ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978
LITERATURE CITED J. A. Holcombe and R. D. Sacks, Specfrochlm., Acta, Part B , 28, 451 (1973). C. S. Ling and R. D. Sacks, Anal. Chem., 47, 2074 (1975). C. S. Cling and R. D. Sacks, Anal. Chem.. 48, 1500 (1976). D. V. Duchane and R. D. Sacks, Anal. Chem., preceding paper in this issue. (5) "Exploding Wires", W. G. Chace, and H. K. Moore, Ed., Plenum, New York, N.Y., Vol 1, 1959. Ref. 5, Vol. 2, 1962. Ref. 5, Vol. 3, 1964. Ref. 5, Vol. 4, 1968. J. A. Holcombe, D. W. Brinkman, and R. D. Sacks, Anal. Chem., 47, 441 (1975). F. A. Cotton and G. Wilkinson. "Advanced Inorganic Chemistry", Interscience, New York, N.Y., 1972, p 852. Ref. 10, pp 990-1000. 0. Kubaschewski and B. E. Hopkins, "Oxidation of Metals and Alloys", Academic Press, London, 1962, pp 102, 103, and 230.
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(13) R . D. Sacks, "Shock Tubes, Exploding Conductors and Flashlamps". in Anarnica Uses of Plasmas", R. M. Barnes, Ed., Wiley-Interscience, New York, N.Y., in press. (14) R. D. Sacks and J. A. Holcombe, Appl. Specfrosc., 28, 518 (1974). (15) U. R. Evans, "Metallic Corrosion, Passivity and Protection", E. Arnold & Co., London, 1946. (16) S. Greenfield, Metron 3 , 224 (1971). (17) D. V. Duchane, "The Application of Expldng Thin Films to Trace Metals Analyses", Ph.D. dissertation, University of Michigan, Ann Arbor, Mich., 1978. (18) P. Thomas and R. D. Sacks, Anal. Chem., 50, 1084 (1978). (19) L. A. Arzimovich. "Elementary Plasma Physics", Blaisdell, New York, N.Y., 1965.
RECEIVED for review June 13, 1978. Accepted August 7, 1978. Work supported by the National Science Foundation through grant number CHE76-11646 A01.
Atomic Emission Determination of Selected Trace Elements in Micro Samples with Exploding Thin-Film Excitation D. V. Duchane' and R. D. Sacks* Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48 109
The highly luminous metal-vapor plasma obtained from the electrical explosion of 400-A thick, 13-,ug AI thin films has been used as a free-atom generator and excitation source for the analysis of selected trace elements in aqueous media. Ten-microliter samples of metal salts are applied to the film surface. The film strips are exploded in 300 Torr dry air with a 4-kV, 180-5 capacitive discharge. Analytical curves and reproducibility data are presented for Mn, Sn, Cd, Pb, and Pd, both with and without an internal reference technique. The relative standard deviations for these elements at the 100-ng level are 5, 11, 8, 9, and 5 % , respectively. Detection limits, usually in the low to sub-ng range, are presented for 14 elements. Concomitant effects are found to be relatively minor if the total solute content is less than about 0.01 M.
When furnace techniques are used for the volatilization of micro solid or solution residue samples, the relatively low rate of furnace heating results in reducing analyte free atom number densities ( 1 ) as well as significant concomitant effects (2). Since noncapacitive power sources generally are used for furnace heating, the heating rate is limited by laboratory wiring as well as the heat capacity of t h e relatively massive furnace. Peak power dissipation in the furnace is usually no more than a few kW. If a high-voltage capacitive discharge power source is used to heat a thin metal film of low mass and heat capacity, explosive vaporization of the film and a sample deposited on its surface probably is complete in about 1 FS. When an A1 film of 1.3 X mm2 cross sectional area is vaporized by a 4-kV, 22.5-wF discharge, a current of 3.7 kA is measured 1 1 s after the start of the discharge. If the film material still exists 'Present address, Los Alamos Scientific Laboratory, P.O. Box 1663, Los Alamos. N.M. 87544. 0003-2700/78/0350-1765$01 .OO/O
as a metallic conductor a t this time, it would carry a current density of over 10' A/mm2 and dissipate over 10 MW, assuming room temperature resistance. This probably is conservative. If the film is exploded from a polymeric substrate such as polyethylene, complete scavenging of the film and sample is observed (3). Since a fresh film is used each time, memory effects and furnace deterioration problems are obviated. Since only a few micrograms of high-purity metal are vaporized from a hydrocarbon substrate, the analytical blank is minimal for most elements. If dielectric breakdown of the gas surrounding the film occurs during or after film vaporization, a high current density plasma is formed which excites and to some extent ionizes the analyte vapor. Since the plasma is in close proximity to the substrate surface, ablation may augment film and sample atomization. This report considers exploding thin films for volatilization and excitation of trace elements in micro-volume solution samples. Companion reports consid'er thin film preparation and control (3) and the effects of various parameters on exploding thin-film excitation ( 4 ) .
EXPERIMENTAL Apparatus. The capacitive discharge circuit used for the explosive vaporization of thin films has; been described (3). The thin-film production apparatus and ancillary hardware also are considered. All spectra were recorded on Kodak SA1 photographic plates. Emulsion processing and calibration have been discussed ( 5 ) . A 1.0-m Czerny-Turner spectrograph (Jarrell-Ash model 78-460) with a first-order reciprocal linear dispersion of about 0.8 nm/mm and using a 35-wm entrance slit was used throughout this study. Entrance slit illumination is the same as i n Reference 4. Procedures. Aluminum films prepaired by vacuum deposition on high-density polyethylene substratles were used exclusively. Film preparation and control is described in Reference 3. Each film had a tensile bar shape with a 0.95-cm2region on each end for electrical contact and a 1.9 cm X 0.32 cm center region on which a 10-pL aqueous solution sample was placed as five small, evenly C 1978 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978
loor
Table I. Thin-Film Specifications and Explosion Conditions thin-film specifications film thickness, A surface area exploded, cmz film mass exploded, pg film material mean film resistance, substrate material explosion conditions
I
/'*
/fca
400 1.2 13 aluminum 5.9 high density polyethylene
discharge energy, J 180 discharge voltage, kV 4 circuit capacitance, p f 22.5 ringing frequency, kHz 15.5 chamber gas composition dry air chamber gas pressure, Torra 300 a Exception, all work with Sn done a t 700 Torr.
ox4I
0. I
0.01
yg
i.O
10
50rnPl.
Figure 1. Analytical curves for Mn, Sn, Cd, and Pb without internal referencing
spaced drops. The solvent was completely evaporated with a heat lamp. Prior to each experiment, the excitation chamber was evacuated to less than 1Torr and then filled to operating pressure. Sample Preparation and Explosion Conditions. Sample stock solutions (1000 ppm) were prepared from reagent grade materials. Volumetric dilutions were prepared daily. Sample disposable-tip solutions were applied to the films with a 1 0 - ~ L syringe. Table I summarizes the thin-film specifications and explosion conditions. The bases for selection of parameter values are discussed in Reference 4.
terms of both thermodynamic properties and excitation potentials of the lines used. Holcombe and Sacks (6) and Ling and Sacks ( 7 )evaluated the use of a convenient emission line from the exploding conductor material as a built-in internal reference for exploding wire and exploding foil excitation, respectively. This procedure also was evaluated here using a convenient line from the A1 thin film matrix. Figure 1 shows a composite of analytical curves for all elements except P d . In general, these curves are linear over a t least two t o three decades of concentration. Analogous curves for exploding foil excitation ( 7 ) frequently showed a negative deviation with sample mass greater than about 1 pg. I t is interesting that the Cd curve is linear a t least u p to 10 pg. This is only slightly less than the 13-kg film mass. T h e curvature a t the low sample mass end of the P b curve is caused by a spectral interference of unknown origin. These curves have slightly different slopes, all of which are less than unity. This may be the result of a nonlinear atomization or excitation process or a change in the emulsion contrast. Exploding foils were used as a radiation source for the calibration procedure. Since both the intensity and temporal variation of radiation from foils and films are quite different, reciprocity failure is suspected. Analytical curves using a n added internal reference have slightly different slopes and considerably more point scatter than the corresponding curves in Figure 1. This is in strong contrast with exploding foil excitation (7) where point scatter was considerably reduced with internal referencing. I t was also observed that the analytical curve for Sn with an added internal reference has some curvature a t low sample mass. Very similar analytical curves were obtained using the A1 film material as an internal reference. The point scatter was about the same as with an added internal reference. Pd is treated as a special case since, a t high concentrations, the solutions were sufficiently acidic to cause noticeable deterioration of the A1 films. Test solutions of P d were prepared by dissolving the metal in 10 N HN03. After di-
RESULTS AND DISCUSSION Relatively intense neutral-atom and ion lines were detected for nearly all elements tested. As was the case with exploding wire (6) and foil ( 7 ) excitation, the spectra are more spark-like than arc-like in general features. While numerous lines from neutral-atom, singly-ionized and doubly-ionized A1 were present, significant line interference problems were infrequent even on a multielement basis. Cyanogen band spectra were observed in the 360 nm to 390 nm range, but their intensity over background was much lower than that usually observed with graphite-electrode dc arc excitation in air. Analytical Curves. Curves were prepared for hln, Sn, Cd, P b , and P d . The curves were determined on a single-element basis. These elements were chosen because of their wide range of thermodynamic properties. Each point on these curves represents the average intensity or intensity ratio from five determinations a t the indicated concentration. All spectra for a given element and concentration were recorded on a single photographic plate to minimize photographic processing error. Since exploding thin-film excitation is based on a transient, nonrepetitive event, conventional noise reduction devices such as lock-in amplifiers cannot be used. Thus. an internal reference technique was evaluated as a means for compensating for certain problems such as positional instability of t h e plasma. Table I1 summarizes pertinent date for the analyte and internal reference species. In all cases, attempts were made at matching the analyte and reference species in Table 11. Data for Analyte and Internal Reference Materials int. ref. species Ni(I1) WI) Zn(1) TW) V(I)
concn of int. ref., ppm 10 10 50 50
10
boiling pt., K
anal. 2420 2540 1040
2000
ref. 3000
2000 1180 1730 3730
emission line measured, nm excitation potential, eV _ _ anal. ref. anal. ref. 5.35 6.70 254.6 294.9 4.31 5.61 287.3 286.3 7.37 7.75 334.5 340.3 4.36 4.46 276.8 283.3 4.44 3.94 318.5 340.4
4250 . . __ _____._________
ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978
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Table 111. Exploding Thin-Film Detection Limits line measured, detection detection element nm limit, ppm" limit, ng Ag( 1) WI) Bi(1) Cd(I) CO(I) &(I) Li(I) Mn(I1) Ni( I ) PWI) Pd(I) SnU) Tl(1) V I ) J
'01
,
I
0.01
0 1
1 I
a
328.0 278.0 302.5 346.6 345.4 253.7 323.3 294.9 341.5 283.3 340.4 317.5 351.9 327.6
0.0087 0.69 2.1 1.3 0.13. 0.76 3.0 0.007 6 0.087 0.96 0.033 0.27 1.0 0.027
0.087 6.9 21 13
1.1 7.5 30 0.076 0.37 9.6 0.33 2.7
10 0.27
Based on 10-pL sample size.
1.0
PP Pd
Figure 2. Analytical curves for Pd without an internal reference, with ratioing to a line from the AI film, and with ratioing to a line from the V added internal reference lution, the 1.0-ppm solution (10 ng per aliquot) was 0.01 N in FINO3, while the 50-ppm solution (500 ng per aliquot) was 0.5 N in "OB. The high acidity of this latter solution caused visible holes in the film a t the locations of the sample spots. In addition, the resistance along the film length increased by a factor of two or more. At P d concentrations greater than 100 ppm, the acidity was so high that rapid attack of the film surface ensued, resulting in complete loss of film continuity, thus rendering subsequent explosion of the film impossible. Figure 2 shows analytical curves for P d without an internal reference, with ratioing to an A1 film line, and with ratioing to a line from the V added internal reference. Without ratioing, the curve is linear up to about 0.05 pg Pd. A discontinuity occurs a t P d mass greater than 0.1 pg with a decrease in intensity for larger sample mass. This is hardly surprising since the film was completely dissolved a t the locations of the sample spots. T h e discontinuity is less pronounced but still significant when the A1 film material is used as an internal reference. This indicates a decrease in film vaporization efficiency for the larger Pd samples. With the V internal reference, the curve is linear over three full decades of concentration. This indicates t h a t even under very unfavorable circumstances, reliable analytical data can be obtained with an added internal reference. In general, however, with regard to analytical curve linearity, there appears to be no compelling reason to use an internal reference unless the film matrix is severely attacked by the sample solution. P o w e r s of Detection. Detection limits were determined for the 14 elements in Table 111. These values are defined as the minimum amount of the element required to produce a line intensity equal to three times the intensity equivalent of the root-mean-square noise on the microdensitometer trace in a nearby wavelength region of continuum background. T o obtain reliable extrapolated detection limits, the SA1 photographic plates were prefogged with a Kodak Wrattan series OA filter to obtain an absorbance sufficient to ensure operation on the linear region of the emulsion calibration curve. Absolute detection limits generally are in the low t o sub-ng range. T h e relative detection limits in Table I11 are based on 10-pL aliquots. Decreasing concentrational detection limits by using larger sample volume is considerably easier with films than with foils because of the larger film surface area. These detection limits were obtained on a simultaneous.
multielement basis using a single set of operating conditions. Element-specific parameter manipulation could lead to lower detection limits for some of these elements. The higher quantum efficiency of photoelectric detection also might provide greater powers of detection than the rather low optical speed emulsion used here. The detection limits shown in Table I11 are comparable to the better of the two sets of detection limits reported by Ling and Sacks ( 7 ) using exploding A1 foil excitation. However, these foil excitation values were obtained in 50-Torr Ar, which is experimentally more difficult than the 300-Torr air used in the thin-film work as well as being a rather less favorable gas and pressure regarding analytical precision with either foil or thin-film excitation. These multielement detection limits typically are one to two orders of magnitude better than reported single-element values using flame atomic absorption and one to two orders of magnitude poorer than typical values using flameless atomic absorption 12). Reproducibility of Exploding T h i n - F i l m Excitation. The reproducibility of the film preparation techniques has been discussed ( 3 ) . T h e reproducibility of the sample introduction techniques was previously evaluated in conjunction with exploding foil excitation ( 7 ) . T h e relative standard deviation of the dried sample residue mass was found to be 11.4%. The overall method reproducibility was determined for the replicate determinations used in obtaining the data for the analytical curves in Figures 1 and 2!. Table IV summarizes the relative standard deviations for the 0.1-pg data points. For the unratioed emission line intensities, values generally are in the 15-10% range. Only for P d is the reproducibility significantly poorer than this. These values are similar to those reported for flameless atomic absorption (2). In the case of Pd, ratioing to the 'V internal reference line reduces the relative standard deviation from f18 to f570, thus making it comparable to the other values. In no other instance does ratioing to either a line of an added internal reference or to one from the A1 film material result in improved reproducibility. In fact, ratioing often results in larger relative standard deviations. This is particularly true for data obtained by ratioing to an A1 line. The larger relative standard deviations for the unratioed P d line probably originate from deterioration of the film by the acidic sample medium. I t should be noted that the discontinuity in the Pd analytical curve occurred with sample mass just greater than the 0.1-pg value for which the relative standard deviation was computed. It is also interesting that ratioing the Pd line to an Al line resulted in little improvement in the shape of the analytical curve. On the other hand,
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978
Table IV. Relative Standard Deviations of 0.1-Mg Data Points from Analytical Curves analyte element Cd Mn Pb Pd Sn
rel. std. dev., % reference element no ref. added ref. A1 ref. Zn 8 18 14 Ni 5 8 9 TI 9 10 17 V 18 5 14 Pb 11 15 29
ratioing the P d line to a line from the added internal reference not only significantly reduced the relative standard deviation but also eliminated the discontinuity in the analytical curve. I n work with A1 foil excitation using sample introduction techniques essentially the same as those utilized in this work, Ling and Sacks (7) reported relative standard deviations for unratioed emission line intensities in the range of A15-30%. Also they reported that an added internal reference reduced these values to t h e f5-10% range; although, like the results reported here, ratioing to a line from the A1 matrix resulted in poorer reproducibility relative to t h e unratioed values. Thus, films appear to be superior to foils from the standpoint of analytical reproducibility. T h e greater relative variance using an added internal reference suggests that a significant fraction of the total variance with thin film excitation, unlike foil excitation, is a result of photometric error from the emulsion. This further suggests that analytical reproducibility may be significantly improved using photoelectric detection. Concomitant Effects. Previous studies with exploding wires (6) and foils (7) have indicated that compound form and the presence of relatively high concentrations of concomitant species have relatively little effect on analyte line intensities. This is probably the result of rapid total sample vaporization along with high energy density in the plasma. Fractional volatilization, which is troublesome with furnace volatilization techniques as well as with arc excitation, should not be significant when sample vaporization is complete in about 1 p s . This time is short with respect to both analyte vapor loss by diffusion and the duration of radiation from analyte species in t h e plasma. In this respect, the smaller film mass with its attendant shorter vaporization time together with experimental indication of more complete film and sample vaporization (3, 4 ) may render thin-film excitation freer of concomitant effects than wire or foil excitation. T h e very high energy density during the first current half-cycle, when most of the analytically useful radiation occurs, should minimize compound formation in the plasma. For example, band spectra from the second positive N2 system and from CN, when carbon electrodes are used in the film cassette, are detected only during the very early stages of the discharge before analytical radiation is detected. On the other hand, the much smaller mass of the film material relative to wires or foils may result in more significant changes in excitation environment in the presence of variable concentrations of concomitant species. T h a t is, the total sample mass will not be insignificant with respect to the film mass a t high sample loadings. In the preliminary studies reported here, the analyte was present a t fixed concentration, and the concomitant concentration was varied from zero to IO3 times the analyte concentration. In every case, an attempt was made to utilize as the concomitant a species often associated with the analyte in practical situations. The results are summarized in Table V. In the case of the acidic P d samples, addition of relatively high concentrations of the chloride salt increased deterioration of the film. In the presence of 1000 ppm Ni as NiCl,, the film was so degraded by t h e sample t h a t it could not be exploded. For the other
Table V. Effect of Concomitant SDecies o n Line Intensities analyte element concomitant concomitant and concn species concn, ppm T1 Zn 0 50 500 5 PPm (ZnC1,) Pb
Zn
4000 0
5 PPm
(ZnC1,)
50 500 4000
Pd
Ni
1 ppm
(NiC1,)
Mn
Fe
0 10 100
1000 0
5 ppm
(Fe(SO,),)
Ni
Fe
50 500 4000 0 50
Analyte relative analyte line intensity 57.8 59.7 56.3 21.6 30.5 34.7 35.7 19.3 62.4 64.3
57.7 film attacked by acid 48.7 53.3 43.8 12.9 46.2
51.3
elements examined, significant concomitant effects were observed only when the concomitant element was present at the 40-wg level. Only substrates from those samples showed significant residues of unvaporized material a t the spots where the sample had been placed. Thus, for these high total mass samples, the decrease in emission intensities may be due primarily to overloading the film and consequent incomplete vaporization of the sample. I t should be noted that 40 wg of concomitant element represents a mass more than three times the mass of the A1 film material. It would appear t h a t concomitant effects may pose a problem in special situations. Certainly, when the concomitant material results in destruction of the film, results will be affected. In addition, the micro nature of this technique is emphasized by t h e overloading apparent in cases where relatively large samples have been used. Other than these instances, concomitants do not appear to be a serious problem for the conditions tested with exploding thin-film excitation. Further studies in this area clearly are warranted, however.
CONCLUSIONS Line interference problems from the film material cannot be completely eliminated, but variation of film material can minimize the compromises which might emerge in a specific multielement determination. Recent studies in Ar-0, gas mixtures have shown t h a t CN line interferences can be eliminated by using an N,-free atmosphere with no significant loss in precision or sensitivity. Since the maximum sample size appears to be in the 4- to 40-pg range (neglecting counterions), solutions with a total solute content greater than about 0.01 M might pose problems with a 10-pL sample. The parameters which control maximum sample size are as yet unknown. Film thickness and support gas pressure, however, are prime suspects (3, 4 ) . While exploding thin-film vaporization and excitation appear to offer some analytically attractive features for multielement analyses of micro solution samples, photoelectric detection will be required to verify the linearity and the slope of t h e analytical curves as well as the speculation of greater analytical precision. These studies are in progress. LITERATURE CITED (1) D. J. Johnson, 9.L. Sham. T. S. West, and R. M. Daanall. Anal. Chem., 47, 1234 (1975). (2) A. Syty, Crit. Rev. Anal. Chem., 4, 155 (1974).
ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978 (3) D. V. Duchane and R. D. Sacks, Anal. Chem., accompanying paper in this issue. (4) R. D. Sacks and D. V. Duchane, Anal. Chem., preceding paper in this
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(7) C. S. Ling and R. D. Sacks, Anal. Chem., 47, 2074 (1975)
icwm .----.
(5) J. A. Holcombe, D. W. Brinkman, and R. D. Sacks, Anal. Chem., 47, 441 (1975).
(6) J. A. Holcombe and R. D. Sacks, Spectrochim. ~ c t a part , 6 ,28, 451
(1973).
RECEIVED for review June 13, 1978. llccepted August 7 , 1978. Work supported by the National Science Foundation through grant number CHE76-11646 A 0 1 .
Nebulizer for Analysis of High Salt Content Samples with Inductively Coupled Plasma Emission Spectrometry Ronald F. Suddendorf and Kenneth W. Boyer” Division of Chemistry and Physics, U.S. Food and Drug Administration, Washington, D.C. 20204
A new mechanically simple nebulizer is described for analysis of high salt content samples with the inductively coupled plasma (ICP). Because of its design, the nebulizer is capable of continuous operation without clogging, and thus is free from drift commonly associated with capillary bore pneumatic nebulizers. Detection limits are found to be equal to those obtained with a conventional pneumatic nebulizer. In addition, the nebulizer possesses rapid cleanout and convenient sample changing capability.
T h e current trend toward multielement analysis has been accelerated by t h e availability of t h e inductively coupled plasma (ICP). However, most analytical procedures currently employing the ICP require that the sample be made available in the form of a solution for introduction by a nebulizer into t h e ICP as a finely dispersed aerosol. One of the major problems of t h e ICP has been t h e absence of a totally satisfactory nebulizing device, especially for solutions that have a high salt content. Sample introduction devices for direct analysis of solutions with the inductively coupled argon plasma (ICP) must meet two general requirements. First, t h e nebulizer must conveniently produce a stable generation of aerosol and, second, t h e aerosol must be produced with a n argon flow rate compatible with the ICP. The argon may serve as both the aerosol generating force and t h e carrier gas for t h e aerosol, as occurs with conventional pneumatic nebulizers, or it may serve as t h e carrier gas only, as with ultrasonic nebulizers. In either case, its flow rate must be approximately 1 L/min t o be compatible with most commercially available ICPs. Because of t h e restraint placed on t h e argon flow rate, nebulizers commonly used in atomic absorption or flame emission with a higher flow rate of aspirating gas will not operate a t optimum efficiency and thus will not produce a sufficient quantity of aerosol to be of value with the ICP. For this reason, several new nebulizer designs have appeared which are capable of efficient aerosol production a t low gas flow rates. Two of t h e most popular types currently in use are t h e crossflow (1)and concentric glass nebulizers (2). Both devices rely on capillary tubes in their design to generate aerosol using low flow rates of argon gas. Although these nebulizers are capable of efficient aerosol generation, i t is possible for t h e capillary tubes t o become partially or completely clogged, especially when analyzing high salt content samples. Thus, they require frequent cleaning t o restore the original rate of aerosol generation or necessitate restandardization of the ICP.
Several designs based on ultrasonic nebulization have been reported for use with the ICP (3-7). One of the advantages of ultrasonic nebulizers is the absence of restricted capillary tubes for sample introduction. -4s a result, instability due to clogging is eliminated. However, a disadvantage is the inconvenient and time consuming sample changing procedure along with the requirement of electronics to drive the piezoelectric transducer. A more recent design (8) has improved t h e sample changing procedure with ultrasonic nebulizers. Fritted disk nebulizers (9) are also being investigated as sample introduction devices for the ICP. Like ultrasonic nebulizers, the fritted disk nebulizer does not require the solution to pass through restricted capillary tubes for aerosol generation. At the present time, relatively little data are available documenting the use of t h k nebulizer with the ICP. Application of the Babington nebulizer for analysis of high salt content samples by flame atomic absorption analysis has been reported (10). T h e nebulizer was designed for atomic absorption and for t h a t purpose operates a t a gas flow of 9 to 12 L/min, far in excess of t h e 1 IJ/min flow rate suitable for use with the ICP. However, the nebulizer possibly could be redesigned with a smaller orifice to reduce the total gas flow, making it more compatible with the ICP. This paper describes t h e design and operation of a mechanically simple nebulizer suitable for analysis of high salt content samples with the ICP. Data are reported for analysis of high salt content samples showing improved precision over t h a t obtained with a conventional crossflow nebulizer. Included are data showing detection limits and freedom from memory effects.
EXPERIMENI’AL Inductively Coupled Plasma. The ICP used in this work was a Jarrell-Ash model 975 Plasma Atom Comp (Jarrell-Ash Co., 590 Lincoln St., Waltham, Mass. 02154) direct reading spectrometric system with dynamic background correction, capable of the simultaneous determination of 23 elements. Data handling was accomplished with the aid of a PDP-8 minicomputer. Forward power to the plasma was maintained at 1100 R with reflected power less than 2 W. Argon flow through the nebulizers was 1 L/min. Nebulizers. Two different nebulizt3rs were used in this work. One was a commercially available crossflow nebulizer (Jarrell-Ash Co., 590 Lincoln St., Waltham, Mass. 02154) similar in design to that reported in the literature ( I ) . The nebulizer described here consists of a goldplated stainless steel base 5 cm long and 8 mm wide (Figure 1) in which a “V”-shaped groove has been cut. A small hole (0.23-mm diameter), which serves as a gas exit port, is drilled half way from the top of the base perpendicular to the center of the “V”-shaped groove.
This article not subject to U.S. Copyright. Published 1978 by the American Chemical Society
