The technique of freeze-drying has been applied to the determination of the SO4*- ion by Tai and Underwood (15). From the spectra obtained from nine different sulfates they chose KzS04as the most suitable for quantitative measurements. The band contour obtained by freeze-drying KBr and K2SOris similar to that obtained by the fusion technique, and (15) H. Tai and A. L. Underwood, ANAL.CHEM., 29,1430 (1957).
the Beer's law plots obtained by the two methods are almost identical. Though more time consuming, freeze-drying should have application for inorganic ions which decompose at the temperatures required for the fusion method. RECEIVED for review February 28, 1966. Resubmitted and accepted November 28, 1967. Work supported by U. S . Atomic Energy Commission Grant N. AT-(40-1)-2760.
Spectrophotometric Determination of the Perchlorate Ion N. L. Trautweinl and J. C. Guyon Department of Chemistry, University of Missouri, Columbia,Mo.
SIMPLE,direct spectrophotometric methods for perchlorate ions do not exist. Present methods involve a precipitation or an extraction step prior to measurement. Nobar and Ramachandran ( I ) precipitated perchlorate 'with excess methylene blue, filtered the precipitate, and determined the excess methylene blue. Swasaki, Utsumi, and Kang (2) eliminated the problem of the solubility of the precipitate in the methylene blue procedure by extraction of the methylene blue-perchlorate complex into 1,2-dichloroethane. Other precipitation methods include the precipitation of perchlorate by ferroin (3) and salts of copper tetrapyridine complex (4). Golosnitskaya and Petraschen (5, 6) complexed perchlorate ion with brilliant green and malachite green and extracted the complexes. Zatko determined perchlorate by the oxidation of VSOl to (VO)*+, and measurement of the (VO)2+ formed (7). Fritz, Abbink, and Campbell (8) extracted a ferroinperchlorate complex with n-butyronitrile. This paper presents a novel approach to the determination of the perchlorate ion. The resulting method is simple, selective, and has good color stability. The sensitivity of the technique is comparable to that of the ferroin method (8) and superior to that of other techniques. The approach presented here has a simple procedure, involving no precipitation or extraction steps. EXPERIMENTAL
Apparatus. All spectral measurements were made on a Cary Model 12 automatic recording spectrophotometer using matched 1.000 9 0.002 cm fused quartz cells. Temperatures were controlled to 90.3" C using a water bath with a Sargent Model 3554 thermoregulating unit. 1 Present address, Department of Chemistry, Arkansas State University, State University, Ark.
(1) G. M. Nobar and C. R. Ramachandran, ANAL. CHEM.,31, 263 (1959). (2) I. Swasaki, S. Utsumi, and C. Kang, Bull. Chem. SOC.Japan, 36, 325 (1963). (3) Z. Greaorowicz, F. Buhl, and Z . Klima, Mikrochim. Ichnoanal. Acta, 1963, p 116. (4) W. Bodenheimer and H. Weiler. ANAL.CHEM., 27.1293 (19551. ( 5 ) V. A. Golosnitskaya and V. I. Petraschen, Zh. Analif. Khim,, 17, 878 (1962); A n d . Absf., 10, 2264 (1963). (6) V. A. Golosnitskaya and V. I. Petraschen, Tr. Nouocherk. Politekhn. Znsf., 141, 73 (1964); CA, 64, 1351e (1966). (7) D. A. Zatko, ANAL.CHEM., 37, 1560 (1965). (8) J. Fritz, J. E. Abbink, and P. A. Campbell, Zbid., 36, 2123 (1964).
1.200
0.700
'! 4"
0.600
r
1
t
J
2
0.500
0.400 0.300 0,200
o.ino 0
1
2
3
4
5
6
8
i
nil of 100.0 g/l SnC12
9
10
11
12
. 2H-0
Figure 1. Effect of SnCI, concentration (1) No added Clod(2) 10 ppm Clod(3) A absorbance, 1-2
Reagents. All reagents used were of the highest quality obtainable. The a-furildioxime was purchased from Eastman Kodak Co. and used without further purification, A solution of this ligand was prepared by dissolving 7.0000 grams in methanol and diluting to 1 liter with methanol. The potassium perrhenate was obtained from the University of Tennessee and used without further purification. Recommended General Procedure. Prepare a calibration curve by adding up to 0.75 mg of perchlorate ion to 50-ml volumetric flasks and bringing to a total volume of 6 ml with deionized water. To each flask add 5.00 ml of aqueous 0.0950 gram/liter potassium perrhenate solution, 4.70 ml of 1 :1 hydrochloric acid, 17.00 ml of methanol, and 7.00 ml of 8 . 5 x tin(I1) chloride. Mix and transfer each flask to a 55" C water bath for 30 minutes. Add 5.00 ml of the afurildioxime solution, dilute to 50 ml with deionized water, mix well, and return to the 55" C water bath. After exactly 30 minutes, read the absorbance at 532 mp. The calibration curve of log absorbance us. concentration is linear within experimental error. VOL. 40, NO. 3, MARCH 1968
639
1.500
1.400
1.400
1.300
1.300
1.100
1.200
t-
0.900 -
F -
-
1,000
Ic
2
0,900
0.800-
2
0.700 0.600
0.500 0.400
o.so0 0.200 0.100
0.700
-
F I
I
I
I
I
I
I
I
0
1
2
3
4
5
6
7
"
8
"
2 I
I
I
4I
GI
,8
10 I
12 I
14 I
16 L
18I
22,
20I
24
9 1 0 1 1 1 2
ml of Methanol
ml nf 1:l HC1
Figure 3. Effect of methanol concentration (1) No added c104-
Figure 2. Effect of 1:l hydrochloric acid concentration (1) No added c104-
(2) 10 ppm c104(3) A absorbance, 1-2
(2) 10 ppm c104(3) A absorbance, 1-2
An analysis for perchlorate ion may be performed by adding a solution of the ion to 50-ml volumetric flasks, adjusting the volume to 6 ml, and proceeding as above.
ride is an effective reductant for perrhenate. Figure 1 indicates that the maximum perchlorate interference is achieved when 7.00 ml of the Sn(I1) reductant is added.
EFFECTS OF VARIABLES Temperature. Best results were obtained at elevated temperatures. The system was not strongly temperaturedependent but a temperature of 55" C f 5" produced the largest interference of perchlorate ion. Reductant. Previous work (9) indicates that Sn(I1) chlo-
1,500 1.400
1.300
F
1.200
1.100
(9) V. W. Meloche, R. L. Martin, and W. H. Webb, ANAL. CHEM.,29, 527 (1957).
1.000 0,900
Table I. Effect of Diverse Ions Amount Ions permitted* 31 Cr207e 56
45 CIS 20 100 100
Si032-
100
FNil+ CUE+ Zn2+
33 67
ICHaOz-
100
v5+
CI
Mgz+ s04'-
100
"
100
Pbz+ Citrate
100
4+
Zr4+
UOZZ+
100
14 100 CI
Fesf Br-
100
108-
100
BF4-
7 100 32 56
NOzNOa-
CI CI
100
100 ppm. 2% error considered tolerable.
c
CI = complete interference.
640
Amount permitted
CI
b
5
P
ANALYTICAL CHEMISTRY
0.800
c . 0
2
