decomposition, a judicious choice of absorption tubes or cold traps placed in the system should permit the detection and measurement of the one gas of primary interest. ACKNOWLEDGMENT
The authors are indebted to Donald R. Dickerson, David B. Heck, and Sei1 R. Shimp for their helpful discussions and assistance during portions of this work. LITERATURE CITED
(1) Bessey, G. E., J . SOC.Chem. Znd. 5 8 , 178 (1939). ( 2 ) Carpenter, F. G., AXAL.CHEM. 34, 66 (1962).
(\ 3- ,) Clarke. B. L.. Hermance. H. W.. IND. ~
~
ENG.CHEM.,ANAL.ED. 9, 597 (1937). (4) Colson, A. F., Analyst 6 5 , 638 (1940). ( 5 ) Daeschner, H. W., Stross, F. H., ‘ ANAL.C H E ~34, . 115i) (1962): (6) Dimbat, M., Porter, P. E., Stross, F. H., Zbid., 2 8 , 290 (1956). (7) Doerffel, K., Chem. Tech. 6,391 (1954). (8) Fuller, C. H. F., Analyst 70, 87 (1945). (9) Galle, 0. K., Runnels, R. T., J . Sediment. Petrol. 30, 613 (1960). (10) Haley, A. J., J . A p p l . Chem. (London) 13, 392 (1963). (11) Hillebrand, W. F., Lundell, G. E. F., “ADdied Inorganic Analvsis.” ” , .D. 623. a i i & , New Ygrk, 1929. (12) Kolthoff, I. AI., Sandell, E. G., “Textbook ’ of Quantitative Inorganic Analysis,” 3rd ed., p. 372, hIacmillan, Xew York, 1952.
(13) Pielsen, F. &I., Eggertsen, F. T., ANAL. CHEM.30, 1387 (1958). (14) Pobiner, H., Ibid., 34, 878 (1962). (15) Schollenberger, C. J., Whittaker, C. W., Soil Sci. 8 5 , 10 (1958). (16) Stevens, R. E., and others, U. S. Geol. Survey Bull. 1113, 126 pp., (im). (17) Thhmas, J. Jr., Hieftje, G. M., Orlopp, D. E., ANAL. CHEY. 37, 762 (1966). (18) Williams, D. E., Soil. Sci. SOC.Am., Proc. 13, 127 (1948). (19) Wise. K. V.. Lee. E. H.. ANAL. ‘ CHEX 34, 301 (1962).‘ \ _ _ . _
JOSEPHUS THOMAS, JR. GARYhl. HIEFTJE Illinois State Geological Survey Natural Resources Building Urbana, Ill. 61803
Fructose-Reso rcin01-H yd rochlo ric Acid Test for Detection and Determination of Acetaldehyde SIR: While investigating various procedures to determine fructose by means of the resorcinol-hydrochloric acid test, we found that the wavelength of maximum absorption (Amax) was shifted from 480 mp to 555 mp when acetaldehyde was incorporated in test mixtures which contained a high concentration of hydrochloric acid (2, 8). R e used this finding to develop a new, highly sensitive test for the qualitative detection or quantitative determination of acetaldehyde. The purpose of the present communication is to describe this new test which provides an alternative with different specificity to the sodium nitroprusside test for acetaldehyde (.$). EXPERIMENTAL
Apparatus a n d Reagents. Absorbance measurements were made with a Beckman DU spectrophotometer a n d 1-cm. borosilicate glass cells. Acetals, aldehydes, and acetone were purchased from commercial sources, and all liquids were purified by distillation prior to use. The resorcinol reagent was prepared just before use by adding 100 ml. of concentrated hydrochloric acid (specific gravity 1.188-1.192) to 10 ml. of aqueous resorcinol stock solution (1.2 x lO-?JI). Procedure for Quantitative Determination. T h e reaction was carried out in diffuse light. T o a boiling tube (25 X 150 m m . ) was added 1 ml. of 4.0 X 10-4JI fructose solution and 1 ml. of acetaldehyde solution. The tube was covered with a glass marble, cooled in an ice bath for a t least 3 minutes, and the resorcinol reagent (10 ml.) was added. The contents were mixed in the ice bath and cooled for a further 3 minutes. The tube was placed in a water bath a t 20” C. for 4 minutes, heated for 10 minutes a t 80” C.,
cooled for 1.5 minutes in an ice bath, and the absorbance was measured 10 minutes later at 555 mp against a blank in which water had been substituted for the acetaldehyde solution. Procedure for Qualitative Detection. T h e same procedure as for the quantitative determination was used except t h a t t h e rigid time schedule was not required. T h e test solution and the blank were heated for 10 minutes at 80’ C. or for 2.5 minutes in a boiling water b a t h , cooled in a n ice bath, and compared visually. A positive test was indicated by a red tinge to the test solution. The blank was light-orange. RESULTS AND DISCUSSION
The absorption spectra of colored solutions obtained using a procedure comparable t o that described above have been published ( 2 ) . The absorption spectrum of EL test mixture containing acetaldehyde, after correction for the blank, has maximum absorbance at 555 nip. The curve of color development showed that the absorbance of 555 mp reached its maximum and \yas constant between 9 and 12 minutes of heating at 80” C. It decreased thereafter with longer heating time. Fading of the color after completion of the test was almost linear during the first hour, being 87, after one hour in artificial light or in the dark. The color fades drastically on exposure t o sunlight. Beer’s law was adhered to for solutions containing u p to 100 mpmole of acetaldehyde per ml. As expected from previous results ( 2 ) , the slope of the straight line increased slightly when acetaldehyde was diwolved in purified acetic acid rather than in mater. The amount of fructose (0.4 pmole) in the
proposed procedure was selected because if affords the best compromise between sensitivity of the test, range of adherence to Beer’s law and size of blank. The .mallest amount of acetaldehyde which may be visually detected is 10 mpmole per ml. or 0.4 p.p.m. The respor se of carbonyl compounds and acetal3 cnder standard test conditions may be divided into four groups and is shown in Table I. Group I comprises acetaldehyde and 1,l-diethoxyethane which afford identical results within experimental error. 1,lDiethosyethane is hydrolyzed to acetaldehyde under test conditions. Group I1 is made up of propionaldehyde and butyraldehyde which, if present, would invalidate the determination of acetaldehyde. It is probable that higher n-aliphatic aldehydes would also interfere. Compounds with a phenyl ring are placed together in group 111. M‘hile these compounds might interfere somewhat with the determination of acetaldehyde, their presence in mixtures can always be detected as they have a different position of A,, (Table I). Other carbonyl compounds are included in group IV. These compounds will not cause interference unless their concentration greatly exceeds that of acetaldehyde. The acetaldehyde content of eight brands of 99.5+% acetic acid as determined by the fructose-resorcinolhydrochloric acid test varied from 10 to 486 mpmole per ml. Acetic acid prepared by present methods ( 5 ) should contain no aldehyde other than acetaldehyde. S o trace of propionaldehyde or butyraldehyde was found in the single brand of acetic acid examined earlier ( 2 ) . The single brand of absolute ethanol analyzed contained 195 mpmole of acetaldehyde per ml. VOL. 38, NO. 3, MARCH 1966
503
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
