purity as indicated by their analytical values (Table I). Although in most cases crystallization was not necessary for purification] several of the salts could be crystallized in good yields from ethyl acetate. The salts were not hygroscopic or otherwise sensitive to the atmosphere, so special precautions need not be taken with solvents or in isolation and drying. One illustration of the usefulness of this type of derivative was in connection with recovery of indoleacetic acids from a thin layer chromatogram. When 5-methoxyindoleacetic acid was chromatographed on a thin layer of silica on a glass plate, then recovered from the silica, it lost its characteristic infrared spectrum, indicating extensive degradation during chromatography although a discrete spot was obtained. However, a 5-methoxytryptamine salt prepared from an identical fraction gave an infrared spectrum matching that of the authentic salt. Both isolation and a high degree of purification were easily effected in one step. A further advantage of the salt derivative described here was that very
small amounts of acid could be converted. It was easily possible to start with 5 mg. of acid and recover a quantitative yield of derivative without using any special equipment. Of 15 acids tried, only salicylic acid did not form a precipitate even after standing several days, though 3-nitrosalicylic produced a salt immediately in quantitative yield. The salts of the longer chained fatty acids, stearic and octanoic, were soluble in the chloroform-ether solutions used. However, when large quantities of n-heptane were used in the preparations, salts could also be obtained in quantitative yields as gelatinous precipitates.
ether (used without drying). An immediate precipitate formed and the mixture was cooled for 15 minutes in ice, filtered, and the salt dried in air. All yields were quantitative. A slight departure in procedure was used for longer chain fatty acids, octanoic and stearic. Thus, 3.9 ml. of 5-methoxytryptamine (10 mg. per ml.) in chloroform were added to 0.3 ml. of octanoic acid in 110 ml. of nheptane. A gelatinous precipitate formed and the mixture was cooled a t 5" C. overnight t o obtain 60 mg. of the pure salt on vacuum filtration. A stearic acid salt was made in a similar manner, but it was too gelatinous to filter and was isolated by centrifugation. LITERATURE CITED
EXPERIMENTAL
(1) Cheronis, K. D., Entrikin, J. B.,
Preparation of Salts of 5-Methoxytryptamine and Organic Acids. A stock of 5-methoxytryptamineJ m.p. 120° t o 123" C. (Regis Chemical Co., Chicago 10, Ill.), in chloroform was used (10 mg. per ml,). I n one instance, 3.9 ml. of the stock solution was added to 41 mg. of 5-methoxy-3indoleacetic acid dissolved in 2 ml. of
"Semimicro Qualitative Organic Analysis," Chap. 14, Interscience, New York, 1957.
ROBERTG. TABORSKY Research Division The Cleveland Clinic Foundation Cleveland, Ohio RECEIVEDfor review March 30, 1964. Accepted May 4, 1964.
Detection of Dichlorophene, Hexachlorophene, and Other Related Bisphenols by Gas Liquid Chromatography SIR: A gas liquid chromatographic method has been developed which permits the investigation of common halogenated bisphenols, particularly those found to have commercial application. Conditions have been devised so that these high melting and even higher boiling materials can be injected and eluted from a column in symmetrical peaks with no noticeable decomposition (Figure 1). The novelty of the technique as here presented is the use of short columns in the range of 8 to 12 inches, moderately high temperatures (200" to 250" C.)] relatively short retention times (5 to 15 minutes), and DICHLOROPHENE.
5.0 MIN.
HEXACHLOROPHENC
15.0
fast flow rates (100 to 150 ml. per minute). This technique is of special value in mixtures since the methods in current use have shortcomings in this respect. The colorimetric methods (6, 8, 9) are not specific for any one member in the class. Ultraviolet absorption is the other approach] but these methods (3,7, 10) are often useless in the presence of interferences. Derry, Holden, and Newberger ( 4 ) have employed liquidliquid partition chromatography with subsequent ultraviolet determination of the eluates. They have applied the method to synthetic dichlorophenehexachlorophene mixtures and to cosmetics with some success. The separations are not sharp and the subsequent ultraviolet determinations are still subject to the limitations of that method. Table I.
Common name ,..
Dichlorophene (G-4Q) Bithionol Hexachlorophene (G-11Q) Figure 1 .
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Typical chromatogram
ANALYTICAL CHEMISTRY
Bravo and H e r n h d e z ( 2 ) have developed paper and plate chromatographic methods for resolving mixtures of dichlorophene and hexachlorophene. I n the paper method, detection is made with ferric chloride and potassium ferricyanide while ultraviolet measurement is used after elution from the plates. I t is now possible with gasliquid chromatography to detect bisphenols by direct injection of many cosmetic or pharmaceutical preparations containing them. EXPERIMENTAL
An F&M model 609 flame ionization unit was used in this work with helium carrier gas. A '/(-inch 0.d. glass column 12 inches long was made into U-tube shape and filled with a packing made of 10% DC-710 silicone oil on Chromport
Relative Retention Data
Chemical name 2,2'-Methylenedi-p-cresol
2,2'-Thiobis( 4-chlorophenol) 2,2'-Methylenebis( 4-chlorophenol) 2,2 '-Thiobis( 4,6-dichlorophenol) 2,2'-hlethylenebis( 3,4,6-trichlorophenol)
Relative retention 0.38 0.61
1 .oo
1.30 3.00
MICROGRAMS
35
25
LFigure 2.
Empirical calibration of hexachlorophene concentrations at
XXX *o/lw-mesh solid support (MicroTek) in the usual manner. Teflon ferrules were used with conventional Swagelok nuts to fasten the glass column to the instrument. We have also used 1/4-inch 0.d. copper 8 inches long as.the column sheath with no noticeable impairment to the symmetry or efficiency of separation. Column temperatures used were 225' to 250" C. The flow rate was 130 ml. of helium per minute. Preconditioning a freshly prepared column by heating at 250' C. for a t least 2 hours with a flow of purging gas was necessary. A solid sample injector (Hamilton SS-SO) or a solvent with conventional syringes can be used to
0
MINUTES
IO
-
15
Figure 3. An industrial emulsion a t 2 5 0 " C. indicating measurement of peak height of hexachlorophene a t slightly faster gas flow
inject these solids which melt over 160' C. The former technique is preferred. RESULTS AND DISCUSSION
The problem of getting the bisphenols to elute in a reasonable time of less than 30 minutes with good gaussian peaks has been resolved satisfactorily. Several substrates were investigated, DC-710, a phenylmethyl silicone, proved to be both most efficient and thermally stable. Ten per cent concentration was found to be adequate to cover the solid support and to keep a t a minimum teiling due to absorptive effects. Low loaded Carbowax 20 M , as an example of a polar substrate, even to 0,5y0 on 60/80 glass beads, showed a great tendency to hold the bisphenols by hydrogen bonding. Retention times were excessive to the degree of no elution after 1 hour at the temperature and flow conditions used with DC-710. Injection ports well packed with glass wool heated in the range 300" to 325' C. showed no tendency to cause decomposition. A few of the more prominent halogenated bisphenols were chromatographed at 225" C. and the relative retentions are given compared to dichlorophene chosen as a standard (Table I). Actually, bithionol and hexachlorophene, are more conveniently eluted a t 250" C. The technique of gas liquid chromatography thus makes any combination of mixtures easy to investigate since there is a good degree of resolution among the group investigated. ;In empirical quantitative calibration was made of hexachlorophene by dissolving it in acetone to contain 5 pg./pl, (Figure 2). At the specified conditions, a straight line plot of peak heights to concentration is obtained. The maximum detector sensitivity a t these con-
250" C.
ditions is from 5 to 10 pg. At more sensitive instrument settings, where background noise is noticeable, 5 pg. is easily detected. We have been successful in detecting hexachlorophene by direct injection of lotions and creams (Figures 3 and 4). The solid sample injector was inserted into a cream in repeated tamping fashion to partially fill the bore. Sample sizes varied from 1 to 2 mg. This technique could be applicable to soaps and powdered detergents also. The industrial lotion in Figure 3 was prepared to contain 0.27,. We found 0.157, by ultraviolet determination and 0.257' by gas liquid chromatography. I t was
1 0
5
10
15
20
MINUTES
Figure 4. Cream shampoo-injected as is a t 2 3 0 " C. Hexachlorophene is the last peak VOL. 36, NO. 8, JULY 1964
1665
run a t a slightly faster gas flow of 140 ml. per minute. When interferences make the results of the conventional methods ambiguous, the proposed method can be of confirmatory value. Quantitative measurements can be made with creams ( I ) . Instances where the particular vehicle does not lend itself to any of these approaches, perhaps, could be subjected to a prior separation ( 6 ) . There is no doubt that the electron capture detector, being extremely sensitive to electronegative materials, such as those containing halogen, would be
exceedingly more sensitive and specific for the bisphenols. This field has not been investigated. LITERATURE CITED
(1) Bahjat, K., J . Pharm. Sci. 5 2 , 1006 (1963). (2) Bravo, R., Hernhdez, F., J . Chromatog. 7 , 60 (1962). (3) Clements, J. E., Newberger, S. H., J . Assoc. Ofic. Agr. Chemists 37, 190 (1954). (4) Derry, P. D., Holden, M., Newberger, S. H.. Proc. Sci. Sect. Toilet Goods Assoc.'36, 25 (1961). ( 5 ) Johnson, C. A,, Savidge, R. A., J . Pharm. Pharmacol. 10, Supp. 171T (1958).
(6) Johnston, V. D., Porcaro, P. J., ANAL. CHEM. 36. . ~ _ _ 124 ~( 1 964). ~ . (7) Jungermann, E., Beck, E. C., J . Am. Oil Chemists' SOC.38, 5 13 (1961). ( 8 ) Klinae. K.. Seifen43ele-Fette- Wachse Feb. 4 and 18 (1959). 85, 61,-87) , 19) Aar. , , Larso n. H. L.. J . Assoc. Offic. * Chemists'28, 301 11951). (10) Lord, J. W., McAdams, J. A., Jones, E. B., Soap Perjumery Cosmetacs 26, 783 (1953). I
- - - \ - - - - I
PETERJ. PORCARO Sindar Corp. A4nalyticalLaboratory Delawanna, K.J. RECEIVEDfor review March 9, 1964. Accepted April 27, 1964.
Determination of Ferrous Oxide in Ferrites SIR: In many ferrites the magnetic properties are fixed by the ratio of ferrous and ferric ions. Hence, both valency states must be determined before the ferrite composition can be related to the magnetic measurements. There is very little information in the literature on determination of ferrous iron in ferrites. Analysis for ferrous and ferric iron is simple in solution and if a solid sample can be dissolved in hydrochloric acid under an inert atmosphere, determination is not difficult. However, many ferrites do not dissolve in hydrochloric acid so that methods must be developed. This report describes a method of decomposing ferrites with phosphoric acid in the presence of a known amount of phosphatocerate a t a temperature of approximately 200" C. for 15 to 30 minutes. The excess phosphatocerate is then back titrated with a standard ferrous sulfate solution using ferroin as indicator. The determination takes 1 hour and several samples may be run simultaneously.
phenanthroline indicator solution, and back titrate the excess phosphatocerate with 0.02A' ferrous ammonium sulfate ammonium sulfate hexahydrate in IN solution. The end point is from light sulfuric acid and standardized. blue FERROUS ~,~~-PHENANTHR INOLIN E to orange yellow. Run a blank along with the sample. DICATOR, 0.01M, available from The G. Frederick Smith Chemical Co. Procedure. A finely powdered DISCUSSION A N D RESULTS sample (100-mesh) of 30 to 100 mg. is h mixture of hydrofluoric acid and decomposed with a mixture of 3 ml. of dichromate has been used for determin0.1,V phosphatocerate solution and 10 ml. of 85% phosphoric acid (sp. ing ferrous oxide in rocks and silicates gr. 1.7) in a dry 100-ml. beaker on a ( 4 ) , a mixture of phosphoric acid and hot plate (heated a t 280' to 300' C.). sulfuric acid containing vanadium T h e decomposition requires from 15 pentoxide has been used for determining to 30 minutes depending on the nature ferrous oxide in chromite (S), and a and size of sample. After decomposimixture of phosphoric acid and sulfuric tion, cool a while, pour into a 400-ml. acid containing ceric sulfate has been beaker containing approximately 100 used for determining ferrous oxide in ml. of water, 10 ml. of concentrated chromite ( 2 ) . It was found that fersulfuric acid, and 1 drop of ferrous 1,lO-
FERROUS h t M O N I U Y SULFATE SOLU-
TION,0.02N. Prepared from ferrous
EXPERIMENTAL
P H 0 S PH A T 0 C ER ATE Reagents. SOLUTIOK,0.1N. H e a t a t 280" to 300' C. on a hot plate 5.4286 grams of primary standard grade ceric ammonium nitrate (available from The G. Frederick Smith Chemical Co., Columbus, Ohio', i r i a drv 100-ml beaker with 10 ml. of 85% phosphoric acid until no nitric acid fumes are evolved (30 minutes are usually sufficient,). Cool somewhat and transfer to a 100-ml. volumetric flask. Rinse with 10 ml. of 8570,phosphoric acid and some water, then rinse with 20 ml. of concentrated sulfuric acid and water. Cool, make to volume. and mix well. The solution should be clear. If the presence of sulfuric acid is objectionable, rime with 20 nil. of 857, phosphoric acid in place of sulfuric acid.
1666
ANALYTICAL CHEMISTRY
0.1
MINUTE Figure 1 .
Effect of time on titer of oxidant solution
Mixture o f IO ml. o f 65% phosphoric acid a n d 2 or 3 ml. o f 0.1 N phosphatocerate solution contoining 20 ml. o f 65% phosphoric ocid a n d 20 ml. o f concentrated sulfuric acid p e r 100 ml. volume 8. Mixture of IO ml. of 65% phosphorjc acid a n d 2 or 3 ml. of 0.1 N phosphatocerate solution containing 4 0 ml. o f 65% phosphoric acid p e r 100 ml. volume C. Mixture of IO ml. of 65% phosphoric acid a n d 2 or 3 ml. o f 0.1 N dichromate solution in w a t e r The hot p l a t e w a s h e a t e d a t 290' to 300' C. A.
