has been determined using the Washburn equation by measuring the rate of imbibition of water, ethanol and their mixtures into cores and thin rectangular sections. The rocks behaved as low energy surfaces with a critical surface with a critical energy of spreading as defined by Zisman, of 28 mN m−1. This behaviour is believed to be caused by clay particles or organic material present on the pore surfaces. A discussion of the validity and limitations of the Eashburn equation for obtaining effective wettabilities in consolidated porous media is presented. The general conclusion is that effective wettability depends on the preparation and general conditions of the samples.
Hydrolysis of ricebran oil in a fluidised‐bed recycle reactor using immobilised lipase on nylon‐6
Authors: Padmini P. , Iyengar K. K. S. , Baradarajan A.
Published: May 2005

A recycling fluidises‐bed Immobilised enzyme reactor for the hydrolysis of ricebran oil employing an inexpensive Nylon‐6 matrix as the immobilisation carrier is described. The catalyst has high initial activity and excellent long term stability. The tractor design exploits the fact that fluidisation permits the use of small catalyst particles, so overcoming the yield‐limiting diffusion‐associated problems encountered in the case of conventional fixed‐bed reactors. The conventional fluidised‐bed reactor did not plugging and high pressure drop problems typical of fixed‐bed reactors. Conversion yields of 72% were achieved in the reactor, which generally showed superior performance to that of a fixed‐bed design.
The cocurrent downflow contactor (CDC) as a fixed bed and slurry reactor for catalytic hydrogenation
Authors: Boyes Adrian P. , Chugtai Arshad , Khan Zaffer , Raymahasay Sugat , Sulidis Andrew T. , Winterbottom John M.
Published: May 2005

The Cocurrent Downflow Contactor (CDC) has been studied as a three phase reactor and in addition, chemically enhanced mass transfer studies have confirmed the very high gas hold‐up values previously indicated by photographic methods (εg = 0·5–0·6). Mass transfer measurements for the O2/H2O system have shown that volumetric mass transfer coefficients (kL a) are in the range 0·25–0·3 s−1 for unpacked and packed CDC reactors, while Co2+ ion‐catalysed sulphite oxidation exhibited enhanced (kL a) are in the range 0·25–0·3 s−1 for unpacked and packed CDC reactors, while Co2+ ion‐catalysed sulphite oxidation enhibited enhanced (kLa) values of 0·55 s−1 with interfacial areas in the range of 1000–6000 m2 m−3. A model first order reaction, the palladium‐catlysed hydrogenation of itaconic acid, was examined both in a small stirred batch reactor and in the CDC. Low degrees of mass tranfer resistances were observed (both gas–liquid and liquid–solid) especially in the case of the CDC when used as a slurry and fixed bed reactor, with liquid‐solid mass transfer resistances being the the range 1–10%. This was confirmed by energy of activation measurements in the range 30–45 kJ mol−1. The CDC was used in slurry and fixed bed form for the respective hydrogenation of the triglycerides, rapeseed and soyabean oils. The reaction was predominantly surface reaction rate controlled with energies of activation in the range 47–58 kJ mol−1, using palladium and nickel catlysts. Reaction selectivities were high, especially in respect of linolenate removal and the fixed bed CDC was slightly superior to the slurry reactor.
Affinity chromatography of glucose‐specific lectin using silica‐based support
Authors: Lee Wen‐Chien , Hsiao Cheng‐Chung , Ruaan Rouh‐Chyu
Published: May 2005

Four silica‐based adsorbents were prepared from covalent attachment of four carbohydrates: i. e. maltose, cellobiose, N‐acetyl‐D‐glucosamine and p‐aminophenyl‐β‐D‐glucopyranoside, respectively. These adsorbents posses either terminal D‐glucose or N‐acetyl‐D‐glucosamine as the ligand on their surfaces with a ligand density ranging from 20 to 29·2 μmol g−1. The binding of the glucose‐specific lectin, concanavalin A (Con A), to the immobilized ligand on the silica surface depended on the configuration of the immobilized glucose and the linkage of the glucose to the support. Con A showed strong affinity for maltose‐immobilized silica, which contains terminal α‐D‐glucose, and p‐aminophenyl‐β‐D‐glucopyranoside‐immobilized silica. On the other hand, Con A showed no affinity for cellobiose‐immobilized silica, which contains terminal β‐D‐glucose groups, and N‐acetyl‐D‐glucosamine‐immobilized silica. The binding constants for the interactions between Con A and immobilized ligands were determined. The columns packed with the resultant affinity adsorbents were then adopted for the purification of Con A from Jack bean meal. As the diluted NaCl extract of Jack bean meal was applied to the column packed with maltose‐immobilized silica, a 13·2‐fold purification was achieved by stepwise‐elution.
Gelling of alginate fibres
Authors: Thomas Adrian , Gilson Christopher D. , Ahmed Tanveer
Published: May 2005

Equipment was developed to measure the time for complete gelling of sodium alginate fibres in calcium chloride solution, taken as the time to achieve maximum tensile strength. The effects of fibre diameter, alginate concentration, alginate composition and calcium chloride concentration on gelling time were investigated. A diffusional model, developed to predict the gelling time, agreed with experimental results except for the effect of calcium ion concentration which was modelled empirically.
Recovery of vegetable tannins from divi‐divi pods
Authors: Pérez‐Tello Carlos , Quintana‐Hernéndez Pedro
Published: May 2005

An experimental survey was developed to determine optimal operational conditions when extracting tanning materials from mied divi‐divipods with a 10% (v/v) alcohol–water solution. The study included runs at both laboratory and pilot levels. The percentage of extracted tanning materials from samples was measured when varying the following variables: (1) temperature, (2) solvent to solute ratio, (3) extracting time, (4) type of solvent, (5) agitation, and (6)average particle size. The optimal values were as follows: 50°C, 120 cm3 of solvent: 1 g of divi‐divi, 20 min, 10% (v/v) ethanol–water, agitation on, and 0.087 cm average particle size. The maximum yield of extracted tanning materials was 54 by weight (dry basis) when divi‐divi pods up to 6 months old were used, but the tannic content in pods decreased by 15% and 32% after 12 and 42 months of storage respectively.
Application of membrane filtration to glutamic acid recovery
Authors: Huang Shaoxun , Wu Xingyan , Yuan Cengxiang , Liu Tiemin
Published: May 2005

A method for recovery of glutamic acid from fermentation broth using microfiltration, diafiltration, and reverse osmosis has been proposed. Coupled with the technique of semi‐continuous isoelectric crystallisation, the method gave a product of 3·3% higher purity with 11.1% higher yield compared with the conventional method.
Physico‐chemical methods for characterization of the physiological state of microorganisms
Authors: Zentgraf Brigitte
Published: May 2005

The physiological state of microorganisms should be considered in biotechnology and biosciences since this influences the rate and efficiency of cellular processes. Physico‐chemical methods, such as biocalorimetry and laser flow cytometry, and other spectroscopic methods for determination of biochemical data, such as concentration of NADH, ATP and cytochrome c, are suitable for describing the physiological state.
Flat‐sheet and hollow fiber membrane bioreactors: A study of the kinetics and active site conformational changes of immobilized papain including sorption studies of reaction constituents
Authors: Ganapathi Sowmya , Butterfield D. Allan , Bhattacharyya Dibakar
Published: May 2005

Papain, a sulfhydryl protease has been immobilized on flat‐sheet modified polysulfone membranes and hydroxyethyl cellulose coated polyethersulfone hollow fibers. Amidase activity of the enzyme in solution on the membranes has been assayed. Immobilized papain on the modified polysulfone membrane and the hollow fibers retains 12% and 25% of its activity (with 1 mmol dm−3 substrate) in solution, respectively. Loading experiments revealed decreased activity on the modified polysulfone membrane with increased enzyme loading. Adsorption experiments for the reaction product, p‐nitroaniline, have been performed and an attempt has been made to correct for this in activity calculations. Apparent Michaelis–Menten parameters were determined for the modified polysulfone and hollow fibers with both Km and Vmax being lower in the immobilized cases. Electron paramagnetic resonance study of the changes in active site conformation of an enzyme on a hollow fiber membrane are reported for the first time. Experiments using the sulfhydryl‐specific (1‐oxyl‐2,2,5,5‐teetrahyl‐Δ3‐pyrroline‐3‐methyl)methanethiolsulfonate spin label depicted the presence of two subpopulations of immobilized papain on the hollow fibers, one of them active and one denatured.
Production of L‐aminoacylase by fermentation of Pseudomonas sp. BA2
Authors: Santoyo Antonio Bódalo , Rodríguez Josefa Bastida , Carrasco José Luis Gómez , Gómez Elisa Gómez , Teruel María Luisa Asanza , Rojo Isabel Alcaraz
Published: May 2005

The growth and enzymatic production of Pseudomonas sp. BA2 a new L‐aminoacylase‐producing microorganism, were studied in a bench‐top fermenter. Multiple fermentations were carried out in order to determine the optical pH and temperature values. The influence of the substrate concentration on both growth and Laminoacylase activity was also investigated. The maximum growth rate and the greatest yield of enzyme were obtained when the fermentation was carried out at pH 7·5, 25°C and DOT ≥ 50%. N‐Acetyl‐DL‐alanine, at a concentration 20 g dm−3, was used as the sole carbon and nitrogen source. The fermentation process provided a maximum biomass concentration of 3·36 g dry weight dm−3. The highest L‐aminoacylase production (11429 U g−1 dry weight) was obtained after 39 h of cultivation. The results were a significant improvement over those previously reported.
Applicability of continuous membrane bioreactor in production of phenylacetylcarbinol
Authors: Liew Michelle K. H. , Fane Anthony G. , Rogers Peter L.
Published: May 2005

A continuous membrane bioreactor (CMB) with Ceraflo ceramic microfilter was evaluated for the production of phenylacetylcarbinol (PAC) using 12–15 g dm−3 Candida utilis. Compared with the classical continuous fermentation, the CMB process was shown to have higher biomass concentration (from 40% to 400% increase) and greater growth rate (from 3‐ to 9‐fold) at dilution rates varying from 0·03 h−1. These advantages were partially offset by the reduced permeate flux caused by the increased biomass. Furthermore, an addition of only 3·0 cm3 h−1 benzaldehyde for 17 h (a typical bioconversion protocol) was found to kill the yeast, resulting in 27% dead organisms and 35% lysed organisms and their associated species. This led to a 100% flux decline during the course of PAC production over the above period.
Penicillin G extraction by amberlite LA‐2—a study of interfacial reaction kinetics by interfacial tension measurements
Authors: Lee Chau Jen , Wang Shih Sheng
Published: May 2005

The concentration of reactants at an interface cannot be determined directly. The concentration at the interface has been estimated by measuring the interfacial tension at the interface between two immiscible solutions. An aqueous phase, de‐ionised water containing penicillin G, and an organic phase containing amberlite LA‐2 were used as a typical system to study the kinetics of interfacial reaction. The interfacial tension was measured by a spinning‐drop tensiometer at 25 ± 0·1°C. The interfacial tension was found to correlate well with the concentrations of penicillin G, Amberlite, LA‐2 and proton in each respective phase.
Multi‐substrate analysis of carbon oxidation and nitrification in an upflow packed‐bed biofilm reactor
Authors: Beg Shafkat A. , Hassan Mirza M. , Chaudhary Muhammad A. S.
Published: May 2005

The performance of an upflow packed‐bed biofilm reactor (UPBR) was analysed under multi‐substrate limitation by considering simultaneous carbon oxidation and nitrification reactions. Numerical solutions of the proposed model defining the system were obtained for a wide range of operating conditions of illustrate individual substrate limitation behavior. For an inlet concentrating of 75 mg dm −3 of NH4‐N and 25 mg dm −3 of methanol., the organic substrate was consumed rapidly near the inlet of the reactor while most of the NH‐N was converted in the central region. The concentration profiles within the biofilm indicated that oxygen was limiting near the inlet of the reactor while organic substrate was laminating at the middle of the reactor. Both NH‐N and methanol became limiting near the reactor exit. Detailed analyses were carried out for a wide range NH‐N concentration and for a given concentration of methanol which showed that oxygen could also become limiting even at the middle of the reactor.
Lignocaine ion‐selective electrodes based on its ion‐associates with cobalt thiocyanate, phosphomolybdate and reineckate complex ions
Authors: Issa Yousry M. , Shoukry Adel F. , Rizk Mahmoud S. , Atia Ehab M.
Published: May 2005

Lignocaine (Lg) selective PVC membrane electrodes based on the ionassociates lignocaine‐cobalt thiocynate (I), lignocaine–phosphomolybdate (II) and lingnocaine–reinckate (III) were constructed. The electrodes exhibited linear response over the concentration ranges 0.02–100, 0.01–100 and 0.01–10 mM for I, II and III, respectively. pH did not effect the electrodes performance within the ranges 3–6, 3–7 and 3–6·5 for 10−2, 10−3 and 10−4 M LgHCl, respectively. Interferences are negligible for many inorganic cation, sugars and amino acids. The isothermal coefficients were found to be 0·000459, 0·000698 and 0·000404 V °C−1 for I, II and III, respectively. The life spans of the electrodes are more than 2 months of continuous work. Potentiometric titration and the standard addition method were used to determine LgGCl in pure solutions and in pharmaceutical preparations with high accuracy and precision.
Liquid and gas chromatographic separation of isomeric methylated dibenzothiophenes
Authors: Berthou F. , Dreano Y. , Sandra P.
Published: May 2005

Trace amounts of a dibenzothiophene (DBT) series in complex matrices were detected by gas chromatography with flame photometric detection (FPD) after purification and isolation by normal‐phase high performance liquid chromatography. The gas chromatographic behavior of eleven methylated DBTs was studied on six common stationary phases. Complete resolution of the four monomethyl DBT isomers was only achieved on a capillary column coated with a methylphenylsilicone phase gummified in situ by heat‐curing.

The determination of the relative distribution of the four monomethylated isomers is proposed as a powerful method for monitoring oil pollution in marine environment.
Influence of temperature on FTIR spectra of various organic compounds analyzed by on‐line carbon dioxide SFC/FTIR
Authors: Morin Ph. , Beccard B. , Caude M. , Rosset R.
Published: May 2005

The development of an on‐line SFC‐FTIR method with supercritical carbon dioxide as mobile phase requires information about the nature of the FTIR spectrum of a solute dissolved in supercritical or liquid CO2. The wavenumber of maximum absorbance of the carbonyl stretching vibration was quantitatively studied versus temperature and CO2 density. FTIR spectra recorded in supercritical or liquid CO2 have been compared to their vapor‐phase and condensed‐phase spectra for various solutes.
Quantitative analysis of polymer additives in low density polyethylene using supercritical fluid extraction/supercritical fluid chromatography
Authors: Ashraf‐Khorassani Mehdi , Levy Joseph M.
Published: May 2005

Analysis of low concentration polymer additives has been a challenging problem. The commonly used methods of analysis involve the initial extraction of polymer additives with solvents, often in a Soxhlet apparatus, followed by liquid, size exclusion, or gas chromatography. This paper describes the on‐line super‐critical fluid extraction (SFE)‐supercritical fluid chromatographic (SFC) determination of different additives from low density polyethylene. Cryogenic collection was used as an interface between SFE and SFC to focus the extraction eluate before transfer to an analytical SFC column for quantitative analysis.
New on‐line concentrator for LC‐GC: Analysis of PAHs with LC‐GC
Authors: Heo Gwi Suk , Suh Jung Kee
Published: May 2005

A new, versatile, and low cost on‐line LC‐GC interface has been devloped for the fast and reliable introduction of large volume samples into a cappillary GC column without using the conventional retention gap. PAHs in soot were analyzed by on‐line normal phase HPLC‐capillary GC. A glass, vial‐shaped on‐line concentrator provides a zone for solvent evaporation and sample concentration. Large volumes of HPLC eluate can be concentrated with the on‐line concentrator and then transferred directly into the cappillary column. Trace levels (< 10 ppb) of PAH compounds can be efficiently concentrated with the on‐line concentrator and determined without loss or contamination.
Selectivity tuning of serially coupled columns in high performance liquid chromatography
Authors: Welsch Thomas , Dornberger Uwe , Lerche Dietmar
Published: May 2005

The tuning of selectivity by changing the flow rate has been investigated in HPLC: two columns with different retention characteristics were coupled in series via a T‐piece and the relative retention of components chromatographed on the system were changed by varying the individual flow rates in the coupled columns. The flow rate alteration was performed by adding a second flow after the first column. The flow rate ratio necessary for optimum resolution can be easily calculated on the basis of the capacity factors measured on the individual columns. The performance of this method for adjusting selectivity has been demonstrated by using different column combinations to separate several mixtures containing chlorophenols, nitroaromatic compounds, and aromatic hydrocarbons.
Adjusting the selectivity of inorganic anion separation by capillary electrophoresis
Authors: François C. , Morin Ph. , Dreux M.
Published: May 2005

The separation of the principal inorganic anions (bromide, carbonate, chlorate, chloride, fluoride, nitrate, nitrite, sulfate, phosphate) has been achieved using a capillary electrophoresis system with indirect UV detection at 260 nm. Several types of cationic surfactants (quaternary ammonium, phosphonium or methonium) were tested as electroosmotic flow modifiers and added to a chromatebased buffer prepared from potassium dichromate. The influence of many physicochemical parameters such as nature and concentration of cationic surfactant, buffer pH, dichromate concentration buffer, voltage and temperature upon the migration time of an analyte anion, peak efficiency, asymmetry factor, and finally resolution has been investigated. A linear relationship between the corrected area and the anion concentration in the 2.5–50 ppm range was obtained, thus allowing the quantitative analysis of anions in mineral water. Finally, by increasing the hydrodynamic injection time, the separation of inorganic anions at a low concentration level of 50 ng/ml was achieved without any loss of resolution.
Development and evaluation of an interface for coupled capillary supercritical fluid chromatography/magnetic sector mass spectrometry. Application to thermally unstable and high molecular mass compounds
Authors: Mertens Manuel A. A. , Janssen Hans‐Gerd M. , Cramers Carel A. , Genuit Wim J. L. , van Velzen Ger J. , Dirkzwager Henk , van Binsbergen Herman
Published: May 2005

An interface for coupling supercritical fluid chromatography to a magnetic sector mass spectrometer was developed and evaluated. The interface is based on direct introduction of the mobile phase, carbon dioxide, into the ion‐source of the mass spectrometer. The SFC‐MS system was optimized with respect to the signal‐to‐noise ratio. Under optimized conditions, the estimated detection limit for n‐pentadecane is approximately 30 ppm. Spectra obtained in the electron‐impact ionization mode show a very good similarity with library spectra. The performance of the SFC‐MS system was evaluated by the analysis of a number of test mixtures. A sample containing several low molecular mass, thermally unstable compounds, which could neither be analyzed by GC‐MS nor by LC‐MS, was analyzed. Also for the analysis of high molecular mass compounds, the coupled system showed a good performance.
Testing the polarity and adsorptivity of nondeactivated GC capillary surfaces
Authors: Grob Konrad , Vorburger Thomas
Published: May 2005

Split injection of 1‐pentanol headspace on to raw or treated fused silica tubing yields information on the characteristics of its surface (silanol concentration, polarity, adsorptivity). Fused silica tubing from three sources was compared. The effect of various leaching and etching procedures used for column preparation was studied, as was the stability of uncoated fused silica precolumns towards water and some organic solvents.
A new look at light hydrocarbon separations on commercial alumina PLOT columns: Column selectivity and separation
Authors: Ji Zhenghua , Chang Imogene L.
Published: May 2005

Alumina‐coated porous layer open tubular (PLOT) columns are widely used for analyses of light hydrocarbons (C1 to C6). There is, however, a need for improved selectivity for complex analyses such as the determination of impurities in high purity petrochemical products. Some commercial alumina PLOT columns do not have sufficient selectivity for such analyses. The selectivity of four commercial alumina PLOT columns is evaluated for analyses of propylene and ethylene, and differences in column selectivity discussed. Requirements of column selectivity and retention are presented for several applications including the analysis of refinery gas, transformer oil gas, and fuel gas.
Simultaneous capillary GC of acids and sugars as their silyl(oxime) derivatives: Quantitation of chlorogenic acid, raffinose, and pectin substances
Authors: Tisza Sándor , Molnár‐Perl Ibolya , Friedman Mendel , Sass Pál
Published: May 2005

Our GC‐MS method for the simultaneous quantitation of sugars and acids as their silyl(oxime) derivatives, from one solution by one injection, has been extended to the reproducible determination of high molecular weight compounds sensitive to decomposition yet requiring a high evaporation temperature (e.g. chlorogenic acid and rffinose) and for the quantitation of the decomposition products of pectin (i.e., for the determination of galacturonic acid at low ng levels in the presence of a 10–100 fold excess of glucose eluting just before the acid). The optimized GC procedure has been used for quantitation of the sugar and acid (including chlorogenic acid) composition of potato samples, and for the determination of the increasing amount of the decomposition products of pectin substances in apple pulp after different storage times.
Solid phase extraction GC/ECD method for the analysis of organochlorine pesticides in wildlife plasma
Authors: Johnstone John J. , Petty Eric E. , Volz Stephanie A.
Published: May 2005

A gas chromatographic method for the analysis of nine organo‐chlorine pesticides in wildlife plasma is described. Reversed‐phase solid phase extraction is utilized to extract the organochlorine pesticides from plasma. This is followed by a normal phase solid phase extraction clean‐up as the pesticides are recovered by elution with hexane:ethyl ether (1:1) and quantified by gas chromatogra‐phy/electron capture detection. Method limits of detection range from 7.0–25 μg/L. The mean recovery for all pesticides is 81%.
Identification of migratable substances in recycled high density polyethylene collected from household waste
Authors: Huber Monika , Franz Roland
Published: May 2005

High Density polyethylene regranules reprocessed from separated household waste collection were investigated for migratable con‐taminants which were not present in virgin material. Although the material originated from different European reprocessors, the de‐tected recycling‐specific compounds were similar in most of the investigated samples. At a chosen threshold concentration of 0.5 μg/g more than 70 compounds were tentatively identified. Aroma compounds and preservatives were found in the range of 0.5 to 10 μg/g. Limonene, di(ethylhexyl) phthalate, and the isopropyl esters of myristic and palmitic acids were detected in concentrations up to 200 μg/g. These compounds were found in almost all the regranules. Most of the substances identified are constituents of personal hygiene products and cleaning agents and are therefore absorbed by the package during the storage. Owing to European food legislation and German cosmetics regulations, the use of such recycling packaging material appears suitable only for filling with technical products.
Flow of the carrier gas in open‐tubular capillary columns in temperature‐programmed gas chromatography
Authors: Hevesi Tibor , Krupcík Ján
Published: May 2005

A second‐order non‐linear partial different equation was derived to describe the dependence of carrier gas pressure in the column on the column distance and the time under temperature programmed conditions. This equation was solved numerically by the modified finite difference method for various column parameters. Constant inlet and outlet pressures were used as boundary conditions. The retention times calculated on assumption of a constant pressure profile along the column. Significant differences between retention times of corresponding solutes calculated by the two methods were found, especially when relatively long columns(L>50m) with small internal diameter(d<0.3mm)and high temperature program rates (r>5°/min)are used.
Drug—DNA sequence‐dependent interactions analysed by electric linear dichroism
Authors: Bailly Christian , Hénichart Jean‐Pierre , Colson Pierre , Houssier Claude
Published: May 2005

The interactions between 20 drugs and a variety of synthetic DNA polymers and natural DNAs were studied by electric linear dischroism (ELD). All compounds tested, including several clinically used antitumour agents, are thought to exert their biological activities mainly by virtue of their abilities to bind to DNA. The selected drugs include intercalating agents with fused and unfused aromatic structures and several groove binders. To examine the role of base composition and base sequence in the binding of these drugs to DNA, ELD experiments were carried out with natural DNAs of widely differing base composition as well as with polynucleotides containing defined alternating and non‐alternating repeating sequences, poly(dA).poly(dT),poly(dA‐dT).poly(dA‐dT),poly(dG).poly(dC) and poly(dG‐dC).poly(dG‐dC). Among intercalating agents, actinomycin D was found to be by far the most GC‐selective. GC selectivity was also observed with an amsacrine‐4‐carboxamidederivative and to a laser extent with methylene blue. In contrast, the binding of amsacrine and 9‐aminoacridine was practically unaffected by varying the GC content of the DNAs. Ethidium bromide, proflavine, mitoxantrone, daunomycin and an ellipticine derivative were found to bind best to alternating purine‐pyrimidine sequences regardless of their nature. ELD measurements provided evidence for non‐specific intercalation of amiloride. A significant AT selectivity was observed with hycanthone and lucanthone. The triphenyl methane dye methyl green was found to exhibit positive and negative dichroism signals at AT and GC sites, respectively, showing that the mode of binding of a drug can change markedly with the DNA base composition. Among minor groove binders, the N‐methylpyrrole carboxamide‐containing antibiotics netropsin and distamycin bound to DNA with very pronounced AT specificity, as expected. More interestingly the dye Hoechst 33258, berenil and a thiazole‐containing lexitropsin elicited negative reduced dichroism in the presence of GC‐rich DNA which is totally inconsistent with a groove binding process. We postulate that these three drugs share with the trypanocide 4′, 6‐diamidino‐2‐phenylindole (DAPI) the property of intercalating at GC‐rich sites and binding to the minor groove of DNA at other sites. Replacement of guanines by inosines (i.e., removal of the protruding exocyclic C‐2 amino group of guanine) restored minor groove binding of DAPI, Hoechst 33258 and berenil. Thus there are several cases where the mode of binding to DNA is directly dependent on the base composition of the polymer. Consequently the ELD technique appears uniquely valuable as a means of investigating the possibility of sequence‐dependent recognition of DNA by drugs.
Structure and expression of proteolipid protein in the peripheral nervous system
Authors: Kamholz J. , Sessa M. , Scherer S. , Vogelbacker H. , Mokuno K. , Baron P. , Wrabetz L. , Shy M. , Pleasure D.
Published: May 2005

Proteolipid protein (PLP), the major myelin protein in the central nervous system (CNS), is also made by Schwann cells (SC) in the peripheral nervous system (PNS) but is not incorporated into the SC myelin sheath. We analyzed several PLP cDNA clones isolated from a rat sciatic nerve cDNA library and found that their coding sequences were identical to PLP cDNAs previously isolated from the CNS. In addition, we have discovered an unusual form of PLP message, present in both brain and sciatic nerve RNA, that is likely formed by alternative splicing within the 3′ untranslated region of the primary PLP transcript. The absence of PLP from the SC myelin sheath thus cannot be explained by an alteration in its amino acid sequence. Steady‐state levels of PLP mRNA in SC cultures treated with the cAMP analogue dibutyryl cAMP (dBcAMP) were not increased, whereas dBcAMP increased steady‐state levels of mRNA encoding the major myelin protein, PO. We have also shown that expression of PLP, unlike that of PO, is regulated in SC in vitro at a posttranscriptional level. Finally, the steady‐state levels of PO mRNA are much more dramatically reduced than those of PLP mRNA during Wallerian degeneration of the peripheral nerve. Thus PLP expression in the PNS is probably controlled by different molecular mechanisms from PO, and may not be part of the coordinate program of myelin gene expression. In contrast to its expression in the PNS, transcription of PLP in the CNS is coordinately regulated along with the other myelin protein genes, suggesting there may be differences in the cis‐acting elements and trans‐acting factors involved in the regulation of PLP transcription in SC and oligodendrocytes (OC). Consistent with this notion, we have found that most PLP transcripts are initiated at the more proximal of two start sites in the PNS, while in the CNS proportionally more PLP transcripts are initiated from the distal start site. We propose that the proximal site, utilized predominantly in SC, is responsible for maintenance expression of PLP and is not inducible, while the distal site is responsible for the rapid, inducible increase of PLP message during brain development.