volatility of the resin fraction usuallv containine a n aupreciahle amount of oxygen. Since there is the possild i t y of aromatic ethers an< on., benzofurans occurring in thL rmmatir fl.rt;nnI. 0ftc.l eI_Iuration' high resolution mass spectroscopy (70 was used t o analvze for oxygenated components. The only oxygenated species iclentified were molecular ions correspondI
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ing t o dihenzofurans. No aryl alkyl or diary1 ethers (which have relatively strong molecular ions) (20) were detected. Received for review September 10, 1973. Accepted January 11, 1974. (20) H. Budzikiewicz, C. Djerassi, and D. H. Williams. "Mass Soeclrometry Of Organic Compounds," Holmden-Day. In;., San Fkancisi3 0 . Calif.. 1967,pp 237-48.
Bead Homogeneity in the Fusion Technique for X-Ray Spectrochemical Analysis Roland LeHouillier and Simon Turmel Mineral Research Center, Department of Natural Resources, Quebec, Canada X-Ray Fluorescence Analysis is sometimes complex because of absorption, enhancement, heterogeneity, particle size, and surface roughness effects. One technique which gets around most of these effects is the so-called "borax fusion" technique developed by Claisse ( 1 ) and modified by several other workers (2-6). Essentially, the method consists of heating at a high temperature a mixture of sample and flux until it is melted and cooling the product to obtain a solid bead with a flat surface which is examined in thebpectrograph. The quality of t h e analysis depends on the homogeneity of the head, a n d to obtain it, melting is done either in a furnace for a period of about 1 hour or over a Meker hurne r for about 15 minutes with occasional agitation every 3 or 4 minutes. Furnace melting is a slow process and hurne r melting is a tedious operation which is time consuming a n d which may present some hazards when several fusions are made simultaneously: heat radiation, hand burning. Furthermore, melting time cannot he reduced significantly without some risk in the homogeneity ofthe heads. Obviously continuous agitation during melting should reduce the time required to obtain homogeneity. This paper investigates the effect of continuous agitation on t h e quality of the beads as compared to occasional manual aeitation as is usuallv done. This research has been made " possible through the recent a-tailability of the "Claissie Stirrer" designed to agitate the samples during melting.
continuous agitation auring melting was mamtained by the use of a Claisse Stirrer. In that instrument (Figure I), the crucible and the Meker burner as a whole are agitated in B movement similar to hand agitation: the tilted axis of the crucible rotates around the vertical while the crucible moves in a circle, but the crucible does not rotate around its own axis. In a first series of experiments, 36 identical samples were prepared by accurate weighing and mixing the following -200 mesh powders: 50 rng quartz, 30 mg specular hematite, 20 mg rutile, 1 gram BaOz, 1 gram BaSO1, and 10 grams anhydrous borax. The samples were divided in six groups of six samples each. Samples of the first group were fused over stationary Meker burners for 5 minutes and agitated once for 10 seconds during fusion. Samples of the second group were fused for 10 minutes and agitated twice, and those of the third group were fused far 15 minutes and agitated three times. Samples of the last three groups were fused with a Claisse Stirrer for 5, 10, or 15 minutes, respectively. In a second series of experiments, 24 identical samples were prepared which contained 5 grams cement and 6 grams lithium tetraborate. Group of 6 samples were fused for 5 and 15 minutes as in the preceding experiments with occasional and continuous agi tation. The fluorescence intensities were measured in B eonventiona1 manner on each head, for Ba, Fe, Ti, and Si in the first experi ide.
.TS AND DISCUSSION --^_+ .".-: +I ." 1" &.".A e,. In each series of myrrllLlnrrr, Lllr uaL"AyLc~ Id 15 minutes were assumed to be homogeneous, whether ~
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EXPERIME:NTAL The degree of homogeneity of a bead was determined by measuring the fluorescence intensity of one of its elements and camparing it to that of a homogeneous bead of the same composition. A number of beads were obtained with the original technique ( I ) as follows: the sample and borax mixture was placed in a platinum crucible aver a Meker burner, heated at the highest temperature possible for a predetermined period of time and agitated by hand occasionally far a few seconds; then the melt was poured in a ring an an aluminum hot plate, and after 1or 2 minutes the bead formed was removed from the hot plate to prevent shattering and to cool it more rapidly in air. The other beads were. prepared in the same way except that (1) F. Ciaisse. Quebec Dept. Of Natural Resources P.R. 327 (1956). 12) H. J. Rose, I. Adler. and F. J. Fianagan. Appl. Spectrosc.. 17, 81 (1963). (3) W. J. Campbell and J. W. Thatcher. Advan. X-Ray Anal.. 2, 313 (1958). (4) T. J. Cullen, Anal. Chem., 32. 516 (1960). (5) R. J. Longobucco,Anal. Chem.. 34. 1263 (1962). (6) G.Andermannand J. D. Allen,Anal. Chem.. 33, 1695 (1961). 734
ANALYTiCAL CHEMISTRY, VOL. 46, NO. 6, MAY 1974
Figure 1. Ciaisse Stirrer for 6 simultaneous fusions, holding 4 samples. Speed controller, casting dishes, and prepared borax disks are also Shawn
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melting time and agitation for a synthetic ore sample
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melting time and agitation for a synthetic ore sample
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they had been continuously agitated or not, and the average measured intensity for an element was considered as t h a t of an ideally homogeneous sample. This value for each element has been normalized to 1.00 in Figures 2 to 7, and the number of accumulated counts per sample it represents is given in each figure. The measured intensities for each individual bead as a function of melting time and the standard deviation a in counting are also shown. In the first experiments with synthetic ore samples (Figures 2-5), and with agitation on the Claisse Stirrer the elements Ba, Ti, and Si give fluorescence intensities which differ little from the counting standard deviations even after only 5 minutes of fusion. But with static heating and occasional agitation, 15 minutes of fusion is required to prepare beads with the same homogeneity. The 5-minute heating is specially indicative of the effectiveness of the stirrer as compared to manual agitation. In Figure 4, for example, with manual agitation, one Ba measurement is 33% off from the mean, which represents a deviation of 325u! Similar results are found for Si with
deviations up to 57% and for Ti with deviations up to 37%. The results for Fe (Figure 5 ) are not as good as for the other elements. We do not know the exact reason for that b u t we suspect that it is due to some abrasion of the steel plates of the crusher which was used for grinding specular hematite. Metallic particles are usually found in ground materials and they react with borax very slowly since they must oxidize first and only occasionlly do they reach the surface of the melt where oxygen is available. In the beads obtained after 5 minutes of fusion, gas bubbles are still present in the manually agitated samples but are absent in the continuously agitated samples. In the experiments with cement (Figures 6 and 7), the scattering of Ca and Si intensities about the mean is smaller than in the first series of experiments because lithium tetraborate has a lower melting point than sodium tetraborate. Even then 5 minutes of fusion seem to be sufficient with continuous agitation but not with intermittent agitation. A N A L Y T I C A L C H E M I S T R Y , VOL. 46, N O . 6, M A Y 1974
735
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Figure 7. Variation of Ca fluorescence intensity as a function of
melting time and agitation for a cement sample Agitation. 0 manual, 10 sec every 5 min. 0 continuous
CONCLUSION Continuous or intermittent agitation during fusion yields beads with the same quality (homogeneity and absence of bubbles) if the melting time is sufficiently long. The minimum melting time is about 5 minutes with continuous agitation and about 10 to 15 minutes with occasional agitation for the samples examined. These minimum values are expected to increase when heating temperature is lower or when less reactive samples are fused. If some security factor is allowed for this, the melting time is not changed significantly with automatic agitation but it may become prohibitive with manual agitation.
Automatic agitation also has some additional advantages: the radiation effects on arms and face of the operator are minimized; the operator is free to do other work during fusion; and the productivity is increased.
ACKNOWLEDGMENT The authors wish to thank Regent Marcoux for his contribution to the experimental part of this study and the Minister of the Department of Natural Resources for the permission to publish this manuscript. Received for review June 25, 1973. Accepted November 16, 1973
New Method of Analysis Based on Room-Temperature Phosphorescence R. A. Paynter, S. L. Wellons, and J. D. Winefordner' Department of Chemistry, University of Florida, Gainesville, Fla. 32601 Until recently, with few exceptions, strong phosphorescence of organic molecules had been observed only in the gas phase, in rigid media, or a t liquid nitrogen temperatures (2-3). Room temperature triplet state emission has recently been reported by Walling and Schulman (4, 5 ) from ionic organic molecules adsorbed on a variety of supports, including silica, alumina, paper, asbestos, and oth-
A u t h o r t o w h o m r e p r i n t requests s h o u l d b e sent.
(1) M. Zander, "The Application of Phosphorescence to the Analysis of Organic Compounds." Academic Press, New York, N.Y.. 1968. (2) J. D. Winefordner, P. A. St. John, and W. J. McCarthy, Chapter on "Phosphorimetry" in "Fluorescence Assay in Biology and Medicine, Vol. 1 1 , " S. Udenfriend, Academic Press, New York, N.Y., 1969. (3) J. D . Winefordner, "Phosphorimetry," in "Accuracy in Spectrophotometry and Luminescence Measurements," in Proceedings of a Conference held at NBS, March 22-24, 1972, NBS Spec. Pub/. 378, Washington, D.C., 1973. (4) E. M . Schulman and C. Waliing, Science, 178, 53 (1972): (5) E. M. Schulman and C. Walling, J. Phys. Chem., 77, 902 (1973).
736
ANALYTICAL CHEMISTRY,
VOL. 46, NO. 6 , M A Y 1974
ers. Also, phosphorescence a t room temperature, involving either particularly rigid molecules (6) or the use of a spin forbidden transition enhancer such as dimethylmercury (7), has been observed in fluid media. In these previous reports, room temperature phosphorescence (RTP) was simply reported, and no analytical applications of the phenomena were dealt with. In the present note, the authors developed and applied the phenomena observed by Walling and Schulman ( 4 , 5 ) toward analytical usefulness. As this report will further illustrate, RTP appears to offer a fast, economical, and convenient method of analyzing a variety of molecules, many of biological interest.
EXPERIMENTAL Apparatus. I n t e n s i t y measurements a n d e x c i t a t i o n / e m i s s i o n spectra were d e t e r m i n e d w i t h a n A m i n c o - B o w m a n Spectrophotofluorometer (SPF) w i t h a phosphoroscope a t t a c h m e n t (phospho-
(6) R. 8. Bonner. M. K . DeArmond, and G. H. Wahl, J. Arner. Chem. SOC.. 54, 988 (1972). (7) E. Vander Donckt, M. Matagne, and M. Sapir. Chem. Phys. Lett.. 20, 81 (1973).
