Tunable diode laser absorption spectroscopy (TDLAS) is an excellent analytical technique for gas sensing applications. In situ sensing of relevant hydrocarbon gases is of substantial interest for a variety of in-field scenarios including environmental monitoring and process analysis, ideally providing accurate, molecule specific, and rapid information with minimal sampling requirements. Substrate-integrated hollow waveguides (iHWGs) have demonstrated superior properties for gas sensing applications owing to minimal sample volumes required while simultaneously serving as efficient photon conduits. Interband cascade lasers (ICLs) are recently emerging as mid-infrared light sources operating at room temperature, with low power consumption, and providing excellent potential for integration. Thereby, portable and handheld mid-infrared sensing devices are facilitated. Methane (CH4) is among the most frequently occurring, and thus, highly relevant hydrocarbons requiring in situ emission monitoring by taking advantage of its distinct molecular absorption around 3 μm. Here, an efficient combination of iHWGs with ICLs is presented providing a methane sensor calibrated in the range of 100 to 2000 ppmv with a limit of detection at 38 ppmv at the current stage of development. Furthermore, a measurement precision of 0.62 ppbv during only 1 s of averaging time has been demonstrated, thereby rendering this sensor concept useful for in-line and on-site emission monitoring and process control applications.
O teor de ferro total e ferro bioacessível foram determinados em carne através da espectrofotometria na região do visível pelo método da 1,10-fenantrolina. As amostras foram cozidas, desidratas e algumas preparadas como carne de sol. Elas foram submetidas a uma simulação da digestão gastrointestinal para a avaliação da bioacessibilidade de ferro. Entre as amostras analisadas, o coração e fígado apresentaram os maiores teores de ferro total e bioacessível. Após o cozimento, houve um aumento da bioacessibilidade do ferro. O fígado e o coração contribuíram respectivamente com 28 e 20%, em termos de bioacessibilidade. A inserção da bioacessibilidade em tabelas de composição de alimentos é importante, pois se trata de informações nutricionais mais próximo da realidade. Foi possível quantificar o teor de Fe 2+ em todas as amostras analisadas, no entanto, o Fe 3+ só foi quantificado na amostra de carne de sol cozida e nas amostras de coração. O método empregado não foi sensível para à detecção do ferroheme e observou-se que houve um aumento do ferro iônico com o cozimento devido à liberação do ferro a partir do complexo heme. Palavras-chave:Carne; ferro; bioacessibilidade; especiação. ResumoThe content of total iron and total bioaccessible iron were determined in beef through visible spectrophotometry by the method of 1,10-Phenanthroline. The samples were cooked, dehydrated and prepared as jerked beef. They were submitted to a simulation of gastrointestinal digestion for the evaluation of bioaccessibility. Among the samples analyzed, the heart and the liver had the highest levels of total iron and total bioaccessible iron. After cooking the samples, there was an increased bioaccessibility of iron. The cooked liver and heart contributed respectively with 28% and 20% in terms of bioaccessibility The insertion of bioaccessibility in food composition tables is important, as it comes to nutritional information closer to reality. It was possible quantify the amount of Fe 2+ in all samples, however, only Fe 3+ was quantified in samples of cooked sun meat and in the samples of heart. The method was not sensitive enough to detect the heme iron and it was observed that an increase of ionic iron with cooking due to liberation of iron from the heme complex.
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