ANALYTICAL CHEMISTRY
1204 Table I.
Recovery of Ribose and Glucose from Paper by Periodate Method
Calcd. Absorbance Correc- Corrected Absorbance RecovAssay Prepara- Amt.. R e a d i n g s tion Standard ery, Factor" Absorbance Curve y 0 hr. 3 hr. 3'% tion 0.657 0.650 98 Ribose 4 . 0 0,810 0 , 6 6 0 - 0 , 0 0 3 0.470 0.467 99 10.0 0 801 0 . 4 6 4 +0.006 0.757 0.758 100 Glucose 2 5 0 . 7 9 0 0.740 f0.017 5 0 0.796 0.713 + O 011 0.724 0.728 101 Paper blanks 0.811 0.799 Periodate blank 0.795 0.795 a Correction factor. =tDifference in absorbance reading of paper blank a t 0 and 3 hours. & Difference in absorbance reading of 0-hour assay and 0-hour periodate blank (see t e x t ) .
unknoivns and standards, blank sections of paper of the same size and from the same chromatogram for which the sugar spots were cut. This correction, expressed as the difference in absorbance between the paper blank at zero-hour and assay-hour pclriod, is added to the readings a t the various time intervals. The treatment of typical data is illustrated in Table I.
In these runs known amounts of the monosaccharides were spotted by micropipet on a sheet of Whatman No. 1 paper which had been run two-dimensionally in collidine: HOH (saturated) and BuOH :H.4c :HOH (4: 1:5 ) and dried. The paper n.as freed
of lingering solvents by the steaming procedure previously described. The areas corresponding to the deposits of sugars were rut out, folded, and immersed in 10 ml. of water for 4 hours with continued shaking a t 37' C. This method of elution has been found fully effective and convenient. The eluate was centrifuged in order to remove paper lint which might otherwise interfere with the absorbance reading. One milliliter of the eluate was then assaved according to the general quantitative procedure, vielding the data in Table I. Paper blanks and periodate blanks kere run simultaneously. At least one level of standard is always run, in order to br certain that standard conditions are prevailing. ACKNOWLEDGMENT
The author wishes to acknowledge gratefully the many helpful suggestions of C. A . Knight, E. K. Putman, and D. L. MacDonald, :dl of this university. This investigation was supported in part by a research grant, RG-4559, to C. A Knight from the Sational I n s t i t u t ~ sof Health, Public Health Service, and by grants from the Lederle Laboratories Division, American Cyanamid Co.. and the Rockefeller Foundation. LITERATURE CITED
(1) Dixon, J. S.. Lipkin, D., ANAL.CHEM.26, 1092 (1954). (2) Flood, A . E., Hirst, E. L., Jones, J. K. N., J . Chem. Soc. 1949,
1659.
(3) Frommhagen, L. H., Knight, C. A , , unpublished data. (4) Ilarinetti, G. V., Rouser, G., J . 4 m . Chem. Soc. 77, 5346 (1955).
RECEIVED for review December
27, 1955.
Accepted .ipril 13, 1956
Determination of Traces of Fatty Amines in Water ALBERT M l L U N and FRANCES MOYER Research Laboratories, General
Mills, Inc., Minneapolis, M i n n .
A method has been developed for determining traces of high molecular weight fatty amines in water. The procedure should be applicable to the control of amine concentration in steam condensate systems where fatty amines are added to inhibit corrosion. Amine concentration is determined by titrating with an anionic surface active agent to the disappearance of pink color due to an amine-eosin complex. A calibration curve is given for the concentration range of 0.5 to 10 p.p.m.
F
ATTY amines of high molecular weight have been used successfully for some time in steam condensate systems to inhibit corrosion. The efficient control of this treatment requires a constant check on the concentration of amine in the condensate waters at the 1 to 10 p.p.m. level. Therefore, a direct, rapid test for determining the concentration of fatty amine in water a t these low levels is desirable. This paper describes such a test, which should be applicable to steam condensates. Bouilloux ( 2 ) found that very dilute solutions of fluorescein, or its derivatives, in organic solvents are colorless, but form colors upon the addition of certain amines. Eosin, in particular, was very sensitive, forming a pink color in the presence of very small quantities of amine. He attributed the pink color to a quinoid-type structure resulting from the formation of an eosinamine salt. Prudhomme ( 4 ) used this color formation of amine with eosin to determine quinine in urine. A buffered sample solution containing eosin was extracted with chloroform and the chloroform extract containing the colored quinine-eosin salt was compared with the color of standard solutions. Harper, Elliker, and Mosely ( 3 )utilized the red color resulting
from the reaction of eosin and quaternary aninionium salts in a quantitative titration procedure for determining the latter at the 10 to 300 p.p.m. level. The titration was carried out with an anionic surface active agent which replaced the eosin in the quaternary-eosin salt and destroyed the color. The procedure described below is essentially that used by Harper, Elliker, and RIosely ( 3 )for quaternary ammonium salts. A buffered sample of water containing fatty amine is shaken up with a dilute solution of eosin in tetrachloroethane. The amine forms a pink tetrachloroethane-soluble compound with eosin. The resulting mixture is then titrated with a solution of sodium lauryl sulfate, previously calibrated against known quantities of amine, until the pink color in the nonaqueous layer has disappeared. Analyses by this method of known mixtures containing fatty amine in water in the range of 0.5 to 10 p.p.ni. indicate an accuracy within 0.5 p.p.m. of amine. REAGENTS AND APPARATUS
Indicator Solution. Dissolve 10 mg. of Eosin yellowish (sodium salt of tetrabromofluorescein) in 100 ml. of analytical reagent grade acetone. Add 10 ml. of the acetone solution to 90 ml. of tetrachloroethane. Remove the reddish color from the tetrachloroethane solution by adding 0.5 gram of citric acid and shaking for 1 minute. Filter through Whatman S o . 1 (or equivalent grade) filter paper. Buffer Solution. Prepare a 5% aqueous solution of citric acid and adjust to p H 3.5 with 0.1N sodium hydroxide. Add 1% tetrachloroethane t o prevent mold growth. Anionic Surface Active Agent Solution. Prepare a 0.01% aqueous solution of sodium lauryl sulfate. This solution should be recalibrated frequently and discarded when deterioration becomes evident. Test tubes, X 5 inches, are rinsed with alcohol and acetone and dried before use.
V O L U M E 28, NO. 7, J U L Y 1956
1205 Table I.
Adsorption of Amine on Polyethylene
2 4 5 7 11 13 24 Hr. Days Days Days Days Days Days Amine H26Da, p.p.m. 10 8.8 3.7 2.8 2.2 1.2 1.0 0.3 7D b , p.p.rn. 10 9.2 5.9 5.1 4.1 2.7 '7.3 0.5 a Distilled hydrogenated tallow amine, b Distilled octadecylamine. Immediately
Figure 1.
Amine adsorption in coated 0aske X
Hydrogenated tallow a m i n e Ootadeeylamine
DISCUSSION
One-Liter Volumetric Flasks. Coat inside of flasks with Beckman Desicote ( I ) to cut down adsorption of amine on the flask surfaces. Buret, 10-ml. capacity. PROCEDURE
Standardization. Prepare a series of standard aqueous amine solutions covering the desired concentration range in the following manner. Weigh the required amount of amine (or equivalent amount of amine acetate) into a 5-ml. beaker. Dissolve the amine in about 1 ml. of isopropyl alcohol and pour into a 1-liter volumetric flask containing approximately 900 ml. of water. Wash out the beaker into the flask with a total of 9 ml. of iscpropyl alcohol. I n this transfer do not allow the amine to touch the inside of the flask neck, but pour directly into the water, using a stirring rod. Swirl the flask to disperse the amine, then make up to volume with water and shake. For very low concentrations (0.5 to 3 p.p.m.) dilute aliquots from a 10 p ~ p . m . stock solution in a 1-liter flask. Titrate a 5-ml. aliquot of each standard solution as described below within 1 hour of preparation. Prepare a calibration curve by plotting milliliters of anionic solution against parts per million of amine.
16-
14-
IPI-
=5 10-
0
I
Z
3
Figure 2. X
4
5 . P P M AMNE
6
7
8
9
Calibration curve
Hydrogenated tallow a m i n e Octadeeylamine
Determination. Fill a 1-liter volumetric flask with the sample solution. Within 1 hour, rinse a 5-ml. volumetric pipet three times with the sample solution in the flask, discarding the washings; then pipet 5 ml. of the same sample solution into a test tube. Add 1 ml. of the indicator solution, followed by 0.1 ml. of the buffer solution. Place thumb over the test tube mouth, shake vigorously for approximately 30 seconds, and allow the two liquid layers to settle. A pink color in the bottom layer indicates the resence of amine. A polyethylene thumb covering was found el ful in protecting the thumb. '&rate with the anionic solution to the disappearance of the pink color in the lower liquid layer. During the titration, shake the test tube between additions of each 0.05 ml. of the anionic solution, allowing the bottom layer t o settle partly, and comparing the color of the bottom layer against a white background with that of a blank which contains 5 ml. of water and the prescribed volumes of indicator and buffer solutions and which is shaken simultaneously. Approximately 0.1 ml. before the end
E
point there is a noticeable increase in the rate of settling of the two layers. This rate of settling decreases on the addition of more titrant
A number of compounds which might be present in small amounts in technical grade, primary fatty amines were tested for color formation in this procedure. Dioctadecyl and trioctadecyl amines also gave a pink color, stearamide gave a very faint pink color in concentrations greater than 30 p.p.m., whereas stearonitrile, N-octadecylacetamide, and stearic acid gave no color even in very large concentrations. Smmonia in larger than 30 p.p.m. concentrations gave pink color only in the upper aqueous layer. Tap wat'er gave no color and behaved like distilled water when primary amine was added. Several samples of steam condensate water with added amine behaved normally when checked by this procedure. Considerable difficulty was encountered in the early part of this work because of the adsorption of fatty amines from water onto surfaces of glass and polyethylene containers. Standard aqueous solutions containing amine in the parts per million range gave appreciably lower titrations on standing, amines of slightly different molecular weight or extent of unsaturation gave appreciably different titrations, amine acetates gave titrations different from equivalent amounts of amine, and transferring amine solutions from one container to another resulted in significantly lower titrations. This loss of amine by adsorption onto the container surface was appreciable in glass and prohibitive in polyethylene. Table I shows the extent to which amine was lost by adsorption when 10 p.p.m. aqueous solutions of a hydrogenated tallow and an octadecylamine were stored in polyethylene bottles. However, this undesirable adsorption could be cut down appreciably by coating the inside of glass flasks with a silicone such as Beckman Desicote. When aqueous solutions containing equivalent amounts of amine were prepared in flasks coated with Desicote, there was no significant difference in titration with tallow, hydrogenated tallow, or octadecylamine. The corresponding acetates a t equivalent amine concentration also gave the same titrations. Figure 1 shows the extent of adsorption from 5 p.p.m, aqueoue amine solutions in flasks coated with Desicote. It is evident that, if coated flasks are used for both sample and standard solutions and if titrations are carried out within 1 hour, adsorption losses are negligible. Figure 2, a calibration curve obtained with octadecylamine and a hydrogenated tallow amine, shows the linear relationship between amine concentration and volume of titrant. The corresponding acetates at the 5 p.p.m. amine level gave titrations within 0.4 p.p.m. of those obtained with the amines. LITERATURE CITED
(1) Beckman Instrument Co., Bull. 262-B. (2) Bouilloux, G., Bull. me. chim. France 1954, 1347. (3) Harper, W. J., Elliker, P. R., Mosely, W. K., Soap Sanit. Chemi C d 8 24, N O . 2, 159 (1948). (4) Prudhoinme, R. O . , Bull. SOC.pathol. esotique 31, 929 (1938).
RECEIVED for review January 30, 1956. Accepted April 12. 1956. Paper 190, Journal Series. General Mills, Inc.
