Table 111. Distribution Ratios of Zirconium as a Function of Organic Phase Composition Phase compositions Organic Aqueous Da 100% TEHP 8.ON HNOs 7 9770 TEHP-370 HDEHP 8.ON "01 86 95% TEHP-5% HDEHP 8.ON "03 260 90% TEHP-10% 8. O N "0s 1170 HDEHP 80% TEHP-20% HDEHP 8. O N "03 2580 a Average of 3 determinations.
results were calculated from the relationship D = M0r,/M&9,where M,,, = M,,, - Msq.Based on these data, an organic phase composition of 95% TEHP-5yo HDEHP was used as the stationary extraction phase in column operations. DISCUSSION
An experimental survey of reagents for application in partition chromatographic column separations indicated that the neutral organic phosphates and phosphonates, although efficient extractants for plutonium(1V) and uranium(VI), were not satisfactory for the quantitative retention of zirconium(1V) if present in macro concentrations.
Therefore, contrary to earlier expectations (S),tri-n-butyl phosphate (TBP) did not extract zirconium(1V) effectively when present above the trace level. On the other hand, HDEHP was shown ( 4 ) t o have a high affinity for zirconium over a wide nitric acid concentration range. The use of this reagent alone proved unsatisfactory in that the ternary alloy matrix, particularily plutonium(IV), could not be stripped from the column with simple mineral acids. Since a separation procedure was desired in which chromatographic columns could be reused for several elutions, mixtures of a neutral organic phosphate for the extraction of uranium(V1) and HDEHP for the retention of zirconium(1V) were found to be more acceptable. TEHP was chosen because this reagent showed exceptional stability in nitric acid, as evidenced by the absence of phosphorus during repeated elutions. The previously reported (3) line intensity suppression in the spectrographic analysis by column degradation products was not observed in these experiments. Generally, the zirconium content in the effluent was less than 1% of the original value, causing no significant interferences in the evaluation of impurity concentrations. 4 HDEHP concentration in excess of 5% resulted in incomplete stripping of plutonium with a mixture of 0.4N nitric-
0.02N hydrofluoric acid. Because of the insolubility of plutonium tetrafluoride, a higher fluoride concentration could not be used. The application of column separations to the analysis of high purity metals and alloys is particularly useful from the standpoint of the large number of elements that can be determined. Furthermore, blank contaminations are minimized by the use of highly purified reagents and inert plastic laboratory ware. This presents a distinct advantage over liquid-liquid extraction techniques, where several equilibrations have to be used to effect a preconcentration comparable to a one-pass column elution. LITERATURE CITED
( I ) Argonne National Laboratory Rept., ANL-7000, p. 11 (1964). (2) Fred, M.,Nachtrieb, N. H., Tomkins, F. S., J. Opt. SOC.Am. 37, 279 (1947). (3) . . Huff, E. A.. ANAL. CHEM.37. 533
(1965): (4) Japan Atomic Energy Research Institute Rept,. JAERI-1047 (1963).
A. HUFF EDMUND J. KVLPA STANLEY Argonne National Laboratory Argonne, Ill.
BASEDon work performed under the auspices of the U. S. Atomic Energy Commission.
A Semiautomatic Device for Measuring and Drawing Mass Spectra Richard N. Stillwell, Department of Biochemistry, Baylor University College of Medicine, Houston, Texas
and most commonly used T method of obtaining mass spectra from a low-resolution mass spectromHE BEST
eter equipped with a direct or gas chromatographic inlet system is by means of a three- or five-galvanometer oscillographic recorder. These records, however, are unsuitable for handling and study. They are cumbersome and light-sensitive (unless fixed), and they are difficult to study because the top of a large peak on the bottom trace is easily lost among the smaller peaks of the upper traces. Comparison of spectra in this form is difficult because, in general, they are of different intensities. The primary records, then, should be converted into a more useful form, that is, either a table of mass numbers and relative intensities or a bar graph showing relative abundance us. mass-to940
ANALYTICAL CHEMISTRY
charge ratio, preferably including a "per cent of total ionization" scale (1). Normally a spectrum is counted, then measured by means of a variable-scale comparator to make the table of intensities. The spectrum is then drawn from the table by conventional draftsman's techniques. Counting and measuring a spectrum over the mass range of, for example, 50 to 300 takes 15 or 20 minutes; drawing it takes 20 minutes or more, depending on the number of peaks present. To deal with a large number of spectra which were to be studied and filed, but not necessarily reproduced for publication, it was desirable t o have a rapid method of producing a mass and abundance table and, at the same time, of drawing a compact spectrum and of calculating the total ionization. Conventional commercial digitizers were not
considered suitable for a number of reasons, but primarily because of the frequency response necessary for scanning during a gas chromatographic peak, and because of the uncertainty of mass determination a t large values of m/e. Hence, a method was wanted for measuring and drawing spectra from selected oscillographic charts. For this purpose the device described below was constructed from components a t hand in the author's laboratory. Once the peak count has been marked on the original spectrum and the instrument adjusted to the base lines and intensity of the chart, the spectrum is measured and drawn a t the rate of one peak every 3 seconds. The mass range of 50 to 300 mentioned above, for example, is covered in 12.5minutes. A Leeds and Northrup Speedomax H recorder was used for reading the oscillo-
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EDUCATIONAL COYPUTER
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INTEGRATOR INPUT I OSLOPEClRCUlT INPUT I I
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INFOTRONICS CRS-I
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Schematic diagram of device for measuring and drawing mass spectra
graphic traces. The following minor modifications were made. The faceplate and pen were removed, the chart drive gears disengaged, a pair of guide collars placed on the chart roller, and an index marker was attached to the pen carrier. The oscillographic record could then be fed over the roller from front to back and pulled through by hand. A Heath analog computer was used for most of the connecting circuitry (Figure 1). An initial-condition voltage source (marked Peak Height) was used to activate the read-in recorder through a 1OOO:l voltage divider. The same voltage was fed through an amplifier (3) with unity gain to a potentiometer (lOOyo Adj.) and thence to another amplifier (l), with unity gain. The output of this amplifier was used to record peaks on the lowest trace of the oscillographic chart. The input of a third unity-gain amplifier (2) was taken from the center tap of the 100% Adj. potentiometer through a potentiometer labeled Amp. 2 Gain. The resistance ratio of this potentiometer is nominally 10: 1, the ratio of the sensitivities of the traces. Two more initial-condition voltages were fed (for easier adjustment) through potentiometers (Trace 1 Zero and Trace 2 Zero) to amplifiers 3 and 2 for zeroing on the base lines of the traces. The output of amplifier 1 or 2 was selected by a foot-operated switch (normally on position 2 ) and presented to the readout recorder, a Bausch and
Lomb VOX-5 with its function switch set to 10 volt4 full scale and its pen slightly overdamped. X variable voltage divider was used to couple the amplifier output to the integrator input of an Infotronics Corp. hIodel CRS-1 digital chromatograph readout system. (A printing, digital voltmeter, suitably controlled by switches, could, of course, be substituted.) The timer section of the Infotronics unit has a motor-driven toothed wheel which actuates a switch, producing a square wave alternating between 0 and -18 volts with respect to ground. d fiberboard disk was cut and mounted on the motor shaft so as to allow the switch to close for only two 1/2-second periods during each revolution (6 seconds). A switch was wired into the timer motor circuit to allow interruption of the timer. A wire was connected to feed the square wave to the input of a unity-gain amplifier (8) which served to reduce the slope of the square wave to a finite value and to reverse its phase; the output of this amplifier was divided by 1000 and connected to the input of the slope detector circuit of the Infotronics unit. The instrument then automatically integrated the voltage presented to it during the llrsecond period. The %volt square wave was also used to actuate a sensitive relay (PhillipsAdvance SV 1C10000D) which kept the input of the readout recorder grounded except during the '/+xond pulse,
when it was connected to the appropriate amplifier through the foot switch. To use the system, an oscillographic chart is placed in the read-in recorder and pulled through to the largest peak. The Peak Height potentiometer is adjusted to position the index of the recorder over the base line of the lowest trace (the second trace in the case of a weak spectrum). With the relay in the grounded position, the readout recorder and the integrator are zeroed. The foot switch is depressed to position 1, the timer started, and the Trace 1 Zero control turned to zero the output of amplifier 1. The read-in recorder is then set with the Peak Height control to the top of the base peak and the integrator set to Auto. The 100% Adj. potentiometer is set so that the peaks produced by the readout recorder are about four fifths of full scale. The 50K potentiometer is set so that the integrator reads 1000 counts in each cycle. (This adjustment need be made only once. For subsequent spectra, the integrator is set by means of the 100% Adj. potentiometer.) The read-in recorder is then adjusted to the base line of the second (or third) trace, the foot switch released to position 2 , and amplifier 2 zeroed with the Trace 2 Zero control. The setting of Amp. 2 Gain is adjusted until a peak which is on scale on both traces gives the same count when read on the first trace with VOL. 38, NO. 7 , JUNE 1966
941
METHYL VACCENATE, M.W.296 CH3 (CH&CH = CH(CH2)gCOOCH3
Figure 2.
Mass spectrum drawn in 1 3 minutes using the device described
From a spectrum obtained a t 2 0 e.v. on an Atlas-Werke CH-4 mass spectrometer equipped with a gas chromatographic inlet system. The sample was the maior p e a k from a mixture of methyl esters of bacterial origin) the structure was assigned on the basis of this spectrum and that of the isopropylidene derivative of the corresponding diol (2). The tick marks for the mass numbers, relative abundance, and per cent of total ionization, and the lettering were added by hand.
the foot switch depressed as on the second trace with the witch released. The timer is allowed to run until it reads the mass number a t which reading of the spectrum is to begin. The readout chart paper drive is started at 1 inch per minute, and each peak of the spectrum is read by manipulating the Peak Height potentiometer and the foot switch during the intervals when the relay is grounded. The readout recorder produces a trace suitable for storage and study (Figure 2), while the integrator prints out a list of mass numbers and
relative intensities (in tenths of a per cent) which are comparable in accuracy to those measured manually. When the spectrum is completed, the Total button on the printer is pressed to give the total ionization in tenths of a per cent of the base peak. A number of possible modifications of this system suggest themselves. For example, if the chart drive of the readout recorder were arranged to advance in steps, a reproduction-quality spectrum might be obtained and, a t the same time, speed and accuracy could be
improved by providing switches t o permit stopping the system between peaks (for example when there is a large change in intensity), or by scanning rapidly through a region of no peaks. LITERATURE CITED
(1) Biemann, K., “Mass Spectrometry;
Organic Chemical Applications,” pp. 42-6, McGraw-Hill, New York, 1962. (2) McCloskey, J. A., McClelland, M. J., J. Am. Chem. SOC.87,5090 (1965).
WORK sup orted by National Institutes of Health &rant No. HE-05435.
Stainless Steel Capsule with Iron ”Window“ for Determining Hydrogen in Alkali Metal by Vacuum Extraction Joseph W. Glass, Chris M. Larsen, and James M. Scarborough, Atomics International, A Division of North American Aviation, Inc., P. 0.Box 309, Canoga Park, Calif. YDROGEN in alkali metals is normally Hdetermined by a technique wherein the alkali metal sample is sealed in an iron capsule ( 1 ) and hydrogen is extracted by heating in a vacuum at 700750’ C. The total quantity of gas produced is measured and the hydrogen is converted to water which is trapped. The residual quantity of gas is measured and the hydrogen is determined by diff erence. Usually, the iron capsule which contains the alkali metal sample is sealed by welding. However, welding is very often inconvenient, expensive, and requires expert care to prevent contamination of the sample. A simple, time-saving technique has been developed in which the welding operation for each sample is eliminated by substituting a reusable stainlesssteel capsule having an iron “window”
942
0
ANALYTICAL CHEMISTRY
1
-IRON DISC, 10 mil THICK, NOMINAL, WELDED TO END OF REDUCER
-0.75
in. OD
u2Oin
Figure 1. sule
CROSS SECTION OF MODIFIED SWAGELOK REDUCER (3/41n TO5/16ih) AND 5/16 in PLUG (TYPE 316 S$
is welded over the large end of the reducer. The sample is transferred to the capsule in an inert atmosphere box and the plug fitting is sealed. The capsule is then placed in the hydrogen analyzer, with iron “window” a t the top, and the analysis is performed in the conventional manner. This technique has been used successfully for Ea, K, and Na-K samples. No capsules have ruptured or leaked and it has been demonstrated that the capsules may be cleaned and reused.
Hydrogen extraction cap-
for the iron capsule. The stainless steel capsule can be made from a commercially available Swagelok reducer and plug as shown in the Figure 1. A thin iron window (nominally, 10 mils)
LITERATURE CITED
(1) Pepkowitz, L. P., Proud, E. R., ANAL.CHEM.21, 1000 (1949).
WORK done under the auspices of the U. S. Atomic Energy Commission, Con-
tract AT(ll-l)-GEN-S.
