arc prcwnt in packed columns, although their relative magnitudes cannot be estimated. Experiments which are desiqned to solve this problem could possilily 1~ carried out by eliminating the wall effect-e.g., by roughening thc column u-alIs--or by employing a Ixicking containing prrfectly uniform c.harinc3ls. ACKNOWLEDGMENT
1'. C. H., of the ;itomic Energy Board, c y r e s w s hi. thanks for permission t o 1iarticipato in this project. LlTERATURli CITED
1) Anderson, J. R.. Sapier, K. H., ~ u s t r c d z a nJ . CIzeni. 10,250 (1957). ( 2 ) Bcrge, P. C. var,, Haarhoff, P. C., Prrtorius, V., l'ranr. Faraday Soe. 58, 2272 ( 1962 1.
(
(3) Berge, P. C. van, Pretorius. T,, Pretoria University, Pretoria, South Africa, unpublished data, 1962. ( 4 ) Bohemen, J., Purnel!: J H., "Gas Chromatograph\. 1958, I). H. Ilrstv, ed.. D. 6. Buttemorths. London. IOFih. ( 5 ) Bihemen, J., Purnell, J. H., /. C'heni. SOC.1961, 360. (6) Ibzd., p. 2630 (7) Carman, P. C., "Flow
of
(iases
through Porous Media," 13. 45, Butterworth;, London. 1956. 18) ~, Deemter. J. J. van. Zuiderwcv. F. J.. Klinkenberg, -4.,Chri~l. Eng. "hi.5 ; 271 (1956). ( 9 ) Giddings, J. C., A s a ~ .C'im>i. 34, l l S 6 (106%). (10) (iiddinga, J. C., J . C'hroiiintog. 5 , 46 (1!)61). i l l ) Giddines. J. (1.. .Ycit~(r~184. 357 11959). ( 1 2 ) Giddings, J. C., Robison, R. A , A \ IL. CHEM.34, 885 (1962).
(13) Glueckauf, E., "T'apour Phase Chromatography," I). H. Destv, ed., p. 29, Buttrrworths, London, 19.57
(14) Hartman, AI. E., Revers, C. J. H., Kraniers, H., C h r m Eng. Sci. 9, 80 (1958). (15) Kieselbach, R., ANAL. CHEM. 33, 23 (1961). (16) Turner, I). 11- , Sature 181, 1265 f 1958). (17) Wilke, C. R , Chang, P , d.I.Ch.E J . 1, 261 (1955). s. hT. GOREON
G. J. KRIGE P. C. HAARHOFF VICTORPRETORICS
I>rJpt.of Physical anti Theoretical Chemistry University of Pretoria Pretoria, South Africa RECEIIEEL) for review January 8, 1963. Resubmitted March 18, 1963. Accepted Mav 6, 1963. S. RI G is indebted to the South African Atomic Energv Board, and G. J. K to the Council for Scientific and Industrial Rrse:irch. for the :\\\ard of bursaries.
Ina dve rtent Iso merizat io n of PoIy umaturated Acids Duiring Ester Preparation Highly un.aburatet1 fatty acidslinoleic. aciti-may be inadvertently iwiiierizcd (conjuga1:ed) during the ;irc'paration of esters for gar chromatography when the nicthod involve. a saponifiration step. Daniels and Richnond ( I ) have shown in a similar study that iwnierized 11oly.insaturated acids Iiave ,+ignificantiylonger retention time. than the parent acic Y and empliasizthc iniiiortance of Liqing mild condition. for the saponification of lipids containing s m h acids durinp; the preparation of fatty acid esters for gas chromatogral)hy. 'I'hc esters of isomerized linoleic acid have an emergent time almost identiral to that of the corre:yonding ester of Iinolcnic acid when chromatographed oil a conventional 'diethylene glycwl succinate Iwlyester :degs) gas chromatograph colmnn. Because of the possibility of niisintrm-pretation of the data as a result of this inadvertrnt isomerization. the following study va.: niade. Si11:
P.A.,
EXPERIMENTAL
'l'o demonhtrate that polyunsaturated acids of a glyceride c , m be easily isonierized during the preparation of esters for ga- chromatography. methyl eqterz n e r e prepared from saffloner oil as folio\\-. ' General Ester Preparation Procedure. Aibout 200 mg;.of sample n a s reactctl with about :L 50% eycesq of p o t a s i u m hydroxide ( K O H ) in ap-
proxiniatrly 2 nil. of anhydrou- mcthaiiol. The mixture was heated on a steaiii bath until the bulk of t h e alcohol n-a. removed. Ahout 0.25 nil. of ivater wan added, and t h r iniuturr TI traces of methanol. .lbout 2 ml. of viater was added and the iiotassium soaps w r e converted to acids i\-ith 4.Y aqueous HCI. The fatty acids were extracted with hexane. and the extracts were concentrated on a steam bath. The free fatty acids were disolved in ebhyl &her and converted to methyl esters with diazomethane. The ether was removed and the esters were stored under nitrogal until chromatographed. Preparation of Methyl Esters of Safflower Oil. I n the preparation of methyl ester sample S o . 1, the saponificat'ion and methanol removal st'cps. as n-cll as other solvent removal -'tc.ps. were prolonged. The s t q ) involving the removal of the bulk of tlir niet,hparticularly p r o l o n g d to about 45 minutes. The preparat,ion of methyl eater sanii)le S o . 2 was performed as rapidly as feasible. I n addition, the step involving the removal of the bulk of the mpthanol was controlled such t'hat alcohol reinoral prior to the addition of n-ater vias not complete. Conditions for the preparation of methyl ester sample S o . 3 were Fimilar to those used for sample No. 2 n.ith esceytion that' the solvent removal stcps were performed under a nitrogen atmosphere. The methyl ester sample S o . 3 was prepared from fatty acids derived from safflon-er oil ~-1iichwas isomerized in ethylene glycol-KOH reagent a t 180" C. for 2 hours.
The nicthyl e-tcr- were chroniatographed on a Barber-Colman Jlodel 20 argon ionization detector chromatograph, equipped with a &foot X 3/lsinch 0.d. column packed with 60- to 80-meah Chromosorb IT coated with 30% by weight of degs. The qamplcx chromatographed was 50 f i g . ; gas prebsure was 17 p.7.i.g.; column, detector. and flash heater temperature. wrre 193", 206', and 332" C., rey2ectively. RESULTS A N D DISCUSSION
The rewlt. of chromatography of the-e samples are \honn in TalAe I . The weight per cent compodions (not corrected for nonlincwity of rrq)on>e) nere determined b j the conventional triangulation method. Carhoii nunihers n ere determined by the conventional graphic procedure ( 3 ) . Sample 4 1- known, by the iwthod of preparation, to contain conjugated diene. The greatly diminished prak for .ample 1 a t carbon number 19.5 (linoleic acid) and the appearance of the large peak at carbon nunitier 20.6 drongly sugge-t that the latter reprerents conjugated diene. This indication 1'; supported by thc cloy agreement betn e m the iodine valuccalculated on thii as.umption nith t h r original R'ijs iodine value. This a
