Alkaline Reagents Research Articles

Influence of pH and added gums on the properties of konjac flour gels

SummaryThe gel strength and texture of konjac gel and mixed gels of konjac and various gums were measured after gelation at various concentrations of alkali. A selection of different alkaline reagents was used. Regardless of alkali concentration, increasing konjac levels caused a decrease in pH but an increase in hardness and strength of konjac/gellan gum mixed gels. The highest gel strength and hardness were given by mixed konjac/gellan gum gels using sodium carbonate as the gelling medium. Under similar gelling conditions, the addition of gellan gum resulted in the greatest gel hardness. Of the gums examined, a possible synergistic effect on konjac/gellan gum mixed gel texture was observed.

Preparation and magnetometric characterization of iron oxide-containing alginate/poly(vinyl alcohol) networks

Alginate-based magnetic gels were prepared in a sequence of procedures for in situ synthesis of iron oxides: crosslinking of alginate in ferrous salt aqueous solution, immersion of the resulting gels into alkaline-earth metallic hydroxide solution, and treatment of the partially cation-exchanged gels with hydrogen peroxide. Magnetometry measurements revealed that the lyophilized gels showed superparamagnetism or ferromagnetism at room temperature, depending on the sort of the metallic cation employed in the alkali treatment. An interpenetrating network (IPN) type of alginate/poly(vinyl alcohol) (Alg/PVA) gels containing iron oxides was also designed and fabricated from mixed polymer solutions by a modified preparation method; the gelation and alkali treatment were carried out with the aid of a metallic borate. Viscoelasticity of the magnetic IPN composites in the gelatinous state was controllable by changing the mixing ratio of the compatible carbohydrate/viny polymer pair. Magnetization versus magnetic field curves were constructed at different temperatures for the IPNs freeze-dried. Their magnetic character was variable according to alterations of the Alg/PVA composition, alkaline reagent adopted, and measurement temperature.

Applications of the ninhydrin reaction for analysis of amino acids, peptides, and proteins to agricultural and biomedical sciences.

The reaction of ninhydrin with primary amino groups to form the purple dye now called Ruhemann's purple (RP) was discovered by Siegfried Ruhemann in 1910. In addition, imines such as pipecolic acid and proline, the guanidino group of arginine, the amide groups of asparagine, the indole ring of tryptophan, the sulfhydryl group of cysteine, amino groups of cytosine and guanine, and cyanide ions also react with ninhydrin to form various chromophores of analytical interest. Since its discovery, extensive efforts have been made to apply manual and automated ninhydrin reactions as well as ninhydrin spray reagents to the detection, isolation, and analysis of numerous compounds of interest across a broad spectrum of disciplines. These include agricultural, biochemical, clinical, environmental, food, forensic, histochemical, microbiological, medical, nutritional, plant, and protein sciences. This reaction is unique among chromogenic reactions in that at pH 5.5 it results in the formation of the same soluble chromophore by all primary amines which react, be they amines, amino acids, peptides, proteins, and even ammonia. Because the chromophore is not chemically bound to the protein or other insoluble material, it is not lost when the insoluble substrate is removed by centrifugation or filtration after the reaction is completed. The visible color of the chromophore is distinctive and is generally not affected by the yellow colors present in many food, plant, and tissue extracts. Adaptations of the classical ninhydrin reaction to specialized needs in analytical chemistry and biochemistry include the use of acid, alkaline, and fluorogenic ninhydrin reagents. To cross-fertilize information among several disciplines wherein an interest in the ninhydrin reaction has developed, and to enhance its utility, this review attempts to integrate and correlate the widely scattered literature on ninhydrin reactions of a variety of structurally different compounds. Specifically covered are the following aspects: historical perspective, chemistry and mechanisms, applications, and research needs. A better understanding of these multifaceted ninhydrin reactions provide a scientific basis for further improvements of this important analytical technique.

Dissolution procedure for the determination of major and minor elements in La-Sr-Ga-Nb oxide by inductively coupled plasma-optical emission spectrometry

This paper describes a dissolution method for La-Sr-Ga-Nb (LSGN) oxide samples, which are hardly decomposed by conventional acid treatments. The LSGN oxides are not dissolved in any acid solution and do not undergo fusion with alkaline reagents, such as Na2CO3. However, the sample can undergo fusion with Na2B4O7 powder. A sample (50 mg) was fused with 1 g of Na2B4O7 in a Pt crucible, whose inside wall was covered with pre-melted Na2B4O7 (1 g). The melted product was cooled and then dissolved with a mixture of 30 ml HNO3 (1 : 1), 2.5 ml H2O2, and 1 g tartaric acid. After the addition of 1.5 ml of H2O2 and 5 ml of an Y solution (5 mg/ml) as an internal standard, the solution was diluted to 100 ml and measured by inductively coupled plasma-optical emission spectrometry. Two samples having different chemical compositions were analyzed to yield each in good agreement with the analytical values between two individual measurements.

Diagnosis of deactivation sources for vanadium catalysts used in SO 2 oxidation reaction and optimization of vanadium extraction from deactivated catalysts

Physico-chemical analysis (X-ray, FTIR) and/or methanol oxidation reaction test were performed on fresh and deactivated vanadium catalysts used in H 2SO 4 manufacturing. It allowed the diagnosis of catalyst deactivation sources, as well as the processes of regenerating and recycling the worn out catalyst in converter. One of these processes is hydrometallurgical method. It consists in treating the deactivated catalyst with alkaline or acidic reagents and forming vanadate solution. A simple and non-costly operation of chemical attack permits the extraction of vanadium from silica in deactivated catalyst. The extracted vanadium can be used for the confection of regenerated catalysts or metallic tools. After optimization, this method can be used for industrial application.

New method for the immobilization of glutaryl-7-aminocephalosporanic acid acylase on a modified epoxy/silica gel hybrid

In this study, glutaryl-7-aminocephalosporanic acid (ACA) acylase was immobilized on a silica gel modified with a mixture of 3-glycidoxypropyltrimethoxysilane (3-GPTMS) and N,N-diisopropylethylamine ( N,N-DIPEA). Unfortunately, the immobilized acylase showed very poor values for protein binding yield and activity. These results are believed to be caused by a discordance between the ring opening condition of epoxide groups and the immobilization condition for glutaryl-7-ACA acylase. Therefore, a new immobilization method for glutaryl-7-ACA acylase was introduced. Ethylenediamine, a strong alkaline reagent, was used as a spacer after epoxide silanization, and followed by glutaraldehyde as a crosslinking agent. The optimal conditions for each step of the immobilization procedure developed in the present study were as follows: epoxide silanization by a mixture of 30% (v/v) 3-GPTMS, 3% (v/v) N,N-DIPEA, and 10% (v/v) ethylenediamine and a 4-h reaction time between ethylenediamine and silica gel activated with epoxide silanization and crosslinking with 2% (v/v) glutaraldehyde. The immobilized glutaryl-7-ACA acylase was also tested for long-term stability. It was found that the activity was about 62% of the initial value after reuse of 20 times.

Effect of dark and salinity treatment in the yield and quality of agar from Gracilaria cornea (Rhodophyceae)

The alkali treatment used previous to agar extractions from the Gracilaria genus reduces, among other reactions, the sulphate content and improves the gel strength; however, at an industrial level it requires expensive effluent processing to reduce its polluting charge. The red alga Gracilaria cornea was cultivated under dark and salinity treatments to replace this alkali treatment. The different treatments tested were: (a) darkness and 33‰ salinity for 8 days, [dark treatment]; (b) darkness and 50‰ salinity for 4 days, followed by darkness and 25‰ salinity for 4 days, [4+4]; and (c) darkness and 50‰ salinity for 8 days, followed by darkness and 25‰ salinity for 4 days, [8+4]. The treatment [4+4] increased the agar yield in 26% (from 36.6 to 46.1%). All treatments reduced the sulphate content of the agar in approximately 24% when compared with agar obtained without any treatment. For G. cornea the [4+4] treatment might become in the future an additional treatment to a mild alkali treatment using less alkaline reagents for agar extraction.

STUDYING THE INTERACTIONS BETWEEN AN ARABIAN HEAVY CRUDE OIL AND ALKALINE SOLUTIONS

ABSTRACT An experimental study to examine the effectiveness of alkaline flooding for the recovery of an Arabian heavy crude oil is presented. The interfacial tension (IFT) behavior of crude oil/alkali systems over a wide range of parameters (pressure, temperature, alkali concentration and time) was studied. These alkaline reagents react with the acidic species in crude oil to form surface-active soaps in-situ. This leads to a lowering of interfacial tension (IFT) and subsequently the mobilization of residual oil. The equilibrium IFTs obtained through alkaline flooding are compared with the IFTs when a synthetic surfactant (dodecyl benzene sulfonic acid sodium salt) is used in EOR recovery. A mathematical model representing the complete chemistry of the transient process is also presented. The model consists of a set of differential equations describing reactions, diffusion, and adsorption at the oil/alkaline solution interface. The kinetic parameters in the model are obtained through a differential algebraic optimization technique. The concentration of the surface active species are related to the measured IFTs through an independent step that is based on isolating the surface active species formed by the reaction between the acids in the crude oil and the alkaline solution. A sensitivity analysis using the model is carried out to study the effect of surface potential and alkaline concentration on the transient interfacial tensions.

New Method for the Immobilization of Glutaryl-7-Aminocephalosporanic Acid Acylase on a Modified Epoxy/Silica Gel Hybrid

In this study, glutaryl-7-aminocephalosporanic acid (ACA) acylase was immobilized on a silica gel modified with a mixture of 3-glycidoxypropyltrimethoxysilane (3-GPTMS) and N,N -diisopropylethylamine ( N,N -DIPEA). Unfortunately, the immobilized acylase showed very poor values for protein binding yield and activity. These results are believed to be caused by a discordance between the ring opening condition of epoxide groups and the immobilization condition for glutaryl-7-ACA acylase. Therefore, a new immobilization method for glutaryl-7-ACA acylase was introduced. Ethylenediamine, a strong alkaline reagent, was used as a spacer after epoxide silanization, and followed by glutaraldehyde as a crosslinking agent. The optimal conditions for each step of the immobilization procedure developed in the present study were as follows: epoxide silanization by a mixture of 30% (v/v) 3-GPTMS, 3% (v/v) N,N -DIPEA, and 10% (v/v) ethylenediamine and a 4-h reaction time between ethylenediamine and silica gel activated with epoxide silanization and crosslinking with 2% (v/v) glutaraldehyde. The immobilized glutaryl-7-ACA acylase was also tested for long-term stability. It was found that the activity was about 62% of the initial value after reuse of 20 times.

O-GLYCOSIDES OF N-HYDROXYINDOLES[1

First O-glycosides of N-hydroxyindole were synthesized by the interaction of the indoles containing electron withdrowing substituents with acyl halogenoses in the presence of alkaline reagents. 1-O-β-D-Glucopyranosides of 1-hydroxy-5-(or 6)-nitroindoles, 1-O-β-D-ribofuranoside of 1-hydroxy-5-nitroindole and also 1-[(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)oxy]-2-methoxycarbonylindole were obtained. 1-[(2,3,4,6-Tetra-O-acetyl-β-D-glucopyranosyl)-oxy]-6-nitro-indole was transformed into 1-[(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-oxy]indole.

Preparation of deacetyl-, lyso-, and deacetyl-lyso-GM3 by selective alkaline hydrolysis of GM3 ganglioside

Three methods (using GM3 quantities ranging from a few milligrams to grams) have been developed to prepare, in high yield, the three derivatives of ganglioside GM3 [α-Neu5Ac-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-ceramide]: deacetyl-GM3 [α-Neu-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-ceramide], lyso-GM3 [α-Neu5Ac-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-sphingosine], and deacetyl-lyso-GM3 [α-Neu-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-sphingosine]. This is the first report of the preparation of lyso-GM3 by a one-pot reaction. We can now define the optimal conditions for the different preparations. Preparation of deacetyl-GM3: alkaline reagent, 2 M KOH in water; GM3 concentration, 33 mg/ml; reaction temperature, 90 °C; reaction time, 3.5 h; nitrogen atmosphere. Preparation of deacetyl-lyso-GM3: alkaline reagent, 8 M KOH in water; GM3 concentration, 10 mg/ml; reaction temperature, 90 °C; reaction time, 18 h; nitrogen atmosphere. Preparation of lyso-GM3: alkaline reagent, 1 M sodium tert-butoxide in methanol; GM3 concentration, 10 mg/ml; reaction temperature, 80 °C; reaction time, 18 h; anhydrous conditions. The percentage yield of deacetyl-GM3 was 70–75%, that of deacetyl-lyso-GM3 100%, and of lyso-GM3 36–40%. Deacetyl-GM3, deacetyl-lyso-GM3, and lyso-GM3 were purified by column chromatography, and chemical structures were confirmed by electron spray-mass spectrometry. —Valiente, O., L. Mauri, R. Casellato, L. E. Fernandez, and S. Sonnino. Preparation of deacetyl-, lyso-, and deacetyl-lyso-GM3 by selective alkaline hydrolysis of GM3 ganglioside.

Effects of Flow Rate and Alkali-to-Acid Ratio on the Displacement of Acidic Oil by Alkaline Solutions in Radial Porous Media

Alkaline flooding is a method of enhanced oil recovery that relies on the formation of surface-active substances in situ by a chemical reaction between acidic components in the oil and an alkaline reagent. As the injected alkali advances through the porous medium, it keeps contacting fresh oil. At some moment dependent on the alkali/acid concentrations and the velocity, the alkali at the advancing front may become depleted and the flood becomes interfacially nonreactive. The present study is aimed at investigating the above-mentioned phenomena. Displacement studies were conducted in radial cells containing sintered glass beads as a porous medium. Light paraffin oil acidified with 10 mmol/L of linoleic acid served as the displaced (oil) phase while the displacing aqueous solution contained 0–25 mmol/L of sodium hydroxide. The highest oil recovery was obtained under the conditions of low flow rate and high alkali concentration. Increasing the flow rate at high NaOH concentration resulted in decreasing oil recovery up to a certain threshold flow rate. Conversely, the amount of oil recovered by waterflooding only (no alkali) initially increased with increasing flow rate up to the same threshold flow rate beyond which there was no difference between the alkaline flood and a waterflood.

Formic Acid Dissolves Aggregates of an N-Terminal Huntingtin Fragment Containing an Expanded Polyglutamine Tract: Applying to Quantification of Protein Components of the Aggregates

Huntington's disease (HD) is caused by an expansion of the CAG repeat that encodes polyglutamine in huntingtin. Transient expression of an N-terminal huntingtin fragment containing an expanded polyglutamine tract induced formation of protein aggregates in cultured cells. The turnover of protein components in such aggregates has been difficult to study because of their insolubility in aqueous solutions. Here we describe a method of solubilizing the aggregates and quantifying their protein components. Insoluble pellets were collected from COS7 cells expressing an N-terminal huntingtin fragment containing an expanded polyglutamine tract and subjected to treatment with various detergent, acid, and alkaline reagents. Treatment with 100% formic acid at 37°C for 30 min induced essentially complete dissociation of the aggregates to monomer. We used this solubilization technique to quantify huntingtin fusion protein in the aggregates formed in transient expression experiments. The frequency of aggregate formation increased when the proteasome inhibitor β-lactone was added to culture media. However, the total amount of accumulated huntingtin fusion protein did not differ between cells cultured with or without β-lactone. These results suggest that other protein components which are degraded by the proteasome, in addition to huntingtin, might be related to the dynamics of polyglutamine protein aggregates.

Ammonium fluoride extraction for determining inorganic sulphur in acid forest soils

Current methods for determining inorganic sulphur (S) in aerated mineral soil horizons often result in underestimates. To overcome this defect we developed a new method combining a batch extraction with 0.5 M NH 4 F solution at a soil:solution ratio of 1:5 with a subsequent analysis of the mobilized SO 4 2- by ion chromatography. The ammonium fluoride extraction enables us to characterize inorganic sulphate in non-calcareous forest soils. It is more efficient than conventional procedures in which inorganic S is extracted with phosphate or bicarbonate solution. In contrast to the extraction with strongly alkaline reagents (NaOH, KOH, LiOH), the NH 4 + -NH 3 buffer system in NH4F prevents the pH of the suspension from exceeding 9.0 and thus the undesired conversion of organic S into SO 4 2- by auto-oxidation and hydrolysis of ester sulphate. In a comparison we demonstrated that the inorganic S in six German forest soils is underestimated by up to 50% or 200 kg S ha -1 in the uppermost 60cm, if it is assessed by extraction with 0.016 M KH 2 PO 4 or 0.5 M NaHCO 3 instead of 0.5 M NH 4 F. Conversely, the pool of ester sulphate is overestimated almost threefold.

Preparation of strontium carbonate from celestite

A novel method for the preparation of strontium carbonate from celestite ore has been investigated. The ore is reduced by brown coal at a temperature of 1000°C for a period of 3 h. The reduced product is leached with water at a liquid : solid ratio of 3 : 1 at 90°C and the slurry is then leached with hydrochloric acid at a solid : liquid ratio of 2 : 1. By controlling the pH at 1.5-2 and adding 20% H2O2 at the rate of 0.5 dm3/m3 of solution the oxidation process HS-→So is accomplished. Barium is precipitated with dilute sulphuric acid; and more than 90% Ca2+ + Mg2+ (and Fe) is removed when the pH is increased to 12. Addition of 1.2 times the theoretically required amount of NH4HCO3 at a solution strength of 2 mol/l at 60°C and at pH in the range 9-11 results in the precipitation of SrCO3. The precipitate is washed and dried at 220-250°C. The proposed flowsheet is simple, has low consumption of acid and alkaline reagents, gives a high recovery of strontium and accepts a wide range of raw material.

Investigation of different natural sources of chitin: influence of the source and deacetylation process on the physicochemical characteristics of chitosan

Several sea sources for chitin have been investigated, and the chitin content and crystallographic polymorph of the extracted chitin determined. Deacetylation of the chitin was carried out and the physicochemical characteristics of the resulting chitosan studied. The influence of the reaction parameters (reaction duration, temperature, nature of alkaline reagent, etc) was followed. Thus it became possible to determine adequate reaction conditions for obtaining chitosans with the required properties. The physicochemical characteristics of the obtained chitosan are closely related to the taxonomy of the source. New sea sources for chitin have been investigated and considered for industrial purposes. © 2000 Society of Chemical Industry

A rapid method to discriminate between free and esterified fatty acids by pyrolytic methylation using tetramethylammonium acetate or hydroxide

Tetramethylammonium acetate (TMAAc) was found to be a selective reagent for the methylation of free acids. It was shown that free fatty acids and their salts could be fully derivatised by TMAAc in the presence of esterified fatty acids. This was performed on extracts containing mixtures of wood extractives and directly on pulps containing extractives. The alkaline reagent tetramethylammonium hydroxide (TMAH) was efficient in hydrolysing and derivatising all fatty acids present, both as free acids and in different esters. Even steryl esters, which are difficult to hydrolyse, were completely cleaved and the fatty acid part was obtained as the corresponding methyl ester. The results from the pyrolytic technique were in agreement with the results of other more laborious techniques. Polyunsaturated fatty acids, such as linoleic acid and linolenic acid, were isomerised to a number of different octadecadienoic and -trienoic acids, due to the strongly alkaline conditions when TMAH was used. When the samples containing polyunsaturated fatty acids, were pyrolysed in the presence of TMAAc, no isomerisation was observed. The resin acids can be considered to be always non-esterified. Thus, when they are present, they can be used as a reference similar to an internal standard in the analytical pyrolysis experiments. The use of different ammonium salts in combination with Py-gas chromatography (GC) offered a rapid method for the estimation of free, esterified and total acids.

Influence of hydroxypropylation on retrogradation properties of native, defatted and heat-moisture treated potato starches

Recent studies have shown that defatting and heat-moisture treatment cause structural changes within the amorphous and crystalline regions of potato starch. Furthermore, the alkaline reagents (NaOH and Na 2SO 4) used during hydroxypropylation has been shown to cause structural changes within the amorphous and crystalline regions of native, defatted and heat-moisture treated starches. In this study, we have compared (using different techniques) the retrogradation properties of potato starch before and after physical (defatting and heat-moisture treatment), and chemical (alkaline treatment and hydroxypropylation) modification. Turbidity measurements showed that changes in turbidity during storage (4°C for 24 h and then at 40°C for 29 days) of native, defatted and heat-moisture treated gelatinized starch pastes were influenced by the interplay of two factors: (1) interaction between leached starch components (amylose–amylose, amylose–amylopectin, amylose–amylopectin), and (2) interaction between granule remnants and leached amylose and amylopectin. In alkali treated gelatinized native, defatted and heat-moisture treated starch pastes, turbidity changes on storage was influenced by aggregation of granule remnants. Hydroxypropylation decreased the rate and extent of increase in turbidity during storage of native, defatted and heat-moisture treated starches. The change in turbidity during storage of hydroxypropylated starch pastes was influenced by the interplay between: (1) steric effects imposed by hydroxypropyl groups on chain aggregation, (2) aggregation between small granule remnants, and (3) settling of large granule remnants beneath the path of the spectrophotometer beam. Stored gelatinized pastes of native, defatted and heat-moisture treated starches gave a `B' type X-ray pattern. A similar pattern was also observed after alkaline treatment, and hydroxypropylation. However, the X-ray intensity of the strong reflection at 5.2 Å decreased after alkaline treatment and hydroxypropylation. The retrogradation endotherm (monitored by differential scanning calorimetry) occurred after 2 days storage in native, defatted and heat-moisture treated starches. A similar trend was also observed after alkaline treatment. However, the retrogradation endotherm appeared only after 7 days in hydroxypropylated starches. The enthalpy of retrogradation in all starches decreased on alkaline treatment and hydroxypropylation.

Improvement of the Productivity of Preparation Process for Ultrafine Metal Sulfide Particles Using Reverse Micellar Systems.

An improvement of the productivity of the preparation process for ultrafine ZnS and CdS particles using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micellar systems is studied. Sufficient quantities of reactants are provided to the reverse micelles by using H2S gas and the functionalyzed surfactants, Zn(AOT)2 and Cd(AOT)2. Bis(2-ethylhexyl) sulfosuccinic acid formed as by-product restrains the formation of ZnS particles, and destabilizes the CdS particles. Neutralization of the acid by addition of an alkaline reagent, triisooctylamine, improves the conversion for ZnS particles and the stability for CdS particles. Ultrafine ZnS and CdS particles containing about 0.02 M of constituting ions are successfully prepared in the presence of the amine. The particles can be recovered from the reverse micelles and redispersed in non-micellar solvent via the surface capping of the particles with thiols. The proposed route using reverse micelles is applicable for the practical production of ultrafine particles.

The Reactivity of Porcine Pancreatic alpha-Amylase Towards Native, Defatted and Heat-moisture Treated Potato Starches Before and After Hydroxypropylation

Potato starch was defatted (hot 75% n-propanol) and heat-moisture treated (100°C, 30% moisture) for various time intervals. The results showed that the above treatments increased the susceptibility of potato starch granules (heat-moisture treated > defatted) towards hydrolysis by porcine pancreatic α-amylase. These differences can be accounted for by the structural changes that occur within the amorphous and crystalline regions of the starch granule during defatting and heat-moisture treatment. Native, defatted (7 h) and heat-moisture treated (100°C, 30% moisture, 16 h) potato starches were hydroxypropylated (to different levels of molar substitution [MS]) with propylene oxide (2 → 20 %). The results showed that the alkaline reagents (NaOH and Na2SO4) used during hydroxypropylation increased the susceptibility of the above starches (native > defatted > heat-moisture treated) towards hydrolysis by α-amylase. Addition of propylene oxide to alkali treated starches, further enhanced their susceptibility, towards α-amylase. However, granule susceptibility towards α-amylase did not increase exponentially with increase in MS. The extent of hydrolysis began to decrease at MS levels of 0.29 (native), 0.28 (heat-moisture treated) and 0,26 (defatted).