Pilar Gómez

Determination of caffeine in solid pharmaceutical samples by FTIR spectroscopy

Fourier transform infrared spectroscopy has been used for the quantitative determination of caffeine in several pharmaceutical products: acetyl salicylic acid, paracetamol and propyphenazone. The method is simple, rapid and selective, and allows the determination of caffeine without sample pretreatment and without separation from the matrix. Two techniques for measuring the infrared spectra of caffeine are described: transmission through pellets and diffuse reflectance from powder (DRIFT). In both methods, samples were diluted (1%) with KBr. Caffeine in pharmaceutical matrices was recovered within 5% error in pellets and 10% by DRIFT. Relative standard deviations were generally ⩽1.5% for repeated measurements on a single pellet and ⩽ 5% for measurements on different pellets. DRIFT in the vacuum mode gave rather large RSDs. The limit of detection of the pellet technique was about 0.5% caffeine in the original sample.

Quantitative analysis of caffeine applied to pharmaceutical industry

Abstract The direct determination of some compounds like caffeine in pharmaceutical samples without sample pretreatment and without the separation of these compounds from the matrix (acetyl salicylic acid, paracetamol,…) is very worthwhile. It enables analysis to be performed quickly and without the problems associated with sample manipulation. The samples were diluted directly in KBr powder. We used both diffuse reflectance (DRIFT) and transmission techniques in order to measure the intensity of the peaks of the caffeine in the pharmaceutical matrix. Limits of detection, determination, relative standard deviation and recovery using caffeine in the same matrix as in the pharmaceutical product are related. Two methods for the quantification of caffeine were used: calibration line and standard addition techniques.

Quantification of dodecylbenzenesulfonate and tripolyphosphates in solid commercial samples of detergents

Abstract Fourier transform infrared spectroscopy has been used for the quantitative determination of dodecylbenzenesulfonate and tripolyphosphate in solid commercial samples of detergents. The only sample treatment consisted of a separation with ethanol. Dodecylbenzenesulfonate was dissolved and tripolyphosphate remained in the insoluble fraction. The method consisted of transmission measurements of KBr pellets. Precision, recovery and determination using both calibration line and standard addition have been optimized. The determination of dodecylbenzenesulfonate has been compared with the UV method.

El grajo de Esopo: Luciano y la tradición yámbica

As obras de Luciano de Samosata respondem a um complexo mecanismo de criacao literaria, em que o uso paradoxal dos generos literarios e pratica habitual. N’ O critico falaz ou sobre o termo nefasto [= Pseudologista ], o samosatense escreve um virulento ataque contra um individuo que se dedica a fazer declamacoes publicas, mas que exerce mal o oficio de sofista e, por causa disso, merece ser o destinatario de uma implacavel invectiva. Para que nao reste duvida alguma de qual e a tradicao literaria, poetica neste caso, que inspira a satira de Luciano, nos primeiros capitulos da obra aparecem citados os mais ilustres jambografos gregos – Arquiloco, Hiponax ou Semonides – e, com eles, tambem e mencionado Esopo. O objetivo deste trabalho e analisar como Luciano, que conhece bem o corpus esopico e recorre a ele em diversas ocasioes, quando associa, em Pseudologista , Esopo e a poesia jâmbica, nao so mostra mais uma vez com que intencao pode servir-se das fabulas e adapta-las de forma variada nas suas obras, mas tambem, como critico literario, ensinanos sobre os conteudos de burla e ataque verbal proprios da tradicao em que este genero funda as suas raizes.