Table 1.
Typical Powders and Alloys Analyzed with the Pm147/AI Source
RCL-256 channel analyzer,
Sample composition Representative powders Synthetic mixtures ( 1 ) Zr02 25.66y0 Zn SnO 57.58 Sn ( 2 ) Ce02 57.13%,Ce NiO 8 . 1 2 Ni PbO 18.04 Pb
NBS portland cement #lo14 Si02 19.495% CaO 63.36 Fee02 2 . 5 0 Typical alloy NBS 1204 Cr
Ni
Mo
12.75y0 70.6 4.28
peak height Found Deviation, 7,
Miniaturized apparatus (Rustrak recorder). peak height Found Deviation, yo
26.34 55.99 57.14 8.12 17.49
+2.65 -2.76 0.0 0.0 -3.05
27.5 58.1 58.1 8.6 16.9
63 39 2.47
:
+o. 05 -1.20
63.1 2.6
-0.4 +4.0
12.82 69.31 4.19
+0.55 -1.83 -2.10
11.9 70.4 4.1
-6.7 -0.3 -4.2
...
+7.2 +0.9 f1.7 +5.9 -6.3 ...
ides from t h e following: COO, NiO, ZrO,, SnO, CeO,, a n d PbO. Figure 3 depicts a typical set of curves obtained from a group of standard 'ternary mixtures. The NBS cements analyzed were portland cements 1011, 1014, and 1016. It is possible to analyze the cements only for the CaO and FetOa content. The alloys analyzed were the NBS series 1190, 1203, 1205, and 1204. The results are shown in Table I. The samples were analyzed both with a multichannel analyzer, and with the miniaturized single channel analyzer and Rustrak recorder. LITERATURE CITED
(1) Goulding, F. S., Robinson, L. B., At. Energy Comm. Ltd., AECL 767, CREL 778 (January 1959). (2) Karttunen, J. O., Evans, H. B.,
Henderson, D. L., Markovich, P. J., Niemann, R. L., ANAL. CHEM. 36,
ventional fluorescent x-ray unit is that a radioisotope source replaces the x-ray tube, and that the proportional counter not only detects the characteristic radiation but also resolves the radiation, thereby eliminating the need for a dispersive crystal. The finite resolution of the detector rauses some difficulty in situations where
the components are separated by one atomic number. I n such cases, peak shift, selective filtration, or unfolding techniques, etc., must be used. I n cases where A 2 2 2, the conventional straightforward analytical procedures are used. Applications. T h e powder mixtures analyzed quantitatively include ox-
1277-1282 (1964).
JOHN 0. KARTTUNEN DALEJ. HENDERSON
Chemistry Division Argonne National Laboratory Argonne, Ill. 60440 Work performed under auspices of U. S. Atomic Energy Commission.
Possible Errors in Interpreting Results of Two Channel Gas Chromatography SIR: In some recent developments in the field of two channel gas chromatography (1,%'),acertain assumption has been made that is not warranted and could give misleading results. This assumption is that two peaks from the same column in two different detectors that vary in retention times by even a few seconds can be positively stated to represent two different components. This situation is best illustrated in peaks B and I31 in the figure from Reference ( 2 ) . There is, however, at least one possible case where this assumption will not be true. Let us assume that the detector represented by the upper curve is sensitive to two Components h and R having overlapping peaks, while the lower detector is sensitive to only component A. This situation is illustrated in Figure 1. Keulemans (3) has shown that, the effect of a n unresolved impurity on a peak can shift the retention time of the
peak maximum. This effect will be to shift the maximum of the peak in the
upper curve but not in the lower. As a result, we now observe only C in the upper curve and A in the lower and the two have different retention times. If, observing this result, we applied the above assumption, we would conclude that C and A must represent different substances while they, in fact, represent the same major component. Considering the complexity of the natural materials now being investigated by two channel chromatography and the widely varying sensitivities of different detector systems, the possibilities for errors of this type should be kept in mind. LITERATURE CITED
Oaks, D. M.,Hartrnann, H., Dimick, K. P., ANAL.CHEM.36, 1560 (1964).
(1) A (observed)
Figure 1 . Situation where one detector is sensitive to two components (upper curves), while other detector is sensitive only to component A (lower curve)
(2) Ibid., No. 10, 36, 82A (1964). ( 3 ) Ettre, L. S., Ibid., No. 8, 31A (1964).
C. L. TEITELBAUM Coty, Div. Chas. Pfizer & Co., Inc. 423 West 55th St. S e w York, N. Y. 10019 VOL. 37, NO. 2, FEBRUARY 1965
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