modified procedure because of the form of Equation 2. For unknown samples in this region it is necessary to determine the absorbance 'of the sample, followed by a similar determination on a carefully diluted sample using HzO of normal deuterium content to ascertain whether the samples were greater or less than 62%) H. I t is also possible to determine the H content of samples containing greater than 90% HzO or more correctly the D content of HzO samples by means of Equation 5 using HzO ,as the reference sample.
(5)
where %D
atom % of heavy hydrogen of the total hydrogen atoms All = absorbance of a hypothetical 1-cm. layer of H D O us. HzO -4,' = 10.0 times the measured absorbance of a 0.1-cm. layer of sample water The values of A I 1 and ilZhave been determined experimentally and are given in Equations 4 and 6 Ai' = AHDO- A H 2 0 = 3 52 (6) The results of samples containing 2 to 10% D using Equation 5 are shown in Table IV. I n conclusion, it is possible to rapidly and routinely determine the H content of small samples of water using a spectrophotometric method based on measurement of the absorbance of the H D O band at 16,680 A4. =
D Content in Samples Containing 2 to 10% D
Table IV.
70
A,' 0 183 0 318 0 610
5%
Dcaiod
2 69
4 82
2 49 4 98
9 98
9 96
LITERATURE CITED
(1) Kirshenbaum, "Physical Properties and Analysis of Heavy Water," pp.
27-62, McGraw-Hill, Xew York (1951). (2) Leconite, L., Ceccaldi, M., Roth, E., J . Chzm. Phys. 40, 166 (1953). GILBERTGORDOK HIDEOYAMATERA Department of Chemistry University of Maryland College Park, Md. WORK supported by grants from the Atomic Energy Commission and the National Science Foundation.
Spectrophotometric Determination of Cerium with Thenoyltrifluoroacetone after Cupferron-Chloroform Extraction SIR: A previous papw ( 2 ) described a method for the spectrophotometric determination of cerium with thenoyltrifluoroacetone (TTA). However, the interference study was not very extensive, and elimination of interfering elements was not discussed. Further study of interference has shown that the proposed method is reasonably selective. The most serious drawback in the method is the interference of iron. Maganese also has been found to interfere. I n the present work, iron, together with several other metals, have been removed by cupferronchloroform extraction. -4 method is described for the determination of cerium in the presence of small amounts of manganese. EXPERIMENTAL
Apparatus. Absorbance measurements were made with a Hitachi EPU-2-4 spectrophotometer, using 1cm. cells. A shaking machine with a time switch was used for TTAxylene extractions. Reagents. Cupfenon solution, 6 grams in 100 ml. of water, was prepared fresh daily. Sodium bromate solution, 1M. TT.1 solution, 0.5.11, 45 grams in 400 ml. of xylene (Dojindo & Co., Ltd., Kumamoto-shi, Japan). Ammonium hydrogen fluoride-nitric acid solution, 0.1M in SH4HF2 and 0 . 2 X in nitric acid was stored in a polyethylene bottle. Standard cerium solution, 1.00 mg. of Ce(II1) per ml., was prepared as described previously ( 2 ) .
Procedure. Cupferron-Chloroform Extraction. Transfer the sample solution containing 10 to 100 pg. of cerium(II1) to a small (50 to 60 ml.) separatory funnel. Adjust the amount of sulfuric acid to 15 meq. and dilute to 10 ml. with water. Add 2.0 ml. of 6% w./v. cupferron solution and mix. Add 15 ml. of chloroform and shake the system for 1 minute. Drain off and discard the organic phase. Add 1.0 ml. of cupferron solution and mix. Shake the solution with 10 ml. of chloroform for 1 minute. Discard the organic phase. Wash the aqueous phase by shaking it for 30 seconds with 10 ml. of chloroform and discard the organic phase. Transfer the aqueous phase to a small quartz dish and evaporate just to fumes of sulfuric acid. T o decompose residual organic matter, add 1 ml. of 30% hydrogen peroxide, and heat gently. Evaporate the solution until white fumes appear. TTA-Xylene Extraction. Transfer the residue to a small separatory funnel with a total volume of 10 ml. of water. Add 3 ml. of 1.11 sodium bromate solution and allow to stand for 5 to 10 minutes. Add 10.0 ml. of 0.5M T T A solution and shake the system for 10 to 15 minutes. Allow the funnel to stand for about 5 minutes to allow water droplets to separate from the organic phase. Drain off and discard the aqueous phase. Filter the organic phase through a small plug of glass wool into a 1-cm. cell. Measure the absorbance of the solution a t 440 mp or 450 mp using the reagent blank or xylene as the reference. Procedure in the Presence of Manganese. Take two aliquots of the sample and carry out the cupferron-chloro-
form and TTA-xylene extractions in duplicate. Measure the absorbance (AI) of one organic phase. T o another organic phase in a separatory funnel add 10 ml. of ammonium hydrogen fluoride-nitric acid solution. Shake the system for 3 minutes. Allow the funnel to stand for about 5 minutes. Drain off and discard the aqueous phase. Filter the organic phase through a small plug of glass wool into a 1-cm. cell. Measure the absorbance (A2) of the solution a t 440 mp or 450 mp against the reagent blank or xylene. From the calibration curve determine the amount of cerium that corresponds to (A1 - A). Calibration Curve. Take, for example, 0, 20, 40, 70, and 100 pg. of cerium and proceed as described in TTA-xylene extraction. Run a blank through the entire procedure. RESULTS AND DISCUSSION
Interference Study. A brief study on interference was reported (a). Additional data on interference are given in Table I. The present study was made under the experimental conditions described in TTA-Xylene Extraction. hlore than 10 mg. of the diverse ion was not tested. The oxidation state of metals in Table I refers to that before addition of bromate. The relative standard deviations for 8 determinations of 50 pg. of cerium were 3.2 and 3.3y0at 440 and 450 mp, respectively. Thus, a t the 95y0 confidence limits, the allowable limits for the average of VOL. 36, NO. 9, AUGUST 1964
8
1867
duplicates for 50 pg. of cerium at 440 mp are 47.3 to 52.7 pg. I n addition to iron ( d ) , manganese interferes seriously with the determination of cerium. Manganese gives a greenish yellow color in the organic phase. The absorption curve of manganese-TTA solution is similar to that of cerium-TTA solution. Milligram amounts of molybdenum and titanium also interfere. Slightly low results were obtained with 2 mg. of fluoride. The low results with 5 mg. of niobium may be due to fluoride which was introduced in the dissolution of niobium metal. Protactinium will interfere ( I ) . Because of the precipitation of lead sulfate in the aqueous phase, more than 1mg. of lead was not tested. Cupf erron- Chlorof o
m
Extraction.
For the separation of cerium from other elements the method described
Table 1. Interference Study (50.0 pg. of Ce taken)
Table II.
Determination o f Cerium with TTA after Cupferron-Chloroform Extraction (50.0 pg. of Ce taken)
Addition, mg.
Ce found, pg."
None Cu(I1) F (NaF was used) Fe(II1) Mo(V1) P(KH2P04was used) Th(1V) Ti( IV)
5.0 1.0 10 10 0.10 5.0 10 5.0 0.50 0.10 10
440 mu 50, 49, 50 52 49 50, 50 50 49 49 50 38 44 48 50
450 mu 51, 50, 50 52 50 51, 51 50 50 50 50 39 45 49 50
49
49
49
49
Fe(II1) 10, Mo 1.0, P 1.O, Ti 0.10, V 0.10, Zr 1 . 0
Al5.0,Ca5.0,Cul.O, F 1 . 0 , La 5.0, Th 5 . 0 a Av. of two detns.
Cerium found, Addition, mg. Al( 111) 5.0 10 1.0 10 5.0 10 1.0 5.0 10 10 5.0 10 1.o
Bi(II1) Ca(I1) Co(I1) Cr(II1) Cu(I1) F (NaF was used)
400 mp 450mp 52 52 52 52 48 49 49 49 51 51 50 50 50 50 51 51 53 53 51 51 53 53 58 58 50 51
2.0 5.0 5.0 10 10 0.010 0.10 1.0 1.0 5.0 10 1.0 10
46 31 50 47 49 57 52 59 49 32 51 50 52
47 32 50 47 50 57 50 52 50 34 51 50 52
;Cv(VI)
1.0 5.0 10 0.10 5.0 5,O 10 5,O
Zn(I1)
5.0
10
50 49 50 51 86 49 49 51 51 49 50
10
BO
49 49 51 51 63 48 49 50 52 50 51 50
La(II1)
Nb(V) Ni(1I) P(KHzPO4 was used ) Pb(I1) Th(1V) Ti(1V) U( V I )
Zr(1V) Av. of 5
two
detns.
~
1868
ANALYTICAL CHEMISTRY
by Onishi and Banks (3) may be used. It is, however, rather tedious. Iron(III), titanium, and some other metals are known to be extracted as cupferrates with chloroform from mineral acid solution. Sandell (4) suggested the use of cupferron for the separation of iron and other metals from cerium. I n the proposed procedure, the sulfuric acid concentration for the cupferron-chloroform extraction was chosen from the consideration of the sulfuric acid concentration suitable for the TTA-xylene extraction. J17hen the TTA-xylene extraction was carried out immediately after the cupferron-chloroform extraction-Le., without the evaporation of the aqueous phase-a low absorbance for cerium was obtained. Consequently, the aqueous phase from the cupferron-chloroform extraction was evaporated just to fumes, and residual organic matter was decomposed by hydrogen peroxide. Results obtained in applying the proposed procedure are collected in Table 11. Six determinations of 50 p g . of cerium gave averages of 50 and 50 pg. a t 440 and 450 mp, respectively. The relative standard deviations were 1.5 and 1.8% a t 440 and 450 mp, respectively. As much as 10 mg. of iron can be removed satisfactorily from 50 pg. of cerium. I n the presence of 5 mg. of vanadium, the recovery of cerium was 78%. The reason is not known. D e t e r m i n a t i o n of Cerium in t h e Presence of Manganese. As mentioned above, manganese interferes seriously. I t is not removed by the cupferron-chloroform extraction de-
scribed in the procedure. When t h e T T A solution containing both cerium and manganese is shaken with aqueous solution that is 0.1M in ammonium hydrogen fluoride and 0.2M in nitric acid, the color due to cerium disappears completely. On the other hand, the color due to manganese remains unchanged, Therefore, cerium can be determined from the difference in absorbance. The aqueous phase was analyzed for cerium, and it was confirmed that cerium was back-extracted from the organic phase. Instead of the dilute nitric acid containing fluoride, varying concentrations of nitric acid or dilute nitric acid solution containing hydrogen peroxide were tried to backextract cerium. The results were unsatisfactory. (4 spectrophotometric method for the determination of manganese with TTA will be reported elsewhere.) Results obtained in applying the proposed procedure are shown in Table 111. The ranges of the recovery of 6 determinations were 98-110 and 100l l O ~ oa t 440 and 450 mp, respectively. The average recoveries were 105 and 107% a t 440 and 450 mp, respectively.
Table 111. Determination of Cerium in the Presence o f Manganese
Mn(I1) Ce taken, taken, Pg.
pg.
50 50 100
20 50 50
Ce found, pg.
440 mp 22, 21 50, 49 54, 54
450 mp 22, 22 50, 50 55, 55
A i t18” C., the absorbance of the TTX-
xylene solution containing both cerium and manganese remains almost constant for 3 hours. The absorbance of the organic phase after back-extraction remains almost constant for 2 hours. Manganese greater than
100 pg.
must be separated from cerium by a suitable method.
( 3 ) Onishi, H., Banks, C. V., Talanta 10, 399 (1963).
B., “Colorimetric Determination of Traces of Metals,” 3rd ed., p. 382, Interscience, Sew York,
( 4 ) Sandell, E.
LITERATURE CITED
( 1 ) Wassoedov, B., Muxart, R., Bull. SOC.Chim.France 1962, 237. ( 2 ) Onishi, H., Banks, C. V., ANAL. CHEM.35, 1887 (1963).
1959.
HIROSHI OEISHI YUKIOTOITA
Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki-ken, Japan
X-Ray Fluorescence Spectrometric Analysis of Iron(lll), Cobalt(II), Nickel(ll), and Copper(l1) Chelates of 8-QuinolinoI SIR: In a previous paper (I) we have reported the use of x-ray fluorescence spectrometric analysis, with the copper (11) and mercury(1I) complexes of 6chloro - 2 - methoxy - 9 - thiolacridine. I t was of interest to us to investigate whether this method rould be extended to metal chelates of other chelating agents. 8-Quinolinol was selected as the organic chelating reagent and the metal ions iron (111) , cobalt (11), nickel(I1), and copper(I1) were used for this study. Secondary fluorescence effects or interelement effects are extremely large for these metal ions, making quantitative analyses difficult; thus, if this method of analy:,is is effective for these metals, it should be effective for others as well. All binary Combinations of the 8hydroxyquinolates of iron(III), cobalt (11) , nickel(I1) , and copper(I1) were prepared and subsequently analyzed 10.0
Ia
0
t
J
E>
JO
J
F
Y
EXPERIMENTAL
---
,006
20
40
60
10.0
P
Metal Ion Solutions. T e n t h molar solutions of FeC1s.6Hz0, CoS04’7Hz0, ?iiS04.6H20, and Cu(C2H30&:H20 were prepared. Previous experience has shown that these solutions, yrepared by weighing, were well within the 3% experimental error of our x-ray analysis method. Preparation of Metal Chelates. T h e metal chelates were prepared in the same manner as in a prerious paper ( 1 ) . Three milliliters of 8-auinolinol solution, prepared by disso1;ing 2.0 grams of 8-quinolinol (Eastman Organic Chemicals) in 33 ml. of 95% ethyl alcohol, were added to each beaker. This was a sufficient amount to chelate quantitatively the binary combinations of the metal ions. Apparatus. The x-ray analyses were conducted with a Philips x-ray fluorescence spectrometer using a tungsten target tube operated a t 40 kv. and 40 ma., a lithium fluoride analyzing crystal, a n d a scintillation counter detector. Analysis of Binary Mixtures. All of t h e binary combinations of iron (111), cobalt(II), nickel(II), and copper(I1) mere prepared and subsequently analyzed. T h e analytical procedure was the same as described previously ( 1 ) . The peaks of all four metals were easily discerned and did not overlap (Table I).
Table I.
.Ol
50.0
with x-ray fluorescence spectrometry. I n addition, six quaternary samples of these metal chelates were prepared and analyzed. The advantages and disadvantages of metal-organic reagents in x-ray fluorescence analysis have been discussed in a previous paper (1).
B -
I.o
d5,
J
B
.IO
.03
I
I
I
20
40
60
I 80
0
W L E FER CENT METAL I
Figure 2. Metal I to Metal I1 peak ratio vs. mole % of Metal I Sym bo1
Metal I
M e t a l I1
A
Iron Copper Nickel
Cobalt Cobalt Cobalt
0
From the calibration curves (Figures 1 and 2), the mole fractions of the metal ions in the binary mixtures can be obtained. This procedure was tested with Fe(III), Co(II), Ni(II), and Cu(I1) in the range of 0 to 12 mg. These analyses were conducted with a relative error of =t30/,. Analysis of Lower Concentrations. T h e copper(I1) and nickel(I1) metal ions were selected for analysis at lower concentrations because their
X-Ray Emission Peaks in 2 8 Degrees for Metals Chelated with 8-Hydroxyquinoline
80
MOLE PER CENT METAL I
Figure 1 . Metal I to metal II peak ratio vs. mole 7 0 of nietat I Sym bo1
A 0
cl
Metal I Iron Iron Copper
M e t a l II Copper Nickel Nicke I
Iron Cobalt Nickel Copper Tungsten
26 27 28 29 74
57 52 48 44 5
45 74 61 96 95
57 52 48 45 6
58 86 71 08 06
51 47 43 40 5
72 46 73 43 24
40 46 5 26
42 99
49 24
~
VOL. 36, N O . 9, AUGUST 1964
1869
