Nalini Kanta Sahoo

Oblique angle deposition of HfO2 thin films: quantitative assessment of indentation modulus and micro structural properties

Oblique angle deposition of oxides is used routinely for fabricating inhomogeneous thin films with proven correlation between refractive index and the angle of deposition. Inhomogeneous layers play a key role in the development of rugate interference devices for photo-physical applications. Such obliquely deposited thin films show high porosity which is a critical issue related to their density, mechanical and environmental stability. Hence, it is important to investigate elastic properties of such film in addition to optical properties. Using atomic force acoustic microscopy, we report indentation modulus of HfO2 thin films deposited at angles 80, 68, 57, 40 and 0 degree with normal to substrate plane on Si (100) substrate. Such films were measured to have indentation modulus of 42 GPa for extreme obliquely deposited film and indentation modulus increases with decrease in angle to become highest with a value of 221 GPa for normally deposited films. We also report microstructural properties and density of films measured by FESEM and grazing angle x-ray reflectometer, respectively. Both indentation modulus and density depict a nonlinearly decreasing behavior with angle of deposition. Variation of density is again confirmed from FESEM cross-sectional morphology.

Validation of assay for bulk clopidogrel and for some tablet forms by reverse-phase high-performance liquid chromatography

Abstract A novel, simple, economical reverse-phase high-performance liquid chromatography (RP-HPLC) method was developed for quantifying clopidogrel in bulk and tablet form with greater precision and accuracy. Separation was achieved on a Develosil ODS HG-5 RP C18 (15 cm × 4.6 mm, i.d. 5 μm) column in isocratic mode with a mobile phase consisting of acetonitrile:phosphate (65:35) buffer (pH 2.85) with a flow rate of 1 mL/min. Detection was carried out at 225 nm. The retention time of clopidogrel was 7.48 min. The method was validated as per the guidelines of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). Linearity was established for clopidogrel in the range 10–60 μg/mL, with an r2 value of 0.999. The recovery of clopidogrel was 99.71–100.03%. The high recovery and low relative standard deviation confirm the suitability of the proposed method for estimating the concentrations of the drug in bulk and tablet dosage forms. Validation studies demonstrated that the proposed RP-HPLC method is simple, specific, rapid, reliable and reproducible for the determination of clopidogrel for quality control.

Solid phase extraction and quantification of diclofenac sodium in human plasma by liquid chromatography-tandem mass spectrometry

A novel liquid chromatography-tandem mass spectrometry (LC-MS-MS) method is described for the quantitative determination of diclofenac in human K2EDTA plasma in negative ion mode and validated using zidovudine as internal standard (IS). Sample preparation was accomplished by solid phase extraction technique. The eluted samples were chromatographed on Zorbax XDB phenyl column (75 × 4.6 mm, 3.5 μm) Agilent Technologies, using a mobile phase consisting of HPLC grade acetonitrile—0.2% acetic acid in HPLC water (80: 20, v/v).The injection volume was 15 μL and the total run time was 2.0 min. The method was validated over a linear concentration range of 25 to 4004 ng/mL diclofenac. The precursors to product ion transitions m/z 294.10 to 249.90 (diclofenac) and m/z 266.0 to 222.90 (zidovudine, IS) were used for quantitation. The retention times were 1.12 and 0.86 min for diclofenac and zidovudine, respectively. Validation results show that the method is selective and capable of quantifying the analyte with good precision and accuracy. The method is stable for the studied parameters. Therefore, a rapid, sensitive LC-MS-MS method for quantification of diclofenac in human plasma was developed and can be used in therapeutic drug monitoring of this drug.