1484
Anal. Chem. 1981, 53, 1484-1487
that, at room temperatures, the pumps do meet that criterion (23). However, from data obtained in a simulated field sampling experiment (24), the volume correction for personal sampling pumps under conditions of actual use was found to be 0.99 f 10.3% ( N = 128). Thus a higher RSD for the samples collected in areas 3-5 (Table IV) is not unexpected. The large differences between total and respirable dust levels found in locations (3-5) is not surprising. Size distribution data for this type of amorphous silica (Silica F) indicate a mean particle size of 9 pm. Since the 10-mm nylon cyclone passes only about 10% of 9-pm particles, a much higher concentration of total dust is expected.
ACKNOWLEDGMENT The authors express their appreciation to D. D. Dollberg and M. T. Abell for helpful discussions not only during the course of the work but also in the preparation of the manuscript.
LITERATURE CITED (1) Sosman, R. B. "The Phases of Silica"; Rutgers Universlty Press: New Brunswick, NJ, 1965; Chapter 7. (2) Titie 29, Part 1910 "Occupational Safety and Health Standards" Fed. Regist. 1971, 36, (no. 157), 15 101. (3) Taylor, D. G., Ed. "NIOSH Manual of Analytical Methods", 2nd ed.; Cinclnnati, OH, 1977; No, 106, 109, 110, 259, S315. (4) Day, A. L.; Shepherd, E. S. J. Am. Chem. SOC. 1906, 28, 1069. (5) Rieke, R.; Endel, K. Silik. 2.1913, 1 , 6. (6) Endeil, K.; Rieke, R. Tschermaks Mineral. Pefrogr. Mitt. 1912, 31, 501. (7) Verduch, A. G. J. Am. Ceram. SOC. 1958, 41(11), 427.
(8) Das, S. K.; Mookerjee, S. K.; Niyogi, S. K.; Thakur, R. L. J. Therm. Anal. 1976. 9. 43. (9) Austrheim, I.T. J. Br. Ceram. SOC. 1977, 76(6), 134. (IO) Graf, J. L.; Ase, P. K.; Draftz, R. G. "Preparation and Characterization of Analytical Reference Minerals"; DHEW (NIOSH Pubi. No. 79-139); Cincinnati, OH, 1979. (11) Lange, B. A.; Haartz, J. C. Anal. Chem. 1979, 51, 520. (12) Sosman, R. B. "The Phases of Silica"; Rutgers University Press: New Brunswick, NJ, 1965; Chapter 6. (13) Thompson, A. B.; Wennemer, M. Am. Mineral. 1979, 64, 1018. (14) Ekstrom, T.; Tiiey, J. D. J. Cryst. Growth 1977, 38, 197. (15) Taylor, N. W.; Lin, C.-Y. J. Am. Ceram. SOC. 1941, 24, 57. (16) Lang, H. U.S. Bureau of Mines, Bruceton, PA, personal communicatlon, 1979. (17) Edmonds, J. W.; Henslee, W. W.; Guerra, R. E. Anal. Chem. 1977, 49, 2196. (18) Waipoie, R. E. "Introductlon to Statistics"; MacMiilan Co: New York, 1968; p 291. (19) Birks, L. S. "X-Ray Spectrochemical Analysls"; Interscience: New York, 1959; p 54. (20) Jenkins, R.; DeVries, J. L. "Worked Examples in X-Ray Analysis"; Springer-Veriag: New York, 1970; p 51. (21) Haartz, J. C. I n "Proceedings of the Symposium on Silica"; Industrial Health Foundation: Pittsburgh, PA, 1976; pp 38-55. (22) Title 30, Part 74: "Coal Mine Dust Personal Sampler Units" Fed. Regist. 1970, 35, (No. 51), 4326. (23) Parker, C. D.; Lee, M. B.; Sharpe, J. C. "An Evaluation of Personal Sampling Pumps in Sub-Zero Temperatures"; DHEW (NIOSH Pubi. No. 78-1 17); Cincinnati, OH, 1977. (24) Marks, G. E.; Knutson, E. 0. "Complete Testing of the NIOSH Method for the Determination of Trace Metals by Atomic Absorption Spectrophotometry"; Final Report, Contract No. CDC 99-74-46, NIOSH, Clncinnati, OH, 1975.
RECEIVED for review July 10, 1980. Resubmitted April 17, 1981. Accepted April 17, 1981.
Microcomputer-Controlled Reagent Preparation System R. Balciunas, F. J. Holler,' P. K. Notz,* E. R. J ~ h n s o n L. , ~ D. R ~ t h r n a nand , ~ S. R. Crouch" Department of Chemistry, Michigan State University, East Lansing, Michigan 48824
The deslgn, operatlon, and evaluation of a microcomputercontrolled, syringe-based reagent preparatlon system with a dilution range of up to 5 orders of magnltude is reported. Reagents are prepared from up to three different stock solutlons and one dlluent. Reproduciblllty of the dellvered stock solutlons and of the diluted reagent Is better than that of class A glassware for all cases tested. The results of several chemical cornplexatlon and klnetlcs studies are presented as a demonstration of the preclslon and utility of the system.
The microelectronics revolution that we are witnessing is spawning a new generation of automated laboratory instruments that, because of microprocessors, are intelligent, versatile, easily programmable, and highly reliable. This new breed of scientific instruments promises to enhance greatly the efficiency with which instrumental measurements can be carried out in the laboratory. Despite the high degree of 'Present address: D e p a r t m e n t of Chemistry, University of K e n , Lexington, KY 40506. Jresent address: G e t t y Oil Co., Houston, TX 77099 Present address: Departments of Chemistry a n d Psychology, W a y n e State University, Detroit, MI 48202. Present address: A n a l y t i c a l Laboratories, T h e D o w Chemical Co., M i d l a n d , MI 48640.
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automation of the measurement steps in UV-visible spectrophotometers, atomic absorption spectrometers, gas chromatographs, electrochemical analyzers, and other instruments, the chemist in most laboratories is still faced with the tedious, time-consuming, and error-prone task of manually preparing the solutions to be used for chemical studies and chemical analyses. With automated instrumental systems, the preparation of solutions can easily be the step that limits the rate of information production. In stopped-flow chemical kinetics studies in our laboratory, for example, we commonly prepare for a single experimental session 10 or more solutions each containing two or more reagents often in buffered or constant ionic strength media. The mixing of the two reactant solutions and the recording of data that describes the reaction progress can be accomplished in our automated stopped-flow apparatus (2-3) in a few seconds or less for rapid reactions. Complete kinetics studies involving replications and several levels of reactant concentrations can often be carried out in an hour or less once the requisite solutions are prepared. However, preparing even moderately complex reaction mixtures usually requires a good deal more time than the mixing and measurement steps. In analytical procedures, the preparation of standard solutions for constructing calibration curves, for implementing standard addition methods, and for evaluating and optimizing instrumental performance can easily require 0 1981 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 53, NO. 9, AUGUST 1981 .......................................
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