LITERATURE CITED
( 1 ) Bjerrum, J., “Metal Ammine Forma-
tion in Aaueous Solution.” P. Haaae and Son, dopenhagen, 1941. (2) Cheng, K. L., ANAL.CHEM.27, 1582
(1955).(3) Cheng, B. L., Bray, R. H., Ibid., 27, 782 (1955). ( 4 ) Cheng, K. L., Williams, T. R., Jr., Chemist Analyst 44, 96 (1955). (5) Euler, H., B o b , I., 2. physik. Chem. 66, 71 (1909). (6) Flaschka, H., Abdine, H., Chemist Analyst 45, 2 (1956). (. 7. ) Flaachka, H., Abdine, H., Mikrochim. Acta 1956,.770’.
(8) Flaachka, H., Sadek, F., Chemist Analyst 47, 30 (1958). (9) Flaachka, H., Sadek, F., Mikrochim. Acta 1957, 1. (10) Freiser, H., Charles, R. G., Johnston, W. D., J . Am. Chem. Soc. 74, 1383 (1952). (11) Gill, H. H., Rolf, R. F., Armstrong, G. W., ANAL.CHEM.30, 1788 (1958). (12) Goldstein, G., Manning, D. L., Menis, O., Ibid., 31, 192 (1959). (13) HniliEkov6, M., Sommer, L., Collection Czechoslw. Chem. Communs. 26, 2189 (1961). (14) Iwamoto, T., Bull. Chem. SOC.Japan 34, 605 (1961).
(15) Langmeyer, F. J., Kristiansen, H., Anal. Chim. Acta 20,524 (1959). (16) Mellor, D. P., Maley, L., Nature 161. 436 (1948). (17) Pe aae. B. F.. Williams. M. B.. ANAL.c ~ E M . 31, io44 (1959): (18) Pollard, F. H., Hanson, P., Geary, W. J., Anal. Chim. Acta 20,26 (1959). (19) Shibata, S., Ibid., 25, 348 (1961). (20) Wehber. P.. 2. anal. Chem. 158. 10 ~~
(21) Zbid., 166, 186 (1959). (22) Woldbye, F., Acta Chem. S c a d . 9, 299 (1955).
RECEIVEDfor review March 12, 1962. Accepted May 7, 1962.
Polarographic Determination of Methyl Pentoses A. H. WARD1 and Z. P. STARY Departmenf of Biochemistry, Warren State Hospital, Warren, Pa.
bA
method for the determination of 0.2 to 1.0 mg. of methyl pentose with an average error of l.8Y0is presented. It involves oxidation of methyl pentoses to acetaldehyde with periodate, removal of periodate with an anion exchanger, and polarography of acetaldehyde in 0.1 M LiOH. Other sugars do not interfere.
M
such as fucose and rhamnose, occur as constituents of polysaccharides and glycosides in various plants. I n recent years, the occurrence of fucose-containing mucopolysaccharides and oligosaccharides in animal and human blood, tissues, and secretions has been demonstrated. The determination of methyl pentoses has become increasingly important for a number of branches of clinical and general biochemistry. For the determination of methyl pentoses in small amounts of material, the color reaction described by Dische and Shettles (2) is most frequently used. In this method, the methyl pentose-containing material is heated with H2S04 and cysteine; the red color produced is determined. spectrophotometrically. However, other sugars produce a similar color reaction; to eliminate this interference the absorption must be read at 2 wavelengths, and the methyl pentose value is estimated from the difference. The polarographic determination of formaldehyde and acetaldehyde has been used by Warshowsky and Elving (6) for the analysis of mixtures of ethylene glycol and 1,2propylene glycol (which are oxidized to aldehydes with periodate). Elving and Rutner (3)described a polarographic method for the determination of acetaldehyde in Liquid mixtures obtained in the conversion of ETHYL PENTOSES,
ethanol to butadiene. de Almeida (1) used the polarographic method for the determination of acetaldehyde in wine. Filov (4) determined vinyl alcohol in water after its conversion to acetaldehyde. The method described in this paper approaches the problem by way of oxidation with periodic acid. Methyl pentoses differ from other sugars in giving acetaldehyde on oxidation with periodate (6) ; ketoses and aldoses which do not possess a methyl group give formaldehyde in this reaction. Acetaldehyde and formaldehyde differ considerably in their reduction potential, and the polarographic method permits simultaneous determinations of both aldehydes. REAGENTS
Standard methyl pentose solution, 100 mg. of fucose in 100 ml. of 0.25y0 benzoic acid solution. 0.5% periodic acid solution. 0.4M lithium hydroxide solution. 0.1M lithium hydroxide solution. IRA-401 anion exchange column The resin (Mallinckrodt Chemical Works) in the chloride form is washed with distilled water until the washings are neutral to litmus. 30attempt was made to regenerate the column since it was possible to use the column for a t least 10 determinations. The resin is renewed when its color at the top of the column changes from bright yellow to orange. PROCEDURE
To 1ml. of the analyzed solution (containing 0.2 to 1.0 mg. of methyl pentose) in a stoppered tube 1 ml. of 0.5% periodic acid solution was added. The solution was mixed, allowed t o stand 1 hour a t room temperature, and then mixed with 1 ml. of 0.1M LiOH solution. The mixture was transferred to a 20 X 1.2 cm. IRA401 anion exchange
column. The tube was washed twice with 2 ml. of distilled water and the washings were also transferred to the column. The solution together with the washings was allowed to paas through the column a t a rate of 6 drops per minute. The column was then washed repeatedly with distilled water. The first 10 ml. of the effluent was discarded; the second 15 ml., which contains the acetaldehyde, was collected and placed in a constant temperature water bath a t 12” C. for 1 hour. It was then diluted to 20 ml. with 0.4M LiOH, transferred to the polarographic cell, and scanned between -1.5 to -2.0 volts. The removal of oxygen or the addition of maximum supressor was unnecessary. DISCUSSION AND RESULTS
Preliminary experiments showed that methyl pentoses are oxidized quantitatively to acetaldehyde with excess periodic acid and that excess periodic acid together with the iodic acid formed has to be removed prior to the polarography of acetaldehyde. Precipitation of periodic acid as mercuric periodate or reduction with ascorbic acid was tried without success. The use of an anion exchange resin (e.g., IRA-401) for the removal of periodic acid gave satisfactory results provided that the acid is first neutralized with lithium hydroxide solution. To study the effect of pH on the polarography of acetaldehyde in concentration range of 1 to 5 mg./100 mi., the polarographic measurements were conducted in the following solutions: 0.05M LiCl and 0.05M Li acetate (pH 6.8), 0.05M LiOH and 0.05M LiCl (pH 12.7), and 0.1M LiOH solution (pH 13). No characteristic wave was obtained a t pH 6.8 since a t this p H interference by the hydrogen ion is considerable. VOL. 34, NO. 9, AUGUST 1962
1093
In a mixture of LiCl and LiOH the wave height is not a linear function of the concentration. Polarography in 0.1M LiOH solution was found to be very satisfactory. Methyl pentoses (fucose and rhamnose) give after oxidation with periodate a single wave at El/z = -1.81 volts us. saturated calomel electrode and at a concentration of 1 to 5 mg. per cent. Aldohexoses (mannose,
Table 1.
Polarographic Determinaiion of Fucose
Table 11.
KO.
1 2
3 4
Polarographic Determination of Fucose in Presence of Other Sugars
Fucose Added, Mg. 0.60 0.60 0.60 0.60
Glucose, hlg. 0.20
0.40 0.60
Xylose, Mg. ...
0.80
0.60 ... 0.60 ... Average of three determinations.
9 10 0
Glucosamine, Mg.
...
... ...
...
...
...
... ...
Fucose Found,a Mg. 0.60 0.63 0.61
%
Error 5' '
1.6
...
0 59
1.6
0.6
0.60 0.60
...
0.8
...
Cufrent No. 1
2
3
4
a
mM. Fucose 0.00122 0.00244 0.00366 0.00488
in
Current ua./Concn. in ~ a . 5 in mM. 0.059 48.4 0.116 47.5 0,173 48.6 0.236 48.4 Av. 48.2
Std. dev. 0 . 8 Average of five determinations.
glucose, and galactose) and glucosamine give a single polarographic wave at E I ,= ~ - 1.61volts. Mixtures of methyl pentoses with other sugars give (after oxidation with periodate) two polarographic waves, one at El/*= -1.61 and another at Eliz = - 1.81 volts; the first wave corresponds to formaldehyde and the other to acetaldehyde. The height of the acetaldehyde wave is a linear
function to the concentration of methyl pentoses treated. A series of fucose standard solutions was prepared and subjected to the above method of analysis. The polarographic measurements were conducted under identical conditions of temperature, pH, and the rate of mercury drops. The sensitivity of the instrument was set a t 0.5 pa. throughout the experiment. All solutions were kept in a water bath at 12' C. prior to the analysis; the electrolysis cell was immersed in a water jacket of the same temperature. The acetaldehyde wave in each case was corrected for the wave produced by the base solution. Some of the typical r e sults obtained are shown in Table I. In another experiment, mixtures of fucose and other monosaccharides were prepared. In each mixture the amount
of fucose was determined polarographically and compared to the amount of fucose added. Results of this experiment are shown in Table 11. LITERATURE CITED
(1) de Almeida, H., tlnais Inst. Vinho Porto 1947, 13-28; C . A . 46, 7705b (19.52) \ - - - - I .
(2) Dische, Z., Shettles, L. B., J. Biol. Chem. 175, 599 (1948). (3) Elving, P. J., Rutner, E., IND. ENO.
CHEM.,ANAL.ED. 18, 176-9 (1946). (4) Filov, V. A., Gigienu Truda i Prof. Zaholevaniya 4, 54-5 (1950); C.A. 55, 7170b . - . .. (1961). (5) Nicolet, B. H., Shinn, L., J. Chem. SOC. 63, 1456 (1941). (6) Warshowsky, B., Elving, P. J., IND. ENQ.CHEM.,ANAL.ED.18,253 (1946). \ - - - - I
RECEIVEDfor review January 25, 1962. Accepted May 18, 1962.
A Polarographic Study of the Copper(l1) Complexes of Mono-, Di-, and Triethanolamine J. F. FISHER and J. L. HALL Department of Chemistry, West Virginia University, Morgantown, W. Va.
b The polarographic method has been used to determine the nature of the complex species formed between copper(l1) ion and each of the three ethanolamines, at values of pH greater than about 8. For each amine, studies were made b y varying the pH as the concentration of free amine was held constant and b y varying the concentration of amine as the pH was held constant. Representing the complexes formed b y CuA,(OH), where A represents 'the amine molecule and OH represents a hydroxide ion coordinated or a proton removed from an amine molecule, the following species were identified. For monoethanolamine (MEA), CU(MEA)~(OH)~ was found above pH 9. Other species were formed 1094
ANALYTICAL CHEMISTRY
near pH 9. For diethanolamine (DEA), CU(DEA)~(OH)* was formed from pH 9 to 1 1 with at least one other species being formed above pH 1 1 . For triethanolamine (TEA), Cu(TEA)(OH), was formed from pH 7 to 11.5 and Cu(TEA)(OH),- was formed above pH 1 1. The over-all formation constants for the various CuA2(0H)2 species are of the order log K = 20.
T
FORMULAS of the complexes formed in aqueous solution between copper(I1) ion and each of the three ethanolamines remain in question in spite of a considerable amount of experimental work. In some respects, HE
the behavior of the ethanolamines toward copper(I1) salts resembles that of ammonia. For example, if monoethanolamine is added to a dilute solution of a copper(I1) salt, a precipitate appears which redissolves if the ratio of amine to copper(I1) ion reaches approximately 4 to 1. As with ammonia, the copper(I1)-ethanolamine complexes may be kept in solution a t any p H if a sufficient excess of amine salt is present. Unlike ammonia, however, the amount of amine needed to produce a clear solution may be reduced if a strong base such as sodium hydroxide is present. Although the formation of precipitates prevents the application of the usual spectrophotometric method of continuous variations to such sys-
