(7) M. Novotny, M. L. Lee, and K. D. Bartle. J. Chromatogr. Sci., 12, 606 (1974). (8) H. J. Klimisch, J. Chromatogr., 83, 11 (1973). (9) W. Giger and M. Blymer, Anal. Chem., 48, 1663 (1974). (10) E. HlucMn, M. Jenik. and E. Maly, J. Chromatogr. 91, 531 (1974). (11) R. J. Gordon and R. J. Bryan, Environ. Sci. Techno/.,7, 1050 (1973). (12) J. F. McKay and D. R. Latham, Anal. Chem., 45, 1050 (1973). (13) T. Doran and N. G. MacTaggart. J. Chromatogr. scj,, 12,715 (1974). (14) S . E. Hrudey, R. Perry, and R. A. Wellings, Environ. Res., 7, 294 (1974). (15) R. S. Sholtes, Health Lab. Sci., 7 , 279 (1970). (16) American Chemical Society, "The Ring Index", McGregor 8 Werner, Inc., 1960.
(17) R. C. Pierce and M. Katz, Environ. Sci. Techno/.,submitted for review (1975).
RECEIVEDfor review March 17, 1975. Accepted May 16, 1975. This work was partially supported by the National Research Council of Canada (Special Project Grant No. 028-2370) whose financial assistance is gratefully acknowledged.
Utilization of Ultrasonic Nebulization in Atomic Absorption Spectrometry: Trace Metal Analysis in Samples of High Salt Content Haleem J. Issaq1s2 and Lawrence P. Morgenthaler3 DepaHment of Chemistry, Georgetown University, Washington,D.C. 20007
The possibility of applying ultrasonic nebulization to trace metal analysis in samples of high solid (salt) content was explored. The system used consisted of an "Ultramist" nebulizer connected to a temperature controlled heater in series wlth a condenser and burner head. No memory effects were detected after continuous nebulization for ten minutes of aqueous solution of metal chlorides corresponding to 1000 pg/ml copper, calcium, and magnesium, and to 500 pg/mi lead. The system tolerance for solutions of high salt content (1-3% by weight) was very good: no burner slot clogging and no deposits inside the system were observed over 10-20 minute nebulization periods. Continuous nebulization of 1% to 3 % sample up to 20 minutes gave very iittie memory, corresponding to less than 1 pglmi. Also, quantitative results for the analysis of copper in a solution of synthetic ocean water and in 4 w/w % NaCl solution, both without dilution, were obtained.
Since its introduction as an analytical tool, atomic absorption has found a wide variety of applications in many different fields; biological, clinical, oceanographic, and others. These fields require not only a sensitive technique, but one which can handle samples with high solid content, Le., 2 w/w% or greater. In most cases, the laminar flow burner cannot tolerate concentrated salt solution and the sample has to be diluted in dilution factors of 50 or greater, depending on the concentration of the salt in solution and time of nebulization. The dilution is necessary in a laminar flow burner, because when a droplet of solution containing a large amount of salt hits the hot slot of the burner, the water (solvent) vaporizes, leaving behind the solid salt particles which collect more solid particles with time, leading to clogging of the slot of the burner head. Hell and Ramirez-Munoz ( 1 ) developed a new burner, the Autolam Burner, for trace analysis in samples of high salt content; with this burner, a dilution of biological samples was necessary. For blood serum, the dilution is 1:25. Author to whom correspondence should be addressed. Present address, Litton Bionetics, Frederick Cancer Research Center, P.O. Box B, Frederick, Md. 21701. Present address, Fisher Scientific, Waltham, Mass. 02154. 1748
Venghiattis (2) used a heated chamber-condenser system for 200 Mg/ml lead, but reported a memory a t these levels. Morgenthaler ( 3 ) reported memory effects with a commercial heated chamber burner system. The system under investigation will be tested with high salt content solutions for memory effects, high solid tolerance, and quantitative measurements.
EXPERIMENTAL Apparatus. The apparatus used was described earlier ( 4 ) . Reagents. All stock solutions were prepared from Baker analytical grade reagents in deionized water and acidified (0.1-1.ON) with hydrochloric acid. Procedure. Samples of High Salt Content. Memory: The present system was tested for memory effects using solutions of Mg, Ca, Pb, and Cu. The procedure followed is outlined below. The conditions used are: heating chamber temperature, 350 " c ; sample aspiration rate, 0.75 ml/min. A solution of 200 pg/ml of the element to be analyzed was nebulized for five or ten minutes. Nebulization was stopped and the sample compartment only, was washed with deionized water. Then deionized water was nebulized to see if there was any absorption; if no absorption was observed, a higher concentration was used, usually up to 1000 pg/ml or more; while, if absorption was observed, lower concentrations were used. Ten percent absorption was considered as negligible memory, because it would correspond, in most cases, to less than 1 pglml of the analyte. This is justified considering the high concentration of the samples used. Tolerance to Samples of High Salt Content. The procedure followed is the same as in the previous section. A stock solution of 5 w/w% MgC12 in 1N HC1 was prepared, then diluted to the required concentration. The conditions used are 1 ml/min sample aspiration rate, 350 "C chamber temperature, lean air-acetylene flame, and 12 mA lamp current. A multi-element hollow cathode lamp was used containing calcium and aluminum. When the previous experiment was repeated, with 5 w/w% MgClz solution, under the same conditions but with the temperature of the chamber increased to 650 "C, the flame extinguished after 2 to 3 minutes. This is believed to be due to deposits of salt particles on the spikes in the mixing area, thus blocking the passage of air and acetylene, and will be discussed in greater detail later. When the temperature was decreased to 150 "C and the sample nebulized for ten minutes, no deposits in the slots or in the mixing area were formed. There were some deposits around the slot on the burner head. When water was aspirated, 20% absorption was obtained. The temperature was increased again to 200 "C and the sample was aspirated for ten minutes; no deposits were observed in the mixing area or inside the slot, but there was slight memory.
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
I
Table I. Standard Addition Results for Cu in 3.4 w/w% NaCl Solution
0.4
Flow rate,
Cu, as CuCI, u g / m l
0.4 0.8 0.4 0.8
I'
I
1
mlimin
Absorbance
Std dev
0.75 0.75 1.o 1.o
0.103 0.208 0.092 0.185
0.005 0.005 0.005 0.005
0.3
(Y
C
n
8 0.2
~~
n
Table 11. Absorbance of Copper Using the Standard Addition Method Concn, u g i m l
Absorbance
Std dev
X
0.025 0.104 0.189 0.268
0.001 0.003 0.007 0.009
x + 0.32 x + 0.64 x + 0.96
0.1
ou
Another experiment was performed using NaCl solution. A solution of 1, 2, 3, and 4 w/w% NaCl was nebulized for ten minutes a t approximately 1 ml/min and 350 "C. There were no observable deposits for l, 2, and 3%. The 4% solution did not clog the burner and there were no deposits formed in the slot; however, some salt deposited on the spikes in the mixing area. When the temperature of the heating chamber was lowered to 250 O C , the deposits on the spikes almost disappeared; Le., less salt particles were seen in the flame with tapping on the drain area. Because a t lower chamber temperatures less salt particles deposited, the heater was turned off. After ten minutes of nebulization, there were no deposits in the slot or in the mixing area but there was a memory. A 10 w/w% NaCl solution was nebulized without using the heater. After ten minutes (longer times were not attempted), no deposits except around the slot on the burner head were formed. Again, the 10% NaCl solution was nebulized for 10 minutes, but this time with the heater a t 250 "C. The burner did not clog, and no deposits were observed except on the burner head around the slot. Trace Analysis i n Samples of High Salt Content. To test the system under consideration for trace analysis in samples of high salt content, 3 solutions of 0.8 Wg/ml CdCL in water, 5 w/w% MgC12, and 4 w/w"h NaCl solution were prepared. These solutions were nebulized a t a flow rate of 0.75 ml/min and 0.47 l./min air. The temperature of the heating chamber was a t ambient temperature, -23, 250, and 350 " C . Standard Addition Method. To test the present system for trace metal analysis in samples of high salt content by the standard addition method, two copper chloride solutions in approximately 4 w/w% NaCl solution were used a t two different flow rates and a t 350 " C . The values given in Table I are averages of 8 readings. Assuming a linear calibration curve, the amount sought, X , may be calculated from the equation
x
=
Ax2
Ax+, - Ax where A , and A,+, are the absorbances of the solution without and with additions respectively, 2 the amount added. If 0.4 Wg/ml is as0.4 pgl sumed to be an unknown consideration, X,and 0.8 is X ml. From Equation 1 and values in Table I, X is found to be 0.398 Wg/ml, respectively. Calibration Curve for Copper in 4 u/w% NaCl Solution Using the Standard Addition Method. A solution of 10 w/Wh sodium chloride which contained an unknown concentration of copper was used. Into each of four 25-ml volumetric flasks, 10 ml of the sodium chloride solution and 0.0, 2, 4, and 6 ml of standard copper chloride solution were pipetted, respectively. The flasks were diluted to calibrated volume with deionized water. This gave a solution of 4 w/w% NaCl containing an unknown concentration of cop0.96 pg/ml copper. The samples per, x , x + 0.32, x 0.64, and x were nebulized at 0.75 ml/min a t 350 " C . Results are given in Table 11. Trace Analysis of Copper i n Q Solution of Synthetic Ocean Water. The solution was prepared in a 100-ml volumetric flask according to specifications of Thompson (5), by dissolving 2.11 g NaCl, 0.41 g MgC12, 0.12 g CaC12, 0.08 g KCl in 50 ml deionized water. T o this was added 0.4 ml concentrated HCl and 0.2 ml concentrated H2S04 and the solution was diluted t o calibrated volume
+
+
+
I
I
I
I
04
08
12
16
Cu in Sea Water Concentration l l g i r n l
Figure I.Calibration curve for copper in synthetic ocean water
Table 111. Memory Effects of Mg, Ca, Pb, and Cu Concn,
Time,
Element
ugiml
min
Mg, (as
1000
10
None
1000
10
None
800
5
1000
10
MgC1z) C a , (as CaC1,) P b , (as PbC1,)
Cu, (as CUC1,)
Memory Observations
Negligible
None
... When w a t e r w a s nebulized after t h e sample, it gave 10% abs o r p t i o n which decreasedto 0% a b s o r p t i o n after -1 m i n . A b l a c k powder band w a s formed around the burncr s l o t . When water w a s a s p i r a t e d , it gave 9% a b s o r p t i o n a f t e r 10 s e c onds. The b l a c k powder w a s wiped away with a d r y Kimwipe. W a t e r w a s aspirated and gave 0% absorption.
with deionized water. Traces of MgC12, PbC12, and AsC13 were also present as impurities in the NaCl sample used. Four copper solutions were prepared using the above solution and the following concentrations: 0.4, 0.8, 1.2, and 1.6 pg/ml. A blank of the above solution was used before measuring the absorbance of the above copper solutions. Plotting absorbances vs. concentration gave the theoretical straight line, Figure 1, which suggests that the determination of copper in ocean water is possible. The sensitivity of copper was determined and found to be 0.018 pg/ml/l% absorption.
RESULTS AND DISCUSSION Table I11 shows that 1000 p g l m l MgC12, CaClZ, CuClZ, and 500 pglml PbClz gave no m e m o r y effects, no deposits,
ANALYTICAL CHEMISTRY, VOL. 47, NO. l!, SEPTEMBER 1975
= 1749
and no salt accumulation in the burner slot after ten minutes of constant nebulization. The system tolerance for solutions of high salt content (1-3% by weight) was very good; no burner slot clogging and no deposits inside the system were observed over 10-20 minute nebulization periods. Continuous nebulization of 1%to 3% sample up to 20 minutes gave very little memory, corresponding to less than 1 pg/ml. One should remember that continuous nebulization for 20 minutes is a long time in atomic absorption where a single measurement would take approximately 20 seconds; in our system, a measurement would take about 20 seconds after warm-up time, which is about 1 minute. One problem encountered with salt concentrations exceeding 4% was the deposition of salt material on the mixing spikes above the drain area of the burner. This is due to static charge and temperature effect, which are explained below. Static Charge. It is quite possible that the droplets formed in the system either bear a static charge or develop such a charge with respect to the walls of the burner during their passage. The charged particles will be attracted to the walls, and will deposit if possible. The obvious area in which they would be found is just past the drain area a t the turbulence-inducing spikes which are dry. While it is not possible to prevent electrostatic charges from developing, it is possible to prevent attraction between the charged particles and the walls of the tube by plating the walls of the tube with metal, in this case platinum, and electrically grounding the wall. The grounded wall system alleviated the electrostatic problem a t salt concentration up to approximately 1.5% by weight. Some deposition of material still occurred at salt concentration of 2% and greater. This is attributed to incomplete drying of the droplets and random collisions with the tube walls. Temperature Effect. When solutions containing 4 w/w% salt or more were nebulized, a solid salt was deposited above the drain area. This was noticed when the temperature of the heater was high; for example, the burner would turn off because of clogging of the tube after approximately two minutes of nebulization of 5% MgClz solution, if the temperature of the heater was 650 "C, while a t 350 "C the burner did not go off during 10 minutes. No deposits were observed after 10 minutes of aspiration a t 200 "C. Moreover, when the heater was turned off, 10% NaCl solution was nebulized for 10 minutes without any clogging or deposition. Therefore, it is quite clear that there is a relation between the temperature of the heater and depositions inside the mixing section and above the drain area. The reason for the deposition in these areas and its relation to temperature is very simple. When the sample comes off the condenser a t high temperatures, it is still hot due to the inefficiency of the condenser.. This hot mixture heats the quartz tubing around and above the drain area. When a sample passes through, some droplets deposit in the area above the drain, the solvent evaporates leaving the salt behind. The salt cannot be evaporated because the temperature of the mixture and the quartz is not high enough. The burner turns off because more solid accumulates with time and blocks the passage of air and fuel. At low temperatures, say 200 "C, the condenser is efficient enough to cool the mixture which is passing through it. So the area above the drain is not heated and consequently no salt deposits are observed. If droplets are deposited, the temperature of the mixture coming off the condenser is not hot enough to evaporate it. At about 0.75 ml/min of sample flow rate of 5% MgC12, the temperature of the mixture was measured in the gas 1750
stream by using a mercury thermometer. This technique was used earlier for the same purpose (6). It should be mentioned here that the higher the flow rate, the higher the temperature. At 650 "C, the temperature of the mixture was found to be 151 "C; for 350 "C, the temperature was found to be 108 "C; for 250 "C, it was 94 "C; and for 200 "C, it was 83 "C. To prove the relation between temperature of the chamber and salt deposition, another experiment was performed. The area around the drain was wrapped with a wet (cold) Kimwipe paper, which was kept cold all through the experiment by spraying it with cold water. There was no clogging or deposits in the burner after constant nebulization for 10 minutes of 5 w/w% MgC12 a t -0.8 ml/min and 350 "C. At 650 "C, after 10 minutes of nebulization of the 5 w/w% MgClz at -0.8 mllmin, the burner did not go off and there were no deposits around the drain area, but there were salt deposits inside the burner around the slot. It is obvious that 10 minutes of continuous aspiration is a very long time; when shorter times were used, there were no deposits. Trace Analysis in Solutions of High Salt Content. Cadmium in 5 w/w?h MgC12 and 4 w/w% NaCl was analyzed. Three different temperatures were used, room temperature (-23 "C), 250 "C, and 350 "C, to find the optimum temperature. As anticipated, the optimum temperature was 350 "C. Results are given in Table IV. It was also observed that the signal decreases as the salt concentration increased. Depression of the cadmium absorption signal in 5 w/w% MgC12 and 4 w/w?h NaCl may be attributed to any or all of the following factors: (a) Incrustation and volatility factors (7, 8). The high NaCl and MgC12 concentration may lead to the formation of particles too large to evaporate completely. These particles may occlude some of the CdC12, thus decreasing the concentration of atomic vapor in the flame. (b) Reactions in the flame (9). The presence of large amounts of NaCl and MgC12 will increase considerably the concentration of chlorine atoms, which in turn will act on the dissociation of CdC12, decreasing the number of free cadmium atoms and decreasing the signal. A similar interpretation was suggested ( 3 ) for the depression of 0.001% RbCl signal in 0.1-4% NaCl and KCl solutions. A similar phenomenon was also observed and interpreted in a similar vein by Haldt (3) in his work on the radiation of CsCl in the presence of a large excess of KCl. L i g h t Scattering. Solid particles in the flame can scatter the light beam that impinges on them, giving rise to false absorption signals. Willis (10, 11) observed this when aspirating urine solutions which were free from the element being determined. Other workers (12, 13) reported light scattering as a source of interference. Koirtyohann and Pickett (14) investigated the mechanism of light scattering and showed that the process may in actuality be molecular absorption. They postulated that some other mechanism, such as molecular absorption, variation of the refractive index within the flame caused by vaporization of the particles or continuous absorption owing to atom ionization, may give rise to the observed light loss. Rains (15) believes that both light scattering and molecular absorption play a role. Ouerloading of t h e Flume (16, 17). When cadmium chloride in water is nebulized, the flame has to atomize 1.3 wg/ml cadmium salt (0.8 wg/ml cadmium). When, on the other hand, CdClz in 4 w/w% NaCl and 5 w/w% MgC12 is nebulized, the flame has to atomize 40,000 wg/ml NaCl and 50,000 pg/ml MgC12 in addition to 1.3 pg/ml CdC12. This would lead to losses in the flame energy which is used in evaporating the sample, which results in decreased efficien-
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
Table IV. Effect of Temperature of the Heated Chamber on the Absorbance of Traces of Cadmium in Different Solutions Solution, 0.8 u g / m l Cd in
HZO 5% MgC1, 4% NaCl HZO 5% MgC1, 4% NaCl
HZO 5% MgC1,
4% NaCl
T OC
Absorbance
Std dev
23 23 23 250 2 50 2 50 3 50 350 350
0 .lo4 0.102
0.004
0.094 0.529 0.3 16 0.385
0.624 0.400 0.518
0.005 0.003 0.003 0.008 0.008 0.008 0.009 0.012
cy of atomization of cadmium. Although the signal dropped by 17% in 4 W/WO NaCl and by 36% in 5 w/w% MgC12 solution, a t the optimum temperature, this loss is not much if compared to the loss in signal due to a dilution ratio of 1:1, where the decrease is 50%. The S/N for 0.8 wg/ml Cd in 4% NaCl and 5% MgClz are 48 and 44, respectively. Quantitatiue Analysis. As mentioned earlier, atomic absorption is frequently used for trace analysis in samples of high salt content. This is usually done by diluting the sample to be analyzed by a ratio of up to 150 or more (10). Diluting the sample means a loss in sensitivity equivalent to the dilution factor. Therefore, if dilution of sample could be avoided, this would mean an increase in sensitivity which could go up to fiftyfold or more. The system under investigation was tested for quantitative application by analyzing for copper in 3.4 w/w% sodium chloride solution. The results show good accuracy (see Table I). Plotting absorbance vs. added concentration, gave a linear calibration curve. The sensitivity of copper was found to be 0.017 gg/m1/1% absorption. The value of x may be evaluated by using a calibration curve or from the values in Table 11; X was found to be 0.10 wg/ml. The system was also used for the analysis of copper in a solution of synthetic ocean water ( 5 ) . Four different concentrations of copper were run and their absorbances were measured. Plotting absorbance vs. concentration gave a straight line calibration curve, Figure 1. Therefore, it is expected that this system can be applied successfully to trace metal analysis in samples having high total salt content without or with relatively minor dilution. Comparison of the P r e s e n t System w i t h O t h e r s Which Use Heated S p r a y Chamber-Condenser-Burner Systems. A comparison of the present system in terms of sensitivity, aspiration rate, efficiency, and applicability to trace analysis in high solid content samples with those examined by Hell et al. (18),Venghiattis ( 2 ) ,and Uny et al. (19) which use a heated spray chamber-condenser-burner system will be made below. Also, the present system will be compared with the Autolam burner ( I ) . The present system is generally more sensitive than the Autolam burner ( I ) and the Hell et al. (18) system, and comparable to the others (2, 19). Our system has the lowest nebulization rate per unit time and the highest efficiency of atomization in the flame, i.e., production of neutral atoms which absorb in the flame. Note that absorption is a function of the concentration of neutral atoms in the flame, and sensitivity is expressed in wg/ml/l% absorption. Therefore, sensitivity is a measure of the number of free atoms which absorb in the flame. Let us calculate, approximately, the amount of analyte reaching the flame, a t the optimum conditions, in each case. In' the system discussed in this study, the optimum aspiration rate is 0.75 ml/min and the effi-
ciency is 86%. This means that the available sample rate introduction into the burner, i.e., amount of sample reaching the flame, is equivalent to approximately 0.65 ml/min. Venghiattis (2) reported an aspiration rate of 6 ml/min (depending on the element analyzed). The efficiency of the system is not given, but it is understood that a high percentage reaches the flame, certainly it is greater than 10%. Let us assume that 50% of the sample reaches the flame. This means that the available sample rate introduction is equivalent to about 3 ml/min, which is five times as much as in the present system. Hell et al. (18) do not give any numbers as to flow rate and efficiency. They report that 90% of the solvent is condensed and most of the analytes reached the flame (it is not specified how this was determined). No flow rate of air or sample is reported. They used a total consumption burner which usually uses approximately 5 ml of sample per min. If most of the analyte reaches the flame, as reported, then the available sample rate introduction is equivalent to about 4 ml/min (assuming 80% efficiency). Uny et al. (19) used a pneumatic nebulizer with 54% efficiency of sample to flame. If we assume an aspiration rate of 6 ml/min, therefore 3 ml of the sample reached the flame. In the above three systems, the gain in sample density in the flame is not represented in the reported sensitivity. This means that atomization of the sample in the flame is not a t its best. In terms of air and sample flow rate, the present system required 0.5 l./min of air to give an optimum sample flow rate of about 0.75 ml/min. The other systems require a much higher flow rate of air and sample per unit time. None of the above researchers reported using their system for trace metal analysis in samples of high salt content, i.e., 1 W/WO or greater. Memory effects were reported by Venghiattis (2) after 200 wg/ml lead were nebulized for 15 min. Uny and coworkers (19) reported no memory when they nebulized water after 5.42 and 0.0542 pg/ml silver. In the present system, no memory was observed after nebulization, for 10 minutes, of 1000 pg/ml of magnesium, calcium, copper, and of 500 kg/ml lead, and 10% absorption was observed after nebulization of 800 wg/ml lead for 10 min. Ramirez-Munoz et al. ( 1 ) reported the use of the Autolam burner for trace analysis in samples of high salt content. The sensitivities reported are lower than those of the system investigated here. Direct comparison of systems is impossible, as the paper lacks experimental detail. The paper does not report the time of aspiration, except in one case, the analysis of milk: in which case, an aspiration time of 3 minutes was used. The paper does not report the amounts of salt in the samples nebulized. In one instance, it reports that serum was diluted in a ratio of 1:25, which suggests that their system does not have a tolerance to concentrated salt solutions. The salt concentration in serum is about 2.5 w / ~ o , which means that the sample nebulized contains 0.1% salt by weight. The present system can tolerate a higher percentage of salt concentration, up to 4 w/w% or greater depending on the temperature of the heater which can easily be adjusted. The present system, overall, appears to be superior to the others in the following respects: Applicability to trace metal analysis, and greater tolerance to samples of high salt content, which with some samples leads to an increase in actual sensitivity; lower aspiration rate of sample, Le., greater efficiency in terms of sample to flame, approximately 86%, which is extremely high for a chamber type system (20); and improved sensitivities. The system produced an improvement in sensitivity over conventional nebulizers and cold spray chamber-condenser-burner systems.
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
1751
CONCLUSIONS The system was tested for trace metal analysis in concentrated salt solutions with or without a small dilution factor. The system tolerance for such solutions is approximately 4% by weight. This system is believed to have great potential in the application of atomic absorption to trace metal analysis in biological, clinical, oceanographic, and water pollution samples. LITERATURE CITED A. Hell and J. Ramirez-Munoz, Anal. Chim. Acta. 51, 141 (1970). A. A. Venghiattis, Appl. Opt., 7, 1313 (1968). L. P. Morgenthaler, private communication, 1970. H. J. lssaq and L. P. Morgenthaler, Anal. Chem., 47, 1661 (1975). G. Thompson, The Spex Speaker, Vol. XVI, June (1971). R. Hermann and C. T. J. Alkemade, "Chemical Analysis by Flame Photometry", Interscience Publishers, New York, 1963. (7) M. Margoshes and B. L. Vallee, Anal. Chem., 28, 1066 (1956).
(1) (2) (3) (4) (5) (6)
(8) P. Porter and G. Wyld, Anal. Chem., 27, 733 (1955). (9) R. Mavrodineanu and H. Boiteux. "Flame Spectroscopy", John Wlley & Sons, Inc., New York, 1965, p 169. (10) J. B.Willis, Anal. Chem., 34, 614 (1962). (1 1) J. B. Willis, "Methods of Biochemical Analysis", D. Glick, Ed., Vol. 11, Interscience, New York, 1964. (12) G. K. Billings, At. Absorpt. News/., 4, 357 (1965). (13) D. J. David, Analyst, (London), 86, 730 (1961). (14) S. R. Koirtyohann and E. E. Pickett, Anal. Chem., 38, 1087 (1966). (15) T. Rains, private communication, 1972. (16) J. Ramirez-Munoz, "Atomic Absorption Spectroscopy", Elsevier Publishing Co.. Amsterdam, 1968. (17) H. C. Van Rensberg and P. 8. Zeeman, Anal. Chim. Acta, 43, 173 (1968). (18) A. Hell, W. F. Ulrich, N. Shifrim, and J. Ramirez-Munoz, Appl. Opt., 7, 11968). 1317 > (19) G. Uny, N. Guea Lottin, J. P. Tardif, and J. P. Spitz, Spectrochim. Acta, Parts, 28, 151 (1971). (20) J. B. Willis. Spectrochim. Acta, Part A, 23, 81 1 (1967). - - - I
RECEIVEDfor review August 6, 1974. Accepted April 11, 1975.
Atomic Absorption Spectrometric Analysis by Direct Introduction of Powders into the Flame J. B. Willis Division of Chemical Physics, C.S.I.R.O., P.O.
Box 160, Clayton,
Victoria, Australia, 3 168
A study has been made of the factors influencing the atomization efficiencies of metals such as copper, nickel, cobalt, manganese, zinc, and lead when suspensions of geological materials are sprayed into the flame for analysis by atomic absorption spectrometry. Only particles below about 12 Fm in diameter contribute significantly to the observed absorption and the atomization efficiency increases rapidly with decrease of particle size. With suspensions of samples ground to -325 mesh (
