Shahzad Sharif

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.

1-D and 2-D coordination polymers of cerium(III) with pyridine-2,4,6-tricarboxylic acid: synthesis and structural, spectroscopic, and thermal properties

Two new Ce(III) complexes of pyridine-2,4,6-tricarboxylate (ptc), [Ce2(H2O)2(C8H3NO6)4(C2O4)Na2(H2O)5] n (H2O)4 (1) and [Ce(H2O)3(C8H2NO6)] n (H2O) (2), were crystallized in the triclinic space group P-1 and the monoclinic space group P21 /c, respectively. These polymers were also characterized by elemental analysis, FTIR spectroscopy, and thermogravimetric analysis. The latter shows high thermal stability for 1. Each Ce(III) is ten-coordinate with two nitrogen atoms from two pyridine rings, five oxygen atoms from five carboxylic groups, two oxygen atoms from oxalate and one oxygen from water. Oxygen at the 2,6-position of ptc is a bridge to construct a 1-D polymer for 1. Each Ce(III) is nine-coordinate with five oxygen atoms and one nitrogen from ptc and three water molecules, giving a tricapped trigonal prism for 2. Each ptc bridges three Ce(III) ions with the formation of 2-D polymeric chains, and each carboxylic acid group at the 2,6-position of ptc is only bound to one Ce(III). The other carboxylate at the 6-position is bound to another Ce(III), and the carboxylates at the four-position adopt a chelating mode. Molecules are linked principally by OH···O hydrogen bonds involving water and carboxylate, forming (6), (14), and (27) rings, which link to give a 3-D network.

DEVELOPMENT AND VALIDATION OF LIQUID CHROMATOGRAPHIC METHOD FOR THE SIMULTANEOUS ESTIMATION OF EZETIMIBE AND LOVASTATIN IN HUMAN PLASMA

In the present study conditions were optimized for the development and validation of a simple, sensitive and isocratic reverse phase high performance liquid chromatographic method for the simultaneous determination of ezetimibe and lovastatin in human plasma using gemfibrozil as internal standard. After a single step extraction with acetonitrile, satisfactory elution of both the analytes along with internal standard was achieved on a Merck C-18 column using a mixture of 0.1 M ammonium acetate pH 5.0 and acetonitrile in the ratio of (28:72, v/v) at a flow rate of 1.5 ml/min. The detection was carried out at a wavelength of 240 nm using a photodiode array detector. The method was linear in the concentration range of 0.2-25 |xg/ml for ezetimibe and 0.4-50 |xg/ml for lovastatin. The extraction recovery of analytes was greater than 85 % and within day and between day precision was also satisfactory. The method was validated by performing its linearity, recovery, precision, LOD/LOQ values and stability of solutions. The total eluting time for the analysis is less than twelve minutes. As the plasma peaks did not interfere with the peaks of analytes so the method can be used for the determination of ezetimibe and lovastatin in human plasma and may possibly be for the pharmacokinetic study.

Bis(1,3-dibutylthiourea)dicyanido­mercury(II)

In the title compound, [Hg(CN)2(C9H20N2S)2], the Hg atom lies on a twofold rotation axis. There is only half a molecule in the asymmetric unit. The Hg atom has a distorted tetrahedral coordination involving the S atoms of two 1-butyl-3-propylthiourea groups and the C atoms of the two CN− anions. In the crystal packing, adjacent molecules are connected by intermolecular N—H⋯N and N—H⋯S hydrogen bonds, forming infinite chains in three dimensions.

2-(4-Acetamido-benzene-sulfonamido)-3-methyl-butanoic acid.

In the title compound, C13H18N2O5S, the benzene ring and the acetamide group are almost coplanar [dihedral angle = 5.6 (3)°], and the amine group projects almost vertically from this plane [C—C—S—N = −84.5 (7)°]. A short intramolecular C—H⋯O contact occurs. In the crystal, O—H⋯O, N—H⋯O and N—H⋯(O,O) hydrogen bonds lead to a three-dimensional network. One of the methyl groups of the isopropyl residue is disordered over two orientations in a 0.747 (16):0.253 (16) ratio.

Seven-, eight-, and ten-coordinated cerium(III) with highly connective pyridine-2,4,6-tricarboxylate, oxalate, and glycine ligands

Two new 3-D Ce(III) coordination polymers, [Ce1.3(PTA)2(Oxa)2(Gly)(H2O)2]·(Gly)4H2O (1) and [Ce2.6(PTA)4(Oxa)2(H2O)10]·(MeOH)7H2O (2) (PTA = 2,4,6-pyridinetricarboxylate, oxa = oxalate and Gly = glycine), were synthesized. The oxalate in 1 and 2, generated in situ from the cleavage and chemical rearrangement of PTAH3, assembled into mixed-ligand networks to generate 3-D frameworks. Single crystal analysis reveals that in both complexes, Ce(III) shows coordination numbers of 7 and 10 in 1 and 8 and 10 in 2. PTA adopts four kinds of coordination modes. These complexes were further characterized using elemental analysis, FTIR spectroscopy and thermogravimetric analysis.

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.

Synthesis and structural characterization of cadmium(II) complexes of tetramethylthiourea (Tmtu); X-ray structure of [Cd(Tmtu)2Cl2]

The spectral characterization of cadmium(II) complexes of the general formula [Cd(Tmtu)2X2] (Tmtu = tetramethylthiourea, X = Cl−, Br−, I−, and SCN−) as well as the X-ray structure of one of them, [Cd(Tmtu)2Cl2] (I) is described. In (I), the cadmium atom lies on a twofold rotation axis and has a distorted tetrahedral coordination environment defined by two S atoms of telramelhylthioures (Tmtu) ligands and two chloride ions. The crystal structure is stabilized by non-classical intramolecular C-H⋯N and C-H⋯S hydrogen bonding interactions involving the methyl H and sulfur or nitrogen atoms. The spectroscopic data were discussed in terms of the nature of bonding.

Synthesis and Crystal Structures of a Lanthanum(III) 1D Polymer and a Mixed-Ligand Cerium(III) Binuclear Complex Derived from Pyridine-2,6-dicaboxylic Acid

Lanthanum(III) and cerium(III) complexes of pyridine-2,6-dicaboxylic acid (H2Pydc) have been prepared and their crystal structures were determined by X-ray crystallography. The single crystal analysis reveals that the lanthanum(III) complex, 1 is polymeric consisting of {[La(Pydc)2(H2O)2]·4H2O}n units linked through carboxylate oxygen atoms and exhibiting nine coordination number. Intermolecular O–H···O hydrogen bonds produce R11(6), R44(16) and R44(20) rings, which lead to three-dimensional polymeric chains. The crystal structure of the cerium(III) complex, 2 [{Ce(Pydc)3}{Ce(Pydc)(HO–CH2CH2–OH)(H2O)3}·6H2O)] shows that the complex is a mixed-ligand binuclear system in which one cerium coordinated to three Pydc molecules, while the other cerium is bound to one Pydc, one oxygen atom of the other Pydc, one ethylene glycol and three water molecules. Each of the two Ce(III) ions is nine coordinated. Intermolecular O–H···O hydrogen bonds produce R22(8) and R22(20) rings, which lead to three-dimensional polymeric chains. The complexes were further investigated using elemental analysis, FTIR spectroscopy and thermogravimetric analysis.

4-{[(4-Methyl­phen­yl)sulfon­yl]amino}­benzoic acid

In the title compound, C14H13NO4S, the dihedral angle between the aromatic rings is 35.47 (10)°. In the crystal, adjacent molecules are connected by pairs of O—H⋯O hydrogen bonds, forming head-to-head centrosymmetric dimers typical for carboxylic acids. Adjacent dimers are further linked through C—H⋯O interactions on one side and N—H⋯O interactions on the other, generating [010] chains.