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Biomedical subjects

Y K Agrawal

Publications and source records attributed to Y K Agrawal.

14 recordsLinked to original sources
PubMed2005

Dynamic instability at liquid/vapor interface far from equilibrium.

Attempt has been made to elucidate the mechanism of electric potential oscillations at oil-aqueous solution interface involving adsorption at oil-vapor interface on a semi-theoretical basis. The mechanism stipulates adsorption of ammonia, amines and pheromones at the liquid-vapor interface followed by transfer of ions through membrane-aqueous solution interface and subsequent interaction of ammonium (amine) ions and carbocations from pheromones with diffusing halide ions from the bulk. Relationship of the above mechanism with sensing mechanism of smell by olfactory nerves has also been pointed out.

Adsorption↗
PubMed2005

Chiral chromatographic separation of beta-blockers.

A novel amide based chiral stationary phase m-[(+)-alpha-methyl benzyl carboxamide] XAD-4 has been synthesized by covalently linking R(+)-1-phenylethylamine to chloroformoyl Amberlite XAD-4 under weak alkaline conditions. The synthesized resin has been primarily characterized by m.p., elemental analysis and FT-IR and 13C NMR spectra. beta-Blockers viz. atenolol, metoprolol, and propranolol were successfully separated into their enantiomers using a mixture of sodium acetate-acetic acid buffer (pH 4.1):acetonitrile (4:6, v/v) solution using the synthesized resin. Hydrogen bonding and pi-pi interactions are supposed to be the major analyte-chiral stationary phase interactions.

Adrenergic beta-Antagonists↗
PubMed2003

Separation and trace estimation of benzidine and its macromolecular adducts using supercritical fluid chromatography.

A sensitive, rapid, selective and reproducible method has been developed to measure blood plasma levels of benzidine (BZ) and its acetylated metabolite, N-OH-N,N'-diacetylbenzidine (N-OH-DABZ), using supercritical fluid chromatography (SFC) for the first time. Benzidine and N-OH-N,N'-diacetylbenzidine were extracted from the plasma using ether. Separation was done on a Nucleosil (250 mm x 4.6 mm) 10 microm, Nucleosil-RP-C18 column with 7.4% (v/v) methanol-modified supercritical fluid carbon dioxide (2.5 ml min(-1)) as mobile phase. The column temperature was 45 degrees C and the outlet pressure was set at 8.83 MPa. The detection was done using a UV-Vis detector set at 280 nm. The limit of quantification was 0.10 ng ml(-1) (BZ) and 0.14 ng ml(-1) (N-OH-diacetylbenzidine) using 1 ml plasma specimen. The mean extraction recovery of BZ was found to be 98.6%. The SFC method was directly compared to a published HPLC-UV method. With respect to speed, organic solvent usage, sensitivity, specificity and accuracy, SFC was found to be superior. The method has been successfully used to estimate the BZ, N-OH-diacetylbenzidine levels in blood plasma of the animals who were administered 15 microg kg(-1) body weight of benzidine.Further, this method has been also applied for the detection and quantification of benzidine DNA and hemoglobin adducts from the blood and tissue samples of the benzidine dosed animals.

Animals↗
PubMed1999

Thermodynamic ionization constants of antihypertensive drugs.

The thermodynamic ionization constants (pKa) of indapamide, clonidine and methyldopa have been determined at 25 degrees C and 35 degrees C by pH titration technique. The pKa varies linearly with mole fraction of dioxane. The thermodynamic parameters have been calculated.

Algorithms↗
PubMed1999

Effect of binders on anti hypertensive drugs.

Tablets of antihypertensive drugs, Indapamide, Methyldopa and Clonidine have been prepared and their physico-chemical properties were determined. The effect of various binders viz. starch, acacia, sodium carboxymethyl cellulose (sod. CMC), gelatin and lactose on the properties of these tablets were studied. Formulations of tablets of indapamide, methyldopa and clonidine prepared in combination with acacia, lactose and sod. CMC, respectively result in the best flow properties, minimum percentage fines, low angle of repose and compressibility. The tablets prepared from these granules possess all quality features including a good dissolution profile. Gelatin, sod. CMC and starch have less effective granule formation leading to poor quality of tablets in case of Indapamide, Methyldopa and Clonidine, respectively.

Antihypertensive Agents↗
PubMed1991

Spectrophotometric determination of diclofenac sodium in tablets.

Simple spectrophotometric methods are described for the determination of diclofenac. In the first method diclofenac reduces iron(III) to iron(II) when heated in aqueous solution. The ferrous ions produced react with 2,2'-bipyridine to form a complex having a maximum absorbance at 520 nm. The reaction obeys Beer's Law for concentrations of 10-80 micrograms ml-1. This method can be applied to the determination of diclofenac in tablets. In the second method, diclofenac is treated with Methylene Blue in the presence of phosphate buffer (pH 6.8) and the complex is extracted with chloroform. The complex has a maximum absorbance at 640 nm and the graph of absorbance against concentration is linear in the range 5-40 micrograms ml-1. This method can be applied to the determination of diclofenac in tablets that also contain paracetamol.

2,2'-Dipyridyl↗
PubMed1988

Effect of binders on sulfamethoxazole tablets.

Five batches of sulfamethoxazole tablets were prepared using different binders [starch, acacia, ethyl cellulose sodium carboxymethylcellulose, and povidone (1-vinyl-2-pyrolidinone polymer, PVP)] with water in 3% (dry basis) concentration. Comparative data show that granules prepared with PVP have the best flow properties and minimum angle of repose, percentage fines, and compressibility, while granules of sodium carboxymethylcellulose could not be compressed into well-defined tablets. Tablets containing starch as a binder possess all the quality features. Tablets from acacia, however, give a poor dissolution profile. Ethyl cellulose has less effective granule formation, leading to poor quality tablets. Rank correlation with respect to solubility and absorption characteristics according to granulating agent in the formation is: starch greater than ethyl cellulose greater than PVP greater than acacia.

Absorption↗
PubMed1987

Sulfa drugs: thermodynamic proton-ligand and metal-ligand stability constants.

The thermodynamic proton-ligand stability constants of sulfa drugs have been determined in different mole fractions of dioxane (0.083-0.174) at 25 and 35 +/- 0.1 degrees C. Empirical corrections to pH meter readings in mixed aqueous media have been applied. The pKa varies linearly with the mole fraction of dioxane. Numerical equations expressing this linear relationship have been obtained using the method of least squares, and relevant correlation coefficients have been calculated. The thermodynamic parameters delta G degrees, delta H degrees, and delta S degrees are calculated. The effect of solvent and the change in free energy from mixed aqueous media, delta, is discussed. The thermodynamic metal-ligand stability constants of Cu(II), Pd(II), and Ce(IV) with sulfa drugs in 50% aqueous dioxane at 35 +/- 0.1 degrees C have been determined. The effect of basicity of the ligand and the order of the stability constant is discussed.

Chemical Phenomena↗
PubMed1986

Thermodynamic proton-ligand and metal-ligand stability constants of some drugs.

The thermodynamic proton-ligand (pKa) and metal-ligand stability constants of clioquinol, clofibrate, nitrofurazone, and tetracycline with Cu2+, Zn2+, Mn2+, Mg2+, and Ca2+ have been determined at 35 degrees C in 50% ethanol-water media. An empirical pH correction for mixed-aqueous media has been applied. The metal-ligand stability constants were determined by following the Bjerrum Calvin titration technique as applied by Agrawal to mixed-aqueous solvents. The effect of the basicity of the ligand and the order of stability constants is discussed. The stability constants of the divalent metals follow the order: Cu2+ greater than Zn2+ greater than Mn2+ greater than Mg2+ greater than Ca2+ with all the drugs.

Buffers↗
PubMedDate not supplied

Spectrophotometric determination of sulphacetamide.

A new rapid selective spectrophotometric method for the determination of sulphacetamide is described. The drug forms a orange-yellow colored complex with Cerium(IV) in sulfuric acid media which is extracted into ethyl acetate. The complex exhibits a maximum absorbance at 440 nm with a molar absorptivity of 3 x 10(2) 1 mol-1 cm-1. The system obeys Beer's law in the concentration range of 0.07-1.1 mg of sulphacetamide. The various parameters for the optimum extraction conditions are discussed. The method is applied to the determination of sulphacetamide in dosage forms.

Anti-Infective Agents, Local↗