2020
ANALYTICAL CHEMISTRY
absorption (8-4). The present procedure utilizes the high sensitivity and flexibility of the Cary recording spectrophotometer to scan the paper strip at predetermined wave lengths and t o obtain an absorption spectrum of individual separated spots.
to scan the strip. Absorption spectra on the separated spots serve to identify the separated components. The record obtained by scanning the paper strip across the beam a t a. fixed wave length shows changes in absorption with distance dong the strip. The absorption of spots must be significantly higher than randomvariations in absorption and scattering of the paper t o permit ready recognition of the spats. This involves both the amount and absorptivity of the component. For quantitative work, it has been found desirable t o run a "baseline" manning curve on each individual strip. The strips for such quantitative chromatographic analyses are numbered and scanned in advance at each wave length to be used in scanning the developed chromatograms. These techniques have been applied to the identification of antibiotics, the separation and identification of alkaloids, and the simultaneous quantitative analysis oi four water-soluble vitamins(1).
The device shown in Figures 1 and 2 has been constructed to replace the sample cell-well cover of the Cary spectrophotometer and to provide a means of transporting a 0.75-inch paper strip
0.75-inch t&k unit. When inch p&er strim ;a used, the beam smm about 93% of the width o f - t h e stGp. The paper strip i8 held in 8. channel close to the photdube port to utilize ss lame a solid anele of scattered radiation as oossible. I n this wav most of the li&t nassine. through the pa& is collected bv thk photomultiplier, i i spite of t h e f a c t tha6 essentially all df the light has been scattered. A simple adjustable slit variable from 0 to 0.5 inch permits variation in "resolution" of spots on the chromatoeram. The strio is transoorted bv rubher-covered rollers d r k n by a. synchionous clnik motor "at 3 r.p.m. The rollers bear against small free-turning brass rollers. A 15-inch paper strip can be scanned in appraximstely 2 minutes.
ACKNOWLEDGMENT
The authors gratefully acknowledge contributions to this project, by F. R. Van Abeele, J. A. Brown. and Elmer Lee. LITERATURE CITED
(1) Brown. J. A,, and Marsh, M. M., ANAL.CEEM.,24, 1952 (1952). ( 2 ) Haines, W. J., and Drake, N. A,, Federation Proc., 9, 180 (1950). (3) Sober. H. A., and Kegeles, G., private eommunioation, 1951. (4)
Tennent. D. M.. Whitia. J. B.,and Florey, K., ANAL.CHEM.. 23, 1748 (1951).
P ~ E ~ E N before T E D the Division of Analytioal Chemistry a t the 122nd Meeting of the Aanmrcm CH=MIC*LSOO~ETI, Atlantic City. N. J.
Simple Pipetter. S. L. Hood, University of Tennessee Atomic Energy Commission Agricultural Research Program, Oak Ridge, Tenn. plpetters are necessary in handling radioactive, toxic,'or fuming liquids and are useful generally. A simple hand pipetter has been developed and used for over 2 years by workers in this laboratory. It is preferred over several other such devices available. The flexibility and ease of control of the old method of mouth pipetting are retained. The pipetter is inexpensive, made quickly from common materials, requires no experience to use, and e m be used with m y macropipet. It is practical to have a large number available so that, one can be set aside or discarded if contaminated. AND
Figure 2.
Paper Strip Transporting Mechanism of Soanning Device
The pipetter, shown in the illustration, is assembled from a I-em. rubber disk cut fromGooeh tubing, a rubber bulb of 10- to 30-ml. c& paeity, and a No, 18 to 23 hypodermic needle. The smaller sized needles are best used with the 10ml. bulbs. The needle is broken off to 3/10 inch in length, and the tipfiledsmooth. Theneedleshank is inserted into the bulb, and t h e , pierced disk slipped on the tip. : Flexible 1- t o 4-onnee plastic.. bottles can be substituted for the ruhber bulb, although they are stifferthan the bulbs. The needle is inserted through the cap from the inside nut and the cap screwed on tightly. The rubber disk must be used, as the cap is not flexible enough to make a seal with the pipet. In use the pipet,is manipulated as in ordinary mouth pipetting. The pipetter is held in one hand, and the pipet in the other. The needle is inserted as a guide into the bore of the pipet, the rubber '
~~~~~~
.~~~ ~~~~
~
~
~~
than 15 ml. require more than onehra; with the pipetier to fin.
