Anal. Chem. 1981, 5 3 ,
639-645
These data suggest that ionization and excitation of metal vapors in the graphite furnace occur predominantly by thermal processes.
Sturgeon, R. E.; Chakrabarti, C. L. Prog. Anal. At. Spectrosc. 1978, 7, 9-199. Kornbium, 0. R.; De Galan, L. Spectroch/m. Acta, Part 6 1973, 286, 139-147. De Galan, L.; Samaey, G. F. Spectrochlm. Acta, Part 6 1970, 256, 245-259. Nikolaev. G. I.; Podgornaya, V. I. Zh. Prlkl. SpeMrosk. 1974, 21, 593-598. L‘vov, B. V.; Pelleva, L. A. Zh. Prlkl. Spektrosk. 1078, 31, 16-23. L’vov, E. V.; Pelleva, L. A. Zh. Prlkl. Spekirosk. 1070, 37, 205-210. L‘vov, B. V.; Pelleva, L. A. Zh. Prlkl. Spekirosk. 1970, 37, 395-399. Kitagawa, K.; Ide, Y.; Takeuchi, f. Anal. Chim. Acta 1980, 773, 21-32. Rubeska, I. In “Flame Emission and Atomic Absorption Spectrometry”; Dean, J. A.; Rains, T. C., Ed.; Marcel Dekker: New York, 1989; VOl. I,pp 334-338. Joshi, B. M.; Sacks, R. D. Anal. Chem. 1079, 57, 1786-1791. Weast, R. C., Ed.; “Handbook of Chemistry and Physics”, 57th ed.; Chemical Rubber Co.: Cleveland, Ohio, 1976. Lntiejohn, D.; Ottaway, J. M. Analyst (London) 1977, 702, 553-563. Einbinder, H. J. Chem. Phys. 1967, 26, 948-953. Hofmann, F. W.; Kohn, H.; SchneMer, J. J. Opt. Soc.Am. 1981, 57, snA-si - - - .i.. De Galan, L.; Smith, R.; Winefordner, J. D. Spectrochlm. Acta, Part 6 1968, 238, 521-525. Nemets, A. M.; Nlkolaev, 0. I. Zh. Prlkl. SpeMrosk. 1073, 78, 571-578. Alkemade, C. Th. J.; Herrmann, R. ”Fundamentals of Analyticai Flame Spectroscopy”; Adam Hilger Ltd.: Bristol, 1979; pp 65-89. Boumans, P. W. J. M.; De Boer, F. J. Spectrochlm. Acta, Part 6 1977, 326, 365-395.
ACKNOWLEDGMENT The authors thank M. Epstein for critical comments and suggestions for improving the manuscript.
LITERATURE CITED Boumans, P. W. J. M. “Theory of Spectrochemical Excitation”; Hilger: London, 1966. Ottaway, J. M.;Shaw, F. Analyst(London) 1976, 701, 582-585. Schrenk, W. 0.; Everson, R. T. Appl. Spectrosc. 1975, 29, 41-44. Epstein, M. S.; Rains, T. C.; O’Haver, T. C. Appl. Spectrosc. 1978, 30, 324-329. Epsteln, M. S.; Rains, T. C.; Brady, T. J.; Moody, J. R.; Barnes, I. L. Anal. Chem. 1978, 50, 874-880. Ottaway, J. M.;Hutton, R. C.: Littlejohn, D.; Shaw, F. Wlss. 2. KarlMarx-Unlv. Lelpzlg, Math-Naturwlss. Relhe 1979, 28, 357-364. Littiejohn, D.: Ottaway, J. M. Analyst (London) 1978, 103, 595-606. van den Broek, W. M. G. T.; De Galan, L.; Matousek, J. P.; Crobik, E. J. Anal. Chlm. Acta 1978, 100, 121-138. Alder, J. F.; Samuel, A. J.; Snook, R. D. Spectrochlm. Acta, Part 6 1978, 376, 509-514. Littiejohn, D.; Ottaway, J. M. Anal. Chlm. Acta 1978, 98, 279-290. Littiejohn, D.; Ottaway, J. M. Analyst (London) 1979, 704, 208-223. Sturgeon, R. E.; Chakrabarti, C. L. Spectrochlm. Acta, Part 6 1977, 328 - __ , -231-255 - -- Sturgeon, R. E.; Berman, S. S.; Kashyap, S. Anal. Chem. 1080, 52, 1049- 1053. Sturgeon, R. E.; Berman, S. S.; Desaulniers, A.; Russell, D. S. Talanfa 1980, 27, 85-94. ZaMei, A. N.; Prokof’ev, V. K.; Raiskii, S. M. “Tables of Spectrum Lines”; Pergamon Press: New York, 1961. van den Broek, W. M. 0. T.; De Galan, L. Anal. Chem. 1977, 49, 2 176-21 86.
839
-
RECEIVED for review September 3,1980.
Accepted January 12,1981. This paper was presented at the 7th FACSS meeting, Philadelphia, PA, Sept 2 M c t 3,1980 and the 27th Canadian Spectroscopy Symposium, Toronto, Canada, Oct 6-8,1980.
Laser Fraunhofer Diffraction Studies of Aerosol Droplet Size in Atomic Spectrochemical Analysis Norita Mohamed and Robert C. Fry* Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
David
L. Wetzel
Department of Grain Science and Industry, Kansas State University, Manhattan, Kansas 66506
Near forward laser Fraunhofer diffraction Is shown to be a convenient method for the automated determlnatlon of droplet and partlcie size dlstrlbutions of Interest in aerosol productlon and transport studles related to atomlc spectrochemical analyds. The laser dlffractometer Is based on a combination of optical analog and digHal mlcroprocessor computation. It Is found to be directly applicable to relatively concentrated aerosols and suspenslons wlthout diluting or otherwlse perturblng the aerosol sample. The partlcle or droplet size dlstrlbutlon Is determlned Independent of partlcle composltlon, refracthe Index, transparency, veloclty, aerosol or suspendon concentratlon, ampiHler gain, and measurement time Interval. No user callbratlon Is requlred. The total sample mass or volume also need not be known, such that udmeasured sample quantltles may be Introduced Into the dlffractometbr for automated partlcle slre analysis. The precision, accuracy, and susceptlbllity of laser dlffractometry to muitlple scattering Interferences are studied In spectrodhemlcai systems. The aerosol productlon and transport propertles of a Bablngton slurry nebullzer system are studied.
Numerous authors have made it clear that droplet size is an important parameter in atomic spectrochemical analyeis 0003-2700/81/0353-0639$01.25/0
using nebulizer sample introduction (1-28). The present manuscript describes a laser diffraction approach to the study of aerosol production And transport in atomic spectrochemical analysis. Transport studies aimed at explaining interferences, auxiliary desolvation, and sensitivity effects in the flame and plasma atomic spectrochemicalanalysis of aqueous solutions have been previously described by Skogerboe and Olson (23) and subsequently by Browner et al. (24-28). A combination of cascade impactors, condensation nuclei counters, and electrical mobility analyzers were used to measure droplet size distributions of aqueous and dioctylphthalate aerosols emergent from spray chambers (23-23). These distributions were measured for conventional pneumatic nebulizers as a function of gas flow rate, solution composition, and spray chamber geometry for several configurations(23-28). The appearance of newer ultrasonic, Babington, fritted disk, etc. nebulizing systems and other innovations in the development of flame and plasma systems collectively indicate that there is an ongoing need for studies in the area of aerosol production, transport, and conditioning in atomic spectrochemical analysis. The present manuscript represents an initial attempt to provide a more convenient and less intrusive means to study aerosol production and transport in spectrochemicalsystems. The new approach described herein involves use of a laser beam as a nonperturbing probe for the rapid “real time” 0 I981 American Chemical Society
640
ANALYTICAL CHEMISTRY, VOL. 53, NO. 4, APRIL 1981
determination of droplet size distributions emergent from spray chambers of spectrochemical interest. The laser beam offers the further potential of nonperturbing measurements to be eventually taken directly in burning flames; however, the present manuscript will be confined to laser diffraction measurements involving aerosols emergent from spray chambers used in spectrochemical analysis. Light scattering methods are especially suited to the measurement of droplet and particle diameters in flowing gas streams or flames, since the measurement is made without removing, collecting, or otherwise disturbing the particles and droplets in the flowing system. The scattering of light by particles or droplets which are small with respect to the wavelength of incident light is of the Rayleigh type. The more complex Mie theory has been developed to describe the scattering of light by particles in all size ranges (29,30).These theories have been applied to the characterization of submicrometer soot particles in luminous fuel rich flames (31, 32) and to the measurement of droplet size distributions in naturally occurring terrestrial weather phenomena such as fog (33). Laser Doppler velocimetry has been presented by Hinds and Reist (34),and it appears to be a promising, relatively new, alternative technique useful for the nonintrusive measurement of particle size in the submicrometer range. This new method is independent of refractive index but is generally not applicable for particle diameters much greater than 1.0 pm. The scattering of light by larger particles and droplets may be described more simply in terms of reflection, refraction, and scalar diffraction phenomena (35-54). For near forward scattering angles 8 (10/a)X, Fraunhofer diffraction predominates over reflection and refraction phenomena. For visible incident laser light (e.g., X * 0.6328 pm), Fraunhofer diffraction in the near forward angular region > particle diameter steady-state concentration and distribution of spherical particles of diameter > (10/n)h during the sectored measurement time interval composite Fraunhofer diffraction by a collection of such particles negligible multiple scattering near forward observation ( (lO/?r)X) such that the critical upper limit cutoff region of droplet transport easily falls within the range of the L&N diffractometer. The present laser diffractometer should therefore prove valuable in establishing rapidly determined upper limit droplet transport cutoffs for most spectrochemical nebulizing systems (even though the median droplet diameter cannot be accurately measured when a significant fraction of droplets occur in a range below 2 pm). In a special case where the present high solids Babington nebulizer is operated without an impactor bead in an “unbaffled” Jarrell-Ash tapered cone spray chamber, the near entire droplet distribution (Figure 3B) emergent from the spray chamber falls within the operating range of the present L&N laser diffractometerthereby making
Dean, J. A.; Carnes, W. J. Anal. Chem. 1962, 3 4 , 192-194. Herrmann, R.; Alkemade, C. T. J.; Gilbert, P. T. “Chemical Analysis by Flame Photometry”; Interscience: New York, 1963. Willis, J. B. Spectrochlm Acta, Part A 1967, 23, 81 1-830. Hieftje, G. M.; Maimstedt, H. V. Anal. Chem. 1968, 40, 1860-1867. Hieftje, 0. M.; Malmstadt, H. V. Anal. Chem. 1969, 41, 1735-1744. Ckmpitt, N. C.; Hieftje, G. M. Anal. Chem. 1972, 44, 1211-1219. Ciampitt, N. C.; Hleftje, G. M. Anal. Chem. 1974, 46, 382-386. Bastiaans, G. J.; Heftje, G. M. Anal. Chem. 1974, 46, 901-910. Boss, C. B.; Hieftje, G. M. Anal. Chem. 1977, 49, 2112-2114. Boss, C. B.; Hieftje, 0. M. Appl. Spectrosc. 1978, 32, 377-380. Boss, C. B.; Hieftje, G. M. Anal. Chem. 1979, 51, 1897-1905. Zeegers, P. J. T.; Smith, R.; Wlnefordner, J. D. Anal. Chem. 1966, 40, 28A-47A. Stupar, J.; Dawson, J. B. Appl. Opt. 1968, 7 , 1351-1358. Alkemade, C. T. J.; Rains, T. C. “Flame Emission and Atomic Absorption Spectrometry”; Dean, J. A., Rains, T. C., Eds.; Marcel Dekker: New York, 1969; Vol. 1. Alkemade, C. T. J. “Analytical Flame Spectroscopy”; Mavrodlneanu, R., Ed.; Springer-Verkg: New York, 1969. L’Vov, B. V. “Atomic Absorption Spectrochemical Analysis”; Hilger: London, 1970. Willis, J. B. Spectrochlm Acta, Part 6 , 1970, 25, 487-512. Kirkbrlght, 0. F.; Sargent, M. “Atomic Absorption and Fluorescence Spectroscopy“; Academic Press: New York, 1974. Li, K. P. Anal. Chem. 1976, 48, 2050-2055. Li, K. P. Anal. Chem. 1976, 50, 828-631. Allemand, C. D.; Barnes, R. M. Appl. Spectrosc. 1977, 31, 434-443. Holcombe, J. A,; Eklund, R. H.; Grice, K. E. Anal. Chem. 1978, 50, 2097-2 104. Olson, K. W.; Skogerboe, R. K. Appl. Spectrosc. 1978, 32, 181-187. Novak, J. W.; Browner, R. F. Anal. Chem. 1980, 52, 287-290. Cresser, M. S.; Browner, R. F. Specfrochlm Acta, Part 6 1980, 35, 73-79. Cresser, M. S.; Browner, R. F. Anal. Chlm. Acta 1980, 113, 33-38. Novak, J. W.; Browner, R. F. Anal. Chem. 1960, 52, 792-796. Cresser, M. S.; Browner, R. F. Appl. Spectrosc. 1960, 34, 364-388. Mie, G. Ann. Phys. 1908, 25. 377-445. Van de Hulst, J. C. “Llght Scattering by Small Particles”; Wiiey: New Ywk, 1957. Penner, S. S.; Bernard, J. M.; Jerskey, T. Acta Asfron. 1976, 3 , 93-105.
Anal. Chem. 1981, 53, 645-650 (32) Roth, C.; Gebhart, J.; Heigwer, G. J. ColloM Interface Scl. 1976, 54, 265-277. (33) Ferrara, R.; Fiocco, G.; Tonna, 0. Appl. Opt. 1970, 9 , 2517-2521. (34) Hinds, E.; Reist, P. C. J. AerosolSci. 1972, 3 , 501-514. (35) Young, T. “An Introduction to Medical Laeraturd’; Underwood and Blacki: London, 1818; p 548. (36) Pijper, A. J. Lab. Clln. Med. 1947, 32, 857-877. (37) Polanyi, M. L. Rev. Scl. Instrum. 1959, 30, 626-632. (38) Dobbins, R. A.; Crocco, L.; Giassman, I. AIAA J . 1963, 7(8), 1882- 1886. (39) Roberts, J. H.; Webb, M. J. AIAA J . 1964, 2(3), 583-585. (40) Silverman. B. A.: ThomDson, B. J.: Ward, J. H. J. A.m. / . Meteorol. 1984, 3, 792-801. (41) Hodkinson, J. R. Appl. Opt. 1966, 5 , 839-844. (42) Talbot, J. H. J . Scl. Instrum. 1968, 43, 744-749. (43) Taylor, M. E. U S . Patent 3469921, 1969. (44) 601, J. U S . Patent 3646352, 1972. (45) Corniliault, J. Appl. Opt. 1972, 7 1 , 265-268. (46) Gravatt, C. G. J. Air Pollut. Control Assoc. 1973, 23, 1035-1038. (47) Davies, R. Am. Lab. (FairfleM, Conn.) 1974, 6 , 73-86. (48) Corniliault, J.; Evrard, P. Cem. Technol. 1975, 6 , 178-179. (49) Wertheimer, A. L.; Wilcock, W. L. Appl. Opt. 1976, 15, 1616-1620. (50) Welss, E. L.; Frock, H. N. Powder Technol. 1978, 14, 287-293. (51) Swkhenbank, J.; Beer, J. M.; Taylor, D. S.; Abbot, D.; McCreath, 0. C. “Progress in Astronautics and Aeronautics”; Zinn, B., Ed.; AIAA: New York, 1977; Voi. 53, p 421.
645
(52) Mann, P. J. Foodfng. 1977, 49, 85-88. (53) Caroon, T. A. M.S. Thesis, University of Wisconsin, Madison, 1978. (54) Caroon, T. A,; Borman, G. L. Combust. Scl. Technol. 1979, 19, 255-258. (55) Bachaio, W. D. Appl. Opt. 1980, 19, 363-370. (56) Roberds, D. W. Appl. Opt. 1977, 76, 1861-1668. (57) Mohamed, N.; Fry, R. C. Anal. Chem. 1981, 53, 450-455. (58) Mohamed, N.; Brown, R. M.; Fry, R. C. Appl. Spectrosc. 1981, 35, 153-164.
RECEIVED for review September 17,1980. Accepted January 22,1981. This work was supported in part by FDA Research Contract No. 223-80-2327 CPD (to R. C. Fry) and in part by Kansas Agricultural Experiment Station Project No. 143 (to R. C. Fry). The authors wish to thank the Leeds and Northrup Co. for generous use of the laser diffractometer. This work was presented by N. Mohamed and R. C. Fry in part at the 1979 Pithburgh Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, OH, in part at the 1979 Rocky Mountain Conference on Analytical Chemistry, Denver, CO, and in part a t EXPOCHEM 80, Houston, TX.
Microcomputer-Controlled Intensified Diode Array Data Acquisition System for Chemiluminescence Spectra D. F. Marino‘ and J. D. Ingle, Jr.” Department of Chemistty, Oregon State University, Corvallis, Oregon 9733 7
A KIM 6502 controlled Intensified dlode array system Is described which Is capable of acquiring a 512-point chemlluminescence (CL) spectrum from 200 to 840 nm In as little as 4 ms under dlrect memory access (DMA) control. Thls system has provlslon for subtraction of the dark current spectrum, automated lnjectlon of the last reagent to Initiate the CL reaction, signal averaglng N spectra, and plotting of the CL spectrum on a strlp chart recorder. The use of the Instrument Is demonstrated with three dlfferent CL chemlcal systems.
Solution chemiluminescence (CL) spectra are difficult to obtain with discrete sampling instrumentation in which a reagent or the sample is injected into a reaction mixture to initiate the CL reaction. The typical short duration (ca. 1s) and transient nature of the CL signal are not compatible with conventional scanning monochromators. Most investigators (1-7) in this area have invariably employed either photographic detection or conventional scanning spectrometers, both of which require a great deal of time and a number of repetitive CL reactions. Recently however, the first use of a commercially available intensified diode array (IDA) for the acquisition of fast CL spectra was reported (8),and spectra of the lucigenin and pyrogallol CL reactions were presented. Though such spectra provide principally qualitative information about the CL reaction in question, they are nevertheless useful for (i) choosing PMTs for maximum sensitivity at the wavelengths of maximum CL intensity, (ii) identifying reactant or product absorption interferences, (iii) elucidating the nature of nonanalyte interferences, or (iv) obtaining information about CL reaction mechanisms (e.g., identification of the luminescing species). Present address: E. I. du Pont de Nemours and Co., Wilmington,
DE.
0003-2700/81/0353-0645$01.25/0
Because the commercial data acquisition system used for previous work did not provide the desired versatility for acquiring CL spectra, an in-house microprocessor control and data acquisition system was constructed. This system is much less expensive and acquires spectra faster than the commerical system. One other &bit microprocessor (8080)control system for a diode array has been reported (9) although the data acquisition rate is much slower than reported in this paper. This paper is concerned with the construction that is specifically designed for acquiring CL spectra with a discrete sampling CL system. The application of the IDA system to three different CL chemical systems is reported to illustrate the information provided by CL spectra that is useful in developing routine CL analysis techniques. EXPERIMENTAL SECTION CL measurements were made with a discrete sampling CL photometer previously described (10,11). The reaction sample and reagents are added to the sample cell with Eppendorf pipets, and the reaction is initiated by injection of the last reagent with a precision liquid dispenser which is TTL controlled. The IDA spectrograph was interfaced to the CL sample module a8 previously noted (8). Absorption spectra were acquired with a Cary 118C W-visible spectrophotometer. The absorption spectra of all reaction constituents were taken in solvents of the same pH as that of their respective CL reaction solutions. INSTRUMENTATION Introduction. A block diagram of the KIM-IDA CL spectra data acquisition and plotting system is shown in Figure 1. The operation and general characteristics of the components of the system will be discussed below. Only circuitry which is unique and which could not be constructed from information in other articles or manufacturer’s information will be discussed in detail. Detailed schematics, flow diagrams, and program listings are available from the authors upon request. 0 1981 American Chemical Society
