scintillator to rliminate pliosphorescence observed in the liquid scintillation counting of certain proteinaceous materials. Accordingly, a scintillator system n-as prepared cont'aining xylene (500 nil.)l dioxane (500 nil.), ethyl alcohol (300 ml.) resublimed naphthalene (102 g r a m ) , PPO (6.5 grams), anc-l POPOP 10.13 gram), which will dissolve aqueous acid. To test this system a chromatogram was run b y the ascending technique with five spots of Cl4-1abeled salicylic acid ranging in activity from 313 to 7400 d.p.m. The solvent system used was henzeiie-glacial acetic acid (8 to 2). Upon spot visualization by spra>-ing with ferric nitrate solution. a circle 6.2 sq. cm. in area n-as inscribed about each spot and the spot was cut out and transferred to a vial cont,:hing 15 ml. of the sylcne-dioxane-ethj.1 alcohol scintillator. Counting of these samples before acidification again showed abnorinally high count rates (141 to 2100/, of theoretical), whicli did not decrease with time under the storage conditions mentioned above. Upon the addition of 25 pl. of concentrated hydroc,hloric acid to each jample. the counting rates ~
recorded (Table 11) indicate an essentially linear relationship betn-een applied and observed activities.
Table I. Count Rate Data on Ci4 on Filter Paper in Toluene-Based Scintilla tor I'aper Area, C.P.M. Sq. Cm. Recorded % Theoretical" 2.3 7, 705 616 2.8 3.8 4.6
7.5
19,900 3,940 2,700 1,620
1580 314 216 129
1250 d.p.m. represents 100yo activity.
Using R h a t m a n S o . 1 filter paper and the scintillator system described, the procedure outlined is valid for the quantitative radioassay of C I4-labeled salicylic acid on paper chromatograms. Acidification of the scintillator eliminates the s p r i o u s count rates observed in nonacid media. TF'orkers using different types and grades of paper or different scintillator systems should evaluate their procedure individually to
Table II. Count Rate Data on CI4 on Filter Paper in Acidified XyleneDioxane-Ethyl Alcohol-Based Scintillator Bctivity Activity Applieda Observedb 7 0 Theoretical 313 1480 2960 4440 7400
*
74
23.6 21.4 23.3 24.1 26.0
316 688 1069 1922
D.p.m CI4 activity. C.p.m. corrected for background.
establish counting efficiencies under specific conditions. LITERATURE CITED
( 1) Bousquet, W. F., Christian, ,J. E.,
J . A m . Pharm. Assoc., Sei. Ed., in press. ( 2 ) Herberg, R. J., Science 128, 189
(1958).
F. BOL-SQEET JOHN 11:. CHRISTIAS Bionucleonics Department Purdue University Lafayett,e, Ind. WILLIani
RECEIVED for review January 28; l!)CiO. Accepted Llarch 7, 1960.
Gas Chromatographic Retention Time of Formaldehyde SIR: I n studying the carbonyl components in smoke from cigar tobacco, it was found convenient to separate and fractionate these component's through the medium of their 2,4-(1initrophenylhytlrazonts ( D X P H ' d , For identification purposes, the flash exchange gas chromatographic method of Ralls ( 2 ) was used. X series of known DXPH's was run , t o establish retention times. Among these samples as formaldehydeDW'H. d formaldehyde peak could not be. seen when a short (&foot Craig polyester-succinate) column was used, because of its proximity to the large carbon dioxide peak. (The carbon dioside arises from decarboxylation of the a-ketoglutaric acid eschanger.) Hon-ever, when a longer column (10foot' Carbonax 20x1) was used, a formaldehyde peak was easily detected. Until this time, apparently no one
had been able to report a retention time for formaldehyde ( 1 ) . Presuniabl?- this was due to the difficulty of maintaining the monomer in liquid form for injection into a gas column by yringe. Therefore, the method of Ralls is offeied as a very simple and convenient n a y to obtain this retention time. Although our o n n e-,pericnce ha. been limited, it is felt that any pas chromatography column capable of resolving carbonyls could be used, p r o d e d it is long enough. I n obtaining a retention time for formaldeh) de of 2.30 minutes, our operating conditions IT erp :
Helium flow. 32 ml. per minute. Recorder. 2.5 mv., 3-second pen speed, 30 inches per hour.
Column. Carbon ax 2011 on Chroniosorb (35/80 mesh), 10 feet, in stainless steel ('/a-inch). Detector. 4-filament thermal coilductivity cell. Detector current. 300 ma. Temperature. 90" i 0.3" C.
I ~ E C E I Vfor E Dreview February 4, lY(i0. -1ccepted March 7, 1960. Work supported in part by funds made available by the Cigar hlanufacturers Association of America, Inc. Atention of a specific commercial product does not constitute endorsement by the United States Department of Agriculture over others not named.
LITERATURE CITED
(1) Gager, F. L., Jr., Philip IIorris, IIIC., Richmond, T'a., private communication. ( 2 ) Ralls. J. W.,,4s.4~.CHEM.32, 33'7 (1960).'
A . I. &!HEPkRTZ P. E. ~ ~ C D O U - E I . L
Eastern Utilization Research and Development Division hgricultural Research Service United States Department of Agriculture Philadelphia 18, Pa.
VOL. 32, NO. 6, M A Y 1960
723
