I.U. Khan

Development and validation of a high performance liquid chromatographic method for the simultaneous determination of potassium clavulanate and cefadroxil in synthetically prepared tablets

A simple, sensitive and rapid high performance liquid chromatographic method was developed and validated for the simultaneous determination of potassium clavulanate and cefadroxil in synthetically prepared tablets. Chromatographic separation and detection was carried out on a C-18 column using 0.05 M potassium dihydrogen phosphate buffer (pH 5.0) and acetonitrile in the ratio of 94: 06 (v/v) as mobile phase at wavelength of 225 nm. The method was linear in the concentration range of 3.75–22.5 μg/mL for potassium clavulanate and 15–90 μg/mL for cefadroxil. The flow rate was 1.0 mL/min and the total analysis time was less than 10 min. The mean recoveries was found to be greater than 99% with RSD less than 1.0%. The proposed method was validated by performing linearity, recovery, specificity, robustness, LOD/LOQ and within-day and between-day precision. The chromatographic results obtained from the synthetically prepared tablets show that the method is highly precise and accurate for the simultaneous quantitation of clavulanate potassium and cefadroxil.

Separation of no-carrier-added arsenic-77 from neutron irradiated germanium

Abstract Arsenic-77 (T1/2=1.6 d) was produced by irradiating natural germanium in Pakistan Research Reactor-1. The nuclear reaction 76Ge(n,γ) produces 77Ge, which decays by emission of β- particles into 77As. The neutron irradiated target was dissolved in aqua regia, excess of acid was removed by evaporation and finally the solution in basic media was passed through hydrous zirconium oxide (HZO) column. The Ge was quantitatively retained on HZO, while 77As was present in the effluent. More than 90% 77As was recovered. The chemical impurity of Ge in 77As was <0.01 μg/mL.

4-Chloro-2-[(E)-({4-[N-(3,4-dimethyl-isoxazol-5-yl)sulfamo-yl]phen-yl}iminio)meth-yl]phenolate.

The title compound, C18H16ClN3O4S, is a Schiff base ligand in which the H atom of the hydroxy group has moved to the N atom of the imine group, resulting in a zwitterion. The structure is stabilized by an intramolecular (N—H⋯O) and five intermolecular (C—H⋯O, C—H⋯N and N—H⋯O) hydrogen bonds. The molecules are linked to each other by hydrogen bonds and form a three-dimensional polymeric network. In addition, the aromatic rings are also involved in π–π interactions [centroid–centroid distance between aromatic rings = 3.7525 (11) Å].

Extraction of medically interesting 188Re-perrhenate in methyl ethyl ketone for concentration purposes

The high bolus volumes (20–40mL) of the generator-produced Rhenium-188 require post elution concentration of the eluate for the preparation of a dissolved β− source and radiopharmaceuticals labeled with Re-188 for radiotherapy. Solvent extraction of 188Re in methyl ethyl ketone was studied. With the increase of organic phase volume, extraction of 188Re was enhanced while mixing time of aqueous and organic phases did not show any significant effect on the extractability of 188Re in the organic phase. Almost 80% of 188Re was extracted in methyl ethyl ketone at a volume ratio of 1:2 for aqueous and organic phases. By evaporation/distillation of methyl ethyl ketone, 188Re was concentrated and dissolved in the desired volume of physiological saline.

4-(5-Chloro-2-hydroxy-benzyl-idene-amino)-N-(4,6-dimethyl-pyrimidin-2-yl)benzene-sulfonamide.

The title compound, C19H17ClN4O3S, is a Schiff base compound of 5-chlorosalicylaldehyde and sulfamethazine [4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide]. The geometry around the S atom is distorted tetrahedral, comprising two O atoms of the sulfonyl group, a C atom of a benzene ring and the amino N atom. The title compound has an intramolecular O—H⋯N hydrogen bond and two intermolecular C—H⋯O and N—H⋯O hydrogen bonds, which link neighbouring molecules into 10-membered rings. As a result of an unavoidable conformational arrangement, a slightly short intramolecular contact of distance 2.59 Å exists between an O atom of the sulfonyl group and an H atom of the sulfamethazine benzene ring.

N-(4-Hydroxy­phen­yl)benzene­sulfon­amide

The title compound, C12H11NO3S, synthesized by the reaction of benzene sulfonyl chloride with para-aminophenol, is of interest as a precursor to biologically active sulfur-containing heterocyclic compounds. The structure is stabilized by N—H⋯O and O—H⋯O hydrogen bonds.

Lead (Pb) column for concentration of 99mTc-pertechnetate

Because of the high content of inactive molybdenum in neutron irradiated MoO3, large columns containing alumina or gel are needed to produce chromatographic 99Mo→99mTc generator. This results in large elution volumes containing relatively high 99Mo breakthrough and low concentrations of 99mTcO4-. The decrease in specific volume of 99mTc places a limitation on reconstitution of some kits for 99mTc radiopharmaceuticals applied in diagnostic nuclear medicine. Hence concentration technique is mandatory for effective utilization of (n,γ) produced 99Mo/99mTc generators at the start of its life whereas in case of fission 99Mo/99mTc generator the technique may be quite useful at the end of first week of its life. We report post elution concentration of 99mTc using in house prepared Pb column. The high bolus volumes (10–60 ml saline) can conveniently be concentrated in ∼1 ml of saline.

3-(Piperidin-1-yl)-6-(1H-pyrazol-1-yl)pyridazine

In the title compound, C12H15N5, the piperidine ring adopts a chair conformation with the substituent C atom in an equatorial site and the dihedral angle between the pyridazine and pyrazole ring planes is 10.36 (2)°.

4-{2-[(5-Chloro-2-hydroxy-benzyl-idene)amino]eth-yl}benzene-sulfonamide.

In the molecule of the title compound, C15H15ClN2O3S, the S atom adopts a distorted tetrahedral coordination geometry with two O atoms, one N atom of the amide group and one C atom of the aromatic ring. An intramolecular O—H⋯N hydrogen bond results in the formation of a planar six-membered ring, which is oriented with respect to the adjacent aromatic ring at a dihedral angle of 3.38 (11)°. Thus, the two rings are nearly coplanar. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers.

(E)-2-(2-Fluoro­benzyl­idene)butanoic acid

In the crystal structure of the title compound, C11H11FO2, the methine CH forms an intramolecular hydrogen bond with the carboxyl O atom. The molecules form dimers through hydrogen bonding between carboxyl groups. These dimers are linked to each other by C—H⋯O contacts between the benzene and carbonyl groups of adjoining molecules. In addition, there are weak intermolecular C—H⋯F contacts.