Disposable Transfer Pipets-A
Laboratory Necessity
Stephen S. ~ a w r e n c e ' Saginaw Valley State University, 2250 Pierce Road, University Center, MI 48710
Tessa L. Brandt University of Colorado, Boulder, CO 80309
It is a common occurrence in laboratories that the protective coverings for many items such a s glass electrodes, chromatography columns, and, particularly, pen caps disappear. We describe in this note a readily available and inexpensive replacement for these lost items using plastic disposable pipets (Fisher: Standard, #13-711-5Aand Graduated, #13-711-9A). I n addition to acting a s replacements for the above items, we have employed these pipets for many diverse applications. I t has been shown in our laboratories that the open end of the pipets can be sealed by either heating or immersing in melted paraffin. In addition, gentle heating has been used to reduce the pipet diameter and has also been emoloved to form molded orotective coverines. w e have divided the ~pplicationsof these pipets into two catezories-me for utilization of the bulb and stem and the &her for uses involving the stem and tip. A
Applications for the bulb and stem include: Protective cap for pH and pIon as well as many other types of glass electrodes. Placement over drainaee rack Dees . to minimize accidental breakage. Covering for bath ends of a water-filled buret during storage. Applications for the stem and tip are: Adapter for measuring flow rates from the exhaust jet of a gas chromatograph. The pipet tip and stem have been used to conned the gas jet exhaust of about U16-in. o.d. to standard 5116-in. i.d. laboratorv tuhine leadine to a flow meter. Protectrve covering for pnek~drhromato~aphyrulumnr of vanour diameters. A mct hod used to m m m m the frre space of the rmaller columns employed n glass-wool plug placed
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inside the bulb. Far capillary columns, melted paraffin and a single strand of stripped thermocouple wire (0.010-in.diameter) was placed inside the pipet tip. Upon solidification of the paraffin and removal of the wire a sealed cover with an internal hole of essentially the same dimensions as the capillary column was obtained. Replacement caps far nearly all chart recorder pens using a similar technique as described for the capillary columns. S e a l s for the outlet of polamgraphic capillaries to help prevent blockage, minimize mercury loss, and prevent the formation of obstructing oxides. Insulators for spliced wires that are much more durable than either electrical tape or heat-shrink tubing. Banana plugs for electrical connections. When the live wire is placed in the interior of the pipet and the exposed end is folded over the tip, it has been found that the pliability of these pipets provide for a tight fit into standard receptacles of many voltmeters or other electrical outlets. Placement of an appropriately wed scctton of the ppet at the sumon mlet of a water nsplraror can be made to act asa flow controller by restricting air flaw. Additional a ~ o l i c a t i o n st h a t have been used include placement of thiproperly sized section over jeweler's precision scissors, drafting tools, and lab knife blades (Xacto) followed by heating and then immersion in cold water to form customized casings. The numerous uses and aoolications of this indisoensable laboratory item are lim
