Um aparato para monitorar reações rápidas: um "stopped-flow" artesanal de baixo custo

• Main Authors: Vagner Roberto Batistela, André Luiz Tessaro, Rafael R. da S. Soares, Vagner Roberto de Souza, Noboru Hioka
• Format: Article
• Language: English
• Published: Sociedade Brasileira de Química 2006-10-01
• Series: Química Nova
• Subjects: stopped-flow; kinetics; fast reactions
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422006000500034&lng=en&tlng=en

The modern stopped-flow reaction analyzer has shown high efficiency and flexibility, which provides outstanding sample economy with a dead-time of less than 1 ms. However the cost of the equipment imposes a serious restriction to many Brazilian scientists and teachers. In this work we describe the construction of a low-cost stopped-flow system coupled to a UV-Vis spectrophotometer. The performance of the system was checked by monitoring the kinetics of two reactions: the fading of phenolphthalein in aqueous alkaline solution and the chlorophyll a demetallation in acid medium. The apparatus showed reasonable efficiency with a dead-time of 0.3 to 0.5 s. The very good results obtained in these two illustrative processes show that the system is satisfactory for determining rate constants with mean reaction times ranging from seconds to minutes.