Corrected Retention Volumes of Various Adsorptives on Chromosorb W Chromosorb W-Silica Flour Columns at 100" C. Bare Columns 7 2 ' b I)C _300 _ ldded ~ _ _ Chrom. W Chrom IT' Compound Chrom. \V nith S F. Ratio Chrorn IT' nith 'i F Itatio 2 8 31 8 53 0 1; 11 5 324 n-Octane n-Heptyl aldehyde 23 0 119 0 5 2 53 0 116 0 2 2 Ethvl acetoacetate 30 0 248 0 8 3 74 2 180 0 2 4 E t h i l benzoate 57 6 421 0 7 3 214 0 540 0 2 2 6 5 180 0 134 0 2 4 Benzyl alcohol 117 5 767 0 n-Heptyl alcohol 127 0 443 0 :1 5 95 5 264 0 2 8
Table I.
hours before testing with several t "w_i c a l adsorptives at 100°C. Modification of Columns with Dow Corning 200 Fluid. Ailbout7.2% Dow Corning 200 fluid, 12,500 centistokes viscosity, was added to t h e bare columns desciibed above by t h e frontal analysis procedure using ethyl acetate as a solvent (6). Again, the columns nere conditioned a t 150" C. for several hours, then tcsted as before to determine T+ hether the adsorption effects of the silica flour might be reduced or eliminated by coating it n i t h the silicone fluid. RESULTS AND DISCUSSION
The corrected retention volumes for a few compounds of various types are given in Table I. The adsorption power of the silica flour is clearly shown since in all cases the retention volumes are markedly increased by the presence of this additive. (It should be understood, however, that these effects are exaggerated since a normal silicone grease column IT ould contain only about one fourth this relative quantity of sil-
ica flour.) The over application of Dow Corning 200 fluid had the expected effect of reducing the adsorption effects (tailing and low response-see below), but the retention volumes were still approximately doubled by the presence of the silica flour. The ratio of retention volumes n-as fairly constant' for all compounds tested when the DOKCorning 200 fluid was added, whereas considerable variation was observed on the bare columns. Presumably this is an indication of selective strong adsorption effects on the bare packings but no consistent pattern is evident from these limited data. I n addition to the increases in retention volume noted in Table I, the silica flour had a n even more serious effect' on the peak response and shape. As is typically the case in gas-solid chromatography, the peaks tailed appreciably on the packings containing silica flour and the detector response was lower for these columns than for the corresponding columns without this adsorbing contaminant ( 5 ) . These effects are
probably not too scriou.; where strong adsorption effects are riot encounttwcle.g.! hydrocarbon anulyses-but may conipletcly nullify :in a n d > polar compounds. I n fact, this work is a n outgron-th of a n att'empt to separate certain aliphatic diamines and was undcrtaken to explain the profound differences noted in the behavior of the high vacuuni grrase before and after treatments of the nature describttl herein. It, is coiiclutletl that the use of Dow Corning high vacuum grease as a gas chromatographic partitioning agent should be discontinued where only gasliquid effects are desired, and that Dow Corning 200 fluid (or its equivalent) should he used in its place. I n this connection. E 301 grease has been recommended as a suhetitutc for high vacuum grease by C'rolqier and Heywood, and needs no pretreatment (4). LITERATURE CITED
(1) Cason, J.. XIiller, K. T.. J . Orq. C ' h e ~ i . 24, 1814 (1959). ( 2 ) Cropper, F. R., private commuiiic;ation, l l a y 34, 1960. (3) Cropper, F. R., He)-wood, A , .\-nlicrc~ 174, 1063 (1951). ( 4 ) Cropper, F. R., Heywood, A . , "1-apour-phase Chromatography." p. 319, Academic Press, Xexv l-ork, 1957. (5) Keuleman?, A. I. AI., "Gas Chromatography," p. 14, Reinhold, New York, 1959. ( 6 ) Smith, E. I]., .lsar..C H E X32, 1049 (1960). ( 7 ) Teichthesen, L. -l,, private communication, June 21, 1960.
D. SMITH EDGAR Graduate Institute of TechnologyUniversity of Arkansas Little Rock, -4rk.
Determination of Trace Amounts of Diethylene Glycol in Triethylene Glycol by Gas Chromatography SIR: Several methods in the literature pertaining to gas chromatographic separations and analysis of glycol mixtures (1-4) suffer from the lack of sensitivity to trace contaminant glycols. K e wish to report a much more sensitive method for the determination of diethylene glycol (DEG) in triethylene glycol (TEG). The method is equally effective for the separation of otlier glycols such as monoethylene glycol (hIEG) and tetraethylene glycol (Tet E G ) . The lower limit of detection of D E G appears to be in the order of 5 p.p.m.
Table I. Analysis of High Purity TEG by Three Independent Laboratories (Mutually developed V.P.C. method and comparison analysis by the more sensitive flame ionization V.P.C. method) LaboraKt. % Wt. 50 Sample DEG Peak Ht. Av . DEG Area Av. tory 0 04 0 05, 0 06, 0 04, 0 05 x TEG 101 0 04, 0 04, 0 03, 0 04 0 05 0 06 0 05, 0 06 0 06 B 0 06, 0 06, 0 06 0 09 0 10, 0 09 0 10 c 0 09, 0 09 0 069, 0 O i i 0 0T3 A" 0 03 0 02, 0 03, 0 02, 0 03 A TEG 102 0 03, 0 03, 0 02, 0 03 0 03 B 0 05 0 04, 0 04 0 04 0 05, 0 05, 0 06 0 06 0 06, 0 06 0 06 C 0 06, 0 06 0 055, 0 051 0 053 'lo 0.10 4 TEG103 0.11. 0 . 0 9 , 0.11, 0.11 0 . 0 9 , 0.10, 0.10,
APPARATUS AND CONDITIONS
Instrument, Perkin-Elmer l54D gas chromatograph u-ith flame ionization detector; column, 1-meter 5% Igepal CO-880 (General Aniline and Film 1626
ANALYTICAL CHEMISTRY
a
Flame ionization method.
F i u o i ~ o ~ ~ a80 l ; (20- to SOrt'. 9 1J.s.i.; hydrogen ; air prcssurc, 26 p.s.1.; f l o ~rate, 3.3 flonmeter (40 nil. y r minutc) : c d u m n teiiipc~ature, 200" C.; injcctiori port tcmpcrature, maximum; power. 100 volts; attenuation, DEG 4> data obtained oil t h r w samples of high purity TEG :tnalyzed for DEG by three different c*heniical coriipanies, using a mutually dcvcloped gas chromatographic method.' The method in use ut,ilizes a n instrument containing a thermist'or det&or in conjunction with a %-foot 5% Chrbowax 2011 on Fluoropak column. Hcliuin is the carrier gas. Separations
Flame Ionization Method Peak ht . Area n t .
14 cm./O.lc& DEG, at 4>< 58 mg./O.l('i DEG, attenuation 1 sq. cm. = 14 mg. Conventional Method
Peak ht. 4rea w t .
0.9 cm./O.l% IIEG, a t 1 X 2.4 mg./O.l X DEG, attenuation
Since the sensitivity for the flamc method is much superior to that of the conventional method, the accuracy is considered superior. This nen method is therefore rcc*ommcnded for trace analysis n ork involving polyols-in particular, diethylene glycol. LITERATURE CITED
(1) Clifford, J., ;lnalyst 85, KO.7, 475-8
(1960).
( 2 ) Ginsberg.
Leonard,
CHEM.
SAL.
31. 1822-4 11959).
(8) kadeau, H. 6 , Oaks, I). M., Ibzd., 32, 176WL (1960). ( 4 ) Kisnien-T-ski, D. F., Stalker, G. C., Prtrol. Rejner 40, S o E, 117-20 (1961).
S.inruEL SPENCER HERBERT G. NADEAU Olin Alathieson Chemical Corp. Xew Haven, Conn.
- .. -. r . .. n . -. Activation Analysis ot Iantalum in a Niobium Matrix I
.
SIR: This method was developed a n independent check on the results ohtaincd for the determination of small :mounts of Ta in Kb by x-ray fluoresw n c r and emission spectroscopy. The intthod utilizes beta counting of a w n p l e prcpared by evaporating a solution in ;I counting cup. This technique improvcs t h r sensitivity over other activation methods dependent upon counting the gamma activity of solids :I*
(1 3 ) . PROCEDURE
Sample Preparation. Twenty-one samples of Xb205 containing various a m o u n t s of Taa05 a n d one sample of pure T a 2 0 j \\ere carefully packed in individual aluminum containers a n d iriadiated a t t h e -1rgonne Yational Laboratories. T h e neutron flux 17 as identical for all t h e samples. Previous experiments in t h e pile had indicated t h a t , within experimental error, there was no difference in activity due t o position of the individual sami-les in the pile. After about I0 days, a t a total flux dfnsity of 1.2 X IO1* neutronel w. sq. em., they w r e removed and nlloaed to stand for 4 weeks before work was started, to allow any shortlived activities to decay to a negligible Ievrl. The samplcs a e r e made up as follows: 1. Six samples of c~~mmercially pure of Nb205 prepared from the same lot of PlTb205 with known amounts of pure Ta2O5added to five of these samples. 2. One sample of pure Tan05used to make the five above samples establiqhed as a standard of 100% Ta205. 3. Four different lots of commercially pure KbL05.
.
I
L .
4. Three samples of one lot of Sbz05 \\ith added Ta2O5,S O , , TiO,, and Fe.
steel sample counting cups. Equal aliquots of the solutions, usually 0.100 nil., were deposited onto the filter paper. The sample was immediately absorbed by filter paper, uniformly dispersing the sample over the entire area. In this manner any corrections due to self-
Since the six samples of SblOs described in (1) were prepared from the same lot of S b & , each contains the same amount of Ta205 as a n initial impurity. Therefore, the intercept obtained by plotting the per cent of added Ta206as a function of activity is a measure of the original TanOB Table 1. Determination of Original To present. Present in Nb206 Counting Sample Preparation. T h e piocedure used for preparation of Sample yo TaaOj Counts/ the counting samples was based upon so. Added ?vIin./Mg. a method described by Ruben (4, 1 0 000 17.3 \\hereby total solids and counting ge2 0 195 45 4 ometry are constant for both known 3 0.292 58.5 4 0 683 114 (standard) and unknon n samples. -5 0.975 141 6 1 .XI0 266 Filter paper disks were cemented t o the bottom of I-inch diameter stainless
Sample so. 0 1 2
3
Table II. Comparison of Methods 1 and 2 Ta& 9'0 TanOs Counts/ from Based on Sample Description lIin./AIg, Fig. 1 Sample 0 Pure Ta20s 13,000 ... 100 17.3 0.140 0.132 Nb206, lot 1 with known 45.4 0.335 0.346 amounts of Tal06 58.5 0.432 0.445 added
4
5 6 7 8
9 10 11 12 13
14
High purity Nb205, lot 2 ?;b,O,. lot 3 with added impurities (Ti, Si, Fe, and Ta205) Lots of Nb20schosen a t random
114 141 266 4.8 276 626 1215 95 3 26 8 32 1 277
0.823 1.12 2.09 0.038 2.17 4 94 9 0 0 0
61
770 200 294 2 17
70Dev. from AV.
... 2.94 1.32 1.49
0.854 1.07 2.12 0.037 2.10 4 78 9 26 0 726 0 204 0 308 2 12
VOL. 33, NO. 1 1 , OCTOBER 1961
1.85
2.27 1.39 1.33 1.65 1.64 1.86 2.94 0.99 2.32 1.40
0
1627
