~~~
~~
Table IV.
~
~
Effect o f 8 P.P.M. o f Foreign Ion on %J
Pd
Pt
Rh
Ir
I n 2-Thiobarbituric acid
Ru, P.P.M.
Table V.
0.: Ruthenium
0.6
-22.3
13.6 16.7 19.5
1.1 1.6 1.7
-15.2
5.9 8.9 11.9 14.9 17.8
-0.6
1.1
-0.8 -0.6 -0.4
-19.G -17.6
0.0 0.2
-13.6
In s-Diphenylthiourea (at 630 M u ) 0.1 0.3 . 0.4 -0.4 0.2 0.5 0.6 0.1 0.1 -0.1 0.3 0.9 0.4 0.7
(Ru
24.0
28.0 30.0
Relative Sensitivities for Reagents Studied
=
Reagent CPhenylthiosemicarbazide
-1.1 -0.4 -0,2 0.7 I .(I
-0.5 -0.2
0.6 0.3 0.3
0.0
0 0.6
s-Di-o-tolylthiourea s-Diphenylthiourea s-Di-p-tolylthiourea 2-Thiobarbituric acid Thiosemicarbazide
Relative Sensitivity 1.00 0.481 0.431 0.388 0.364 0.232
0.6
Home, J. L., J . Am. Chem. SOC.49,
0.0
0.2
0.4 0.4 0.0
0.5
Effect of Ruthenium on %J in Various Concentraticins of Foreign Ions with s-Diphenylthiourea
Concn. of Metal Ion, P.P.M. 16.0 20.0
Table VI.
A%T
os 8.3 11.1
~
11.9 p.p.m.)
2393-5 (1927). Ogburn, S. C., Jr., Ibid., 48, 2493 (1926). Sandell, E. B., “Colorimetric Dctcrminntion of Traces of Metals,” 1., 387, Tnterscience, New York, 1944. Snell, F. D. “Colorimetric Methods of Analysis,”’ vol. I, p. 418, Van Nostrand, New York, 1936. Steiger, B., Mikrochenzie 16, 193 (1934-35).
A%T‘ (630 M p )
os
Pd
0.2 0.3 0.7 0.5 0.1
1.0 0.9 1.2
1.2
1.8
Pt 1.0 1.0
1.4 2.0 3.2
Ri
Ir
0.5 0.9
1.o 1.0 1.9
1.0 0 .s
1.2
1.6
1.8
(1942).
RECEIVED for review June 19, 1956. Accepted Kovember 28. 1956.
Application of Anthrone Tesf to Determination of Cellulose Derivatives in Nonaqueous Media E. P. SAMSEL and J. C. ALDRICH The Dow Chemical Co.,’Midland, Mich.
b The extractability of ethylcellulose from films b y light mineral oil was studied in connection with food uses. An analytical procedure was developed in which ethylcellulose was extracted from light mineral oil with a mixed methanol-water solvent, then quantitatively determined with a modified anthrone method. Light mineral oil a t room temperature extracts less than 1 p.p.m. of ethylcellulose a t the end of 4 weeks. Cellulose acetate butyrate was extracted from light mineral oil with a mixed methanolacetone solvent, and was quantitatively determined with the anthrone method to an accuracy within 1 p.p.m.
A
was developed for the quantitative determination of small amounts of ethylcellulose in light mineral oil. This method was used to study the extractability of ethyl&fETHoD
574
ANALYTICAL CHEMISTRY
cellulose from films by light mineral oil in connection witli food uses. Anthrone was chosw as the most suitable reagent. M7hen carbohydrates are heated with anthront: in sulfuric acid, a green to blue-greer color is produced ( 2 ) . Morse (4) used this reaction for quantitative estimations of sucrose solutions; Morris (3) used it for the determination of glucc 138, glycogen, and lactose. Viles and Silverman (’7) applied the anthrone rcxgent to the analysis of starch and cellulose. They discussed the effect of heat on color development and in xoduced the idea of stopping the colcy reaction by immersing the reaction mixture in a cold water bath. Samsel and DeLap (6) determined methy1cc:llulose with anthrone. The foregoing investigators used the heat evolved when tho reagent in concentrated sulfuric tcid was mixed with aqueous carbohydrate solution
to furnish the heat required for the development of the blue-green color. Black ( I ) , who used the anthrone reagent to determine sodium carboxymethylcellulose, eliminated the heat of mixing, dissolved the solid sample in 60% sulfuric acid, added a solution of anthrone in a similar concentration of sulfuric acid, and heatcd the mixture for 15 minutes in a boiling water bath. Scott and Melvin (6) investigated the influence of reagent age, acid concentration, effect of temperature, and anthrone concentration on the analysis of glucose solutions. They recommended a 16-minute heating period a t goo c. Although the above method was satisfactory for the determination of Carbohydrates in aqueous solutions, the authors found it impossible to estimate small amounts of cellulose derivatives in the presence of oils, fats, and glycols because of color interference
due to the reaction of the anthronesulfuric acid reagent with them. To overcome these above difficulties, an extraction procedure was developed in wllich ethylcellulose was first extracted from light mineral oil with a mixed methanol-water solvent, then quantitatively determined with an anthrone method which is a modification of that described by Scott and Melvin (8). An extraction procedure was also developed in which cellulose acetate butyrate was first extracted from light mineral oil with a mixed methanolacetone solvent and then quantitatively determined by the anthrone method.
DETERMINATION OF ETHYLCELLULOSE IN LIGHT MINERAL OIL
Reagents and Apparatus. Anthrone, 0.5 gram was dissolved in 250 ml. of reagent grade sulfuric acid (specific gravity 1.84) and allowed to stand for a t least 4 hours before using. The anthrone reagent should not be used after 12 hours of standing.
n MADE FROM )OHM. BEAKER WITH HOLE
F L A T HEAD STIRRIN6 ROD
P I X Z O O H M . TEST
Figure 1. Apparatus for treatment of anthrone samples a t 90" C.
Sulfuric acid, 72y0,225 ml. of reagent grade sulfuric acid (specific gravity 1.84) slowly added to 75 ml. of water. Benzene, analytical reagent grade. Methanol-water, 5 ml. of water added to 95 ml. of absolute methanol. Light mineral oil, Klearol, a USP grade of extra low viscosity mineral oil, product of L. Sonneborn and Sons. Ethylcellulose. Dow Ethocel Ned. 70, 46.1% OC&. Spectrophotometer, Beckman Model B. Absorption cells, quartz, 5 cm. Test tubes, borosilicate glass, 16 X 150 mm., 25 X 150 mm., 25 X 200 mm., neoprene stoppers. Stirrers and covers, glass, special covers with a hole in the center to fit over rods which have been placed in 25 ;< 200 mm. test tubes (Figure 1). Fritted glass funnel, 60-ml. Biichner, fine porosity.
Filtering flask, 5OGnil. side arm. Filter paper, glass, 3.7 cni. Glycerol bath, maintained a t 90" C. Water bath, cooling. Preparation of Standard Solutions. Benzene standard A, 25 mg. of ethylcellulose dissolved in benzene and diluted t o 500-ml. volume a t 20" C. Benzene standard B, a 50-ml. aliquot of benzene standard A was diluted to 500-ml. volume with benzene a t 20" C. Ethylcellulose-mineral oil standard, a 50-ml. aliquot of benzene standard A was diluted to 500-ml. volume with light mineral oil a t 20" C. Benzene-mineral oil blank standard, 50 ml. of benzene was diluted to 500-ml. volume with light mineral oil a t 20" C. Procedure for Determination of Ethylcellulose in Benzene Standard B. Aliquots from 1 to 10 ml. of benzene standard B were pipetted into dry 25 X 200 mm. test tubes equipped with covers. Sufficient benzene was added to the samples to make a total volume of 10 ml. Blanks were made by pipetting 10 ml. of benzene into two test tubes. The samples and blanks were placed in a 90" C. glycerol bath to evaporate the solvent. After the benzene had completely evaporated, the samples were removed from the bath and 2 ml. of 72% sulfuric acid was added to each sample. The tubes were warmed to dissolve the dry ethylcellulose film remaining after the solvent had evaporated. The same amount of warming was used for each determination to give best reproducibility. Then 8 ml. of distilled mater was added to each test tube and the tubes were placed in a cool bath. After 20 ml. of anthrone reagent had been added to each sample and samples had cooled, stirring rods equipped with special glass covers were placed in the test tubes. The tubes were placed in a 90' C. bath for 16 minutes with frequent stirring. After removal, the samples were cooled and transferred to 5-em. absorption cells. The spectrophotometer was standardized a t a wave length of 625 mm. with the benzene blank as 10070; then the color transmittance of the solutions was measured. Procedure for Determination of Ethylcellulose in Ethylcellulose-Minera1 Oil Standard. Aliquots from 1 to 10 ml. of ethylcellulose-mineral oil standard were pipetted into dry 16 x 150 mm. test tubes equipped with neoprene stoppers. Sufficient benzenemineral oil blank standard was added to the various samples to bring them to a total volume of 10 ml. Two blanks were made up by pipetting 10 ml. of benzene-mineral oil blank standard into two test tubes. At this point 1 ml. of pure mineral oil was added to the samples. This mas done so that the ethylcellulose-mineral oil standard would exactly match the 10-ml. aliquots to be taken later from mineral oil-ethylcellulose extraction samples. Then 5 ml. of 95 to 5 methanol-water solvent was added to each. The test tubes were stoppered, shaken vigorously, and centrifuged, and the methanol-water layers mere carefully poured into 25 X 200
mm. test tubes equipped with covers. This extraction procedure was repeatcd four times. The solutifons were placed in a 90" C. bath to evaporate the solvent. From this point on the procedure for determination of ethylcellulose in benzene standard B was followed, except that after the samples remained in the 90" C. bath for 16 minutes they were filtered through a 60-ml. IBiichner fritted-glass funnel (fitted with 3.7-em. glass filter paper) into :t 25 >: 150 mm. test tube placed in a 500-ml. filtering flask. The clear solutioits were transferred to the 5-cm. absorption cells, and their transmittances were measured with the spectrophotometer which had been standardized with the mineral oil blank a s looyoa t a wave length of 625 mr.
DETERMINATION OF CELLULOSE ACETATE BUTYRATE IN LIGHT MINERAL OIL
Reagents and Apparatus. All reagents and apparatus are the same a s those listed under the ethylcellulose procedure except for t h e following changes : Ethylene dichloride, boiling point 8384" C., used instead of analytical reagent grade benzene in standards A and B. Methanol-acetone, 20 ml. of acetone was added to 80 nil. of absolute methanol. This solvent was used instead of the methanol-water solvent. Cellulose acetate butyrate, Eastman, EBB-272-20, 20.5% acetyl, 26.5% butyryl. Preparation of Standard Solutions. Ethylene dichloride standard A, 25 mg. of cellulose acetate butyrate mas dissolved in ethylene dichloride and diluted t o 500-ml. volume a t 20" C. Ethylene dichloride standard B, a 50ml. aliquot of ethylene dichloride standard A was diluted to 500-ml. volume with ethylene dichloride a t 20" C. Cellulose acetate butyrate-mineral oil standard, :t 5O-ml. aliquot of ethylene dichloride standard il was diluted to 500-ml. volume with light mineral oil a t 20' C. Ethylene d ichloride-mineral oil blank standard, 50 ml. of ethylene dichloride was diluted to 500-ml. volume with light mineral oil a t 20" C. Procedure for Determination of Cellulose Acetate Butyrate in Ethylene Dichloride Standard €3. Aliquots from 1 t o 10 ml. of ethylene dichloride standard B were pipetted into dry 25 x 200 inm. test tubes equipped with covers. Sufficient ethylene dichloride was added to the samples to make a total volume of 10 nil. Blanks mere made in manner described. From this point the procedure followed the determination of ethylcellulose in benzene standard B. Procedure for Determination of Cellulose Acetate Butyrate in Cellulose Acetate Butyrate-Mineral Oil Standard. Aliquots from 1 t o 10 ml. of cellulose acetate butyrate-mineral VOL. 29, NO. 4, APRIL 1957
575
oil standard were pipetted into dry 16 X 150 mm. test tubes equipped with neoprene stoppers. Sufficient ethylene dichloride-mineral oil blank standard was added to the various samples to bring them to a total volume of 10 ml. Blanks mere determined by pipetting 10 ml. of the latter into two test tubes. Then 5 ml. of the methanol-acetone solvent was added to each sample. The remaining steps were carried out as described under the procedure for determination of ethylcellulose in ethylcellulose-mineral oil standard. Procedure for Determination of Ethylcellulose in Mineral Oil-Ethylcellulose Film Extraction Samples. Specimens of seven different ethylcellulose films measuring 21/2 X 5 inches each were placed in separate 1-quart Mason jars and 450 ml. of light mineral oil, sufficient to cover the film, mas added to each. The jars mere allowed to remain a t room temperature for 28 days with occasional swirling to agitate the contents. The light mineral oil extracted less than 1 p.p.m. of ethylcellulose during that time. For analysis, 10-ml. aliquots of each oil sample were transferred to 16 X 150 mm. test tubes equipped with neoprene stoppers. Two 10-ml. aliquots were also transferred from the jar of oil containing no film to test tubes for use as blanks. One milliliter of benzene was added to each tube in order that the film samples would contain the same amount of benzene as the ethylcellulose-mineral oil standard. After 5 ml. of methanolwater solvent was added to each tube, the extraction, evaporation, filtration, and color transmittance procedures were carried out in the same manner as those described for the determination of ethylcellulose in ethylcellulose-mineral oil standard.
procedure are listed for a series of aliquots of benzene standard B solution containing knomr amounts of ethylcellulose. Before evaporation of the solvent and su11sc:quent determination of the ethylcellulot;~,benzene was added to each aliquot to provide a constant volume of 10 ml. Thus parts per million of ethylcellulose mas calculated on the basis of 10 ml. of benzene.
Table 11. Per Cent Transmittance on Ethylcellulose-Mireral O i l Standard" b y Anthr1:me Reagent
P.P. bl . BenzetieEthylUned celluloseh % in 10 Oil Blank Trans- Ml. of Stand:ird, mit- hIineral hll tance Oil 9 96 0 0.5 1 2 8 92.8 1.0 7 87.8 1.5 3 6 84.8 2.0 4 5 82.8 2.5 5 4 81.3 3.0 6 7 3 78.3 3.5 2 75.3 4.0 1 73.3 4.5 9 0 69.3 5.0 10 a 1 ml. ethylcelliilose-mineral oil standard = 0.000005 gram ethylcellulose. * Ethylcellulose, 46.1yo OC2H6, 70 viscosity.
EthylcelluloseMineral Oil Standard, M 1.
s
I n Table I, transmittance values as determined by a modified anthrone
For Table I1 data ethylcellulose was first extracted from the oil samples with methanol-miter extractions, and was then determined by the modified anthrone procedure. Tables I and I1 shorn that essentially all of the ethylcellulose is recovered from each of the ten different aliqiiots of the ethylcellu-
Table 1. Per Ceni Transmittance on Benzene Standard B" b y Anthrone Reagent
Table 111. Per Cent Transmittance on Ethylene Dichloride Standard B" b y Anthro -#eReagent
P.P.M. Ethylcelluloseb in 10 M1. of Benzene
P.P.M. Cellulose Acetate Butyrateb Ethylene % in 10 Ethy [:ne DiTrans- fill. of Dichloride chloride, mit- Ethylene Standard 13, nil. bIl . tance Dichloride 1 9 96.5 0.5 2 8 93.5 1.0 1.5 3 7 89.5 4 6 86.8 2.0 5 5 84.5 2.5 G 4 80.8 3.0 3.5 7 3 78.0 8 2 74.3 4.0 1ml. ethylene jichloride standard B = 0.000005 gram cellulose acetate butyrate. * Cellulose acekite butyrate, EAB-27220.
RESULTS AND DISCUSSION
Benzene Ben% Standard zeng, TransM1. mittance B, hfl. 1 9 95.3 2 8 92.5 3 7 88.8 4 6 85.0 5 5 83.3 6 4 81.3 7 3 78.0 8 2 75.8 9 1 73.5 10 0 70.8
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
a 1 ml. benzene standard B = 0.000005 gram ethylcellulose. b Ethylcellulose, 4 6 . 1 yo OCgHs, 70 viscositJ..
576
ANALYTICAL CHEMISTRY
5
lose-mineral oil standard. This proves that the four successive methanol-water extractions completely removed the ethylcellulose from the 10-ml. mineral oil sample.
Table IV. Per Cent Transmittance on Cellulose Acetate Butyrate-Mineral Oil Standard" by Anthrone Reagent
Cellulose Acetate ButyrateMineral Oil Standard, M1.
Ethylene P.P.M. Dichlo- , Cellulose rideAcetate Mineral Butyrateb yo in 10 Oil Blank Trans- Ml. of Staridard, mit- filineral M1. tancc Oil
3.0 4 79.5 3.5 3 77.3 4.0 8 2 75.0 a 1 ml. cellulose acetate butyratemineral oil standard = 0.000006 gram cellulose acetate butyrate. * Cellulose acetate butyrate, EAB272-20. G
7
Table I11 is quite similar to Table I except that transmittance values, as determined by the anthrone procedure, are listed for eight different aliquots of ethylene dichloride standard B solution, containing known amounts of cellulose acetate butyrate. To obtain data in Table IV cellulose acetate butyrate mas first extracted from the oil samples with methanolacetone extractions, and mas then determined by the anthrone procedure. Tables I11 and IV show that cellulose acetate butyrate is completely extracted from each of the eight aliquots of the cellulose acetate butyratemineral oil standard. LITERATURE CITED
Black, H. C., Jr., ANAL. CHEhl. 23, 1792 (1951). Dreywood, Roman, IND.ENG.CHEM., ANAL. E D . 18, 499 (1946). Morris, D. L., Science 107, 254 (1948). Pllorse,. E. E.] ANAL.CIIEM. 19, 1012 (1947).
Samsel,%. P., DeLap, R. A., Ihid., 23, 1795 (1951). Scott, T. A., Jr., Melvin, E. H., Ihid., 25. 165G (1953). Viles; I?. J.; Jr., 'Silverman, L., Ihid., 21, 950 (1949). RECEIVED for review September 14, 1056. Accepted December 5, 1956. Division of Cellulose Chemistry, 130th National Meeting, ACS, Atlantic City, N. J., September 1956.
