in 30 mL CHzClz distilled from CaClz under nitrogen. The precipitate was allowed to warm to 0 “C and then quenched with 100 mL distilled water. After decanting the water from the CHPClz into a 500-mL volumetric flask, 100 mL 0.1N NaOH was added to the reaction flask, and the CHzClzevaporated at room temperature on a rotary evaporator. The NaOH solution was added to the volumetric flask and the nitrite determination performed as described above, giving a yield of 86%. Attempted Isolation of Nitrosoammonium Salt. Five grams of dried TEA were distilled into a 500-mL 3-neck flask equipped with a Teflon stir bar and a three-way stopcock adaptor. After distilling in 100 mL CHzClzfrom CaClzunder nitrogen, an inlet for NOz was fitted to one neck and the reaction flask cooled to -5 “C in an ice-brine bath under positive nitrogen pressure. Approximately 500 mL NOz/NZO4passed through P z 0 5 was metered via a rotameter into the stirred reaction mixture. After the addition had been completed, the reaction mixture was held at -5 “ C for 10 min and then the CHzClzwas filtered off with nitrogen pressure through a frit placed on one neck. At this point, the formation of bubbles in the precipitate indicated some decomposition. No attempt was made to characterize decomposition products. The reaction flask was briefly evacuated to remove traces of CHzClzand transferred to a glove box under nitrogen where an aliquot was weighed out for determination of nitrite (best yield of three reactions, 54%). A qualitative UV in dry methanol was also taken at this juncture.
Occupational Health Program Harvard School of Public Health 665 Huntington Avenue Boston, Massachusetts 02115
ACKNOWLEDGMENT The author thanks 0. Grubner and G. Dudek for helpful discussions and the Chemistry Department of Harvard University for use of their NMR spectrometer.
RECEIVED for review December 22, 1976. Accepted May 4, 1977. Supported by NIOSH Grant OH00369-05 and Center Grant (ES 00002) from the National Institute of Environmental Health Sciences.
LITERATURE C I T E D (1) B. E. Saltzman, Anal. Chern., 26, 1949 (1954). (2) D. A. Levaggi, W. Siu, and M. Feldstein, J. Air follut. Control Assoc., 23, 30 (1973). (3) J. H. Blacker, Am. Ind. Hyg. Assoc. J., 34, 390 (1973). (4) W. Lijlnsky, L. Keefer, E. Conrad and R. Van de Bogart, J. Natl. Cancer Inst., 48, 1239 (1972). (5) P.A. S. Smith and R. N. Loeppky, J. Am. Chem. SOC.,88, 1147 (1967). (6) H. A. Bent, Inorg. Chern., 2, 747 (1963). (7) C. C. Addison, W. Karcher and H. Hecht, “Chemistry in Nonaqueous Ionizing Solvents,” Vol. 111, PergamFon Press, New York, 1967, pp 3-75. (8) F. A. Cotton and G. Wllklnson Advanced Inorganic Chemistry, a Comprehensive Text,’’ 3rd ed.,Interscbnce, New Ywk, 1972, pp 357-359. (9) S. Patai, “The Chemistry of the Amino Group,” Interscience, New York, 1968, pp 305-320. (10) B. C. Challis and J. H. Ridd, R o c . Chem. SOC.(London), 245 (1960). (11) E. D. Hughes and J. H. Ridd, J. Chem. SOC.,82 (1958). (12) A. E. Comyns, J. Chem. SOC.,1557 (1955). (13) F. P. Scarlngelli, E. Rosenberg, and K. A. Rehme, Envlron. Scl. Techno/., 4, 924 (1970). (14) H. J. Crecelius and W. Forweg, Staub-Reinholt. Luft, 30, 23 (1970). (15) H. Hartkamp and G. Nltz, Staub-Relnhofi Luft, 34, 340 (1974). (16) J. Rosin, “Reagent Chemicals and Standards,” 5th ed., 0. Van Nostrand Co., Inc., Princeton, N.J., 1967, p 471.
Avram Gold
AIDS FOR ANALYTICAL GHEMISTS Modified Inductively Coupled Plasma Arrangement for Easy Ignition and Low Gas Consumption John L. Genna and Ramon M. Barnes* Department of Chemistty, University of Massachusetts, Amherst, Massachusetts 0 1003
Charly D. Allemand Jarrell-Ash Division, Fisher Scientific Company, Wakham, Massachusetts 02 154
Since the initial description by Reed ( I ) of a practical inductively coupled plasma (ICP) discharge and the independent realization of its potential as an analytical tool by Greenfield et al. (2), and Wendt and Fassel (3),developments of the ICP discharge as a spectrochemical source have intensified (4,5). Design of an ICP arrangement specifically for totally automated, unmanned operation with low coolant gas consumption and ease of ignition emphasized optimization of plasma tube geometry in the region near the induction coil (6). The resulting successful configuration required precise machined dimensions obtainable with material like boron nitride but not with quartz. This note describes a simple modification of the gas flow injection region which is readily achieved with conventional materiak such as quartz and which promotes the formation of closed loops of ionized gas to ease discharge ignition. This modification also provides reduced coolant gas consumption. In popular ICP arrangements ( 7 - I I ) , total argon flows reach approximately 11 to 30 L/min with the major portion used in the outer tube (Figure 1) annulus to prevent the outer quartz confinement walls from overheating. In high-power 1450
ANALYTICAL CHEMISTRY, VOL. 49, NO. 9, AUGUST 1977
level ICP discharges, high nitrogen flows in the outer annulus provides effective cooling and low background levels ( I I , I 2 ) . Reed recognized the importance of tangential coolant gas introduction for vortex stabilization ( I ) . Although laminar (3)and other arrangements have been explored (131,tangential gas introduction is popular and effective. Stabilization is attributed t o production of a low pressure region along the central axis of the tubes by the swirling gas flow near the confinement wall (I). This low pressure allows increased amounts of countercurrent gas flow. The low pressure produced by the tangential introduction of gas is a function of the mass flow rates, but, more importantly, the gas velocity. In cylindrical coordinates, the gas velocity comprises the following three components (Figure 1): a radial (V?),an axial (V&, and angular or swirl (V,) component. The swirl velocity travels parallel to the circular torch walls and is critical in the stabilization of the discharge. Control of the swirl component is essential in the improvements described here. To increase the argon flow countercurrent to the main flow, the low-pressure regions in the discharge must be increased. These low-pressure regions may be created, in turn, by the
A
Flgure 1. Illustration of coolant gas flow in a plasma torch and its three
gas velocity components 0 -
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