1838
ANALYTICAL CHEMISTRY
of iron(II1). Other procedures which may employ a lon concentration of perchloric acid and of iron(II1) are conceivable. It is evident from the experimental results that differences between the systems of complexes present in Procedures 1 and 2 must exist, as exemplified by the difference in temperature coefficients, the varying extent of interferences, and the instability of solutions obtained by Procedure 1 when exposed to light. Figure 4 shows the spectral bands of sample and blank in the two procedures. I n determinations of chloride it was found desirable to measure absorbancies a t slightly higher wave lengths than correspond to the peaks of the respective absorption bands, because of the increase in background and extent of interference from certain substances with decrease in wave length. Because of higher background, appreciable temperature dependence, and more extensive interference from certain common ions, such as sulfate, Procedure 2 must be considered inferior to Procedure 1. Yet the advantages of Procedure 2-the fact that no protection from humidity is required and the insensitivity of the solutions towards light-should not be overlooked in practical work. With the exception of mercury(II), a rather uncommon constituent, other ions do not seriously impair the applicability of Procedure 1. Bromides and iodides, which account for heaviest interferences in most classical methods for the determination of chloride, may be tolerated in this procedure. Corrections for bromides are required, if present in quantities above 30% of the chloride content. Iodides may be tolerated up to a 20-fold excess with respect to chloride, provided no precipitate of iodine is formed. Sulfate ion, up to a sixfold excess, does not interfere (corresponding to a positive error of up to +3%). I n Procedure 2, on the other hand, interference from sulfate ion must be considered as serious, where sulfate present to the extent of 50% of the chloride concentration (by weight) causes a deviation of 3%. Larger quantities of sulfate must be removed by precipitation with barium perchlorate and subsequent centrifugation. Re-
moval of sulfate ion by precipitation after iron perchlorate reagent has been added was found to be incomplete. Likewise, an error will be introduced if the unknown solution contains appreciable amounts of acid and iron(II1) in addition to the quantities added as the iron perchlorate reagent. For a chloride concentration of 5 mg. per liter in Procedure 1 the error R-ill amount to 3% if the iron(II1) concentration is increased from 0.010 to 0.014M; the same effect is caused by an increase of perchloric acid concentration from 8.5 to 8.8S. In Procedure 2, a t a chloride concentration of 8 mg. per liter, a 3% error is introduced by an increase of iron concentration from 0.100 to 0.102A1f, or bj- an increase of perchloric acid from 2 50 to 2.55N. These values represent a measure for the amounts of perchloric acid and iron(II1) which may be tolerated in an unknown to be analyzed for chloride. The main advantages of the methods described in this paper over other methods nox in use for the determination of chloride lie in the simplicity of the procedures and their remarkable sensitivities. Generally speaking, only turbidimetric methods can be considered as more sensitive. Applications of this direct spectrophotometric method are anticipated in routine analysis of water, air, and certain physiological systems. ACKNOWLEDGMENT
The authors wish to express their appreciation to the Office of Ordnance Research for finanrial support of these investigations. LITERATURE CITED
(1) Bastian, R., Weberling, R., Palilla, F., - 4 x a ~ .CHEM.25, 284
(1953). (2) Desesa, 11.A , , Rogers, L. B., Anal. Chim. Acta 6,534 (1952). (3) Gamlen, G. B . , Jordan, D. O., J . Chem. SOC.1953, 1435. (4) Smith, G.F., Analyst 80, 16 (1955). (5) Sutton, J., Nature 169, 71 (1952). RECEIVED for review February 17, 1936.
Accepted June 20, 1966.
Ninth Annual Summer Symposium--Rapid Methods of Analysis
Instrumentation for Rapid Spectrochemical Analysis Optical and X-Ray Emission Monochromators and Polychromators J. W. KEMP Applied Research Laboratories, Glendale 8, Calif.
The success of direct-reading optical and x-ray emission techniques in providing high-speed analyses on a routine basis has led to the commercial availability of a variety of instruments for use in these fields. A review of these instruments and their capabilities should be of interest to those concerned with rapid routine analysis.
0
PTICAL spectrographic analysis has been recognized as a high-speed, routine control method for 20 years. The additional time savings afforded by the application of directreading techniques to the optical method have been generally used for the past 10 years. The x-ray fluorescence technique is no%going through its acceptance period as a routine control method. Briefly, a sample brought to a sufficiently high temperature by appropriate means emits optical line spectra of the elements present. Analysis and measurement of these spectra then provide information on the elemental composition of the sample. Thus, the optical method is destructive, as it is necessary to con-
sume a t least a small sample to provide an analysis. However, the x-ray method is nondestructive, Here, the sample is irradiated with high intensity x-rays. This causes the sample to fluoresce in the x-ray region, this fluorescence consisting of the x-ray line spectra of the elements present in the sample. Analysis of these spectra also gives information on elemental composition. Savings in both elapsed time and time per analysis are usually significant, and occasionally startling, with these techniques. I n order to replace the older, slower methods by the new techniques, ho\vever, a sizable capital investment is required. Certain limitations on sensitivity and accilracy must also be recognized. Because both optical and x-ray spectra are atomic phenomentt, these limitations can be correlated with the periodic table of the elements. The optical technique can be used for all metals and metalloids, but requires special equipment for the nonmetals and gases. The x-ray technique has a different $et of restrictions, being useful for all elements of atomic number greater than 19 nithout special equipment. Two classes of instruments are used: parallel and sequential. The parallel instruments give simultaneous determinations of
V O L U M E 28, NO. 1 2 , D E C E M B E R 1 9 5 6 several elements, and are thus faster, but less flexible, than the seauentid tmee. The ~ Is,t,t,w one. ~ nrovide. ~ . . nnnlvses. ~ . ~ ,~ ~time. - ~ - n---t .I.-- in~ a programmed sequence (5).
".~~ ~
~~~
COMPARISON OF OPTICAL AND X-RAY METHODS
The requirements of the first step, preparation of sample, are outlined in Table I. For the analysis of nonconducting materiala, the x-ray technique generally offers considerable savings in time over the optical technique. Table I1 summarizes the important features of the excitation of the two types of spectra. The radiation energy used in the optical technique generally originztetes in energy changes of the
Table I. Preparation of Sample Sample
Type Solid metals Metallic particles Solid
nonconductors
Nonconducting particles Liquids
Optical X-R.%Y Emission Emission Requirements Requirements Surfacing usually required Briquetting or putting into solution may be required Grinding or putting into d u - Surfacing m a y be tion aIw&ysnecessary. Mixrequired
ing and briquetting after grinding may be required Mixing and briquetting may Usually andyzed be required as is Often analyzed as is
Table 11. Excitation Opti&l X-Ray Electron levels Valence electrons Innermost electrons (K & L shell?) High intensity x-ray source of enmgy Electrical discharge, usually in air beam D.c. arcs Equipment High voltage supply and A s . arcs x-my tube Intermittent triggered Festure
ares
Quantity
Controlled a . ~ and . d.c. high voltage sparks Usually less than few -100 mg.
Minimum
-1 mg.
Few mg.
Local analysis
Possible with special techniques
0.040 X 0.040 inch with
sampled aarnple
mg.
reduced sensitivity
1839 valence electrons of the atoms of the sample. The energy to brine is ohtzined from . elect,rird ~ ~ ~ ~ ~ . . . ~ about ~these chanees I ~ . ~ Rnmm or discharges. Only those elements with low excitation energy requirements (alkalies, alkaline earths) can be readily excited in a flame, while electrical discharges at reduced pressure are required t o excite elements requiring high excitation energies (gases, halogens). The majority of the elements can be excited by arc or spark discharges in air, and these discharges are used for routine, high-speed analysis. X-radiation is obtained from energy changes in the innermost shells of the atoms, generally the K and L shells. This requires excitation by a beam of high-voltage electrons in a vaouum, or by irradiation with a high-intensity x-ray beam. The latter technique is very much simpler in practice and allows any material to be used as a sample. Thus, for routine analysis, commercially available, high-intensity x-ray tubes are used as the primary excitation means. X-ray emitting isotopes have been suggested, but these are generally unsatisfactory for routine analysis, principally because of the very low intensities obtained. I~ ~~~
-~
~
~~
~~
~~~~~~~~~
~
~~
INSTRUMENTATION
Prism and grating spectrographs have been used for y e a s for routine analysis. Direct r e d c r s generally use the same bmic optical systems, with slits and multiplier phototubes substituted for the photographic film. In direct readers, however, the space requirements for slits, phototubes, etc., make the use of gratings almost mandatory. X-ray dispersing instruments are not so well known. The only optical dispersing elements useful in the usud x-ray region are single crystals. Electronic dispersion, using proportional counters, has some application. For routine analysis, however, resolution is too ION and circuits are complex. The large single crystals used as optical dispersing elements are usually lithium Buoride, sodium chloride, or quartz, and are used either 0 a t or curved. Flat crystals are similar optically to flat gratings, requiring collimators. Curved crystals are opticdly similar to concave gratings, allowing focusing of the spectra without collimators. I n any direct-reading, multielement analytical system, there are two modes of operation: parallel and sequential. The parallel system determines several elements a t once, and requires the use of polychromators. The sequential system determines one element a t a time, requiring only a monochromator. Obviously,
ANALYTICAL CHEMISTRY
1840
Figure 2.
Complete ARL production control Quantnnieter, including source
structed to fit existing spectrographs. This type has been described by Bryan and Nahstoll ( 6 ) , Bylund and Rudherg (?), Msthieu (24), Naish and Ramsden (E6), and Yoshinaga, Fujita, and Minami (28). Two of these instruments are commercially nvailable, the Mathieu instrument (Cie Radio-Cinhms) and the Yoshinagn instrument (Shimaden Seisakusho, Ltd.) Research instroments using cathode-ray tube presentation have described by Dieke and Crosswhite ( I S , 1 4 ) and by Brehm
A high-resolution monochromator
designed for sequential analysis has been described by Fastie (16). A similar instrument, designed for either the sequential or parallel technique, as well as For use as a photo.IINAILIIICAL GAP graphic instrument, is the Applied Re~ C O I I O E N S L R LENS search Laboratories' Quantograph (la). PHOTOTUBE Figure 3 shows the optical layout of Figure 3. Optical Bystem of ARL Quantograph this instrument. The spectra excited a t the analytical gap pass through the primary slit to tho primary collimator to it flat grating and to the secondary collimator. When used in a the parallel systemis the fastest whereseveralelementspersample sequential system, one element line a t a time is brought to the are to he determined. Parallel System Optical Instruments. Several instruments of monochromator slit by rotation of the grat,ing. Alternatively, this type have been desoribed in the literature. These include the a number of slits and phototubes may be arranged along the focal circle to pick up 2r number of elements simultaneously in s Applied Research Laboratories' Research Quantometer (EO) and Production Control Quantometer (E), the Baird Associatesparallel system. The complete unit is shown in Figure 4, with Atomic Instruments Direct Reader (26), and the Hilger Polyits attendant excitation source and recording console. Sequential System %Rag Instruments. Instruments of this chromators (81). Fisher Scientific Co. and Jarrell-Ash Co. also type, using flat crystals as dispersing elements, include the offer this type of instrument. Most of these instruments use concave gratings, and d l of them are polychromators employing a fluorescence attachment for the General Electric X R D d diffraction instrument, and the various Norelco instruments (4, 17). single primary slit with a multiplicity of secondary slits, mirrors, The Applied Researrh Laboratories' x-ray scanning Quantometer or prisms, and multiplier phototubes. The differences are mainly (23)is a sequentid instrument using curved and gronnd crystals. in optical details and the recording electronics. I t s optical arrangement is shown in Figure 5 . The motions reAs an exrtmple of these polychromators, the optical assembly of the Applied Research Laboratories' Production Control Quantometer is shown in Figure 1. Radiat.ion from the analytical gap enters the instrument a t top center from the far side. It is deflected to the concave grating a t lower left, and the dispersed spectra are received along the focal circle to the right hy slits, mirrors, and phototubes. This particular Quantometer, using a %meter radius of curvature grating, can provide simultaneous measurement of as many .as 68 lines. The camplebe instrument . is shown in Figure 2, with its high-voltage excitation source to the IeFt, and recording console to the right. Sequential System Optical Instruments. A large number of instruments measure one line a t a time, usually with pmvieion far simultaneous measurement of an internal standard. Many of these are one-of-a-kind devices conFigure 4. Complete A R L Quantograph, including source
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
-LocyI
1841
OF OLlrC,OR
WWh
x-nm
60"RCE
SAMPLE
Figure 5. ~
,,
,., .,
.,
~
,,..,,I
t
i ~ of ~ l monochromator
.,I,,
_I
~
x-ray
" . .
-
Geiger countem, proportional counters, or scintillators. Regardless of the detector used, the circuit of Figure 8 is used in all Applied Research Laboratories' direct readers. During integration, the detectors are connected to the integrating condensers, giving simultaneous charging of all condensers. At the end of the integration time (controlled by source intensity), the detectors are disconnected and the vibrating condenser electrometer amplifier is connected to the integrators one a t a time. When a particular integrator is connected to the amplifier, the associated zero and sensitivity controls are also connected into the circuit. Thus, the voltages on the simultaneously charged integrators are read sequentially st the rate of one every two seconds, the results being traced on special chart paper by a Leeds & Northrup recorder. A digital voltmeter and electric typewriter comhinatian is an alternative output system. An obvious future possibility of this system is closing the loop between the Qumtometer output and the equipment manufacturing the samples. Any of these instrumental andyticd systems are sometimes complicated by complex relations between spectral intensity and concentration. I n the simplest systems, the relation is linear, requiring only zero and sensitivity controls in the circuits to give direct concentrational output. When the relation is nonlinear, special chart paper can be prepared to give direct concentrational output with L & N recording. The most complicated system is that in which the changes of concentration of same elements affect the spectral intensities of others. I n other words, the intensity of the analyte is a function not only of its concentration, bnt also of concentrations of other elements present. The optical Quantometers contain circuits for correction of certain types of these functions, and special computers are under development for handling others. When the instrument cannot handle the more complex functions automaticeally, some computation time muat be added to the total analysis time. Other manufacturers of optical direct readers use circuits differing in detail from the circuit of Figure 8. Other types of x-ray equipment generally integrate through the use of conventional sealing circuits.
.
PRECISION AND ACCURACY
Figure 6 . Complete ARL x-ray scanning Quantometer
quired to hold the secondary slit and crystal on the focal circle, while maintaining a fixed primary slit and sample position, are obtained with a single screw driving the appropriate linkage. The instrument is shown in Figure 6, mounted on top of its power supply with the recording console to the right. It contains two monochromators of the sort shown in Figure 5. One of these is provided with a c r p t d bent t o an 8-inch radins and ground to EL 4-inch radius, giving a focal circle of 4inch radius. The other is bent to 22 inches and ground to 11 inches. Either monochromator can he aligned with the single primary slit, allowing efficient coverage of the useful x-ray wave length region. Parallel System X-Ray Instruments. A one-of-a-kind instrument of this type has been described by Adler and Axelrod ( 1 ) . Another instrument, using focusing crystals, is the Applied Research Laboratories' X-ray Industrial Quuantometer (B),shown in Figure 7, mounted on its power supply. It consists of seven semifixed monochromators with the optics of Figure 5 mounted in a circle around the centrally located end-on x-ray tube and sample position. The XIQ provides the simultaneous determination of seven elements. Recording. Optical spectrum lines are generally detected with multiplier phototubes. X-ray spectra. may he detected with
Precision of analysis of high concentrations is determined by all the factors in the analysis. With optical
ANALYTICAL CHEMISTRY
1842
direct readers, the precision is determined by excitation source characteristics and sample homogeneity. I n metal analysis, concentrational coefficients of variation of 0.5 to 1.5% are obtained. For nonmetallics this may be 1 to 37, with the best techniques. With x-ray Quantometers, precision is determined by detector characteristics, giving coefficients of variation of 0.2 to 0.67, regardless of sample type. Piecisiop at low concentrations is dependent on the sensitivity for the element in question. Accuracy should approach precision in these systems providing nniform samples are used and accurate standards have been used to calibrate the system. I n some cases it is possible to standardize the instruments Kith synthetic samples SENSITIVITY
Because optical spectra originate in valence electron structures, the appearance and intensities of there spectra should bear some relation to the position of the elements in the periodic table.
A summary of four semiquantitative systems is given in Table 111. These data represent limits of detectability to order of magnitude only. Each author uses a different definition of sensitivity, etc. A study of Table I11 shows that highest sensitivity can be obtained for light alkalies and alkaline earths, but gases, halogens, and nometals are generally not detected with standard techniques. K i t h special techniques, even these elements can be detected, and the limit of detectability can be reduced an order of magnitude or more on the metallic elements. Although these data were obtained by photographic techniques, similar results can be obtained with direct readers. Table 11-gives the order of magnitude of limits of detectability attainable with an Applied Research Laboratories' x-ray scanning Quantometer for three different modes of operation. The limits for continuous scanning are obtained a t a scanning rate that will cover all elements of atomic number greater than 19 in 3 hours, or about 2.4 minutes per element. The concentration given rep-
Table 111. Optical Emission Sensitivities Reference Source Matrix Sample .__ Z
3 4 5
11 12 13
14 15
19 20 21 22
23 24 25 26 27 28 29 30 31 32 33 37 38 39 40
41
42 44 45 46 47 48 49
Element Li Be B Na
2 Si P K
Ca sc
Ti
v
Cr Mn Fe
co Ni
cu
Zn Ga Ge As Rb Sr
Y
Zr Nb Mo Ru Rh Pd Ag
Cd In
(8:)
D.c. arc Zn 100 mg. powder
(1.9) D.c. arc C 10 m g . powder
10 1 1 1
1000
1
1
10 10 1 1 1 10 1 1 10 1
100 10000 100 100 10 10 1
(.Q)
D.c. arc Biologicals
Reference Source Matrix Sample ~
Z 50 51
1
;;
10 1000
56
10 10 1000 1000
60
1
62
10 100 10 10 10 10 10 1
57 58 59
63 61
1 100 100 10 100 100
100 100 100 100
1000
1000
100
10
10 1000 10 100
10 100 1 10 10
HC1 0.1 nil. sol.
Llillimicrograms on Electrode
P a r t s per Rlillion
10 1 100 100 10
(18)
Cu .park
10
1
100 100
1
10 10 10
100 10 10 100 10 1000 1000
66 67 68 69 70
71
72 73 74 75 77 78 79
80 81
82 83 88 90 91 92
93 94
Element Sn Sb Te CS Ba La Ce Pr Sd Sm Eu Gd D 1.
Hb
Er Tm Yb Lu Hf Ta
(27)
(19)
D.c. arc
Zn
100 mg.
pomder 1 10 10 10000 100 1000 100
BI
:p
Pu
1000
(9) D.c. arc
Biologicals
801.
Millimicrograms on Electrode
1000
10
100
100 100 10 10 100 10 10 10 10 100 10 100 10
100
10
hU
Ra Th Pa
100 100
(16) Cu Bpark HCl 0.1 ml.
1
100 10 10 10 100 1
f:
10 mg.
powder
10000
100 10
T1 Pb
C
Parts per Million
w
Re Ir Pt
D.c. arc
1 100
10000
moo
1000
10 10 100 1000 100 10
100 100 100 100 100 1000 1 10 1000 10 10 10 10 10 100 100 100 100
100
10 10
V O L U M E 28, NO. 12, D E C E M B E R 1 9 5 6
1843
Table IY. X-Ray Emission Limits of Detectability (Standard deviation in parts per million at background) Technique Z Element 1 3 Z Element 1 2 8 Z Element 20 4.5 100 8 Yb Ca 10,000 GO Rh 15 70 300 sc 10 L I1 21 Pd 100 20 71 200 10,000 40 46 22 Ti 10 Hf 100 1,000 10 47 20 72 80 i3 v 20 23 48 1,000 30 Ta 25 8 1,000 Cr 20 IT, 74 24 5 49 1,000 30 1,000 15 2 Mn 30 25 100 50 1,000 60 I I 1 Re 8 40 os 26 Fe 100 3 51 1,000 76 60 6 Ir co 3 52 1,000 50 27 100 100 77 6 Xi Pt 28 100 3 53 1 1,000 I50 70 6 78 cu 1,000 100 Au 29 100 3 .5 4 Xe 200 79 6 Zn 10,000 200 3 400 30 100 55 cs 80 G 200 31 Ga 3 56 Ba 50 10,000 100 8 81 32 Ge 100 3 57 La 10,000 80 30 Pb 8 82 Ri 33 As 100 i o , on0 20 58 83 60 8 Ce 3 Pr 10 34 Se 100 10 1,000 40 84 Po 59 ? Br ?;d -4t 35 100 60 1,000 30 10 10 85 ? Kr P ni 1.000 10 36 100 10 61 20 Rn 86 37 Rb 100 5 63 Sm 1,000 8 Fr 15 20 87 Sr 38 8 Eu 1,000 20 8 Ra 100 15 63 88 Y 3 39 100 64 20 8 A0 1,000 6 Gd 89 Zr 1,000 Th 3 40 20 90 100 65 Tb 6 S b 1,000 41 91 8 20 Pa 100 66 DY ? 20 Mo Ho 1,000 42 92 100 67 8 43 To Er 1,000 20 93 100 10 68 .\JP 5 44 Ru Tm 20 69 1,000 100 10 a Techniques: 1. Continuous scanning. 2. I-minute integration, high resolution. 3. I-minute integration, loiv resolution. Techniquea 2
--
Ff
u
Table V. Time Schedules (20 elements per sample) Parallel Preparation, min. 0 5-18 Integration, min. 0 5- 1 1 Readout, min. Total, min. 2 -20 Time per element, min. 0 1- 1
Sequential 0 5-18 7 -25 1 7 543 0 4- 2
Reported Routine Times Elemental Analysis per Hour Reference Material 30 Author’s laboratory Slag Aluminum alloy 119 (11) Aluminum alloy 550 (10) Aluminum alloy 1500 (8)
resents that a t which a line would be definitely vikible above background. T h e limits given for 1-minute integration a t high resolution (0.005 inch primary and secondary slits) are concentrations a t which a coefficient of variation of 100% would be obtained. The loiv resolution limits are those obtained with slits adjusted for maximum sensitivity (usually 0.030-inch piiniary and secondary), rather than for maximum resolution and are given as the concentrations a t the 100% coefficient of variation level. Again, special techniques can extend the x-ray method to lighter elements and can reduce the limits given here. These ddta can be considered representative of the capabilities of piebent day x-ray fluorescence instruments.
1
1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000
Technique 2 20
20 20 20 20 30 30 30 30 30 30 30 40 40 40 40 40
40 60 60 60 60 60 60
3 8 10 10
10 in 10
10 15
15 15
15 15 20 20 20 20 20 30 30 30 30 30 30 40
technique, however, is easily adaptable to continuous analysis. This characteristic has made possible the design of a variety of x-ray gaging instruments for use in tin and zinc plating thickness measurement, and continuous, single-element determinations in various types of plant streams (18). LITERATURE CITED
(1) Adler, I . , Axelrod, J. AI., J . Opt. Soc. Amer. 43, 769-73 (1953). ( 2 ) Applied Research Laboratorieq, Spectrographer’s A‘ews Letter 3,
Xo. 3 (1950). (3) Ibid., 9 , NOS.1-3 (1956). (4) Behr, F. A., Norelco R e p t r . 3, 80-2 (1956). (5) Brehm, R. K., Fassel, V. L4.,J . O p t . Soc. Amer. 43,886-9 (1953). (6) Bryan, F. R., Nahstoll, G. A., Ibid., 38, 510-17 (1948). (7) Bylund, K. G., Rudberg. H., Jernkontoreis Ann. 133, 507-18 (1949). (8) Callon, R. W., Charette, L. P., ANAL. C m v . 23, 960-6 (1951). (9) Cholak, Jacob, Story, R. V., J . Opt. SOC.Amer. 31, 730-9 (1941). (10) Churchill, J. R., I r o n Age 168, 97-100 (Oct. 11, 1951). (11) Clausen, C. J., Western Metals 6 , 26-9 (May 1948). (12) Davidson, E., Jones, J. L., Goodwin, P. S . , Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, 1955. (13) Dieke, G. H., Crosswhite, H. AI., J . Opt. SOC.Ani. 35, 471-80 (19453 (14) Ibid., 36, 192-5 (1946). (15) Fastie, IT. G., Ibid., 42, 641-7 (1952). (16) Fred, AIark, Kachtrieb, K. H., Tomkins, F. S., Ihid.. 37, 279-88 (1947). (17) Friedman, H., Birka, L. S., Rev. Sci. Iiisfr. 19, 323-30 (1948). (18) Goodwin, P. S.,Jones, J. L., Hasler, hl. F., Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, 1956.
SPEED
Table \- gives estimated time schedules for parallel and sequential direct-reader operation. The lower figures would apply to alloy analysis requiring a minimum of sample preparation. The higher figures would apply to nonmetallic analysis with an optical direct reader where considerable sample preparation may be required. The second part of the table gives results obtained on a routine basis with the Applied Research Laboratories’ Quantometers, the original publications giving time in terms of analysis per shift, or per week. Such figures, then, include calibration time. With the latest direct readers, alloiving 20 or 30 element determinations per sample, element analysis per hour can run over 1000. The nature of the optical emission technique generally precludes its use as a continuous analysis system. The x-ray
(19) Harvey, C. E., “lIethod of Semi-Quantitative Spectrographic Analysis,” Applied Research Laboratories, Glendale, Calif., 1947. (20) Hasler, 11. E.’., Dietert, H. IT., J . Opz. S O C .Anzer. 34, 751-8 (1944). (21) Hilrrer Er Wattj. Ltd.. Hilaer J . 2. 51-8 (1956). (22) Kemp, J. W., Hasler. 31. g., Jones, J. L.,’Zeits, L., Spectrochim. Acta 7, 141-8 (1955). (23) Kemp, J. W.,Jones, J., Zeitz, L., Pittsburgh Conference on .Inalytical Chemistry and Applied Spectroscopy, 1955. (24) llathieu, F. C., Spectrochim. Acta 5, 174-81 (1952). (25) Kaish, J. AI., Ramsden, TV., Ibid., 5, 295-307 (1952). (26) Saunderson, J. L., Caldecourt, T’. J., Peterson, E. W., J . Opt. Soc. Amer. 35, 681-97 (1945). (27) Standen, G. W.,IXD.EKG. CHEM., ANAL. ED. 16, 675-80 (1944). (28) Yoshinaga, Hiroshi, Fujita, Shigeru, Minami, Shigeo, Technol. Rtpts. Osaka U n i t . 2, 147-56 (1952). RECEIVED fw review J u n e 15, 1956.
Accepted October 1, 1996.
