Ablation of poly(methyl methacrylate) and poly(2-hydroxyethyl methacrylate) by 308, 222 and 193 nm excimer-laser radiation

Data on the ablation of Poly(Methyl MetAcylate) (PMMA) and Poly(2-Hydroxyethyl MetAcylate) (PHEMA) with 0%, 1% and 20% of Ethylene Glycol DiMethAcrylate (EGDMA) as crosslinking monomer by 193, 222 and 308 nm laser radiation are presented. Direct photoetching of PMMA at 308 nm is demonstrated for laser fluences ranging from 2 to 18 J/cm². The ablation rate of PHEMA is lower than the corresponding to PMMA and decreases when the amount of EGDMA increases. The determination of the absorbed energy density required to initiate significant ablation suggests that the photoetching mechanism is similar for all the polymers studied and is a function of the irradiation wavelength. The Beer-Lambert law, the Srinivasan, Smrtic and Babu (SSB) theory and the kinetic model of the moving interface are used to analyze the experimental results. It is shown that only the moving interface theory fits well the etch rate for all the selected polymers at the three radiation wavelengths.     

Spectrofluorimetric analysis of cefoxitin in pharmaceutical dosage

A fluorescence method involving sample pre-treatment is investigated concerning the determination of cefoxitin. A fluorescent product is formed when samples containing cefoxitin are subjected to alkaline hydrolysis with 1.0M sodium hydroxide and heated for 60 min at 90 degrees . The fluorescence is measured in ethanol/water medium (50% v/v) at approximately pH 2.0 provided by adding of 0.1M hydrochloric acid. The fluorescence excitation and emission maxima were 317 and 400 nm, respectively. The quantitative range is between 0.020 and 1.40 mug/ml. A detection limit of 2 x 10(-3) mug/ml was found. The proposed method has been applied to the determination of cefoxitin in commercial injections, saline and glucosed physiological serum.