LITERATURE CITED
(1) Caillere, S., Henin, S., Ann. agron. 1945, 50. (2) Duval, C., “Inorganic Thermogravimetric Analvsis,” P. 34, Elsevier, New York. 1953.” ’ (3) Zbid., p. 36. (4) Zbid., p. 41. (5) Zbid., p. 283. (6) Garn, P. D., Flaschen, S. S.,ANAL. CHEM.29,271-5 (1957).
-
AT
(71 ~, Garn. P. D.. Kessler. J. E.. Ibzd..
32, 1563-5 (1960). (8) Ibid., pp. 1900-1. (9) Grim, R. E., Ann. N . Y . A d . Sn’. 53, 1031-53 (1951). (10) Gruver, R. M., J. Am. Ceram. SOC. 31, 323-8 (1948). (11) Herold, P. G., Planje, T. J., Zbid., 31, 20-2 (1948). (12) Keler, E. K., Kuznetsov, A. K., Doklady Akad. Nauk S.S.S.R. 88,10314 (1953). (13) Kissinger, H. E., McMurdie, H. F., Sunpson, B. S.,J. Am. Ceram. Soc. 39, 168-72 (1956). (14) Lodding, W., Hammell, L., Rev. Sci. Znstr. 30,885-6 (1959). (15) McAdie, H. G., Ontario Research
Foundation, Toronto, Ont., private communication, 1960. (161 Newkirk. A. E.. ANAL.CHEM. 32,
1558-63 (1660). ’ (17) Norton, F. H., J. Am. Ceram. Soc. 26,113-19 (1939): (18) Note, J . J., Jaffe, H. H., Zbid., 43, 53-4 (1960). (19) Peters, H., Wiedemann, H. G., Z . anorg. u. allgem. Chem. 300, 142 (1959). (20) Powell, P. A., J. Sci. Instr. 34, 225-7 (1957). (211 Reisman. A.. ANAL. CHEM. 32. ‘ 1566-74 (1LkO). ’ (22) Reisman, A,, Karlak, J., J. Am. Ceram. Soc. 80, 6500-3 (1958). (23) Rynasiewicz, J., Flagg, J. F., ANAL. CHEM.26, 1506 (1954). (24) Stone, R. L., Ohio Slate Univ. Eng. Ezpt. Sta. Bull., No. 146 (1951). ~
Figure 6. Differential thermal and thermogravimetric analyses of copper sulfate pentahydrate A. 6.
Closed sample holder Free diffusion sample holder Pentahydrate decomposes to trihydrate, monohydrate, and finally anhydrous cupric sulfate. Only evidence suggesting a tetrahydrate i s result of deliberate restriction of water vapor. Thermogravimetric heating rate 2’/min.
75” per hour. The weight loss appeared :ISa single step in a shallow pan. Unless the data from each technique have some real significance, attempts t o relate them are seldom gainful even s hen apparently successful. Each set of data must be in itself meaningfuli e., the reaction must have been carried out under reproducible and known
conditions. These conditions must include one of the extremes of atmosphere accessibility or a dynamic atmosphere of known composition. ACKNOWLEDGMENT
The author is grateful to J. E. Kessler for his considerable aid in obtaining data.
’
RECEIVEDfor review January 9, 1961. Accepted May 1 , 1961. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., March 1961. North Jersey Section, ACS Meeting-in-Miniature.
Determination of Beryllium in Ores and Rocks by a DiIuti o n- FIuo romet r ic Metho d with Morin RVING. M A Y and F.
S. GRlMALDl
U.S. Geological Survey,
Washington 25, D. C.
b Beryllium in concentrations as little as a few parts per million is determined fluorometrically with morin in low grade ores by a dilution method without separations. A high sensitivity is obtained b y the adoption of instrumental and reaction conditions that give a satisfactory ratio of beryllium to blank fluorescence and a t the same time minimize iron interference. Data on the behavior of 4 7 ions are
given. The method is applied to ores containing berirandite ar?d beryl as the beryllium minerals.
T
BE MORE IMPORTANT colorimetric regents for determining beryllium are quinalizarin (8),8-hydrosyquinaldime (7), acetylacetone ( I ) , p-nitrobenzeneazo-orcinol (6, 9), and 2-phenoxyquinizarin-3,4’disulfonic acid (IO).
The most popular fluorometric reagents are morin (2’,3,4’,5,7-pentahydroxyflavone) (1.9, 13, I @ , %hydroxyquinaldine (8), and quiniaarin (1,4dihydroxyanthraquinone) (4). A colorimetric or fluorometric method for the determination of less than 0.01% beryllium without separations in rock material has not been published, although the possibility of such a fluorometric morin procedure was pointed out VOL. 33, NO. 9, AUGUST 1961
1251
Table 1. Effect of Morin Concentration on Fluorescence of Beryllium and Blank (Alcohol content, 0.1 ml.) Ratio Net Fluorescence ~ l Morin, r~./25
0.030 pg.
cence
Be 47
23
25 ~.
1.14 - -~
25
65
32 44 55
33 39 41
1.03 0.89
78 88
28
35 50 100 200
83 96 118 116
Blank Net
to Blank
Ml. 15
~~
40
0.75 0.51 0.41
by Sill and Willis (IS). I t has come to our attention that Sill, Willis, and Flygare (14) recently have completed new detailed studies of the morin fluorescence method for the determination of beryllium. In connection with studies by the U. S. Geological Survey of potential beryllium resources, a rapid chemical method capable of determining as little as a few parts per million of beryllium was needed. The morin fluorescence method was reinvestigated to exploit its inherent sensitivity sufficiently to allow determination of beryllium a t these low levels without separations. This was accomplished by the adoption of instrumental and reaction conditions that give a satisfactory ratio of beryllium to blank fluorescence and that minimize iron interference. The method described here enables the direct determination of beryllium in concentrations as low as 2 p.p.m. in an aliquot containing 500 pg. of sample. EXPERIMENTAL
Apparatus. FLUOROMETER. That described by Fletcher and Warner (S), except that the detecting system consists of a 1P21 multiplier phototube powered by an Atomic Instrument No. 306 power supply. The output of the phototube is read with an electronic microammeter, RCA No. WV84A. EXCITINGSOURCE. General Electric H100-A4 lamp operated from a constant-voltage transformer. FILTER SYSTEM. The filter system was selected on the basis of previous studies; our instrument gives a twofold increase in sensitivity over one based on excitation with 365-mp light. Primary Filters. Corning filters Nos. 5113 (l/rinch) blue, 3389 (l/lr inch) sharp cut, and 3961 (3/az-inch) infrared, in the order from sample to lamp. This combination has a maximum transmittance a t 430 mp. Secondary Filters. Two Corning No. 4010 (6/S2-inch) green, peaked a t 520 mp. SAMPLE CELLS. Cubic optical glass cells of 30-ml. capacity. FLUORESCENCE STANDARD. Fluorescent glass filter capable of being po1252
ANALYTICAL CHEMISTRY
sitioned reproducibly on the cell NaOH Concentration. The alkaholder. line medium for the reaction with Reagents. MORIN(dihydrate), T. morin is provided by the addition of Schuchardt, Munich. Stock solu1 ml. of 1M sodium hydroxide solution, 0.050/, in ethyl alcohol; working tion. Allowing for 0.13 meq. of solution, 0.0050/,, dilute 25 nil. of free acid introduced by 1 ml. of sample stock solution to 250 ml. with water. ~ (ETHYLENEDINITRILO)TETRAACETIC ~ ~ ~ solution, the final sodium hydroxide concentration is approximately 0.035M. ACID (EDTA). Neutralized: DisAt this alkalinity, a variation of as solve 25 grams of EDT-4 and 5.38 grams of 1M NaOH in 200 ml. of much as i l O ~ oin the caustic added water. Dilute to 500 ml. with water. does not affect the fluorescence of the SODIUM CARBONATE-BORATE FLUX. morin blank nor of the beryllium comMix three parts of sodium carbonate plex. with one part of anhydrous sodium Morin Concentration, The effect tetraborate. STANDARD BERYLLIUM SOLUTIOKS. of varying the morin concentration is shown in Table I. A morin concenPrepare from pure salts of k n o m tration of 50 pg. in 25 ml. was chosen beryllium content, or standardize primarily to extend the range of the stock solutions. The working snluworking curve. In determining 0.005 tions should be in 0.13N HCl. Procedure. Fuse 0.5 gram of sampg. of Be or less, the morin is reduced to ple with 3 grams of flux in a platinum 25 pg. in order to take advantage of crucible. Dissolve the melt in 50 the higher ratio of fluorescence of ml. of 3:7 HC1 containing a few complex to blank obtained with a drops of alcohol, warming if necessmaller excess of morin. sary. Occasionally some silica may Alcohol Concentration. An inprecipitate, but it does not cause crease in alcohol concentration causes interference. Transfer the solution an increase in the fluorescence of the to a 1-liter volumetric flask and dilute blank without affecting the net fluoto volume with water. The acidity of the resulting solution is approxirescence of the beryllium complex. mately 0.13N. It is therefore desirable to restrict the To a 25-ml. volumetric flask, add 2.5 amount of alcohol added with thc nil. of neutralized EDTA solution morin reagent. and 15 ml. of mater. Add a 1.00-ml. Sensitivity and Stability. With 25 aliquot of the sample solution and mix. pg. of morin, and setting 0.005 pg. of The resulting dilution decreases the conBe a t full-scale deflection (1-pa. scale), centration of ions that precipitate with the blank reads 0.83 pa. These data NaOH and thus delays their precorrespond to a sensitivity of 0.03 cipitation. Add 1.0 ml. of 1M NaOH solution. Mix, add 1.00 ml. of morin pa,./O.OOl pg. of Be. A difference of solution, mix, and make up to mark 0.01 pa,. is clearly distinguishable on with water. Compare the fluorescence this scale. The blank is reproducible of the sample and a blank in a fluoromto 0.01 pa. eter with that from 0.1 pg. of Be set a t The fluorescence intensity of the full scale. morin-beryllium complex is linear from Where many samples are to be read, 0.001 to well beyond 0.005 pg. of Be a standard fluorescent glass can be used with 25 pg. of morin and to a t least 0.4 effectively. For larger amounts of pg. of Be with 50 pg. of morin. beryllium, appropriate dilutions are made with 0.13N HC1 and the same The fluorescence readings of the comprocedure is followed on a 1-ml. aliquot plex are sufficiently reproducible from of the diluted sample. For work in day to day to make a fairly good dethe part per million range, 0.005 pg. termination using a standard curve of Be is set a t full scale and half of the based on a stable fluorescent glass amount of morin is used in blank, reference standard. This is useful sample, and standard. for determining appropriate dilutions when necessary. Final determinations RESULTS AND DISCUSSION are best made by comparing the fluoEDTA Concentration. This acid rescence of the sample with that of has been used by others to eliminate a standard beryllium solution to comthe intereference of several elements, pensate for any temperature effects. particulary calcium (6) and magnesium, Behavior of Other Elements. and to reduce that of several of the Tests of the possible interference of rare earth elements (If). Large various elements were made by checkamounts of iron interfere by forming a ing the effect of a salt solution equivcolloidal precipitate which causes a alent to 1 mg. of the oxide of the reduction in fluorescence. element on the fluorescence obtained I n this procedure, the concentration using 50 pg. of morin alone and with of EDTA chosen allows up to 150 pg. 0.015 pg. of Be. Where interferences of Fe& to be present without interwere obtained, smaller amounts were ference, even after the solutions stand tested to find the maximum amount of for 30 minutes. EDTA produces a the element that could be tolerated. small but detectable enhancing salt No interference was obtained a t the effect on the beryllium fluorescence, but level of 1 mg. of oxide per 25 ml. with variations of EDTA concentration by aluminum, arsenic(V), cadmium, calf10% are without noticeable effect.
Table. II.
Element T _ h_
Lu Y Ce(II1) Cr(I1I) Zr
La sc Cr(V1) Er Tb Sm Pt(V1) Ti
Extent of Interference Various Elements
of
pg. of Oxide In interfering range Equivalent to equiv. to 0.0003 1 pg. Be pg. Bea
6 X 102“
7 X iozh 7 x 102b 2 x 10% 2 x 103s 5 x lo’* 5 x 103h 7 x 103*
x x 2 x 2 x 7 x 1 1
5
3
x x
loa? 104~ 104~ lodr 104~ 104d 10k
1
0.7 0.5 2 10 5 8 8 50 20 20 10 150 125 250 150 250
UWI) e Fe Bi d Tliese amounts in final 25 ml. give an absolute error equivalent to &0.0003 pg. Be; this error is less than 1 p.p.m. of beryllium based on a 500-pg. sample. * Element fluoresces. c Depresses fluorescence. White precipitate forms. e Interference variable, depending on standing time and temperature. cium, cobalt, copper, pallium, germanium, indium, lead, magnesium, manganese, mercury, molybdenum, nickel, selenium, tin, tungsten, vanadium, and zinc. Antimony(II1) and (V) do not interfere at levels up t o 200 pg. of the oxides; higher concentrations were not tested. Table I1 summarizes the data. for the interfering cations. A direct relation does not always exist
between corresponding values in columns two and three of this table, because for some elements the estent of interference is not directly proportional to concentration. A check was also made of anions significant in rock analysis. The anions were added as sodium salts. KO interference was given by 1 mg. of SiO,, by borate equivalent to 10 nig. of B*Oa, by 20 mg. of perchlorate, 20 mg. of sulfate, 20 mg. of nitrate, 1 nlg. of fluoride, and 2 ing. of bromide. Tartrate reduces the fluorescence of the beryllium complex; 40 mg. of tartrate resulted in a 20% reduction in the net fluorescence with 0.1 pg, of Be. Analysis of Low Grade Ores. The results on 10 samples are compared in Table I11 with those obtained spectrographically. T h e samples contained bertrandite and beryl as the beryllium minerals. In general the agreement is good. ACKNOWLEDGMENT
The filter system was selected on the basis of previous studies made by Mary H. Fletcher of this laboratory and a t her suggestion. The spectrographic determinations (Table 111) were made b y a group supervised by -4rmill Hele of this laboratory. LITERATURE CITED
Table 111. Comparison of Fluorometric with Spectrographic Results
75 Be Spectrographically Fluorometric=
