SHORTCOMMUNICATIONS =fj9

3 R. L. PATERSON, JR. AND L. B. LOCKHART, JR., Chicago University Press, rgG4, p. 383.

in Tire Natzrra 2 Radiation. E:l~viro~rment ,

4 G. LAngBERT, B. ARDOUIN, M. NEZA~~I AND G. POLIAN. Tellus. x8 (x966) 421. 5 D. H. PIERSON, R. S. CArdBRAY AND G. S. SPICER, TclI~is, 18 (xgCG) 427. G G. L. TER HAAR, R. B. HOLTZMAN AND H. I?. LUCAS, JR., N~Lzcve. 2r6 (x907) 353, 7 G. LAMBERT AND&~. NEZAMI, Nafttre, 206 (rgG5) 1343. 8 c. R.HILL. Nature, 208 (1965) 423. g T. M. BEASLEY AND H. E. PALBIER, Scielrce, 152 (xgGG) roG2.

IO J. B.LITTLE AND R.B. MCGANDY,NCIIW~, 2x1 (IgGG) 842. II R. B. HOLTZhfAN, Nafrrrc, 2x0 (IgGG) rog4. 12 Ii. D. CHERRY, Nalzrve, 203 (rgG4) 139. .x3 L. V. SHANNON AND R. D. CHERRY,NRI~IYC,~IG(~Z)G~) 352. 14 I<. 13. HoLrZnrAh*, Argomu: Nalional Laboratory, Radiotogicul Plrysics Division ~J~orual Report,

Jtcly 1966 throrrgir Jurre 1967. xgctg, p. 82. 15 T. M.BEASLEY, C.L.OSTERUHKG ANDY. M.JoNEs,~V~~~~Y~,ZZ~ (rgGg) 1207. IG M. I<. HAMA,RI. KOIDE AND E. D. GOLDDXRG, Scieme. 13-t (rgGt) 98. 17 E. D. COLDUERC, ill Radioactive Drcfi?rg, Intcrmtionnl Atomic Energy Agency, Vicnnn, rgG3,

p, 121. . 18 T. R. PoLsont, IhIR-TR-gza-66-A, rg6G. xg Bulelle-Northwest &port BNWL-735-(P&z), IgG8. 20 W. W. FLYNN, A?tal.Cirim. Acta. 43 (1968) 221. 21 G. 1-I. MORRXSON AND H. FRE~SPR, Solvc?~C Estracfiori i*g Rlralylicai Citemisfry, Johr~ Wiley,

New York, 1057. 22 R. C. BRASTED, CorqSrelrc*isive Inorganic Ckouistry. Vnn ISostrancl. New York, S (rgb~) 24. 23 H. &IhLISSA AND E. SCiitjFPhlANN, Miltrochim. A&U, I (1955) X87. 24 C. E. MULPORD. Atonric /Jbsorpfio?z Newslefter, 5 (1966) 88. 25 M. J. ORREN, S.A. Chemical Iustitule Sypbosirrm ow Atomic Absor#io?a -S#eclroscopy. S:cllor-

bosch, x967. 2G R. C.TURNER, J. M. RADIXY AND W V. XAYNEORD, I3riL.J. Rrrdiot..31 (x958) 397. 27 L. V. SHANNON. Li. D. CE~BRRY AND M. J. ORREN, Geocikr. Cosrnoclrim. Acta, it1 press.

(Received April 8th, xg7o)

A wal. Claim. Acta. 52 (1070) rGG-xGg

Determination of naphthacene traces by sensitized luminescence on filter paper

The sensitized luminescence of naphthacene in anthracene crystals has been known for a long time. The observations of ROWEN et a2.l and GANGULY~ proved that pure crystalline naphthacene hardly shows luminescence when excited by ultraviolet radiation, However, if the anthracene crystal lattice contains a naphthacene contami- nation of the order of x0-8-10-4 mole per mole, the anthracene emission considerably decreases, and an intense yellow-green fluorescence appears3*4. The quantitative interpretation of the energy transfer mechanism of the excitation energy has been elaborated by I;~~RSTER~ and BIRKSO.

The sensitized luminescence of naphthacene does not appear to have been applied analytically. The aim of the work described here was to determine traces of naphthacene on filter paper. For this purpose, the intensity ratio of the anthracene and naphthacene luminescence measured at certain characteristic luminescence maxima was used.

Anal. Chim. Acta, 52 (x970) I@-17+

170 SHORT COxnlUNICATIONS

The fluorescence intensities were measured with a I-fitachi Perkin-Elmer MPF- zA spectrofluorimeter. A sample holder suitable for measuring the luminescence of solid materials such as paper and powder was specially designed (Fig. 1). The sample f0rms an atq$e of 45” with the excitation beam.

For the investigations, 1l.a. anthraccnc, naphthacenc and benzene were used. Preliminary tests showed that the anthracene and benzene were free of even traces of naph thacene. For prepnrin~ tile samples, benzene solutions of anthracene and naphthacene were used. The solutions contained 3 .x0-3 M anthracene and 5 *IO-~- ~o--ll 1\1 naphthacene. After Whatman No. I. paper slides had been immersed in the solution, the samples were dried in air at room temperature for about Go min. The paper samples were then placccl into the sample holder and irradiated at 370 nm, which wavelength is near one of tlie active absorption maxima of the anthracene. Fluorescence was measured at the antln-scene emission peak at 420 nm (2420) and at the naphthacene emission peak at 497 rim (1~1~17). For evaluation, no correction of the spectra was ncecled.

The fluorescence spectrum of the system changes considerably when the amount of naphthacene is increased; details have been given by PARICER~. At ultratrace levels of naphthacene, the 4g5-4g7-nm naphthacene band is suppressecl by the emission of anthracene. The optimal amount of anthracene proved to be about 10-3 M.

SHORT CO~;MMUNICATIONS

Pig. 2. Xntcnsity ratio of the fluorcscencc of nnthrnccnc crystals containing nnphthaccnc us. naphthnccnc conccntmtion. IX = nnphttioccnc intensity nt 497 nm; f~ = anthrwcnc intensity kt 420 nm.

In the naphtbacenc concentration range of x0-8 ll8-5 e 10-G fM, the I4~7/142~ factor is linear (Fig. 2). For smaller concentrations, the curve deviates from the linear, but emission can be measured for as little as 5 - IO- 11 M naphthaccnc. This range can be reproduced reliably, and is therefore suitable for quantitative work after suitable calibration. The deviation from tile linearity is most probably due to the fact that in this range of concentration the anthraccne emission as well as other energy-transkr processes interfere to some estcnt.

The relative error of measurements in the range 5. IO-fi-10-8 M increases from 0.5-x.00/~ to i3--100/~, The amount of naphthacene calculated for the Whatman No. I

paper prepared from xo- 11 M solution is of the order of x0-14 g. Under the above conditions this quantity can be measured with good reliability.

The author expresses his thanks to Mr. E. LENDVAY, head of the luminescence group of the Research Institute for Technical Physics of tile Hungarian Academy of Sciences for valuable discussions and for his interest.

Reseurclc Institute for Techrtical Physics, Hungarian Academy oJ Sciences, Bda$est, F&i -u 56 fH~~?gczryj

I IL J. BowsrJ. Nutffrc, 142 (1938) ro8r; f. Ciictn. Ph~s., x3 (x9.15) pG: E. 3. %%OWrSN AND E. fihKII?WXCZ, N&ltYC, 159 (X947) 706; E. J. BOWEN AND P. D. LAWLEY, NatZrYc. 164 t&()49) 572; x. J. ~OWEN. E, itf11C1E~1CZ AND 17, W. SMITH, Proc. Phys. Sot. (ihrdora), ROZ (rgdg) 26.

2 S. C. GANGULY, J. Chem. Phys., 13 (1945) 128; S. C. GANGULV AND N. I<. CHI\UDW.IRY,Z?~~. Mod. Plrys..3r (rq59)5)90.

3 C. A. PARKER. PJtotolzrr?ti?rcsce?rcc of Soltrlions, Blsevier, Amsterclam, x968. 4 M. D. GALASIN AND Z. A. CWZIKOVA, f. ofit. S+cktrosc. (USSR), (l%gl. 7‘rrfmE.), 2 (rggG) 175. 5 %-il. F6RSTER, n?Iti. I>hJ’S.. 2 (19&i) 55.

6 J. B. BIRKS, Phys. Rev., gj (195‘1) x.97.

(Received May zIst, 1970)