No abstract

A capillary gas chromatographic method with flame ionisation detection (FID) has been developed for the analysis of Tamoxifen, Anastrozole, and Letrozole in their pharmaceutical preparations, using Clomipramine as the internal standard in order to achieve quantification. Optimal conditions were investigated: column head pressure (110 kPa), injector and detector (FID) temperatures (both 3258C), time and temperature for the splitless step (0.75 min and 708C), volume injected (2 lL), and an oven temperature program providing analysis times shorter than 8 minutes. The principal aspects of the validation method are examined and discussed. A test of the ruggedness of this method was carried out using the Plackett-Burman fractional factorial model with a matrix of fifteen experiments. Detection limits of 17.0, 9.6, and 30.6 lg L -1 were obtained for Tamoxifen, Anastrozole, and Letrozole, respectively. This method is simple, rapid, and sensitive; it was tested on the analysis of pharmaceutical preparations, achieving recoveries between 98.8% and 100.3%.

SummaryA simple and rapid method was developed for the analysis of Sildenafil Citrate (Viagra) in its pharmaceutical formulations (Viagra 25, 50 and 100 mg) in the presence of excipients, using its metabohte UK-103, 320 as internal standard for quantification. The optimal separation conditions were established in presence of all compounds in the pharmaceutical formulations and provided analysis times of less than 12 minutes. The conditions were: column head pressure (110 KPa), injector and flame ionisation detector (FID), temperatures (325 and 300 ~ time and temperature for the sphtless step (0.75 min and 70 ~ sample size (2 gL) and an oven temperature program.Aspects such as stability of the solutions, hnearity, accuracy, reproducibihty, specificity, limits of detection (LODs) and of quantification (LOQs) are examined in order to validate the method in presence of all excipients. Some of these aspects such as specificity were also assessed by mass spectrometric detection in the SCAN mode. A ruggedness test of this method was made using the fractional factorial model of Plackett-Burman. In our case, this involved designing a matrix of 15 experiments in which the influence of the seven factors mentioned above was tested at three different levels on different chromatographic results such as resolution, efficiency, relative peak areas, etc. The chromatographic results were evaluated statistically by the method of Youden and Steiner. The highly satisfactory results obtained in both the validation and ruggedness tests show that the CG method could be a very valuable option as an official method for the determination of Sildenafil Citrate in its pharmaceutical formulations.

An alternative gate oxide configuration is proposed to enhance the SiO2/SiC interface quality, enabling high mobility 4H-SiC lateral metal-oxide-semiconductor field-effect transistors (MOSFETs). The gate oxide is prepared by the combination of rapid thermal oxidation in N2O ambient, boron diffusion into SiO2, and plasma enhanced chemical vapor deposition of tetraethyl orthosilicate oxide. Capacitance-voltage (C-V) and conductance-voltage (G-V) measurements on fabricated capacitors reveal a reduction of both interface trap and near interface oxide trap densities. The fabrication of MOSFETs with very high field-effect mobility (μfe) values, up to 160 cm2/V s, is enabled. Several channel orientations, with respect to the wafer flat {112¯0}, have been studied to check μfe values and isotropy. Higher μfe values are obtained for a channel orientation of 90°. Boron distribution is studied by secondary ion mass spectrometry (SIMS) and time of flight SIMS. We propose that the combination of boron and nitrogen induces changes in the structure of the gate oxide which are positive in terms of the SiO2/SiC interface quality.