r-7?7
r " " ;added during the distillation, the
Days
Figure 2. Chelate destruction (upper) and peroxide formation (lower) by 1-hexanol containing different amounts of water
alcohol for the purposes of extraction is to store it in a metal container and to saturate it with water. Removal
of Peroxides Formed.
The alcohols purchased commercially are usually contaminated with traces of peroxides unless they have been stored in metal containers. A distillation of the contaminated alcohol will remove the peroxides; however, if anhydrous potassium carbonate is
absorbance values obtained in the subsequent extraction are about 5% higher, indicating that the anhydrous potassium carbonate has removed more of the hydrogen peroxide. The purpose of the potassium carbonate could be to provide potassium hydroxide from the traces of water present. Potassium hydroxide will destroy hydrogen peroxide (6). Therefore, distillation of the 1-hexanol over potassium hydroxide should be much more effective than just potassium carbonate (Figure 3 shows comparative results). Using the undistilled alcohol as a reference solution which forms peroxides a t a certain rate (curve D, Figure 3), the distilled alcohol which has had most of the hydrogen peroxide removed should have less peroxide initially (curves A , B, C). However, the distilled l-hexanol should have less water present and therefore produce peroxide faster. This is also shown to be the case. These effects account for the lower initial value and the succeeding faster formation rate of the hydrogen peroxide. ACKNOWLEDGMENT
The authors express their appreciation for the financial support of this work by the Purdue Research Foundation. LITERATURE CITED
(1) Babko, A. K., Volkova, A. I., J . Gen. Chem. U.S.S.R. (Eng. Transl.) 21, 2163 /14R1) \-.,.,-,. (2) Bolland, J. L., Cooper, H. R., Nature 172,413 (1953). (3) Bonet-Maury, P., Compt. rend. 218, 117 (1944). (4) Corpel, J., Bull. SOC. chim. France 1953, 752.
I6-
I
I
I
I
I
0
3
6
9
12
I
Hours
Figure 3. Peroxide formation in 1 -hexanol irradiated with a mercury vapor lamp A. 5. C.
D.
After distillation over KOH After distillation After distillation over KZCOB Not distilled
( 5 ) Furman. 15'1 Furman, N. H.. H., "Scott's Standard \ - I
Methods 'of of Chemical Analysis," 5th ed., Vol. I, p. 987, Van Nostrand, New York, 1947. (6) Kasosnoskii, I. A,, Neidig, A. B., Dokladu A k a d . Nauk S.S.S.R. 86. 717 (1952)." (7) Klenk, J. v., Klepzig's Teztil. 2. 42, 549 (1939). (8) Meloan, C. E., Brandt, W. W., Holkeboer, P. E., ANAL. CHEM.32, 701 /iacn\ (9) Sutterfield. C. N.. Bonnel. A. H.. Ibid., 27,1174 (1955): (10) Wise, W. M., Brandt, W. W., Ibid., 27,1392 (1955). "I \L""",.
RECEIVED for review May 17, 1960. Accepted October 17, 1960. Abstracted from a thesis submitted by Clifton E. Meloan t o the Graduate School of Purdue University, January, 1959, in partial fulfillment of the requirements for the degree of doctor of philosophy.
Spectrophotometric Determination of Traces of Hydrogen Peroxide C. E. MELOAN, M. MAUCK, and C. HUFFMAN Department of Chemistry, Kansas State University, Manhattan, Kan. Hydrogen peroxide reacts with the colored benzohydroxamic acid chelates of vanadium(V) and uranium(V1) to destroy the chelate and form the metal peroxide complex. The decrease in color of the benzohydroxamic acid chelate is a measure of the amount of peroxide present. It i s possible to mole of hydrogen detect 7 X peroxide using the uranium chelate (pH 6 and 380 mp) and 1 X 10+ mole using the vanadium system (pH 3 and 450 mp). By using a 1 hexanol extraction the color due to
104
ANALYTICAL CHEMISTRY
the metal peroxide complexes formed does not interfere. Hydroperoxides and dialkyl peroxides do not interfere appreciably at the pH's required for this determination.
W
HEN
EITHER
THE CHELATES Of
vanadium and uranium with benzohydroxamic acid (6, 9) are extracted with 1-hexanol, a large decrease in absorbance is observed in some cases. Meloan and Brandt (7) have shown this to be due to the presence of traces
of hydrogen peroxide in the alcohol. This chelate destruction is proposed as a sensitive and selective method for the determination and measurement of hydrogen peroxide. Methods currently in use for the determination of traces of HzOz are the reversal of the standard colorimetric procedure for titanium using H ~ O Z (81, the use of luminol (I),and polarography (4). While each of these methods are in general satisfactory, each one has some undesirable characteristics. The tita-
\
0 0 \ , 0
\
I
0
0
0
I 'C
c=c PH
:'
0:u:o :. \
no-v-0
2
= C'
C-C-N.
PH
5
Figure 1 . Benzohydroxarnic acid chelates nium method is only sensitive to 1 part per 100,000, the luminol fluorescence is too unstable, and polarography is too expensive for the small laboratory. This method circumvents these difficulties.
oxides (ROOR) have the same -0-0group and TJ-ould be expected to provide the major source of interference. Various types of peroxides were examined to determine the extent, if any, of this interference. The compounds chosen are shown in Table I. To guard against the possibility that any interference was actually due to trace HzOzimpurities rather than to these compounds, the hydroperoxides and dialkyl peroxides were treated with a neutral buffered solution of Dee-0 (Takamine Laboratories), an enzyme that reacts specifically to destroy H202
1.6
1.2
. 0 0
a
0.1
\
(5). Hydro- and dialkyl peroxides were 0.1 extracted from the neutral, buffered solution of Dee-0 with hydroperoxidefree ether and the ether solution was mixed with the 1-hexanol solution of the chelate. Dee-0 did not appear to destroy the chelate, but formed a Of EXPERIMENTAL turbid solution which caused interI 2 3 ference. Table I shows the results Apparatus. Beckman D U with an M O L E S O F ti2oe x l o 5 of an average of three independent alternating current power supply, and Figure 2. Vanadium chelate destrucdeterminations. The tert-butyl hydroBausch and Lomb Spectronic 20. peroxide, di-tert-butyl peroxide, and tion All extractions were performed with lert-butyl perbenzoate were completely borosilicate glass 125-ml. separatory soluble in the neutral, buffered enzymic funnels. solution, and since the HzOz was reReagents. The reagents were moved, they showed no appreciable Table I. Interferences-Effect of 0.01M aqueous solutions as used by interferences even when present in a Other Peroxides on Chelate Meloan et al. (6); all were reagent grade hundred-fold excess. This is very imunless specified otherwise. The other Absorbance, portant since a water extraction of compounds used are given in Tables 460 Mp hydrogen peroxide is employed in the I and 11. 10 100 Suggested Procedure. PREPARA- over-all analysis procedure and waterCompounda None t o 1 to I soluble hydroand dialkyl peroxides TIOK O F CHELATE. The chelate is would be extracted also. Hydroxytert-Butyl hydroperprepared such t h a t the final 1-hexanol heptyl peroxide was insoluble in the oxide, (CH& solution of the chelate will contain 1 X neutral buffered Dee-0 and as a result COOH 1.56 1.58 1.54 10-5 mole of either vanadium or uratraces of HzOz could not be removed. nium per 10 ml. (6). The structures are Di-tert-butyl perThe observed interference is therefore shown in Figure 1. The chelates in oxide, (CH& probably due to HzOz and not the COOC(CHa)3 1.55 1.55 1.53 aqueous systems give little color and it is peroxide. It is of little consequence if not until they are extracted with 1tert-Butyl perbenzoit does interfere, because it is waterhexanol that a deep color is formed, ate, CcHaCO(02)Cinsoluble and would not transfer during (CH3)a 1.56 1.53 1.51 particularly the vanadium system. 1the water extraction. Lauroyl perHexanol is the preferred solvent because Hydroxyheptyl peroxide is also insoluble in the enzymic it separates rapidly from water and oxide, [ CHI(CH&solution, but it can be pulverized to because it extracts the chelates the best. CH(OH)120z 1.55 0.80 0.32 such an extent that good contact can The extracted chelates are stored preferLauroyl peroxide, be made and the hydrogen peroxide ably in the metal container that the [CH3(CH2)loCOI2 0 2 1.56 1, 5 7 1.59 destroyed. 1-hexanol is shipped in, but darkened Gifts from Lucidol Corp.; highest Other compounds that will interfere glass bottles are satisfactory. purity available. are strong oxidizing or reducing agents COhlPOUNDS IMhIISCIBLE WITH HzO. that are water soluble (6, 9). Place a measured volume of the sample Table II. Extraction Studies material in a separatory funnel and add 15 to 20 ml. of HzO of about p H 2. ( H202extracted with H 2 0from the DISCUSSION After vigorous shaking allow the layers following compounds) to separate and drain off the water layer Concn.. Total Moles into another separatory funnel, or a Chelates Involved. Mole ratio and Present x 1 0 6 large test tube. To this solution add continuous variations (3) studies have Compound Added Found 10 ml. of the chelate solution from a been performed in both the vanadium Cyclohexyl alcohola 1.0 0.96 pipet and mix the solution thoroughly. and uranium chelates and it was found Benzyl acetate" 1.0 0.92 The uranium chelate will be destroyed n-Hexyl etherb 1.0 0.97 that a t a p H of 2 a 1 to 2 (metal to instantly, but the vanadium chelate Benzaldehyde. 1.0 0.76 ligand) chelate exists for the vanadium will take 5 to 10 minutes. Allow the Cyclohexanonea 1.0 1.01 a pH of 6 a 1 to 2 chelate system, and a t layers to separate and measure the 1-Hexanola 1.0 1.0 exists with uranium. absorbance of the vanadium system a t Isoamyl alcohola 1.0 0.99 450 mp and the uranium system a t 380 Chelate Stability. A 1-hexanol a Fisher Scientific Co. mp. From a previously prepared calisolution of these chelates has been b Carbide and Carbon. bration curve the per cent HzOzcan be stored in a metal container, the same obtained . type that it was purchased in, several COMPOUh-DS LfISCIBLE WITH HzO. months without apparent loss in If the organic compound does not react strength. Ultraviolet radiation detween the amount of H20aconsumed with the chelate the water extraction stroys these chelates slotvly. Water in and the chelate destroyed was deterstep may be eliminated. Otherwise the the alcohol stabilizes them ( 7 ) . mined. Known amounts of HzOl procedure is the same. Chelate Destruction with H202. were added t o a 1-hexanol solution Peroxide Interferences. Hydroperoxides (HOOR) and dialkyl perThe stoichiometric relationship beof the chelate and the absorbance 0
~
VOL 33, NO. 1, JANUARY 1961
105
2
\
\\ Figure 3. Uranium chelate destruction
0 )I
n
