by a modification of the calibration procedure using hydrocarbon oils. The repeatability of the x-ray method over periods up to one year is also extremely good and considerably better than the precision limits of the bomb method. A number of skilled and semiskilled laboratory personnel have been concerned in these long-term correlation programs and the accuracy and reproducibility obtained is indicative that personal bias and the likelihood of human error have been reduced considerably. The various factors, statistical and otherwise, which may influence the accuracy of any one determination have been discussed fully by Hughes and Wilczewski (9). and their findings are in general applicable to this method. It is of interest to point out the significance of the carbon-hydrogen mass ratio: in this respect a n error of 0.5 in the carbon-hydrogen mass ratio will result in an error only of the order of 0.05% S. No apparent errors from metallic impurities present in oils have been encountered. Trace analyses on residual fuel oils for nickel, vanadium, iron, sodium, etc., have shown total metals contents of less than 200 p.p.m, in all cases. Concentrations of this order are unlikely to have any fiignificant effect on x-ray results. The method is, however, not suitable for products contain-
.
= chemical symhols of el+ ments, used i n equations directly and as subscripts b = thickness of absorbing medium, or internal cell length, cm. c = mass fractional concentration N = number of Quantataken for a single reading P” = radiant Dower of x-rav beam leavine absorbing medium, uncorrected;
Al, C, H, S
Table IV. Correlation Tests on Residual Fuel Oils from Unknown Crude Sources
Sulfur, yo I.P. bomba 3.14 3.20 3.62 3 16 3.95 a
X-ray 3.27 3.22 3.62 3.27 3.97
3.23 3.21 3 60 3 25 4.00
Average of 3 determinations.
ing such substances as tetraethyllead, lubricating oil additives, metal soaps, etc. ACKNOWLEDGMENT
The authors thank J. F. Cameron of Atomic Energy Research Establishment (Isotope Division), Harwell, England, particularly for procuring the 10-curie source, and the Technical Services Laboratory, Mobil Oil Co., Ltd., for assistance in setting up the equipment. The authors also thank the Chairman and Directors of Mobil Oil Po., Ltd., England, for permission to publish this paper. NOMENCLATURE
A = angstrom A’ = ahsorbance per centimeter a’ =
mass absorptivity, sq. cm. per gram
c.p.5.
P’ = radiant power of x-ray beam leaving absorbing medium, corrected for resolving error, c.p.3. P = radiant power of x-ray beam leaving absorbing medium, corrected for resolving error and background, c.p.m. Po = radiant power of x-rav heam leaving empty cell. corrected for resolving error and harkp.rorind, c.p.m. r = carbon to hydrogen mass ratio = CC/cH s = standard deviation t = resolving time or quench time, seconds = density of absorbing medium p LITERATURE CITED
(1) Am. Soc. Terting Materia’s, Philadelphia, Pa., Method D 129-5R, 1958. (2) Chemical Rubher Piihlishing Co., Cleveland, Ohio, “Handhonk of Chemistry and Physics,” 32nd ed., p. 2182, 1950.
(3) HugheR, H. K., FT7ilcmwki, J. W., ANAL.CHEM.26, 1889 (1054). (4) Inrtitute of Petroleum, London, England, Method IP61-59, 1059. (5) Kannuna, N. M., J . Inst. Petrol. 43, 199 (1957).
RECEIVEDfor review December 19, 1960. Accepted May 19,19G1.
.Fluorometric Determination of Aluminum in the Pa rt- pe r- B iIIio n Ra nge FRITZ WILL 111 Alcoa Research laboratories, Aluminum Co. o f America, New Kensington, Pa.
b Conditions were established for the fluorometric determination of aluminum with morin in the part-per-billion concentration range. A simple procedure has been developed where the fluorescence of the aluminum-morin complex is determined instrumentally at a p H of 3 with a minimum of sample dilution. The tolerance to diverse ions has been established. A sample can b e run in less than 25 minutes at room temperature, or less than 5 minutes with heating. For example, the method i s applicable to high-purity boiler water condensates.
S
reagents have been used recently for the fluorometric determination of aluminum. Collat and Rogers (2) have determined aluminum EVERAL
1360
ANALYTICAL CHEMISTRY
and gallium in mixtures of their oxinates. Simons, Monaghan, and Taggart (3) used Pontachrome Blue Black R for the determination of aluminum and iron in surface sea water. More comprehensive reviews of fluorescent reagents for aluminum have been written by White (4, 6). In addition, Bozhevol’nov and Yanishevskava (1) reported the use of o-(salicy1ideneamino)phenol for the fluorometric determination of aluminum. In 1940, White and Lowe (6) published a quantitative method for aluminum in the l1.1t o l.Z-mg.-per-liter range using morin (2 ’.3,4‘,5,7-pentahydroxyflavone). The need arose for the determination of microquantities of aluminum (parts per billion) in high-purity boiler water condensates in electric power station boiler condensers using aluminum con-
denser tubes. Morin appeared t o be the most promising reagent of those reported. This paper deals with the use of morin as a reagent for the fluorometric determination of aluminum in the partper-billion range in high-purity water with a minimum of sample dilution in the shortest length of time. These three advantages are not found simultaneously in any other method. EXPERIMENTAL
Apparatus. Fluorometric measurements were made with a Fisher Nefluoro-Photometer, equipped with a mercury arc source, a 440-mp excitation filter, and a 525-mp fluorescence filter. Reagents. MORINSOLUTION. A solution containing 0.1 gram of mofin
t
not
80 w
g
-
2
3
w
5: W 8 2 -I
-
60 ALUMINUM-MORIN
U.
@
40
ACTIVATION- 440 mu FLUORESCENCE- 5 2 5 mp
0
0
-
2
3
4
5
RRb. AI ( 95ml. ALIQUOT)
Figure 1.
,
J
Calibration curve
per 100 ml. of Formula 30 alcohol (86% ethanol, 9% methanol, 5% water) was used. The compound was obtained from L. Light and Coo, Ltd., Poyle, Colnbrook, England. It is completely soluble in the solvent. PURIFIED WATER. Pure water was prepared by passing once-distilled water through a polyethylene tube containing a mixed-monobed ion exchange resin, such as Amberlite MB-1, a t the rate of 10 ml. per minute. The resultant water was used to prepare solutions and for making dilutions. Spectrographic analysis showed an aluminum concentration of only 1 p.p.b. or less in this deionized water. ALUMINUM STOCK SOLUTION. A stock solution of 10 pg. of A1 per ml. was prepared by dissolving 0.1758 gram of A1 K(SO&. 12Hz0 in water, adding 1 ml. of 1 to 1 H&O4, diluting to 1000 ml., and mixing. Solutions of greater dilution were made from the stock solution as required. Satisfactory stock solutions were also prepared from highpurity aluminum wire and from aluminum nitrate. QUININESULFATE SOLUTION.A solution containing 10 mg. of quinine sulfate per liter was prepared by dissolving 10 mg. of quinine sulfate in 1000 ml. of 0.1M H,SOI. This solution is stable indefinitely. Procedure. Dilute 1.0 ml. of 1 t o 1 acetic acid t o 100 ml. with the standards and sample. For high-purity water samples, this results in the optimum p H of 3. Dilute 5.0 ml. of t(hemorin reagent solution t o 100 ml. with the acidified solutions. Allow thc solutions to stand a t room temperature for 20 minutes. If time is of the essence, heat the sample in a hot water bath for at least l / Z minute and cool. Transfer a portion of each solution to B photometric cell. Set the fluorometer to 100 with the
I
I
I
I
1
I
I
ALUMINUM-MORIN 2Rplb. AI+ INTERFERING cu++ IONS READ AGAINST
1
1
80
:: 70 W
L
60
be 50 40
300
10
20
30
50
40
-
i 1
I
P
90
-
0
I
60
70
80
90
DO
RRb. INTERFERING ION
Figvre 2.
Interfering ions
most concentrated standard and the quinine sulfate solution according to the manufacturer's manual. Measure the readings of the other standards and samples. Prepare a calibration curve by plotting the readings of the standard against their concentrations in micrograms of A1 per liter. Obtain the unknown concentration from this curve. For a variety of concentration ranges, several calibration curves may prove helpful (Figure 1). Only one calibration curve is necessary for a specific concentration range. After that, only the highest standard in the calibration range being used need be set to 100 before the unknown samples are run. RESULTS AND DISCUSSION
Effect of Morin Concentration. The recommended procedure was ;allowed except that the morin reagent solution concentration was varied from 0.05 t o 2.0 mg. per ml. to study its effect on the aluminum fluorescence. Over the concentration of 0.1 to 1.5 mg. of morin per ml. the fluorescence was constant. Therefore, the concentration of 1 mg. of morin per ml. was chosen t o ensure an excess of reagent. Effect of pH and Alcohol Concentration. A set of standard aluminum solutions was run by the recommended procedure to study the effect of p H using acetic acid on the Al-morin fluorescence. Over a p H range of 1 to 6, the optimum p H was 3 f 0.3. To avoid dilution of the sample, the amount of the alcoholic reagent morin solution added to 95 ml. of sample was not more than 5 ml. Results indicated that a longer period of time was required to develop maximum fluorescence if the alcohol concentration was lcss than 5 ml. Moreover, this amount of alcohol is required to keep the morin in the aqueous sample solution. Effect of Time and Heat on Fluorescence. A time study was conducted
on a series of aluminum standard solutions after the fluorescence had been developed by '.the recommended procedure. The results indicated that the fluorescence increased with time and became constant after 20 minutes. These standard solutions were then stable for 3 days. The effect of heating on the fluorescence development was studied. The aluminum-morin solution was immersed in a steam bath for a fraction of a minute, cooled under cold water, and the fluorescence measured. Immersion in n steam bath for a t least minute developed the same amount of fluorescence as a similar sample standing for 20 minutes a t room temperature. If time is a factor in the analysis, heating can be used to speed up the maximum fluorescence. However, all
Table 1.
A1 Concn.,
P.P.B.
Standard Deviation No. of
0.25 0.50 2.00
Detns.
Std. Dev.
15 9 10
0.09 0.06 0.06
Table II. Tolerances to Diverse Ions
Ion
Ca +z CO +l Cr +a CU +* +;:3
Mg+a "I+
Ni +1 Pb +2
PO,-
SiO3-2
so,-2 Zn +a
Morpholine
Limiting Concn., P.P.B.
>1000 >1000
30 20 5 100 200 500 > 1000 lo00 3 >1000 > 1000 1000 100
VOL. 33, NO. 10, SEPTEMBER 1961
1361
Table 111.
High-Purity Boiler Water Condensates
Al,P.P.B. Sample
By morin
By
alummon
of the experimental work for this paper was done a t room temperature. Reproducibility. The reproducibility of several aluminum concentrations are shown in Table I.
Effecf of Diverse Ions. The interferences of diverse ions on the determination of aluminum in the concentration .range used in this paper were studied. The effect of each ion on a 2-p.p.b. AI solution was studied in increasing amounts until the fluorescent intensity was outside the limits of the reproducibility for a 2-p.p.b. Al solution (Table 11). Figure 2 shows the interference of C U + ~Cr+S, , and F- above the limiting concentrations. The and CufZ interferences were checked using a 25-p.p.b. Al solution. The limiting concentration was 50 and 500 p.p.b. for PO&-8 and Cu+2, respectively. Application of Procedure. Highpurity boiler water condensates were analyzed for aluminum by the reeommended procedure (Table 111).
ACKNOWLEDGMENT
The author acknowledges the assist. anee of Robert Beduarik in performing the experiments in this investigation. LITERATURE CITED
(1) Boahevol’nov, E. A., Yanishevskayya, V. M., Zhur. Vsemyua. Khim. Obshcheslua im. D. I . Mendelema 5.356-7 (1960). (2) Collat, J. W., Rogers, L. B., ANAL. CHEM.27,961-5 (1955). (3) Simons, L. H.,Monaghm, P. H., Taggart, M. S., Jr., Ibid., 25, 989-90
\_””_,.
11452)
White, C. E., Ibid., 32,48R (1960). (5) White, C. E.,in “Trace Analysis,” J. H. Yoe and H. J. Koch, Jr., eds., Chap. 7, Wiley, New York, 1957. (6) White, C. E., Lowe, C. S., IND. ENQ. CHEM.,ANAL.ED. 12,229-31 (1940). (4)
RECEIVEDfor review April 6, 1961. Accepted July 3, 1961.
A Versatile High-Resolution Spectrofluorometer ROBERT E. REHWOLDT and RICHARD M. KING Department of Chemisiry, lehigh Universiiy, Befhlehem, Pa.
DAVID M. HERCULES Deportment of Chemistry, Juniafa College, Huntingdon, Po,
b Construction and calibration of a versatile, high-resolution, recording spectrofluorometer are described. Commercially available components were used wherever possible. Fluorescence or excitation spectra may b e recorded automatically in the visible and ultraviolet regions of the spectrum. The spectrofluorometer has a sensitivity equivalent to 0.01 p.p.m. of quinine sulfate and a resolution of 4 A., at a slit width of 0.2 mm. The cell compartment was constructed to permit recording of fluorescence spectra at the temperature of liquid nitrogen.
R
investigations of the effect of structure on fluorescence of organio compounds and their metal chelates (6, 8, 14, 16) have indicated the desirability fluorescence spectra a t high r olution. Commercially available spectrofluorometers designed for routine fluorescence analysb (1, 4) do not offer high resolution, although they d o r d good sensitivity. A number of commercial spectrophotometers have heen modified to record fluorescence spectra (2, 3, 6, 7, 10,13), but generally these do not d o r d sufficient sensitivity and versatiity. Two reports of elaborately constructed spectrofluorometen have appeared recently (21,16),hut the cost of constructing such instruments is prohibitive to the ECENT
1362
ANALYTICAL CHEMISTRY
Figure 1. Spectrofluorometer A. Wave lenglh control did B. Power supply for radiation source C. Control box for starting recorder ond wave length drive D. Monochromdor E. Sample c o m p o h e n t F. Cooling comporhent for phototube G. Recorder H. Multiplier phototube ampliflcr 1. Power supply for multiplier phototube and omplifler
