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A liquid chromatography method with indirect fluorescence detection has been developed for simultaneous detection of cysteine, cystine, homocysteine, homocystine, glutathione and glutathione disulfide. After separation in their native forms, a post-column solution of tris(2-carboxyethyl)phosphine (TCEP) at 32 mM, pH 8 is added to reduce the disulfides on-line to the corresponding thiol. The effluent is then merged with a second post-column solution of the highly fluorescent complex Cd(HQS)(2)(2-). The cadmium is complexed by the eluting thiols, effectively quenching the fluorescence. Optimization of the separation, the on-line reduction and the indirect fluorescence detection are discussed. Detection limits from 0.3-4.3 microM (0.04 to 2.6 ppm) are achieved for the six analytes in a 20 min separation.

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A low-cost and easy-to-use water recirculation system for a condenser apparatus was designed and installed in an organic chemistry teaching laboratory. Relying on gravity and a small pump for water circulation, it supplies four stations simultaneously. The water recirculation system works very well with condensers used for distillation and reflux reactions, as well as with rotary evaporators. This innovative idea has led to an annual water savings of more than 14 400 L while running only 2 lab periods per week with up to 24 students per period. Its low cost and easy installation make it convenient and easily adoptable by any laboratory where the waste of water from condensers needs to be addressed, especially in places where water scarcity is already hindering such significant scientific activities.