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A Spectrophotorneter Cell Stopper for Syringe Transfer
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In mak~n~:spcctroprmtnmetrw measurements on s d u r r n s "f a~r-jensiti\ereagent;. whkh art uzuall) rransferwd hv hvpodprmlr s>rinyc, thrrr nrr ieverul difficultir- acsw~atedwith the us? 01 serum taus ns cell stonners. olthe rubber rerum cnp t o n t ~ n o s p h t r ~ c .. .\munr t h r n ~are rhe vrrmc~l~ilitv " " oxygen and the possible contamination of the sample by sulfur from the rubber. We have constructed, from Teflon, the stopper shown in the figure. The assembly holds between two threaded components a soft rubber disc which can be easily replaced. The bottom of the stopper is tapered slightly t o fit snugly into the neck of a spectrophotameter cell. The stopper substantially reduced the area of rubber exposed to the air and also extends the distance between the solution and the rubber surface. The prototype has withstood two years of continuous use.
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Henrique E. Toma John M. Malin Universidade de SHo Paulo Caixa Postal 20780, Sao Paulo, SP, B r a d
272
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Journal of Chemical Education
