349
Anal. Chem. 1908, 60, 349-353
this spatial overlap factor and the transmission/detection efficiency for photoions, then the transmission/detection efficiency for our instrument is about 1.3 X (f0.4 X The transmission/detection efficiency and neutral-to-ion ratio estimated above can be combined with the U+ secondary ion data to perform a particle ejection rate comparison with the total desorbed material estimated from sputter yield data. Because the ionization efficiencies for sputtered molecular neutrals are not known, the calculation is most significant for U metal where Uo and U+ dominate the sputtered particle yield. Additionally, since the population of species desorbed from U metal in turn is dominated by Uo,the sputtered U+ secondary ions can be neglected. From the U+ secondary ion data of Table I (9.3 x lo4 counts/s) and the calculated transmission/detection efficiency, the U+ secondary ion ~ sputter rate is 7.0 X lo7 s-l. Multiplying by the v h / U + ratio estimated above, the ejection rate for Uo is 2.1 X 10" s-l. The desorbed particle rate for a 7.5-nA Ar+ beam (sputter yield 5.3) is 2.5 X 101's-l.
CONCLUSION At one time, high-efficiency laser postionization of sputtered atomic species was thought to offer the possibility for quantitative surface analysis. Such studies performed under ultrahigh vacuum conditions by using inert gas sputtering of metallic targets showed that in some cases quantitative analysis could be accomplished without matrix effects (3). Unfortunately, these laboratory conditions do not exist for the analysis of all samples. The industrially generated, particulate emissions for many reactive metals of environmental significance are often not found in the metallic state; they form a variety of compounds through reaction with the
environment. This work clearly indicates that the population of desorbed neutrals above such sample surfaces may not always be directly representative of ita composition. Just as chemistry in the sputtering region can dominate relative ion yields in SIMS experiments, it may also control the relative sputtered neutral yield detected by RIMS. The possibility that the desorbed neutral fraction can be partitioned amongst a variety of species will complicate the task of relating laser-generated ion abundances to the actual composition of the sputtered surface. Registry No. U, 7440-61-1;UOz, 1344-57-6;U308, 1344-59-8.
LITERATURE CITED (1) Morabito, J. M.; Lewis, R. K. Anal. Chem. 1973, 45,869-880. (2) Winograd, N.; Baxter, J. P.; Kimock, F. M. Chem. Phys. Lett. 1982, 88,581-584. (3) Moore, L. J. Workshop Report, "Laser Mass Spectrometry for the Production and Measurement of Inorganic Ions"; 30th Ann. Conf. Mass Spec. Allied Top.; 1982. (4) Becker, C. H.; Giilen, K. T. Anal. Chem. 1984, 56, 1671-1674. (5) Kimock, F. M.; Baxter, J. P.; Winograd, N. Surf. Sci. 1983, 124,L41L48. (6)Parks, J. E.; Beekman, D. W.; Schmltt, H. W.; Taylor, E. H. Nucl. Instrum. Methods Phys. Res., Sect. B 1985, B 10lllv280-284. (7) Donohue, D. L.; Chrlstie, W. H.; Wringer, D. E.; McKown, H. S. Anal. Chem. 1985, 57, 1193-1197. (8) Downey, S. W. AT&T Bel Labs, personal communication, Sept 1986. (9) Nogar, N. S.; Downey, S. W.; Miller, C. M. Anal. Chem. 1985, 57, 1144-1147. (10) Kimock, F. M.; Baxter, J. P.; Pappas, D. L.; Kobrin, P. H.;Winograd. N. Anal. Chem. 1984, 56,2782-2791. (11) Pellin, M. J.; Young, C. E.; Calaway, W. F.; Burnett, J. W.; Jorgensen, 8.; Schweitzer, E. L.; Gruen, D. M. Nucl. Instrum. Methods. Phys. Res., Sect. B 1987, 818,446-451.
RECEIVED for review March 9, 1987. Accepted October 30, 1987.
Development and Comparative Evaluation of Radioimmunoassay and Gas Chromatographic/Mass Spectrometric Procedures for Determination of Leukotriene B, W. R. Mathews,* G. L. Bundy, M. A. Wynalda, D. M. Guido, W. P. Schneider, and F. A. Fitzpatrick' T h e Upjohn Company, Pharmaceutical Research and Development, 301 Henrietta Street, Kalamazoo, Michigan 49001
Leukotrlene B, (LTB,) was quantified In human neutrophli samples by both radlolmmunoassay and gas chromatography/mass spectrometry. Antiserum to LTB, was generated In rabbits foliowlng Inoculation with an LTB,-BSA (bovine serum albumin) conjugate. At a final antiserum dliutlon of 1:1000, detectlon of 6 pg was possible. Cross reaction for 20 structurally slmllar compounds ranged from
