A "wash-out pipet system" for sampling red blood cells.

For studying plasma and red blood cell (RBc) electrolytes, we have developed a method that allows frequent accurate and reproducible sampling of both plasma and RBC. We determined that for our purposes, a 1.0-nil volume of sample was optimum. Although the 1.0-nil “Class A” Ostwald-Folin blow-out pipet and the standard “Class A” transfer pipet were adequate for sampling plasma, they were not adequate for sampling RBC. When either of these pipets was used, the RBC clumped together at the tip of the pipet, clogging the narrow orifice. Use of a serological or measuring pipet with a larger orifice eliminated the clogging problem, but presented a new problem: a large and variable volume of RBC remained on the walls of the pipet, with a resultingly unpredictable volume being delivered. Consequently, we developed the “Wash-Out Pipet System” for sampling RBC that is described here.