Solvents for the Paper Chromatography of Amino Acids and Sugars without Spraying Hassan S. El Khadem, Zaki M. El-Shafei, and Mohammed M. A. Abdel Rahman, Department of Chemistry, Faculty of Science, University of Alexandria, Alexandria, Egypt, U.A.R.
amino Pacids and sugars were run with the spraying agents already dissolved in the 4PER
CHROMATOGRAMS
Of
solvent mixture. This eliminated the need for their drying and subsequent spraying and in the case of amino acids enabled the movement of the spots to be followed up during the running of chromatograms and avoided their elution from the paper when the solvent was left to drip. -4mino acid mixtures containing 1% glycine, alanine, valine, and threonine were successfully separated by this procedure using the solvent systems (1) shown in Table I after addition of about 0.1% ninhydrin. Soon after the solvent front reached the amino acids, the spots acquired a pink coloration but their contours were not sharp due to tailing. This, however, disappeared when the chromatograms were removed from the solvent and left to dry at room temperature for 3 to 6 hours. The spots were then sharper than those obtained in the usual manner by spraying the chromatograms, so that a smaller amount of amino acids could be detected. Amino acids are known t o react with ninhydrin at low p H (2). We have found however that the R, values of amino acids are not altered by the addition of ninhydrin to the solvent system zuggesting that such a reaction
Table I. Solvent Mixtures for Amino Acids Solvent mixtures Volumes, ml. Wt. of ninhydrin, mg. Ethanol-water 75 :25 100 n-Butanol-2,V acetic acid 20 :20 40 n-Butanol-acetic acid-water 40: 10: 10 60 Methanol-pyridine-water 80: 4:20 100 Isopropanol-phenol-water 7:TO:25 100 Vpper layer of: n-Butanol-acetic acid-water 40: 10:50 50 (in upper layer) n-Butanol-acetic acid-water 68:5:27 85 (in upper laver) n-Butanol-acetic acid-water 40: 10:60 50 (in upper laier) 25:6:25 25 (in upper layer) n-Butanol-acetic acid-water 20:20:5:40 n-Butanol-phenol-acetic acid-water 50 (in upper layer) Table 11.
Solvent Mixtures for Sugars
Solvent mixtures Upper layer of: n-Butanol-acetic acid-water n-Butanol-acetic acid-water
does not take place during the running of the chromatograms. It is probable that this method can be applied to other solvent systems provided they do not contain a compound that gives a color with ninhvdrin such as ammonia. Paper chromatograms of sugars were run with the solvent systems shown in Table I1 which contained benzidine or p-anisidine. I n this case, the spots appeared only after drying the chromatograms at 100’ C. for 10 minutes. Mix-
Volumes, ml.
Reagent
40: 10: 50 40: 10350
Benzidine (100 mg.) p-Anisidine (60 mg. )
tures of glucose, galactose, arabinose, and rhamnose were separated satisfactorily by this method. LITERATURE CITED
(1) Bl;ck,
R. J., Durum, E. L., Zweig, G., Manual of Paper Chromatography and Paper Electrophoresis,” p. 148, Academic Press, New York, 1958. (2) Van Slyke, D. D., MacFayden, D. A., Hamilton, P. B., J. Bid. Chem. 150, 251 (1943).
Simplified Method for Determining Sensitivities in Activation Analysis B. T. Kenna, Sandia Corp., Albuquerque, N. M., and L. A. Kenna, U. S. Army Electronic Proving Ground, Ft. Hauchuca, Ariz. EVERAL RECEST P4PERS
have given
S excellent summaries of sensitivities
for activation analysis (3-5, 10). However, in the computations, specific flu^ levels and/or specific irradiation periods were assumed. Meinke (6-8) has extended thic nork by showing how the sensitivity for activation analysis can be varied and discrimination obtained using different times of irradiation. Although thwe data and compilations are important and serve a yaluable purpose, the assumption of specific fluxes and irradiation periods limits the immediate and general applicability of the data. The method for determining sensitivities in acth ation analysis described in this paper does not have these limitations. There are tn o minor drawbacks, however. nhich nil1 be discussed later. Although this method is not intended to be used evlwively in lieu of other techniques, the user nil1 find that it is a rapid niethod and that he can obtain 1766
ANALYTICAL CHEMISTRY
either accurate results or valid estimates with it. Other useful nomograms pertaining to radioactive buildup and decay are available (2, 11). However, these do not lend themselves readily to sensitivity calculations. Mesler (9) has described an excellent method whereby a rapid assessment of thermal neutron activation, in terms of the activity produced, can be obtained. For some esposure times, however, a correction factor must be applied. Equation 1 is the basis for sensitivity calculations in activation analysis
where W . is the weight of the sample nuclide, 2, in grams; A is the disintegrations per second of the product nuclide; M,is the atomic weight of 2; u is the cross section in square centi-
meters; f is the neutron flux in neutrons per sq. cm. per second; S is the saturation factor; and 8 is the fraction of the target iyotope in the element. S is defined by (1 - e - 0 . 6 9 3 T / twhere )~ T i s the irradiation time and t i s the half life of the radiation product in the same units of time as 5“. If one defines a variable, X, as X = T/t, the variation of S us. X is as shown in Figure 1. Note that a t X 2 6, S approaches the value of 1 very closely. Thus, although saturation is said to occur usually a t X = 10 ( T = lot), one may assume, for approximate calculations, that saturation occurs a t X 2 6. I n Equation 1, the true unknowns, which thus far have prevented a formulation of data of essentially general application, are u,f, and S (or X). While it would be difficult t o correlate these on a conventional X-Y or three dimensional plot, it is a relatively easy matter
