Table 1. Specificity of Fructose-Resorcinol-Hydrochloric Acid Test
Response, b
Compounda 7% 1,l-Diethoxyethanee 99 Acetaldehydec 100 I1 Butyraldehydec 74 Propionaldehydec 71 I11 Benzaldehyded 19 Phenylacetaldehyded 9 IV Formaldehyde 3 2 Diethoxymethane iso-But yraldehyde 2 Acetone 1 Glyoxylic acid 1 Glycolaldehyde 0 a 70 mumole. Absorbance of compound x 100. Absorbance of acetaldehyde Amax at 555 mp. Amax at approximately 570 mp.
Group I
The test should also be applicable to the determination of acetaldehyde in biological fluids where no interference from either propionaldehyde or butyraldehyde would be expected. A possible use, where the lack of formaldehyde interference would be desirable, is to determine acetaldehyde obtained by
periodate oxidation of 2,3-butanediol in fermentation solutions, of rhamnose in hydrolysates of polysaccharides or glycosides, and of threonine in protein hydrolysates. The test could also be used with advantage to determine combined acetaldehyde (3) since no hydrolysis step would be required. The fructose-resorcinol-hydrochloric acid test may be used for aliphatic aldehydes other than acetaldehyde. The wide range of reactivity of aliphatic aldehydes toward the test is encountered in other color reactions (6, 7 ) . However the specificity shown in Table I is different from that of existing methods such as the 3-methyl-2-benzothiazolone hydrazone test ( 7 ) , the o-aminobenzaldehyde-methylamine test ( I ) and the anthrone test (6) for aliphatic aldehydes. A particular need may eventually arise for a test of this specificity which suggests, for example, that it be used for detection or determination of total naliphatic aldehydes other than formaldehyde, of propionaldehyde or butyraldehyde in the presence of formaldehyde, or of butyraldehyde in the presence of iso-butyraldehyde. The chemistry of the reaction leading to color formation in the presence or absence of acetaldehyde has already been discussed (2). The use of fructose
in the proposed test is merely a convenience because it is readily available, An acid degradation product of fructose such as 5-(chloromethyl)-2-furaldehyde could be used in lieu of fructose. ACKNOWLEDGMENT
The authors are grateful for the competent and willing assistance of J. C. Berrigan. LITERATURE CITED
(1) Albrecht, A. M., Scher, W. I., Jr., Vogel, H. J., ANAL. CHEM. 34, 398
(1962).
(2) Arsenault, G. P., Yaphe, W., Anal. Biochem. 13, 133 (1965).
(3) Bowman, M. C., Beroza, M.,Acree, F., Jr., ANAL.CHEY.33, 1053 (1961). (4) Clancv, D. J.. Kramm. D. E.. Ibid.. 35, 1987 11963).’ (5) Faith, W. L., Keyes, D. B., Clark, R. L.. “Industrial Chemicals.” -2nd ed.. p. ll,‘Wiley, New York, 1957: (6) Kwon, T. W., Watts, B. M., ANAL. CHEM.35,733 (1963). ( 7 ) Sawicki, E., Hauser, T. R., Stanley, T. W., Elbert, W., Ibzd., 33,93 (1961). (8) Yaphe, W., Arsenault, G. P., Anal. Biochem. 13,143 (1965). -
7
G. P. ARSENAULT W. YAPHE Atlantic Regional Laboratory National Research Council of Canada Halifax, N. S., Canada
Conductometric Method for the Determination of Carbon on the Surface of Nickel Strip SIR: It is often necessary to know if the concentration of carbon on the surface of a metal differs significantly from the bulk concentration. Such difference may be the result of contamination by lubricant or other organic material. For metals that are to be used inside a n evacuated enclosure , the detection-and elimination-of surface carbon is important to the maintenance of high vacuum. I n devices which are sensitive to surface properties of materials, serious problems may arise from high concentrations of carbon on the surface. Therefore, an application of the conductometric method for the determination of carbon ( 1 ) on Ni strip has been developed which is based on the difference in oxidation rate between surface carbon and bulk carbon. The procedure and apparatus are generally the same as those used in ordinary conductometric carbon analysis. The temperature of combustion, however, is 600’ C., considerably below the usual combustion temperature. At this lower temperature the surface carbon is immediately oxidized, while the rate of oxidation of bulk carbon is diffusion limited. ThereSO4
ANALYTICAL CHEMISTRY
SLOPE DUET0 SAMPLE t SYSTEM
I
bustion train. There is another blank due to oxidation of carbon which has diffused from the interior. Both blanks are subtracted together by extrapolating the line marked “slope due to sample system’’ back to tl, reading RI and calculating A R1. If t 2 - tl is a constant time interval and if the samples do not differ markedly in dissolved carbon content, a constant blank may be subtracted from R2. When the method was applied to a suspect sample of Ni strip, 0.002 inch thick, about 3.9 X 10-5 gram/sq. cm. of carbon were found. Because the sample had been previously cleaned by treatment with trichlorethylene vapor, more rigorous cleaning was clearly indicated. Obviously the method can be applied to other materials and other problems, e.g. rate of diffusion of carbon.
+
TIME
Figure 1 . Diagram of solution resistance during determination
fore, there is a distinct difference in slope when resistance is plotted against time as in Figure 1; the abrupt increase from tl to t2 is due to oxidation of the surface carbon, but the slow increase in resistance after t2 is due to the oxidation of dissolved carbon diffusing to the surf ace. A typical run, therefore, would start with a thorough flushing of the sample and system with oxygen until the resistance becomes stable: either constant or regularly increasing. The regular increase is a system blank and may be due to carbon contamination in the oxygen or in any parts of the com-
LITERATURE CITED
(1) Bennet, E. L., Harley, J. H., Fowler, R. M., ANAL. CHEM.22, 445 (1950).
I. S. SOLET
Radio Corporation of America Electronic Components and Devices Somerville, N. J. 08876
