iably drawn to the need for some assay method or modification thereof. Consequently, papers which were included in this review were selected, for the most part, either because the authors had some preference for the indicated method or, it waa anticipated that it might be of sufficient interest to a wide group of readers. It was found that in many instances, the technique, substrate or even enzyme might have a
common base with some other biochemical system. For these reasons, it was deemed desirable to adopt the format as it appears below REFERENCES
(1) Barman, T..E., “Ens me Handbook,” 2, Spmger-VerL, lg6’. (2) Bergmayer, H. U., Ed., “Methods of Enzymatic Analysis,” Academic Pres, New York, N.Y., 1965.
’,
(3) Bo er,
P. D., Ed. “The Enzymas ”
Press, dew York, N.?., .! Ed., of Enz mology, Academic Press, New Adernic 1971.
(4) Colowick,
Yo& N.Y., 1970. (5) Guibault, G. G., ANAL.CEEM.,42, 334R (1970). (6) Guilbault, G. G., Rec. Chem. Prop., 30,261 (1969). (7) Guilbault, G. G.,“EnzyrnaticMethods of Anal sis,” Pergamon Press, Oxford, Englanl 1971.
X-Ray Absorption and Emission I . S. Birks, Naval Research laboratory, Washington, D.C. 20390
T
is organized quite differently than previous reviews. It makes no attempt to cover all of the literature published. On the contrary, many items discussed are of recent vintage and not yet available in the literature; references for those items are in programs or proceedings of meetings and readers must contact the speaker for details. Those readers who desire an extensive bibliography are referred to the new publication “X-Ray Fluorescence Spectrometry Abstracts” ( 1 ) . Hopefully, some readers will prefer the streamlining made possible by selecting for discussion only significant advances during the past two years. The selection of topics is undoubtedly subjective, and some of the publications neglected may, of course, prove more signjficant than was recognized by this author. It should be noted that electron spectroscopy is now covered by a separate review rather than included here with X-rays. Important advances have indeed been made in both theory and application during the past two years. For instance, the growing concern with ecology finds X-ray fluorescence ready to measure multicomponent air or water pollution samples directly and with improved detectabilities in the few tens of ng/cm2 range for most elements. On the theoretical side, electron transport calculations of absolute X-ray intensities for the continuum as well as for characteristic lines have finally been successful and will allow optimum choice of operating conditions in setting up analysis procedures and interpreting data. Between these extremes lie improvements in theoretical values of fluorescent yields and absorp tion coefficients, simplification of mathematical expressions and computer calculations for quantitative analysis, improved capability for evaluating heterogeneous specimens without costly HE REVIEW THISTIME
grinding or solution, and, finally, improvements in the instrumentation itself. These and related areas of interest comprise the body of discussion in this report. MICRO AND TRACE ANALYSIS
Because of the widespread interest in ecology, perhaps it i s well to start immediately with a discussion of what Xrays can do to measure or monitor pollution. For particulates or precipitates which can be filtered out of air or water, no further specimen preparation is required. A piece of the filter is placed directly in the X-ray equipment. Goulding et al. (B-4) have shown that energy dispersion can detect 10-20 ng/cm2 on Millipore substrate. They excite the specimen with a Mol transmission-target, X-ray tube of only 10 watts power and measure the X-ray spectra with a Si(Li) detector of 14 eV resolution (see the section on Instrumental Improvements for a discussion of detector improvements). Gilfrich, Burkhalter, and Birks (6) have given careful attention to eliminating background interference and have shown detectabilities of 10 to 100 ng/ cm2 using a standard X-ray tube and crystal spectrometer and maintaining sufficient resolution to separat. immediate neighbor elements. Cecchetti et al. (6) have shown detectabilities of 20-50 ng/cm* on thin nitrocellulose substrates. Many workers (7-12) have investigated ion excitation using protons, alpha particles, or heavier ions from cyclotrons or Van de Graaff machines. With ion excitation, background intensity is low because there is no direct bremsstrahlung excitation and only a small amount of bremsstrahlung caused by electrons knocked out of atoms by ion collision. Thus, detectabilities of 1 to 2
ng/cm2 are commonly reported for samples collected on evaporated carbon or thin plastic substrates of 1G20 pg/ cm2 mass thickness. Ordinary paper or Millipore substrates are destroyed quickly by ion beams and cannot be easily used. One grossly misleading statement is often seen in papers on ion excitation, namely, that ionization cross sections for heavy ion excitation are orders of magnitude higher than for proton excitation. This only appears valid because those authors use the parameter Energy/Atomic Mass Unit rather than Energy alone in plotting their curves. Actually, ionization cross section curves for any kind of particle or photon excitation approach a maximum value of about 1od Barns/atom a t some incident quantum energy and then decrease slowly; for electrons the maximum is a t tens of kilovolts, for protons a few MeV, and for heavy ions a few tens of MeV. Radioisotopes have been considered as excitation sources in the past and are still favored (13-16) in instances where portability requirements would mitigate against an X-ray tube and power supply. I n the laboratory however, the extra intensity from X-ray tubes (even if a fluorescer is used to achieve monochromatic radiation) makes tubes more attractive titan isotopes except for major constituents. Figure 1 shows comparative detect abilities for X-ray and ion excitation. All the data are on the same basis, namely for IOO-sec counting time and the limit of detectability defined as a signal equal to 3 U B where U B is the standard deviation of the background (for ion excitation one really measures charge collection rather than time but a few microcoulombs can be collected in about 100 sec). It should be noted that only X-ray tube excitation gives enough
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
e
557
R
IOOC
--
I
,
-
V
to within 5% for K series lines, 13% for
I
L series linas and 50% for the continuum. Such calculations not only allow general comparison of X-ray tubes but give the primary spectral distribution necessary for the fundament,alparameter method of quantitative analysis (80). Thus the need for experimental measurements of spectral distributions is eliminated and the values can be calculated for any target or operating conditions.
X-RAY EXCITATION PROTON EXCITATION
\ FILTER
WPER
7
:IOC
-2
\
0
MILLIPORE
%
$ I
t E -I
IC
L
QUANTITATIVE ANALYSIS
w
J
t
-----
0
w
i
I
I
20
I
I
I
I
I
I
I
80
40 60 ATOMlC NUMBER
Figure 1 . Limits 04 detectability a5 a function of atomic number. The break at Z = 45 is where one changes from K to L spectra
Table I.
Comparison of Chemical Analysis with Old (Linear) and New (Ref. 31 1 Regression Methods
Chem
Fe New
Old
Chem
Ni New
72.5 63.0 47.2 34.3 6.2
72.6 63.0 47.8 34.0 6.6
67.8 58.9 47.1 17.1 6.4
0.15 14.8 23.6 65.6 73.7
0.16 15.1 24.1 65.4 72.3
intensity to use with a crystal spectrometer. The crystal spectrometer has a resolution of about 17 eY a t Fe K a compared with about 100 to 150 eV resolution for the best so!id-state detector; this is important in distinguishing neighboring elements such as Fe, Co, Nil Cu, and Zu in air pollution analysis. Happily the capabilities of X-ray crystal spectrometers seem quite adequate for pollution measurements with short collection times and low-cost analysis. Forensic analysis may involve either microsamples or trace elements in a bulk matrix. Rayburn (17) has reported encouraging results on identifying paint chips, irks. and papers in criminal cases but much greater use of X-ray fiuorescence or electron probe analy,:cis seems warranted. Several intereshg miscel!aneous publications in ttace ardysis might also be mentioned. Green et al. (18) showed that selective ion-exchange resins such as Strafion NMRR (19) can be used to extract a single class of elements from solution and t h i s increase detectability; they &-ereable to detect gold in ores in the ppm range by this technique. Sewell and Mitchell (20) were able to measure 1 ng of oxygen on a Ta surface by exciting with an 1800-V electron gun. 558K
Chem
Cr New
Old
25.8 21.3 27.8 0 15.4
25.0 20.7 26.5 0 14.1
27.4 24.2 27.0 0 14.0
__
Old 0.16 15.9 24.6 82.7 75.2
Quantitative analysis is, of course, the raison d’etre for any analytical technique; all of the ancillary improvements in theory or instrumentation are meaninglass unless the method is accurate and competitive in practice. X-ray spectrometry has led the field in taking advantage of mathematics and computers for the rapid interpretation of data and reduction of requirements for calibration standards. To this author, the significant advances in the past two years have been the refinement of both the regression equations and the fundamental parameter method so they are now easily employed by analysts rather than mathematicians. Of particular significance is the improvement in regression equations (empirical coefficients) reported by Rasberry and Meinrich (31) a t the Colloquium Spectroscopicum Internationale in Heidelberg, They suggest the modified regreasior, equation
Evans (81)detected a few ppn-i of Mg Ai, Si, P, 8, K, and Cu directly in plant tissue. Buchanan and Schroeder (22) employed two detectors similltaneously and two sets of planes in the same analyzing crystal to measure small quantities of P b coliecied on filter paper; the (200) planes measured the Pb La line while the (420) pianes measured the background. Klockenkaniper (23) et al. suggest that double-crystal spectrometers caIz be used to improve detectability by reducing backgromd intensity. ABSOLUTE X-RAY INTENSITIES
Mathematical formulation of electron transport theory was originaily developed for quantitstive electron probe (24) analysis but has now been extended to calcdstion of continuum BS well as characteristic hies (26-27) and placed on an abscllute intensity basis so that a?l X-ray tube target materials and operating conditions can be compared in context. lonization cross sections for continuum end charscteristic production are required parameters in absolute intensity calcu!sticns. The best vdues for bremsstrahlung crms sections seem to be those of I(irkp8,trick and Wiedmann (28) or Tseng and Pratb (29). Figure 2 shows the calculated and measured Rh spectra which agree, on a11 absolute basis,
ANALYTICAL CHEMISTRY, VOL, 44, NO. 5, APRIL 1972
where C, is the concentration of element i and R: is its relative X-ray intensity. The A K coefficients refer to elements whose effect on element i is predominantly absorption; the BK coefficients refer to elements whose effect is predominantly fluorescence (enhancement). The analyst sets one or the other equal to zero, e.g., the effect on Fe by Ni is predominar,tly fluorescence so the absorption terxl A F ~ N = ~0; the eSect on Ni by Fe is predominantly absorption sc, ?he enhancement t e r a B N ~= F ~0. Thus, there are only as many coefficients as element, just as in linear regression eqcations but the accuracy of ailalysis is imprcved con. siderably, ‘Fable I, because the new equation takes better accountj of the physics of enhancement. I n my opinion, they are far superior to previoos regression equations, and shotild be adequate for most roatine analysis (as with a! regression equations the coezcients must be determined empirical!y for the particuiar type of sample and the operating conditions employqd. Mathematics for the fucdamentaiparameter method (50) have not changed but convenience in use of the program was improved by rewriting it
in a convemtional mode for we on time sharing computers (3g) and by updating the inputoutput forinat for the previous program used with batch processing. Accuracy of the resuits has improved with the availability of better parameter values (see section on Improved parameters). Increased flexibility was achieved with the calculated primary spectral distribution discussed in the section on Quantitative Analysis. Figure 3 shows an example of the conversational program where the computer asks the operator for the information needed, Q 1, Q 2, etc. As the operator types in the replies, the computer calculates the composition, sums the concentration so the operator can see how closely it approaches 100% and also prints out the per cent deviations between measured and ca!culated intensities. I n addition to the mathematical approaches, Tertian has continued to develop the “doubledilution” technique (38) which eliminates some of the problems with calibration standards especially for mineral samples. Taylor and Anderman (34) reviewed the use of scattered background radiation to correct for composition variations. Ebel has expiored the “variable-take-offangle” method further (35) and reports stisfactory analysis of alloys when he extrapolates the intensities measured a t intermediate angles to the values expected at grazing emergence. Ebel’s method reduces the secondary fluorescence contribution almost completely but makes the absorption correction less certain because of the increased path length. In addition, the mechanics required for tilting the specimen tire more elaborate than ordinary equipment. HETEROG€NEOUS SAMPLES
With many practical specimens such as driil-hole probes, ores, cermets, agehardened alloys, reactor cores, etc., the particle size is too large to be treated properly by usual ms trix corrections. Yet the cost of grinding or dissolving the samples is considerable and many workers have suggested additional mathematical corrections to account for particle size effects. Figure 4 shows how serious the effect can be even for comrnmplace material. The most efficaciousmethods for treating the data are those of Berry (36) and of Criss (87). The method of Berry is simpier mathematically and does not require the use of e computer. Berry states that his method is satisfactory for mixtures of equa! sized particles but i s of questionable practicality for mixtures of dissimilar size. The method of Criss does require a coniputer but can treat dissimilar particle sizes and particle size distributions. It is important that the analyst know when the particle size is large enough to
I
Rh SEG-SOH 45 kV(c.p.1
K Lines
-
--- Mras. Cole.
6
5B
I
I
I
I
I
2
I
I
I
3
4 WAVELENGTH
I
I
6)
1
5
I
1
6
I
7
Figure 2. Measured and calculated spectral distribution for Rh target X-ray tube (same absdute basis) TYPE O F ANALYSIS 7 011
X-RAY
s
TUbE T A h b L T 7 2
6 2 1 VOLTAGE
?%
Q 3 t HOW aANY LLLMENTS 7 3 Q 4 l ATOMIC N l M b E H S
728 2 E
0 5 : L I N E S MEASURED ?KA KA KA Q 6 1 STANDAH3 O k M K N C W Q81 R X I
?u LL
’S FOk STANDARCS ? l -
8 9 1 I N T E N S I T I E S PEASUHEU l k O K STANDAHUS ? I 8 7 1 1 1 7 6 0 16311
GI01 I N T E N S I T I E S MLASUHED FkON JNKNOW ? 3 8 M 1113M 43U
WEIGHT NI CLI
ZN TOTAL
11.80 56.64 29.11
2 2 4
99.55
X
REL.
I N INT.
ERR. 0.37 0.46 k3.46
x %
Z
Figure 3. Conversational mode of computer program for fundamental-parameter method of analysis
require correction for heterogeneity and also when the particles are too large for a d e q u t e correction by the particle she equations. As a rough ruloof-thumb, if the particles are small enough so that there is less than 10% absorption of incident or emergent radiation in a single particle, the sample may be considered as homogeneous. If there is less than 50% absorption in a single particle, the equations of either Berry or Criss will make adequate correction; for more than Myo absorption, the
equations of Criss give the best correc tion but should not be applied beyond 80% absorption; beyond 80% one must resort to grinding or solution. The latter criterion is, of itself, valuable information because it tells the analyst the coa.rsest grind allowable for quantitative analysis and can save countless hours of needless grinding beyond that point. IMPROVED PARAMETERS
The parameters of most inte;.est in X-ray spectrometry are mass absorp
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
559R
(e).
with the new SEG50G x-ray tubes The thin (5 mil) Be window is the reason for the increased intensity of course. Routine analysis is extended to lower atomic number and/or lower concentrations but the tubes seem more inclined to become gassy (perhaps caused by leaks in the thin Be window). Automatic X-ray equipment for simultaneous analyses of 15-20 elements appeared in new engineering versions (~$9,60) with improved interfacing to computers for data handling and instrument control and improved speed due to higher-voltage tubes and faster sample handling. I n about oneminute time the sample can be inserted into the vacuum spectrometer, irradiated, and measured for up to 23 elements simultaneously, the data adjusted for interelement effects, and the concentrations pfinted out on paper.
cu tta FLUORESCED
B Y 238Pu 10% ( V 0 L . l CUZS I N H20
1.0
.8
-
&
.6-
k
\
=
2 3
E
-
0 4 -
2 .2-
-
ELECTRON AND ION PROBES
0 1
I
I
(0
100
Cu2S -
I
1000
DIAMETER, MICRONS
Figure 4. Variation of Cu Ka X-ray intensity with particle size CUSSin HnO
tion coefficients and fluorescent yields. There has been a disappointing lack of new experimental measurements of absorption coefficients except near absorption edges (38,39) where excursions of a factor of two are not uncommon and are dependent on valence state. Massaging of existing data with various admixtures of theoretical values continues, however, and it does seem that the recent tabulations (40, 41) give better values over a large range of wavelengths and elements than did earlier compilations. The best estimates of accuracy are 1 to 2% for some elements for the 0.7 to 2 A range, 2-5% for most elements for the ~0.2to 5 A range, >10% for all elements for wavelengths greater than 5 A and near the absorption edges. The situation for experimental fluorescent yields is olilly slightly better than for absorption coefficients. Recent measurements (&-44) for the K shell claim improvements and better agreement with the latest theoretical calculations (46, 46). However, nothing much has been done about experimental values for the separate L-shell yields where relative uncertainties are probably two or three times greater than for the K shell. A general comment on direct measurement of parameters seems appropriate. It is the very large difference in incident intensity and transmitted or fluorescent intensity which makes the ratio measurements uncertain. Of course, impurities and porosity in absorption foils add to the uncerhinty. Theoretical values may be adequate but are only dependable if they can be cross-checked 560R
against a few experiments. Are we doomed to suffer endlessly in this area? No panacea can be offered but perhaps some clever experimenter can devise a n indirect method of getting a t the values. Perhaps careful measurements of intensity ratios from several well chosen known-composition standards would be a better way to determine the parameters. If such a technique were attempted, a careful error analysis should be carried out to ascertain the uncertainties. INSTRUMENTAL IMPROVEMENTS
Within the past two years, the resolution of Si(Li) detectors has improved from 250 to 130 eV with commensurate improvement in line/background ratios and separation of neighboring lines. Several factors have contributed to improved resolution and reduced background: A pulsed, optical feed-back from the preamplifier (4) prevents pulse pile-up and allows counting rates up to 10,OOO cps without loss of resolution. Aperturing of the detector (47')or double guard rings (4) eliminates partial loss of charge-per-pulse due to leakage out the side of the Si detector. Experts now predict little further improvement in resolution for commercial equipment, so it appears that the crystal spectrometer (LiF 200 planes) will continue to have the better resolution for wavelengths longer than 0.8 A which includes the characteristic lines of nearly all the elements. I n a different area of interest the usable intensity from X-ray tubes was improved by a factor of 85 times for R h La and extended to 7 b wavelengths
ANALYTICAL CHEMISTRY, VOL. 44,NO. 5, APRIL 1972
As was stated in the previous review (61), there is little significant improvement in electron mobe analvsis to report. The Monte Carlo woik of CurPenven and Duncumb 68) is certainlv Galuable and the dkerential-sig&l circuitry developed by Heinrich et d. (63) improves the visualization of surface features but is more related to scanning electron microscopy than quantitative analysis. One senses a decreased interest in quantitative analysis of individual precipitates and diffusion zones but greatly increased interest in scanning pictures and semiquantitative estimates of constituents. Witness the inclusion of solid-state detectors in many SEM's and secdary-electron detectors in many probes. One might regard this as a quest for mediocrity but perhaps it is a realistic appraisal of what one really needs to know about a specimen. Things have been somewhat ditrerent with ion probes. Anderson has devoted extensive effort to developing relationships between the secondary ion current and the kind of incident ion and its charge (64,66). He showed for instance that bombardment with electropositive ions increases the yield of negative ion emission and vice versa. He proposes that treating the sputtered ion source as a plasma in partial equilibrium will allow prediction of ratios of diflerent ions present, Le., quantitative analyses. Castajng (66)reported considerable improvement in spatial resolution of the CAMECA ion probe with a redesigned mirror lens which passes only a narrow energy distribution of the desired ion. One may say of either the imaging or scanning ion probes that they can detect and identify very small amounts of the elements but quantitative analysis is not at all promsing in anything but the simplest situations.
Ti0 Table II.
New Long Spacing Crystals.
Compound 2d Lead tricontmate 156 A Lead tetracosanate 126 1 Lead octadeconate io0 R Lead tetradeconate 78 IL a Courtesy of A. J. Tousimis, Biodynamics Research Corporation, Rockville, Md.
= 2P
2s
Ti
LOW ATOMIC NUMBER ELEMENTS
There has been little progress in the measurement of atomic numbers below Na. Some of the new long spacing crystals (68) shown in Table I1 offer possibilities for measuring the long wavelengths but have not been fully explored as yet. Gamble (69) has
bond theory
3 d 4s
1 I I II
II I
molecular orbitals
L
VALENCE AND BONDING EFFECTS
X-ray analysts have been painfully aware of the wavelength shift in characteristic lines and changes in their shape with change in valence state of low Z elements. It has sometimes been necessary to prepare calibrations for several known valence states of an element in order to do quantitative analysis. It now appears obvious that we can regard the valence effects as a means to gain more detailed information about specimens, ie., analysis for compounds, determination of atomic surroundings, electronic structure of solids. Beginning in 1969 (67) and continuing through 1970 and 71 (68-67) a t an accelerating pace, theoretical chemists and physicists have begun to calculate the valence shifts from molecular orbital or band theory. Figure 5 shows details of the titanium and oxygen lines from the recent work of Fischer (68),the individual components can now be identified with particular molecular orbital levels. It is not possible a t present to calculate electronic structure directly from measured spectra but the reverse can be done indirectly, i e . , for an assumed atomic configuration one can calculate electronic density of states and from these the X-ray spectra for comparison with measurements. Siegbahn's group (69) using electron spectroscopy have already made use of the valence shifts to distinguish different bonding states of chlorine or sulfur atoms in organic molecules. Baun (66) showed earlier that the composition of Cu-A1 alloys could be determined merely by the energy separation between the two components of the A1 KO doublet. White and his colleagues ( 6 6 , 6 7 ) were able to characterize metaloxide corrosion layers by shifts in the oxygen emission band. Greater use of valence shifts will accompany our advances in the ability to relate them quantitatively to compound structure.
/Fermi level
I
,-
I
)
\
TiK,", /
.--' /'
\
* -\
/
,e-
''.
Figure 5. Molecular orbitals for T i 0 and the corresponding components of the X-ray spectra (Ref. 58)
suggested intercolated metal disulfides for long spacing crystals but only preliminary attempts have been made to prepare such crystals (intercolated crystals are prepared by introducing organic layers between the metal disulfide layers to expand the lattice). Gratings ( 7 0 , 7 1 ) continue in limited use and may find more widespread acceptance in the future. Strasheim and Brandt (72) and Poole et al. (73) reverted to direct electron excitation of low Z elements in geological samples mixed with graphite. Their work is reminiscent of the Beta probe of Lucas-Tooth (74); unfortunately, difficulties in commercialization have prevented fullest utilization of that instrument. Demountable X-ray tubes such as the Henke tube for low Z elements have been out of production during the past two years because of engineering difficulties but Philips Electronics has indicated from time to time that they hope to return to production eventually. RECENT BOOKS AND REVIEWS
Several books and reviews on X-ray and electron probe analysis have been published in the past two years and are listed in the appendix to the references. As a reference handbook, the book by E. P. Bertin is especially comprehensive. The forthcoming book edited by L. V. Aaaroff promises to be valuable for those who wish to go deeper into the theory of X-ray spectrometry; in it the chapter by Nagel and Baun gives especially lucid coverage of valence and bonding effects. CONCLUSIONS
What is the meaning of some of the advances made in the past two years
and where do we look for future improvements? It appears to this author that mathematical methods for homogeneous samples, namely regression methods or fundamental parameter methods, have reached a stage of completion adequate for most applications; further variations will undoubtedly be suggested by eager new workers but there seem to be more pressing needs for their efforts in other areas, uk, calculations for heterogeneous samples. Absolute X-ray spectra and spectral distributions seem to have progressed to the point of fulfilling present needs. It is time to put these capabilities to use serving the analyst. The thrust of X-ray techniques into pollution analysis is timely and it appears likely that X-ray analysis will become the workhorse for large-scale particulate analysis because of the low cost, speed, and detectability. It also has the advantage of being nondestructive which means that samples could be brought to court as evidence in prosecuting violators of pollution laws. Although detectability has been improved by nearly two orders of magnitude by reduction of background intensity, no obvious ways suggest themselves for further spectacular improvement in the next time period. So here again we are ready to apply recent developments and direct our new development efforts elsewhere. From the experience of recent years, it seems nearly hopeless to call for remeasurement of the fundamental parameters. We will probably have to content ourselves with indirect estimates and theoretical calculations. Better mathematics for treating heterogeneous specimens and greater
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
561 R
exploitation of valence and bonding effects appear to promise significant advances in the next two years. LITERATURE CITED
(1) Masek, P. R., Sutherland, I., Grivell, S., Ed., “X-Ray Fluorescence Spectrometry Abstracts,” Science and Technology Agency, 3 Dyers Bldgs., London E-3.1.
(2) Goulding, F. S., Jaklevic, J. M., UCRL-20625, Lawrence Berkeley Laboratory, May 1971. (3) Goulding, F. S.,.Jaklevic, J. M., Jarrett, B. V., Landls, D. A., Lawrence Berkelev Laboratorv Report No. 9. July 1 9 h . (4) Giaque,.R. D., Jaklevic, J. M., 20th Denver X-Ray Conference, Denver, Colo., Aug. 1971. (5) Gilfrich, J. V., Burkhalter, P. G., Birks, L. S., 16th International Spectroscop Colloquium, Heidelberg, Germanv &t. 1971. (6) Cccchetti, G., Monterolo, S.C., Ramusino, F. C., De Sena, C., 8th. Colloy m Sur l’hnalyse de la Materie, lorence, Italy 1969. (7) Johansson, !I‘. B., Aksekson, R., Johansson, S. A. E., Nucl. Instrum. and Meth. 84, 141 (1970). (8) Watson, R. L., Sjurseth, J. R., Howard, R. W., Nucl. Inst. and Methods 93, 69 (1971). (9) Flocchini, R. G. Feeney, P. J., Sommerville. R. J.. bahill. T. A.. ibid.. ( l ~ % % ~ . g eG.r ,A., Joyce, J. M., Lud: wig, E. J., McEver, W. S., Shafroth, S. M., Phys. Rev., Al, 841. (1970). (11) Kraushaar, J. J., Ristiner, R. A,, Rudolph, H., Smythe, W. R., Bull. Amer. Phys. SOC.,16, 545 (1971). (12) Burkhalter, P. G., Knudson, A. R., Nagel, D. J., Berks, L. S., Dunning, X. L., 10th Nat. SOC.for Appl. Spectros. Meeting, St. Louis, Mo., 1971. (13) Rhodes, J. R., Amer. 8oc. Testing Mater.,Spec. Tech. Publ.,485,243 (1971). (14) Burkhalter, P. G., ANAL.CHEM.,43, 10 (1971). (15) Radioisotope X-Ray Fluorescence S ectrometry Technical Reports, Series r?0. 115, International Atomic Energy Agency, Vienna Austria, 1970. (16) Marr, H. Campbell W. J., Evaluation of a RadioisotoGic X-Ray Drill Hole Probe, U.S. Bur. Mines Rep. Invest. 1971. (17) Bayburn, K., Eastern Analytical Symposium, New York, Dec. 1970. (18) Green, T. E., Law, S. L., Campbell, W. J.. ANAL.CHEM..42. 1749 (1970). (19) Aiailable from Azafon Water Conditioning Co., Haifa, Israel. (20) Sewell, P. B., Mitchell, D. F., J. Appl. Phys., 42, 5879 (1971). (21) Evans, C. C., Analyst (London), 95, 919 (1970). (22) Buchanan, E. B., Schroeder, T. D., d p I S ectrosc., 24, 100 (1970). (23) oc! I enkiimper, R., Laqua, K., Massmann, H., Spectrochim. Acta, 26B, 617 -. . (1471 ,-”. -,.\ (24) Brown, D. B., Wittry, D. B., Kyser, D. F., J. Appl. Phv?., 40, 1627 (1969). (25) Brown. D. B.. Gilfrich. J. V.. ibzd.. ’ 42, 4044 (1971). ’ (26) Storm, E., Israel, El., Lier, D. W., X-Ray Spectral Distributions for Thick Tungsten Targets in the Energy Range 12 to 300 kV, 20th Annual Denver X-Ray Conference, Denver, Colo., Aug. 1971. (27) Afonin, V. P., Losev, N. F., Pavlinskii, G. V., Gunicheva, T. N., Revenko, A. G., Zavods. Lab., 36, 431 (1970);
A,,
Hi
562R
translated by Consultants Bureau Div
of Plenum Press, 1970.
(28) Kirkpatrick, P., Wiedmann, L., Phys. Rev., 67, 321 (1949). (29) Tsena. H. K.. Prate. R. H.. ibid.. . 3; 100 6971). ’ (30) Criss, J. W., Birks, L. S., ANAL. CHEM.,40, 1080 (1968). (31) Rasberry, S. D. Heinrich, K. F. J., 16th Internationaf Spectroscopy Colloquium, Heidelbeig, Germany, Oct. 1971. (32) Criss, J. W., Birks, L. S., Eqtern Analytical Symposium, New E ork, Dec. 1970. (33) Tertian, R., Spectrochim. Acta, 26B, 71 -~ (1971). \--.-
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(59) Siegbahn, K., Perspectives and Probl e m in Electron Spectroscopy, Internat. Conf. on Electron Spectroscopy, Asilomar Conference Grounds, Pacifir Grove, Calif., Sept. 1971. (60) Williams, M. L., Dobbp, R. C., Cuthill, J. F., McAlister, A. J., U.S. Nat. Bur. Stand., Spec. Publ. 323 (1970). (61) Nagel, D. J., Advan. X-Ray Anal. 13, 182 (1970). (62) Fischer, D. W., 5th Nat. Conference on Electron Probe Analysis? Pittsburgh, Pa. 1971. (63) Fischer, D. W., J. Appl. Phys., 41, 3561 (1970). (64) Baun, W. L., Solomon, J. L., 6th Nat. Conference on Electron Probe Analysis, Pittsburgh, Pa. 1971. (65) Baun, W. L., J . Appl. Phys., 40, 4211 (1969). (66) Gi 1, P. D., Savanick, G. A,, White, E. J . Electrochem. SOC., 117, 15 (1970). (67) Kiause, H. B., Savanick, G. A., White, E. W., ibid., p 577. (68) Tousimis, A. J., Biodynamics Research Corp., Rockville, Md., private communication, Sept. 1971. (69) Gamble, F. present address-Esso Research and hngineering Co., Linden, N.J. 07036, private communication. (70) S eer R. J., Peacock, N. J., Waller, bsborne, P. J. H., J . Phys. E, W. 3, l(1970). (71) Speer, R. J., Advan. X-Ray Anal., 13. 382 (1970). (72) ’Strasheim, ’ A., Brandt, M. P., Spectrochim. Acta, 25B, 1 (1970). (73) Poole, A. B., Pickard, E. D., Lawrence, D., ibid., 26B, 145 (1971). (74) Lucas-Tooth, d., Burnett, K., Telsec Appl. Rept. No. 18 (1969).
2,
I.,
APPENDIX
Books
Birks, L. S., “X-Ray Fpectrochemical Analysis, 2nd. Ed.,” J. Wiley and Sons, New York, N.Y. 1969. Bertin, E. P., “Principles snd Practice of X-Ray Spectrometric Analysis,” Plenum Press, New York, N.Y. 1970. Birks, L. S., “Electron Probe Microanalysis, 2nd Ed.,” J. Wiley and Sons, New York, N.Y. 1971. Jenkins, R., DeVries, J. L.: “Worked Examples in X-Ray Spectrometry, Macmillan, London, 1970. Azaroff, L. V., Ed., “X-Ra Spectroscopy,” McGraw-Hill, New N.Y., to be published. Af3T.M Spec. Tech.. Pub. 485, “Energy Dispersion,” American Society for Testing and Materials, Philadelphia, 1971.
$ark,
Reviews Frankel, R. S., Aitkin, D. N., Appl. Spectrosc., 24, 557 (1070) (energy dispersion). Malissa, H., Pure Appl. Chem., 21, 473 (1970) (electron probe). Jenkins, R., DeVries, J. L., Met. Rev., 16, 125 (1971) (X-ray spectrometry). Nagel, D. J., Advan. X-Ray A.nal., 13, 182 (1970) (valence and bonding). Rhodes, J. R., Amer. SOC.Testing Mater. Spec. Tech. Pub. 485, p 243 (1371) (isot,opesourcesj. Beaman, D., Mater. Res. Stand., Nov. 1971, p 8; Dec. 1971,. .p 12 (electron probe); Journals Micron., published by Structurltl Publications Ltd., London N. 3. X-ray Spectrometry, published by Heyden & Sons Ltd., London, NW 4.
