Buffer Medium pH Research Articles

Spectrophotometric determination of copper(II) and palladium(II) using 3-hydroxybenzaldehyde thiosemicarbazone

The analytical properties of 3-hydroxybenzaldehyde thiosemicarbazones (HBT) are described for the first time. The reagent gives yellowish green coloured complexes with copper(II), palladium(II) in sodium acetate-acetic acid buffer medium of pH 5.5 and 2.5 respectively. The molar absorptivities of copper and palladium complexes respectively are 8.75 × 10 3 , and 1.25 x 10 4 L mol -1 cm -1 . These colour reactions have been investigated for the spectrophotometric determination of copper(II) and palladium(ll) in aqueous medium.

The flow‐through diffusion cell (FTDC) method: a novel approach to in vitro drug release studies

AbstractA terpolymeric semi‐interpenetrating network (IPN) has been synthesized by carrying out the aqueous polymerization of methacrylamide in the presence of poly(ethylene glycol) (PEG) and natural polysaccharide starch, and its enzymatic degradation has been studied by a newly developed technique, known as the ‘flow‐through diffusion cell’ (FTDC) method, in a phosphate buffer medium of pH 6.8 at the physiological temperature, 37 °C. The hydrogel exhibits different degradation behaviors when studied by the ‘traditional degradation/dissolution test’ (TDT) or the FTDC method. The degradability is suppressed in the FTDC method, owing to the adsorption of amylase molecules onto the filler particles. The nature of the filler particles also affects the degradation behavior of the hydrogels. Finally, the release of the model drug, vitamin B12, from the degrading hydrogels has also been studied by the FTDC method. The results obtained indicated that the release behavior also depends on α‐amylase‐induced degradability. Copyright © 2006 Society of Chemical Industry

Synthesis and characterization of a novel cross-linking complex of β-cyclodextrin- o-vanillin furfuralhydrazone and highly selective spectrofluorimetric determination of trace gallium

A novel host inclusion complex of cross-linking-polymeric-β-cyclodextrin- o-vanillin furfuralhydrazone (β-CDP-OVFH) was synthesized and characterized with IR and 1H NMR spectra to confirm its structure. A highly selective and sensitive fluorescent determination of trace amounts of gallium was proposed based on the reaction between Ga 3+ with β-CDP-OVFH in acetic acid–ammonium acetate buffer medium of pH 4.10. The maximum excitation and emission wavelengths were 392 and 499 nm, respectively. The linear range of this method was 1.5–330 ng ml −1 with a detection limit of 0.44 ng ml −1. The effect of interferences in the determination of gallium was investigated and the results showed that the same race elements such as Al 3+ and In 3+ did not interfere the determination of Ga 3+ even when their concentration is 100 times of Ga 3+, the host reagent had quite high capacity of identifying Ga 3+. This method was successfully applied to the determination of trace amounts of Ga 3+ in artificial and semiconductor samples.

In vitro dissolution studies for release of vitamin B 12 from poly( N-vinyl-2-pyrrolidone-co-acrylic acid) hydrogels

pH-sensitive co-polymeric hydrogels consisting of N-vinyl-2-pyrrolidone and acrylic acid were synthesized and their swelling and network parameters were evaluated. The gels were also characterized by thermogravimetric analysis and Fourier Transformation Infrared Spectroscopy. The gels exhibited nearly 47.8 ± 4.9% swelling in the medium of pH 1.2 while nearly 2164.6 ± 21.8% swelling was observed in the phosphate buffer medium of pH 6.8 at 30 °C. The swollen gel underwent sharp volume-transition in solutions containing Ni 2+ and Ca 2+ ions which was explained on the basis of monovalent–divalent ion exchange phenomenon taking place between gel phase and solution phase. The hydrogel, loaded with model drug vitamin B 12, demonstrated nearly 8.6 ± 2.1% and 83.2 ± 4.8% release in the media of pH 1.2 and 6.8, respectively, as determined by traditional dissolution test. However, in order to incorporate in vivo GI conditions such as acidic pH and high water content in the stomach, low water content and presence of semi-solid mass in the large intestine, a new test model, called flow through diffusion cell was also used to study the drug release behavior of the device. The two approaches yielded almost different release profiles.

Synthesis of a novel host molecule of cross-linking-polymeric-β-cyclodextrin- o-vanillin furfuralhydrazone and spectrofluorimetric analysis of its identifying cadmium

A novel host inclusion complex of cross-linking-polymeric-β-cyclodextrin- o-vanillin furfuralhydrazone (β-CDP-OVFH) was synthesized and characterized with IR and 1H NMR spectra to confirm its structure. The coordination reaction of the host reagent with Cd 2+ was studied and the optimum reacting conditions were observed carefully. A highly selective and sensitive spectrofluorimetric determination of trace amount of cadmium was proposed based on the reaction of Cd 2+ with β-CDP-OVFH in ammonia water–ammonium acetate buffer medium of pH=11.0. The molar ratio of β-CDP-OVFH to Cd 2+ was 1:1. The maximum excitation and emission wavelengths were 393 and 494 nm, respectively. The linear range of this method was from 3.0 to 500 μg l −1 with a detection limit of 0.80 μg l −1. The effect of interferences in the determination of cadmium was investigated and the results showed that the host reagent had quite high capacity of identifying Cd 2+. The proposed method was successfully applied to the determination of trace amount of Cd 2+ in mussel and tea samples.

Synthesis and characterization of a novel cross-linking complex of β-cyclodextrin- o-vanillin benzoylhydrazone and its selective spectrofluorimetric determination of trace amounts of zinc

A novel host inclusion complex of β-cyclodextrin- o-vanillin benzoylhydrazone (β-CDP–OVBH) was prepared and characterized by IR and 1H-NMR spectra. A highly selective and sensitive fluorescent determination of trace amounts of zinc was proposed based on the reaction between Zn 2+ and β-CDP–OVBH in sodium hydroxide–ammonium acetate buffer medium of pH 8.3. The molar ratio of β-CDP–OVBH to Zn 2+ was 1:1.The maximum excitation and emission wavelengths were 396 and 486 nm, respectively. The linear range of this method was 2.5–500 μg l −1 with a detection limit of 0.60 μg l −1. The effect of interferences in the determination of zinc was investigated, the results showed that the host reagent had a quite high identifying capacity on Zn 2+. This method was successfully applied to the determination of trace amounts of Zn 2+ in tea and human hairs.

Two simple methods for the estimation of albendazole and its dosage forms using chloramine-T

Two simple, rapid and reliable methods for the determination of albendazole are described. Both methods involve the use of chloramine-T as the oxidimetric reagent. In the titrimetric method, a known excess of chloramine-T is added to an acidified solution of sample, and after a specified time, the residual oxidant is determined iodometrically. Spectrophotometric procedure also involves the addition of a measured excess of chloramine-T in buffer medium of pH 2.70±0.1 and after the reaction is ensured to be complete, the surplus oxidant is determined by a well established colour reaction involving metol and primary arylamine that results in charge-transfer complex measurable at 520 nm. In both methods, the amount of chloramine-T corresponds to the drug content. Reaction conditions were examined and optimised. Titrimetry is based on a 1:3 stoichiometric reaction between albendazole and chloramine-T and is applicable in the range of 1–15 mg. In spectrophotometry, the absorbance was found to decrease linearly with increasing concentration of albendazole, which is corroborated by the calculated correlation coefficient value of −0.9998. The system obeys Beer's law for 2.5–25 μg ml −1 of albendazole. The molar absorptivity and Sandell sensitivity were calculated to be 6.24×10 3 l mol −1 cm −1 and 42.54 ng cm −2, respectively. The limits of detection and quantification were calculated to be 1.15 and 3.83 μg ml −1, respectively. The proposed methods were successfully applied to the determination of albendazole in commercially available dosage forms. The reliability of the assays was established by parallel determination by the official method and recovery studies.

Novel reagents for the sensitive spectrophotometric determination of flutamide, an anticancer drug in pharmaceutical preparations

Simple and sensitive spectrophotometric methods for the determination of flutamide (FLA) in either pure form or in its pharmaceutical preparations are described. The first method is based on the diazotisation of reduced FLA, followed by coupling with alcoholic iminodibenzyl (IDB) in acid medium to give a purple coloured product having a λ max of 570 nm. In the second method, the diazotisation of reduced FLA followed by coupling with 4-amino-5-hydroxy-2,7-naphthalenedisulphonic acid monosodium salt (AHND) in a buffer medium of pH 12, gives a red coloured product having a λ max of 520 nm. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods. Both the methods are highly reproducible and have been applied to a wide variety of pharmaceutical preparations and the results compare favourably with the reported method.

DNA adsorption onto polyethylenimine-attached poly( p-chloromethylstyrene) beads

In this study, DNA adsorption properties of polyethylenimine (PEI)-attached poly( p-chloromethylstyrene) (PCMS) beads were investigated. Spherical beads with an average size of 186 μm were obtained by the suspension polymerization of p-chloromethylstyrene conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, PCMS beads had a specific surface area of 14.1 m 2/g. PEI chains could be covalently attached onto the PCMS beads with equilibrium binding capacities up to 208 mg PEI/g beads, via a direct chemical reaction between the amine and chloromethyl groups. After PEI adsorption with 10% (w/w) initial PEI concentration, free amino content of PEI-attached PCMS beads was determined as 0.91 mequiv./g. PEI-attached PCMS beads were utilized as sorbents in DNA adsorption experiments conducted at +4°C in a phosphate buffer medium of pH 7.4. DNA immobilization capacities up to 290 mg DNA/g beads could be achieved with the tried sorbents. This value was approximately 50-times higher relative to the adsorption capacities of previously examined sorbents.

A modified spectrophotometric method for the determination of trace amounts of phenol in water

A modified spectrophotometric method has been developed for the determination of phenol in water. The method is based on the reaction between phenol, sodium nitroprusside and hydroxylamine hydrochloride in a buffer medium of pH 10.6–11.8. The linear dynamic range is 0.05–5.0 mg l−1. The optimum determination wavelength is at 700 nm. The molar absorptivity is 1.23×104 mol l−1 cm−1. The relative standard deviation of the standard solution of phenol is 1.3% (n=10, C=0.5 mg l−1). The average recovery of water samples spiked with phenol of 2.0 mg l−1 is 98.8% (n=10). The relative error of standard sample (C=0.394±0.003 mg l−1) is 2.0%. F values of the statistical analysis show that there is no significant difference between the proposed method and the 4-aminoantipyrine method. The crystal of the product of the colored reaction was synthesized. According to its IR spectrum, Raman spectrum, Mössbauer spectrum and elemental analysis, the composition and structure of the product have been deduced and the mechanism of the colored reaction has also been investigated.

4-Methoxy-azomethine-H as a reagent for the spectrophotometric determination of boron in plants and soils

An effective spectrophotometric determination of boron with 4-methoxy-azomethine-H has been developed. In a buffer medium of pH 5.7, B(III) reacts with 4-methoxy-azomethine-H to form a 1 : 2 yellow complex which has a maximum absorption at 420 nm. Under the optimum conditions, Beer’s law is obeyed over the range 0–1.4 μg ml −1 B(III). The molar absorptivity is 1.05 × 10 4 l mol −1 cm −1. The limit of quantification, limit of detection and relative standard deviations were 15.3, 5.3 ng ml −1 and 1.4%, respectively. The interference of various ions is observed in detail. All metal ions studied can be tolerated in considerable amounts. The proposed method is advantageous over the azomethine-H spectrophotometric method in sensitivity, selectivity and stability remarkably, and it has been applied to the determination of boron in plants and soils with satisfactory results.

Simplified derivatization method for the speciation analysis of organolead compounds in water and peat samples using in-situ butylation with tetrabutylammonium tetrabutylborate and GC-MIP AES

A simplified derivatization method for the speciation analysis of organolead compounds in environmental samples followed by gas chromatography-microwave induced plasma atomic emission detection is developed. An in-situ butylation using tetrabutylammonium tetrabutylborate in an acetate buffer medium of pH 4.0 with simultaneous extraction of the derivatized organolead species into hexane was performed; for the analysis of the peat samples, the desorption of the different species from the matrix by acid leaching was also included. Detection limits at the sub-ng L–1 range, comparable to those achieved by Grignard-alkylation, were obtained for the different species. The accuracy of the method was confirmed by analysis of a standard reference material (BCR-CRM 605, road dust). Examples of applications for the analysis of tap water and peat are given.

Integrated sample preparation and speciation analysis for the simultaneous determination of methylated species of tin, lead and mercury in water by purge-and-trap injection-capillary gas chromatography-atomic emission spectrometry

A sensitive and interference-free automated method for the simultaneous speciation analysis of methylated species of mercury, tin and lead, and also inorganic mercury in water, using purge-and-trap injection–gas chromatography–atomic emission spectrometry, was developed. The ionic species are volatilized from the sample after ethylation, using sodium tetraethylborate, in acetate buffer medium of pH 5 and preconcentrated on a capillary cryogenic trap. Desorption is effected by linear heating of the trap, followed by separation of the analytes by capillary gas chromatography and selective simultaneous detection by microwave-induced plasma atomic emission spectrometry. Detection limits of 0.15, 0.20 and 0.60 ng l–1 for methylated tin, lead and mercury species, respectively, and 2 ng l–1 for inorganic mercury can be obtained, on the basis of a 10 ml sample volume. Examples of results for the analysis of river- and soil run-off water samples are given.

Composition and Properties of Linseed Gum

This study investigates the fabrication, characterization and optimization of Linum usitatissimum mucilage (LSM) with sodium alginate mucoadhesive microspheres loaded metformin HCl, a sustained release dosage form prepared by ionic gelation technique. The effect of changing the polymer ratio with drug was studied for drug encapsulation efficiency and in vitro drug release for 12 h. Drug entrapment efficiency of all formulations was in the range of 77.93 ± 3.67 to 92.25 ± 4.08% with sustained release of 80 ± 0.12% to 88 ± 0.33% for 12 h. It followed Korsmeyers Peppas model (R2 = 0.9786–0.9964) with super case II transport mechanism. Average microsphere size of all formulations was within the range of 817–911 μm. SEM, FTIR were also characterized and swelling behavior of microspheres was affected by pH of buffer medium. These microspheres also showed good mucoadhesivity in wash off test. The optimized LSM-alginate mucoadhesive microspheres containing metformin HCl demonstrated significant hypoglycemic effect in alloxan-induced diabetic rats for prolonged period of time.

Heat aggregation studies of phycobilisomes, ferritin, insulin, and immunoglobulin by dynamic light scattering

Dynamic laser light scattering studies on the heat aggregation behavior of phycobilisomes (PBS), ferritin, insulin, and immunoglobulin (IgG) in dilute aqueous solutions has been reported. Except for PBS, results are reported for heat aggregation trends in these proteins for three different pH environments (4.0, 7.5, 9.1). For PBS, studies were performed only in the neutral buffer medium (pH 7.5). The experiments were performed in the very dilute concentration regime (between 0.23 and 1.8 gL-1). For all these samples heat aggregation and dissociation trends were found to be linear with temperature. Upon temperature reversal (self-cooling), hysteresis-like behavior observed in insulin was found to be predominantly large at pH 7.5. PBS, ferritin, and IgG showed no such behavior at any of three pH values, and retraced their path of aggregation while dissociating on temperature reversal. Heat aggregation and dissociation processes in ferritin were found to be independent of pH. The IgG samples showed smooth aggregation tendency only up to 35 degrees C in the buffer media pH 4.0 and 9.1, whereas for pH 7.0 the same could be observed until 60 degrees C. Low polydispersity in the correlation spectra was observed in case of all these samples.

Cationic surfactant induced fractal silica aggregates: A light-scattering study

Fractal silica aggregates are formed when a cationic surfactant, tetradecylpyridinium bromide (TPB), is used a coagulant. To maintain a constant initial surface charge density of silica colloid, a buffer medium of pH = 9.2 was used throughout. Static and dynamic light-scattering measurements were made to study the aggregates' fractal structure in relation to the aggregation kinetics over a broad range of TPB concentrations. Depending on the TPB amount added, three regimes of aggregation—fast, intermediate, and slow aggregation—have been observed for both negatively charged and positively charged silica clusters. In particular, the restructuring of silica fractals has been found to occur rapidly in the limiting regime of fast aggregation as well as in the intermediate aggregation regime, all resulting in a d f value of ∼ 2.10. The time variation of the scattered intensity vs scattering vector curves for both quasi-fast and slow regimes can be interpreted in terms of the polydispersity of the cluster distribution and the structure factor of the crossover region. A comparison between the aggregation behaviors of two different colloids by different coagulants, polystyrene latex/NaCl and silica colloid/TPB, has been made with respect to the fractal structure and the growth kinetics.

Ontrolled-Release Theophylline Tablet Formulations Containing Acrylic Resins. I. Dissolution Properties of Tablets

The dissolution properties of controlled-release theophylline tablets containing acrylic resins are presented. Four different resins (Eudragit RSPM, RLPM, Sl00 and Ll00) were incorporated into theophylline tablets by direct compression techniques and the properties of the resulting dosage form were evaluated in dilute acid, buffer media pH 4.0 and simulated intestinal media pH 7.5. Tablets (500 mg) containing 300 mg of theophylline were prepared with each of the four resins and compressed to a hardness level of 6.5 to 7.5 kg. Excellent flow properties, weight uniformity and drug content uniformity were observed with all tablet formulations. Preliminary data suggest that three of the four resins tested showed great promise as a retardant in a matrix controlled drug delivery system. The dissolution properties of three commercially available sustained-release theophylline tablets were also determined. A comparison of profiles from TheodurR (300 mg) in acid and simulated intestinal media showed a similarity in release properties to those of theophylline in tablets containing the RLPM resin.

Generation of a free α-amino group by Raney nickel after 2-nitro-5-thiocyanobenzoic acid cleavage at cysteine residues: application to automated sequencing

The selective reaction of SH containing proteins and peptides with NTCB (2-nitro-5-thiocyanobenzoic acid) has been reported (Degani, Y., & Patchornick, A. (1974) Biochemistry 13, 1; Jacobson, G.A., Schaffer, M.H., Stark, G.R., & Vanaman, T.C. (1973) J. Biol. Chem. 248, 6583). With this reagent, cysteinyl peptide bonds are selectively cyanylated and subsequently cleaved under alkaline conditions. In the present study we have successfully cleaved the beta-chains of guinea pig hemoglobin at the single cysteine and the peptides thus obtained were separated. However, the C-terminal peptide was blocked at its N terminal by a thiazolidine ring and hence could not be used for Edman degradation sequence analysis. Deblocking of this peptide was successfully done by Raney nickel in the buffer medium of pH 7.0, and also in water, at 50 degrees C for 6 to 10 h. The Raney nickel reagent is used in large excess by weight (at least ten times the weight of sulfur compound) over the compound to be desulfurized. Under these conditions, control experiments on cysteine, methionine, and some other amino acids showed that only the sulfur containing amino acids are degraded by Ni(H). Cysteine and methionine were rapidly converted to alanine and beta-aminobutyric acid, respectively. Gel electrophoresis of the iminothiazolidine peptide after exposure to Ni(H) showed no breakage of the chain.

Titration of L-cysteine hydrochloride with standard nickel sulphate solution employing 1-(pyridyl-2′-azo)-naphthol-(2) as indicator

The estimation of cysteine hydrochloride can be carried out quantitatively against standard nickel sulphate solution using 1-(pyridyl-2′-azo)-naphthol-(2) in carbonate-bicarbonate buffer medium of pH 10.0. Other natural amino acids have no interference with the titration.

Comparative Evaluation of HPMC, PVA and Gelatin as Matrices for Controlled Release Drug Delivery

The present study was undertaken to compare three different polymeric gums- HPMC, PVA and gelatin as controlled release matrices. Diclofenac sodium, a potent analgesic, was used as the model drug. Different ratio of HPMC, PVA and gelatin were incorporated into the lactose loaded Diclofenac tablet to explore their impact on drug release. Matrix tablets of Diclofenac were prepared by using individual polymer with magnesium stearate and aerosil by direct compression process at 5 ton pressure. The release of drug from these matrices was studied over 2 hrs in acidic media where insignificant release was observed. Then, the same formulations were studied over 8 hours in buffer media of pH 6.8 at a temperature of 37± 0.5°C. Statistically significant differences in drug release profile was found among the tablets prepared from different matrices. The study revealed that the average % release of drug from different types of polymer loaded matrix tablet varied with the ratio of different polymers. Among the three polymers, PVA showed best dissolution pattern. A comparison of Higuchi curve and bi-exponential curve was also performed. Key words: HPMC; PVA; Gelatin; Controlled release; Diclofenac DOI: 10.3329/sjps.v2i1.5816Stamford Journal of Pharmaceutical Sciences Vol.2(1) 2009: 51-55