I.
Table
Typical Determinations
Deuterium, Atm. Sample
Present
Water
%
2.01
Found 1.96"
2.026 1.080 0.93* 2.06*
~. ._
1.01
2.01 +Te tradeuterio-Lalanine 54 53.6b Reduction tube of Figure 1 used. b Apparatus of Figure 4 used. 0
u Figure 4. A.
B. C. D.
ACKNOWLEDGMENT
Connections of apparatus to C-H analyzer tube
Moving furnace Platinum boat with sample Silver gauze Platinum foil
of the combustion tube was unavoidable; it must be pretreated twice with each 5 mg. of sample before measurement. A calcium chloride tube waa connected directly to the combustion tube during the pretreatment. When the combustion was completed, screw clamp D was closed and the apparatus was evacuated and cut by a flame a t B and C. The rest of the procedure was similar to that described above. RESULTS
The results are summarized in Table
I. The standard water was prepared by diluting commercially available 99.8 atom % ' deuterium oxide. GAlanine
E.
Polyethylene bottle F. Solid carbon dioxide G. Aluminum foil H. Calcium chloride
which contained deuterium a t positions Q and fl was prepared enzymically (3). The deuterium content of the preparation at position a was estimated to be 94 atom yo from the ratio of infrared absorption peak heights a t wave numbers 1411 and 1308 cm.-1, which corresponded to carboxyl symmetric stretching and a-CH deformation absorptions, respectively (6). If it is assumed that all the hydrogen atoms a t positions CY and of this alanine preparation are replaced by deuterium in the same proportion, the deuterium in hydrogen atoms of the alanine is calculated to be 54 atom %. This value agrees well with mass spectrometric data.
The author is grateful to the Rockefeller Foundation and to A. E. Mirsky for providing the mass spectrometer, to Tairo Oshima of this laboratory for deuterio-substituted alanine and its infrared spectrum, and to Isao Chiba for technical assistance. LITERATURE CITED
(1) . , Dubbs, C.
(1953).
A., ANAL. CnEM. 25, 828
'
(2) Graff, J., Rittenberg, D., Ibid., 24,878
(1952). (3) Oshima, T.,Tamiya, N., J . Biochm. ( T o k y o ) 46, 1675 (1959). (4) Rittenberg, D.,Ponticorvo, L., Intern. J . Avvl. Radiation and Isotopes I ., 208 . (1950j. (5) Suaulfi, S., Oshima, T., Tamiya, *N., Fykushlma, K., Shimanouchi,.T., Miaushima, S., Spectrochim. Acta, in press.
NOBUO TAMIYA Tokyo Medical and Dental University 3-Chome, Yushima, Bunkyo-Ku Tokyo, Japan
Colorimetric Estimation of Aluminum with Pyrocatechol Violet SIR: Pyrocatechol violet has been used for the colorimetric determination of bismuth, thorium, copper (2, 3), and fluoride by measuring the decolorizing action of fluoride on the zirconium complex with the reagent (1). This reagent can be used for the colorimetric estimation of aluminum in the presence of zinc and magnesium within the range of 3 to 15 p.p.m. in a pyridine-acetate buffer ( 4 ) ,establishing a pH of 5. At a pH of 7 and higher, zinc and magnesium complex with pyrocatechol violet. The aluminum complex has an absorption maximum a t 615 nip as compared to 450 mF for the reagent (Figure 1). Iron, bismuth, copper, and tin will interfere. EXPERIMENTAL
Apparatus. A Cary Model 11 MS spectrophotometer equipped with 1em. Corex absorption cells was used for all photometric measurements. Reagents. Standard aluminum solution was prepared by weighing
12.3458 grams of aluminum sulfate, putting them in a [A12(SOJa]. 18H20, 1-liter volumetric flask, and diluting the salt to volume with distilled water. A gravimetric analysis of a n aliquot of the solution with 8-quinolinol gave a concentration of 1.050 mg. per ml. of aluminum(II1). The reagent w&s prepared by dissolving 0.3864 gram of yrocatechol violet (3,3',4'-trihydrox~-f)uchsone-2"-sulfonic acid) in 100 ml. of distilled water. The pyridine-acetate buffer was made b mixing 77 ml. of reagent grade pyric$ne with 63 ml. of glacial acetic acid. Procedure. The concentration curve is constructed by diluting the stock aluminum(II1) solution and then pipetting an aliquot corresponding to 0.3 up to 1.5 mg. of aluminum (111) into a 100-ml. volumetric flask. Ten milliliters of buffer and 2.0 ml. of the reagent are added, and the solution is diluted to volume with distilled water. The absorbance of the solution is then measured against a reagent blank. I n the determination, a known volume
of sample containing no more than 1.5 mg. of aluminum is pipetted into a 100-ml. volumetric flask and treated in the same manner as samples for the concentration curve. The concentration of aluminum is obtained from the curve and the total
0.3-
5 0WAVE 0 LENGTH.600 mu
400
700
Figure 1 . Absorption spectra of aluminum-pyrocatechol complex A. B.
Aluminum-pyrocatechol complex, alumlnum concentration, 15 p . p m Pyrocatechol reagent, concentration 5 X I O - W , pH 5.0
VOL. 32,
NO. 6,
MAY 1960
725
Table I. Colorimetric Determination of Aluminum with Pyrocatechol Violet .41( 111) Concentration, Relative
Error,
Mg.
Present 144 13 21 10 17 42
0 0 4
0 4 3
70
Found 143 0 13.0 22 0 9.5 16 4 43 6
0 0 0 2 8 -5 0 -5 8 3 1 -1
aluminum present 19 calculated using the proper dilution factor and sample weight. Empirical Formula of Complex. The method of continuous variations ( 5 ) \\-as used to establish the ratio of reagent to aluininum(lI1). Equimolar concentrations of reagent and aluminum (111) rolutions were prepared, and the absorbance of solutions containing a a mixture of X ml. of pyrocatechol X ) ml. of aluminum violet and (10 (111) a t a p H of 5 was measured a t 615 m p . The absorbance was corrected
-
for the unreacted reagent because it does contribute to the absorbance a t this wave length. Results indicate that 1 mole of aluminum(II1) will complex 1.5 moles of pyrocatechol violet at a p H of 5 , Interference. Interference from solutions containing more than 2 p,p.m. of iron(III), copper(II), bisniuth(II), and tin(1V) can be expected. KO interference was encountered from zinc (11), niagnesium(II), and manganese (11) in concentrations up to 50 p.p,m. a t this pH. RESULTS A N D DISCUSSION
Samples to be analyzed were prepared by fusing suitablc weights of alumina (99% purity) with potassium pyrosulfate and then dissolving the cake in 0.l.Y hydrochloric acid. The solutions were diluted to known volumes and the total aluminum ion concentration was colorimetrically determined. The results (Tahlr I) indicate that the relative error in tlw nwthod is about 6.07,.
This method is applicable for the rapid estimation of aluminum without any interference from magnesium and zinc. Future investigation will iiwlutie the further verification of the empirical formula of the complex as wcll as the determination of its ionization constant hy spectrophotometric mcans; also, the effect of various masking compounds will be made knoan in an effort to eliminate some of the interferences. LITERATURE CITED
( 1 ) Krabulec, L., Cl'tskosiov. hyy. r p i d e v i i a l . mikrobiol. immuno2. 4, 376 (1955). ( 2 ) Svach, Milos, Z . una!. C'hem. 149, 825, 417 (1950). ( 3 ) Zbid., p. 414. ( 4 ) Suk, V., llalat, Y , , ('hemist .47m!ysl 45, 30-7 (1936). ( 5 ) S'osburgh, K, C.. Cooper, G. It., J . A m , Chem. Sot. 63, 437-42 (19.11). .\lr;THOSY
.dSTON
Textile Fibers Department E. I. dn Pont de hemoure a n t i C'o., Iiic. JVilmington 98, Del.
Wet Digestion of Plant Material Gives Low Boron Values SIR: Many laboratories prefer a wet digestion procedure to dry ignition for the routine analysis of plant material. The n e t digestion is more rapid and probably less subject to loss of mineral constituents than the dry ignition. Because information is lacking as to hetlier boron is lost during digestion or nhether it could be determined in the extract from the wet digestion procedure, a series of plant samples was analyzed by both procedures. The details of the wet digestion procedure have been described (2). The digestions were carried out in borosilicate glassware. The quantity of boron dissolved from the glassware was small, as indicated by blank determinations, but all results were corrected for the blank. The dry ignition procedure is also described in the same reference. Boron was determined colorimetrically with the carmine reagent (1, 2). For confirmation, boron was also determined by the electrometric titration procedure (3)on many of these samples. The plant material samples were :inalyzed in 1954 and again in 1959 by the dry ignition procedure. These
726
ANALYTICAL CHEMISTRY
data, together with the results from the n e t digestions, are s h o m in Table I. Table
I,
Boron in Plant Material
Boron, Mg./Kg. Dry Plant Material Jl'et digesDry -4shing tion Plant Speciesd 1954 Oat grain 18 Sudan grass 1388 Fruitless mulberry 2140 Fruitless mulberry 116 Fruitless mulberry 141 Silver maple 354 Silver maple 440 Silver maple 170 Fruitless mulberry 210 Lemon leaves 545 Lemon leaves 621 Elm leaves 86 Each entry represents sample. 5
1959 23 1390 2212 115 138 365 457 176 200
570
..
,
97
1959 18 1163 1650 51 71 257 329 102 105 372 606 55
a separate
The data of Table I indicate a serious loss of boron during the wet digestion, because boric acid is lost by volatilization from the acid solution during di-
gestion. The values sho\\n for this method are averages of two or more separate analyses. There was much variability among these replicates, indicating a lack of precision. For example, results 011 one sample ranged from a low of 222 to a high of 530 p.p.m. boron. The probable reason for this variability is difference in time and temperature of digestion resulting in different amounts of boron being lost. I t is concluded, therefore, that the wet digestion procedure is not satisfactory for the determination of boron in plant illaterial. LITERATURE CITED
(1) Hatcher, J. T., Wilcox, L. 1- , A s . 4 ~ . CHEM.22,567-9 (1950), (2) United States Salinity Laboratory Staff, U . S. Dept. .4yr. Handbk. 60, 129, 135 (1954).
(3) Wilcox, L. Y,, IKD.ENG. CHEY., A S A L . ED. 12, 341--3 (1941). J O H N T. HATCHER U.S. Salinity Laboratory Soil and Water Conservation Research Division U. S. Department of -4griculture Riverside, Calif.
