the aqueous methanol by the purine is given by the expression
where ACHCand BCHC are the concentrations of the hydrocarbon in the upper phase for the system containing ThIU or for the system without TMU, respectively. JF7hen the equilibrium concentrations of hydrocarbon in the upper phases of the two systems are the same, Equation 3 may be simplified as shown in Equation 4. This simplification is generally valid throughout the range of concentrations of hydrocarbon studied, since distribution coefficients were essentially constant throughout this range.
The simplified Expression 4 may then be substituted in Equation 2 to give
1 1 (z c)
The slope of the plot of log vs. log CPis a n estimate off. For the two compounds studied, pyrene and benzo(a)pyrene, the values of this slope calculated for consecutive pairs of points were 1.11, 1.18 and 1.12, 1.47. WeilhIalherbe found values for the exponent, f, either near 1 or near 2 suggesting reactions involving either one molecule or two molecules of purine per complex. ACKNOWLEDGMENT
The synthesis of tetramethyluric acid used in these studies was performed by Marvin Crutchfield and T. P. Chen. The authors acknowledge the information provided by Charles Keith regarding his preliminary attempts to use purine complexation for the countercurrent separation of closely-related polycyclic aromatic hydrocarbons. LITERATURE CITED
(1) Biltx, H., Strufe, IC, Ann. 413, 197 (1916).
(2) Booth, J., Boyland, E., Riochzni. Riophys. Acta 12, 75 (1953). (3) Boyland, E., Green, B., Brzt. J . Cuncer 16, 347 (1962). (4) Brock, N., Druckrey, H., Haniperl, H., Arch. Ezptl. Puthol. Phamuko2. 189, 709 (1938). (5) Fischer, E., Ach, L., Ber. 28, 2480 (1896). (6) Fischer, E., Reese, L., Ann. 221, 336 (1883). ( 7 ) Fromherz, H., Hartmann, A., Ber. 69B, 2420 (1936). (8) Golumbic, C., ANAL. CHEM.22, 579 (1950). (9) Grimmer, G., Beitr. Tabakforsch. 1, (No. 7), 291 (1962). (10) Haenni, E. O., Howard, J. W., Joe, F. L., Jr., J . dssoc. Ogic. Agr. Cheinzsts 45. 67 (19621. ( 11) 'Hoffman; L, D., Wgnder, E. L., ANAL. CHEM.312,295 (1960) (12) John son, T. B., J . .4m. C h e m SOC. 59, 1261 (1937). (13) Neisl1, W. J. P., Rec. Trav. ChznL. 67,361 (1948). 114) Steid le. W.. dissertation. Tubineen UniversitG. German\-. 1953. ' (15) Wanless, G. G., Eby, L. T., Rehner, J., Jr., ANAL.CHEhf. 23, 563 (1951). (16) Weil-Malherbe, H. , Bzochenr. J . 40,351 (1946). RECEIVEDfor review June 19, 1'363. Accepted August 7 , 1963. Y
A General Method for the Chromatographic Separation of Nonionic Surface-Active Agents and Related Materials MILTON J. ROSEN Department of Chemistry, Brooklyn College of the City University o f New York, Brooklyn, N. Y.
b A general chromatographic method has been developed for separating nonionic surface-active agents from each other and from related nonionic materials, using silica gel as adsorbent. The mixture, adsorbed on a silica gel column, is separated by eluting successively with chloroform, 1 :99 (v./v.) 1 : 1 (v./v.) ethyl ether-chloroform, 1 : 1 (v./v.) ethyl ether-chloroform, 1 : 19 (v./v.) acetone-chloroform, 1 :9 (v./v.) methanol-chloroform, methanol-chloroform, and 1 :2 (v./v.) methanol-chloroform. Results obtained with a number of three- and four-component mixtures are described.
C
nonionic surface-active agents commonly contain more than one nonionic substance. These compositions often contain both water-soluble and oil-soluble surfactants to obtain a better balance of properties, and in addition, usually contain other nonionic, nonsurfaceactive materials, such as hydrocarbon OMPOSITIONS CONTAINING
2074
ANALYTICAL CHEMISTRY
oils, fatty esters, glycols, and unreacted raw materials from surfactant manufacture. The removal of ionic surfaceactive agents present in the composition is conveniently accomplished by ion exchange ( I , 7, 8, IO, l a ) , but all the nonionic surfactants, together with any nonionic nonsurfactant material, pass unadsorbed through the ion exchanger. The analysis of this mixture of nonionic surfactants and related materials is usually a difficult task and, in spite of its common occurrence, only a few attempts have been made to systematize the analysis of this type of mixture. A liquid-liquid extraction procedure has been suggested (9) for separating hexane-soluble nonionics from hesaneiiisolubles and chromatographic techniques have been suggested for separating mixtures of mono-, di;, and triglycerides (4-6) and of fatty acid esters of ethylene glycol and polyoxyethylene glycols ( 3 ) . This paper describes a general columnar chromatographic method which has been developed to separate
the components of mixtures containing various types of nonionic surface-active agents and a number of nonionic nonsurfactant materials commonly encountered with them. A column, rather than a thin-layer or paper, chromatographic technique was used because it permitted convenient qualitative analysis of the eluted fractions by refractive index or melting point, and quantitative measurement by weighing on an analytical balance. EXPERIMENTAL
Column. A 50-ml. buret (60-cm. X 1-cm. i.d.) with ungreased stopcock. Procedure. A few milliliters of chloroform were placed in the column, followed by a small plug of glass wool which was tamped in place below the surface of the chloroform with a glass rod, t o remove air bubbles. Ten grams of the silica gel (Davison KO. 922, through 200-mesh) were slurried with 20 t u 30 ml. of chloroform (U.S.P., dried for a few days over anhydrous CaC12) and poured into the column.
40
I
I
I1
2~
. ) _ I I l _ ,
IV
v
_,
VI CARBOWAX I000
CETYL ALCOIIOL
i
i
BRlJ 98
n
NONYLPHtNOL
IGEPAL CO 430
FRACTION NUMBER
Figure 1 .
Separation of mixture No. 1
20
10
30
40
50
FRACTION NUMBER
Figure 2.
The sample, approsirlately 300 mg., was added t o the colunn as a solution in chloroform. The elution program was: chloroform, 70 ml. (I); 1:99 (v./v.) ethyl ether (anhydrous)-chloroform, 100 ml. (11); 1: 1 (v./v.) ethyl ether (anhydrous)chloroform, 70 ml. (111); 1:l (v./v.) acetone (analytical grade)-chloroform, 80 ml. (IV); 1:19 (v./v.) methanol (U.S.P.)-chloroform, 100 ml. (1;); 1 9 (v./v.) methanol (U.:LP.)-chloroform, 70 nil. (VI); 1:2 jv./v.) methanol (U.S.P.)-chloroform, 70 ml. (VII). The 1: 19 methanol-chloroform elution mas eliminated in most cases where only one highly ethoxylate,l material (containing > 10 moles of ethylene oxide) was present in the mixture. Ten-milliliter fractions were collected at a flow rate of 1 ml. per minJte, the solvents evapoi ated, and the residues weighed. Refractive indices were taken on all
75
fractions wcigliing >10 melted bclow 40” C,
nig. which
1ir.drophilic-hydrophobic balaiic*c?iii tlw eluted surfactant molecule can therefore bc obtained from the nature of the solvent needed to elute it. CHLOROFORM elutes oiily the n u t nonpolar materials-e.g., mineral oil and methyl laurate. It does not elute eren the most hydrophobic surfactants. Triglycerides, such as tristearin, cottonseed oil, or castor oil, are not eluted by this solvent under the conditions used, and this makes possible a convenient separation of hydrocarbon oils from animal and vegetable oils, using chloroform as the eluting solvent,. ETHYL ETHER-CHLOROFORM, 1:gg (u./u.), elutes triglycerides (but not, castor oil) and long-chain fstt,y acids and alcohols-e.g., cet’yl dcohol, lauric
RESULTS AND DISCUSSION
The results obtained, as shown by the data in Table I and Figures 1 through 5, follow the general rule that the more hydrophilic the material, the greater the polarity of the solvent necessary t o elute it. This is consistent with the generally accepted view that the solvent, in order to elute a component adsorbed on a polar surface, must compete successfully for the sites on which the component is adsorbed, thereby displacing it from them. A rough estimate of thc
r
Separation of mixture No. 2
1 ETHOFATCI25
I
1
11
O
I
LOIlONLLEDUlL
L
.
.
.
.
. 10
Figure 3.
ETHOFAT MU15
20 30 FRACTION NUMBER
Separation of mixture No. 3
10
2b
30 FRACTION NUMBER
Figure 4.
40
50
Separation of mixture No. 4
VOL. 35, NO. 13, DECEMBER 1963
2075
acid, oleic acid. Span 80, a highly hydrophobic surface-active agent (HLB = 4.3), is not eluted by this solvent. ETHYLETHER-CHLOROFORM 1:l (u./ u.), elutes oil-soluble surfactants, such as ethoxylated fatty acids and alkylphenols with < 4 moles of ethylene oxide and glyceryl monoesters. ACETONE-CHLOROFORM, 1:I (v./v.), elutes surface-active agents of intermediate polarity-e.g., ethoxylated materials containing no more than about 10 moles of ethylene oxide. This is in accord with the results obtained by Kelly and Greenwald ( 2 ) on a n ethoxylated octylphenol. METHANOL-CHLOROFORM, 1 :I9 ( u s / u . ) and 1 : 9 ( v . / v . ) , elute highly hydrophilic surfactants containing more than 10 moles of ethylene oxide and polyoxyethylene glycols. A separation of these highly hydrophilic surface-active agents from high molecular weight polyoxyethylene glycols may be accomplished by using l:19 and 1 : 9 methanol-chloroform solutions consecutively as eluting solvents, because the former does not elute polyoxyethylene glycols of molecular weight 1000 or greater. METHANOL-CHLOROFORM, 1% : (v./v.), elutes even the most highly hydrophilic substances, such as glycerol and
40
LAURIC ACID
Figure 5. Separation of mixture No. 5
.. 10
1
3
4
Original components ~ Name and/or structure Amt., mg.5 77.5 Mineral oil 78.5 Cetyl alcohol 84.1 Brij 30-lauryl alcohol 4 moles Et0
-
71.6
n P 1 ,4778 b
Eluent I I1
1.4510 1.4616(33")
1;
Recovered material Amt., mg. 75.8 80.1 :;!le 5 60.5 8 . 5 69'0
ti
71.7
1.5100
80.9 78.4
1 ,4976 1.4768(33")
76.9
...
Cottonseed oil Ethofat 142/15-oleic acid Et0 Ethofat C/25-lauric acid Et0
97.2
1 ,4705
131.5
1.4703
51.5
99.0
1.4612
90.0
98.5
1 ,4705
976.01 g . o 95.0
101 .o
1.4764
104.0
1.4720
64.8 72.8 78.9
1.4299
2 9 . 5 105'5 90.0 9,5199.5 48. le 76.1 80.2
+ +
+ 5 moles + 15 moles
Cottonseed Oil Span 80-sorbitan mono-oleate Tween 80-sorbitan mono-oleate 20 moles E t 0 Methyl laurate Lauric acid N,N-bis( 8-hydroxyethy1)lauramide
+
Amounts and refractive indices on 100% active basis. C. e Loss due to volatilization.
* h1.p. >40'
Q
ANALYTICAL CHEMISTRY
84.3
E
m.p., 48.7"49.3" c.
,
nD=
1.4778 b
1.4488 1.4538 1.4619(33")
...
I
Nonylphenol Igepal CO-430-nonylphenol 4 moles E t 0 Igepal CO-850-nonylphenol 20 moles E t 0 Polyoxyethylene glycol, mol. wt. 1000
Ethomid HT/6O-hydrogenated tallow amide 50 moles Et0
2076
different fractions were obtained corresponding to one original material. (Fractions I11 and IV, Figures 1-4; Fractions V and VI, Figure 1; Fractions VI and VII, Figures 3-5.) The refractive indices and other properties of these fractions indicated that in each case they were indeed fractions of the
Recovery of Components of Mixtures
+
5
SO
41
high molecular weight polyoxyethylene glycols. Because almost all the surface-active agents used in these separations were commercial materials, and therefore nii\tures of substances with somewhat differelit hydrophilic - hydrophobic bn1aiic.e-, in a number of cases, two
+ Brij 98-oleyl alcohol + 20 moles E t 0
2
30
FRACTION NUMBER
Table 1.
Mixture No.
20
V
81.8
i.51ii' 1.4998 1.4940 1.4763(33")
VI
75.1
...
42.8
...
I I1 IV I:{:
1.4701 1 ,4698 1 ,4690 1 .4620
...
1.4697' 1 ,4741 1 ,4764 1.4722 .
I
.
1 ,430f
m.p., 48.0'48.5" C. b b
original commercial material and contained no signilkant amount of the other components of the mixture. For example, in mixture No. 1, Brij 30, a polyoxyethylated lauryl alcohol containing an average of 4 moles of ethylene oxide, was separated intN3 two fractions whose refractive indices, n ~ ~1.4488 6 and n# 1.4538, correspond, respectively, to ethoxylated lauryl alcohols containing an average of 3 moles and 5 moles of ethylene oxide (11).
LITERATURE CITED
(1) Ginn. M. E.. Church. C. L.. ANAL. CHEM.~ 551 ~ (1959). , ’ (2) Kelly, J., Greenwald, E. J., J . Phys. Chem. 62, 1096 (1958). (3) Papariello, G. J., Chulkaratana, S., > - I
Higuchi. T.. Martin. J. E.. Kuceski. V.P.. J: Am. Oil Chhists’ Soc. 37. 396
(1960). (4) Privett, 0. S., Blank, M., Lundberg, W. O., Ibid., 38,312(1961). (5) Quinlan, P., Weiser, H. J., Ibid., 35,325 (1958). (6) Ravin, L. V., Meyer, R. J., Higuchi, T., Ibid., 34,261 (1957).
(7) Rosen, M. J., ANAL. CHEW29, 1675 (1957). (8) ( Rosen, M. J., J. Am. Oil Chemists’ SOC. 38,218 (1961). (9) Rosen, M. J., Goldsmith, H. A., “Systematic Analysis Andysis of Surface-Active Agents,” p. 246, Interscience, Kew York. 1960. lQ60. York, (10) Ibid., pp. 260, 288. b z d . p. 376. (11) lIbid., (12) Voog Voogt, R., Rec. Trav. Chim. 77, 889 (1958). RECEIVEDfor review July Accepted September 18,1963.
16, 1963.
Separation and Determination of Iron(l1) and Iron(ll1) with Anthrcrnilic Acid Using Solvent Extraction and Spectrophotometry DONALD
L. DINSEL’
arid THOMAS R. SWEET
Department o f Chemisfry, McPherson Chemical Laboratory, The Ohio Stafe University, Columbus 7 0, Ohio
b Iron(ll1) was extracted as the anthranilate into 1-pentanol in the presence of iron(l1). A dirisct determination of the iron(l1l) ctmtent of the sample was obtained by measuring the absorbance of the pentanol extract. The iron(l1) in the aqueous phase was oxidized and extracted as the anthranilate into a solvent mixture. A direct determination of the iron(ll) content of the sample was obtained by measuring the absorbance of the nonaqueous phase.
A
ACID was first prepared by Fritsche in 1841 (a) and was proposed as an analytical reagent in 1926 (1, 8). Two publications cite the use of anthranilic acid as a reagent for solvent extraction separations (6, 9), specifically, for the separation and determination of plutonium by extraction with amyl acetate. The precipitate formed by iron(II1) and anthranilic acid can be extracted into organic liquids such as alcohols, ketones, and ethers. The copper, cobalt, nickel, cadmium, and iron(I1) anthranilates could not be extracted. The extracted iron(II1) znthranilate in the organic solvent was a red solution with an absorbance proportional t o the concentration of iron(I.11). NTHRANILIC
EXPERIMENTA 1
Reagents. ANTHRANILICACID SOLUTION,0.07M. Five grams of recrystallized acid werrt dissolved in 1 Present address, E. I. du Pont de Nemoum and Co., Wilmington, Del.
approximately 400 ml. of deionized water and 37 ml. of 1N sodium hydroxide. p H of the solution was slowly decreased by the addition of 1N sulfuric acid until a p H of 4.5 was reached and the solution was diluted to 500 ml. with deionized water. Solutions were stored in brown glass bottles and were discardedas soon as a brownish cast was observed. STANDARD IRON(III)SOLUTION. Pure iron wire (99.8%) was polished with fine emery cloth, wiped, cleaned in acetone, and weighed. The wire was placed in a 100-ml. beaker and a slight excess of concentrated sulfuric acid was added slowly. Hydrogen peroxide was added t o oxidize the iron to the ferric state and the excess was then boiled off. During the heating process, demineralized water was added periodically to maintain the liquid volume. After transfer to a volumetric flask, the solution waa diluted to the mark with deionized water. STANDARD IRON(II)SOLUTION. Various amounts of analytical grade ferrous ammonium sulfate hexahydrate were dissolved in acidified deionized water which had been outgassed with oxygenfree nitrogen. The oxygen was removed from the nitrogen by passing the gas through a basic 15% solution of pyrogallol. Fresh solutions were prepared as soon as a positive test for iron(II1) was obtained. ORGANICLIQUIDS. All the organic materials used for the extractions were C.P. grade reagents. AMYLACETATE,ACETOPHENONE, AND ~-PENTANOL MIXTURE. The mixture was prepared by mixing 130 ml. of amyl acetate, 100 ml. of acetophenone, and 19 ml. of 1-pentanol. Apparatus. All p H measurements were made with a Beckman Model G p H meter. Quantitative absorbance
measurements were made with a Beckman Model D U spectrophotometer, equi ped with a Beckman Model 4300 piotomultiplier attachment. Corex cells, 1 cm., were used and slit widths of between 0.06 mm. and 0.08 mm. were maintained for all measurements. Other absorbance measurements were made with a Cary recording spectrophotometer, Model 14. An International Centrifuge, 220-ml. capacity, was used to increase the speed of separation of the aqueous and organic phases. Working Curve. Various amounts of a n iron(II1) sulfate solution were pipetted into each of several 60-ml. ground glass-stoppered bottles. Sufficient deionized water t o bring the volume t o 5 ml. was added t o each bottle. Twenty-five milliliters of a 0.07M solution of anthranilic acid (pH 4.5) were added and then 10 ml. of 1-pentanol were transferred into each of the bottles. The two phases were shaken for 2 minutes and centrifuged. Enough of the organic phase was removed with a medicine dropper to fill the absorbance cell. Absorbance was measured a t 475 mp against a blank prepared by extracting a 60111tion containing 5 ml. of deionized water and 25 ml. of the anthranilic acid 60111tion with 10 ml. of 1-pentanol. The Bame procedure was repeated using a mixture of amyl acetate, acetophenone, and l-pentanol in place of the 1-pentmol. The absorbance of the complex extracted into the mixture was measured at 465 mp. Working curve data are given in Table
I.
Procedure. The aqueous sample containing iron(II1) and iron(I1) was outgassed with oxygen-free nitrogen. With a pipet 25 ml. of a 0.07M anthranilic acid solution at pH 4.5 were transferred t o a 250-ml. ground glassstoppered bottle containing the samVOL 35, NO. 13, DECEMBER 1963
2077
