Quantification of Pyrazinamide in Human Plasma by Validated High Performance Liquid Chromatography Method

Objective: To be able to accurately determine the quantity of Pyrazinamide (PZA) in different tablet preparations and human plasma using an Ultra violet detector equipped high performance liquid chromatography (HPLC). Study Design: Experimental study Place and Duration of Study: Department of Bioequivalence Studies, University of Veterinary and Animal Sciences Lahore and the Department of Pharmacology, University of Health Sciences, Lahore the from 1st April 2017 to 31st March 2018. Methodology: Two mobile phases were used, the first compromised of disodium hydrogen phosphate buffer having a pH of 6.8 and acetonitrile in the proportion of (95:5) and the second was a combination of aforesaid substances in equivalent proportion (50:50 v/v). The gradient for the first 5 min was exclusively Mobile phase “a” after which 5-6 min Mobile phase “b” was raised from 0 to 100% and was kept at 100% till the completion of the cycle. The flow of mobile phase was kept at 1000 µl/min. Determination of PZA was done using a ultraviolet detector at a wavelength of 238 nm. Amount of sample injected was 40 μl. Procedure was done by using Shizmadu Chromatographic System, Japan equipped with a SIL-20AC HT auto-sampler, SPD-M20A, CTO 20 AC, a LC-20AT VP pump, and CBM 20A controller unit. A C18 column was used as well. Results: Retention time of PZA was 6.1±2%. Precision was 0.46 to 2.20% relative standard deviation for intra assay and for inter assay we obtained 0.29 to 34.45% RSD for all quality control levels. The overall recovery of PZA was 96.75%. Conclusion: High selectivity for PZA was seen and no other spikes from drugs present in FDC regimen were observed at the time when PZA is detected in blank plasma samples Key words: Chromatography, High pressure liquid. Pyrazinamide. Tuberculosis

A Study on the Etching and Surface Characteristics of SiOC Thin Films After C6F12O Plasma Etching

Silicon oxycarbide (SiOC) film was etched using a CF4/C6F12O/O2 mixed gas plasma through an inductively coupled plasma etcher. Changes in the dielectric constant and surface chemical bonding properties were investigated using ellipsometry and Fourier transform infrared spectroscopy. Plasma diagnosis was carried out using a double Langmuir probe, ultraviolet detector, and residual gas analyzer. The physical and chemical plasma properties of CHF3 and C6F12O exhibited similar trends. However, the C6F12O mixed plasma exhibited a smaller change in dielectric constant compared to that of a conventional CHF3 mixed plasma, because of the lower ion density, ion energy flux, and UV intensity and thinner fluorocarbon-based polymer formation. Therefore, the liquefied C6F12O gas can substitute for the existing etching process gas and reduce the change in dielectric constant.

Residual characteristics of etofenprox in the processing stages of rice cakes and cookies

The changes in residual amounts of an insecticide (etofenprox) in processed rice cakes and cookies were investigated in this study. Test samples were sprayed with etofenprox during rice cultivation, and brown rice samples were dipped in a pesticide solution to investigate the effects of washing and processing. A multiresidue method for multiclass pesticides was employed for etofenprox analysis using a high-performance liquid chromatography–ultraviolet detector setup. Etofenprox was not detected in polished rice that was processed into rice cakes and cookies. The etofenprox residue levels were 2.13 mg/kg in each processing stage of brown rice products that were dipped in 400 mg/kg etofenprox solutions. The residual amounts of etofenprox in washed/polished rice and rice flour obtained by grinding were 1.25 and 0.77 mg/kg, respectively. The residual levels were 0.38 mg/kg in rice cakes prepared by cooking rice flour in a steamer for 20 min (a decrease of 82.1% compared to that in polished rice), 0.47 mg/kg in rice cookies baked in an oven for 20 min (a decrease of 78.0%), and 0.21 mg/kg in fried rice cookies (a decrease of 90.2%). Overall, the residual levels of etofenprox decreased in a range of 40–100% during the processing of rice cakes and cookies.