1111
Anal. Chem. 1881, 53, 1111-1117
Nonresonant Atomic Emissions of Bromine and Chlorine in the Argon Inductively Coupled Plasma Steven K. Hughes ,and Robert C. Fry” Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
Partial Grotrian diagrams and tables of relative intenstties wtth corresponding wavelengths of 102 inductively coupled plasma (ICP) exclted, nonresonant atomic bromine emlsslon Unes and 85 ICP excited, nonresonant atomic chlorine emission itnes are presented for the air-path, photomultiplier-accessible region 3700-9900 A amid 4200-9900 A, respectively. Several (ICP) excited lines of ionized Br end Ci are listed. Vertlcai emission intensity praifiies of near-Infrared Br I and Ci I ilnes are presented for an extended argon ICP torch. The present detection limit for both Br I and Ci I is 0.05 pg for 8-pL gas sampling loop injectilons of HBr and Ci2 into a low volume transfer line leading dlrectiy into the ICP. The linear dynamic range for quantitative sampling loop analysis is presently >5 X loa for both Br and Ci.
The present paper on inductively coupled plasma (ICP) excited emission spectra of atomic bromine and chlorine is the fifth in a series of reports from our laboratory concerning the determination of these nonmetals which have long eluded ICP quantitation. The first two papers of the series served to introduce the quantitative ICP determination of the “elusive” elements, nitrogen and oxygen, by near-infrared (NIR)nonresonance omission spectrometry (1,2). The third paper of the series involved ICP excited, nonresonance atomic fluorine spectra useful for quantitative determinations in the sub-microgram range (3). The fourth paper of the series involved quenching studies and oxygen-selective gas-liquid chromatography using near-infrared atomic 0 I emissions in the ICP (4). Because all doublet and quartet excited states of atomic bromine and chlorine lie more than 7.5 eV above the corresponding ground-state levels, resonance lines of these neutral atoms all have wavelengths shorter than 1650 A. Although Heine, Babis, and Denton have made preliminary qualitative observations of this short wavelength region of the ICP emission spectrum (5), no quantitative results have been published, and this slpectral region is inconvenient in terms of atmospheric opacity and conventional detector sensitivity. For this reason, the present paper involves exclusive use of air-path instrumentation and nonresonance, near-infrared and visible transitions originating from high-energy states of atomic bromine (Br I) and chlorine (Cl I). Windsor and Denton have reported a 200-pg ICP detection limit and a linear dynamic range listed as “poor” for the 7005.7-A Br I line (6). The same authors report a 7-pg ICP detection limit and II linear dynamic range of 100 for the 7256.7-A C1 I line (6). The present paper includes a report of an approximate 4000X improvement in the detection limit and linear dynamic range of bromine determination and an approximate lOOX improvement in the detection limit and linear dynamic range of chlorine determination using gas sampling loop injectioin into a low volume transfer line leading directly to an argon inductively coupled plasma. Tables of observed ICP excited nonresonance emission lines and relative intensities are presenited here for the region 4200-9900 A for 0003-2700/81/0353-1111801.25/0
Table I. Experimental Conditions 1.75 kW incident rf power 1will produce a group of several lines which are in the same spectral region (e.g., the 4477.72-A, 10.63-eV line of Br I from the transition 5s4P(s~2)-6p4Do(,~2) and the 4441.74-A, 10.65-eV line of BrI from the transition 5s4P(s,*)-6p4Do(~/2). In this case,
ANALYTICAL CHEMISTRY, VOL. 53, NO. 7, JUNE 1981 B r W QUARTET np14s*
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all lines of the group will appear in Table 11or 111, but a single nominal value corresponding to the first line in the group is given (e.g. 4478 A in Figure 1) with fewer significant digits in the low-resolution energy diagrams of Figures 1-6. Tables I1 and 111, however, contain high-resolution data and should therefore be consulted in combination with Figures 1-6 to
determine which indicated "solid line" transitions are really observed as a group of lines which are close in wavelength and whose transitions merely differ in the J values involved. Most of the major transitions with upper state energies below the first ionization limit and predicted from atomic diagrams (Figures 1,2,4,and 5 and ref 8 and 11) are observed
1114
ANALYTICAL CHEMISTRY, VOL. 53, NO. 7, JUNE 1981
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in the ICP and are listed in Tables I1 and I11 with notable exception of the resonance lines (5 x 103.
LITERATURE CITED RELATIVE EMISSION C INTENSITY
Flgure 7. Relative emission intensities (vertical profiles) of Br I and CI Iemission in the ICP for gaseous samples. The symbols indicate the location of observation areas B, C, D, and E. For convenient reference, the symbols have been translated laterally to correlate with the graphs of Ci Iand Br Irelative emission intensity (Xaxis) vs. vertical observation position ( Y axis) in the argon ICP.
+
+
Limited area viewing (0.5 mm) was used to generate the vertical emission profiles of Figure 7; however, when the intermediate image mask was removed for full aperature viewing, the limited height of the emitting area prevented the full benefit of area D from being realized in the present optical configuration. Area B in Figure 7 was therefore used to generate Tables I1 and I11 and all measurements in the remaining section (below) of this paper. Detection Limit and Linear Dynamic Range. The limit of Br and C1 detection was determined by gas sampling loop
Northway, S. J.; Fry, R. C. Appl. Specfrosc. 1080, 34, 332-338. Northway, S. J.; Brown, R. M.; Fry, R. C. Appl. Specfrosc. 1080, 34, 338-348. .- .-. Fry, R. C.; Northway, S. J.; Brown, R. M.; Hughes, S. K. Anal. Chem. 1080. 52. 1716-1722. Brown, R.' M., Jr.; Fry, R. C. Anal. Chem. 1081, 53, 532-538. Helne, D. R.; Babls, J. S.; Denton, M. B. Appl. Spectrosc. 1080, 34, 595-598. Wlndsor, D. L.; Denton, M. B. J . Chromatogr. Scl. 1979, 17, 492-496. HAMAMATSU TV Co., Ltd., Mountain View, CA, Catalog No. SC-1-3, 1970, p 38. Tech, J. L. J. Res. Natl. Bur. Stand., Sect. A 1963, 67A, 505-568. Zaldel, A. N.; Prokofev, V. K.; Ralskll, S. M.; Slavnyl, V. A.; Shreider, E. Ya. "Tables of Spectral Lines"; IFIIPlenum: New York, 1970. Striganov, A. R.; Sventltskil, N. S. "Table of Spectral Llnes of Neutral and Ionlzed Atoms"; Plenum Press: New York, 1968. Bashkln, S.; Stoner, J. 0.. Jr. "Atomic Energy Levels and Grotrian Dlagrams"; North Holland: Amsterdam, 1978; Vol. 11.
RECEIVED for review January 14,1981. Accepted March 16, 1981. This work was presented in part a t the 1980 EXPOCHEM meeting in Houston, TX. This work was supported by the Kansas Agricultural Experiment Station (project no. 143).
