sheathed oxyacetylene, the calcium ion lines 3934 and 3968 1.were as intense as the 5540 CaOH band. I n rich (incandescent) Oxyacetylene, the magnesium line 2852 A. gave a net reading equal to one-third the background. As for precision, readings could be reproduced within 1%, provided the slurry was stirred before reading. Even after settling for many minutes, as during a spectral scan, the intensities dropped very little. Thus, a scan repeated without stirring showed an intensity loss of 5% for manganese and strontium, 12% for iron, 15 to 2070 for aluminum, 10% for rubidium, and less than 1% for sodium and potassium The different behavior of the elements may be due to the heterogeneous nature of the sample and the different composition of particles of different sizes, and perhaps the different volatilities of the elements from particles of a given size. Also, some sodium and potassium may have passed into true solution. It is obvious that a n undissolved, suspended material develops a full,
intense spectrum in the flame, even revealing certain trace elements. The slowly spraying, combustible organic suspending medium helps to keep the flame temperature high enough for efficient vaporization and escitation. Much higher solids contents can be handled in suspension than in solution without difficulty from incrustation a t the atomizer tip. Reproducibility seems to be comparable n i t h that available with dissolved samples, and it is an order of magnitude better than that of earlier polTder methods. There has been no opportunity in our laboratories for further study of this method of powder sprayin%. Prohlcms calling for attention include the effects of particle-size distribution on sensitivity and reproducihility, the choice of medium, the consequences of partial solubility of the sample, the action of interferences under these novel conditions, the preparation and nature of standards, and the possibility of determining minor constituents n ithout separations or difficult elements (alu-
minum, silicon) by proper choice of flame conditions. This method of introducing solid sample into a spectrochemical source should be equally applicable to atomicabsorption spectrometry, spark-in-spray and arc-in-spray techniques, and plasma-jet spectrometry. LITERATURE CITED
(1) Cullum,
D. C., Thomas, D. B., '4nalyst 84, 113-6 (1959). ( 2 ) Ibtd., 85, 688-9 (1960). (3) Garman, V. F., U. S. Patent 2,836,097 (Mav 1958). ( 4 ) Gilbert, P. T., Jr., Analyzer (Beckman Instruments, Inc.) 2 , No. 4, 3-6
(Oct. 1961). ( 5 ) Mavrodineanu, R., Boiteux, H., "L'analyse spectrale quantitative par la flammp," p. 65, Masson, Paris, 1954. (6) kfonvoisin, J., Mavrodineanu, R., Specfrochim. Acta 4, 396-9 (1951). PAUL T. GILBERT, JR. Beckman Instruments, Inc. Fullerton, Calif.
RECEIVEDfor review April 2 , 1962. Accepted hpril 30, 1962.
Comparison of Theoretical and Experimental Efficiencies in Glass Bead Gas Chromatography Columns SIR: Recent developments in the theory of chromatography have led to the suggestion that the performance of packed columns might be quantitatively predicted in terms of theoretical expressions and experimental data acquired in nonchromatographic experiments (a). Such a breakthrough would be of great practical significance in the search for new support materials and the characterization of known supports. Results are given beiow which verify the theoretical predictions regarding glass bead columns. These preliminary results are given here because this is, to the authors' knowledge, the first time in which column plate height has been successfully predicted using nonchromatographic experimental rate data. Even in the case of cxpillniy columns the rate data have been obtained from empirical formulas nith a possible error f:ictor of 4, and the calculated values are fiom 1.75 to 7 times too small ( I , 7 ) . AIthough the present e-qerimental results m e a t this time far less refined than those obtained on capillary columns, the agreement is better. Thus on a column with 0.25Yc liquid phase, n hich i q a good 1)ractical as ne11 as theoretical 1026
ANALYTICAL CHEMISTRY
value, the average theoretical result is too small only by a factor of 1.3. The predicted variation of plate height with particle size is in excellent agreement with experiment, and the variation with liquid loading is in satisfactory agreement. The experimental work \vas done using 2-meter '/,-inch copper columns packed with borosilicate glass beads of 0.540- and 0.976-mm. average diameter. The stationary phase, tri-otolyl phosphate (TOTP), \vas used in amounts ranging from approximately 0.1 to l . O ~ , . After preparing and packing in the standard manner, the columns nere conditioned a t 12.5' C. for 10 hours. Helium \vas used as the principal carrier gas, and all measurements xere made a t 50' C. The plate height was calculated using the peak nidth a t half height. The liquid diffusion coefficients n ere found by applying a thin layer of solute onto a column of TOTP contained in a glass capillary held a t 50" C. The concentration profile wab evaluated by extracting samples directly from the capillary using a syringe and injecting them onto a chromatographic column in which T O T P iyas the stationary phase. A more detailed description of
the experimental procedure will be reported later. The results discussed here refer to the high velocity (nonequilibrium controlled) plate heights which are of the great'est theoretical interest. The C term was obtained as the slope of the Hv vs. v2 plot ( H = plate height, v = flow velocity). As the results were nearly identical whether He or X2 was used for the carrier gas, i t was assumed that the liquid phase term, Ce, could be employed (to a first approximation) in place of the over-all term, C. The generalized nonequilibrium theory of chromat'ography (3, 4)has been used to formulate (2, 5) the Ce term for glass bead columns st' low liquid loads (
