INSTRUMENTATION BY
RALPH
H . M Ü L L E R
Atomic Absorption/Flame Emission Instrument Offers Versatile and Automated Operation "C^ROM D r . Frederick Brech, Director - 1 of Research, we learn details of the new Jarrell-Ash fully compensated atomic absorption/flame emission unit. The unit is manufactured and listed as catalog No. 82-300 of the Jarrell-Ash Division of the Fisher Scientific Co. of 590 Lincoln St., Waltham, Mass. 02154. New York City commissioned Jarrell-Ash to design and manufacture automated apparatus for the quantitative measurement of 12 metallic elements as airborne pollutants collected on filters. The present unit meets these requirements. We say more about this large scale application later. This instrument was designed to correct errors in atomic absorption analyses t h a t arise when determinations are to be made in difficult matrices or under different conditions. When problems do not derive from these causes, the instrument m a y be employed for two determinations made simultaneously in a single sample. The instrument is usable both in atomic absorption and flame emission modes of analysis. T h e a p p a r a t u s carries all logic and command circuits necessary for correction to automated sample presentation and readout systems. Figure 1 illustrates t h e entire unit. Of the 5 separate components, the one on t h e left, termed "robot chemist" holds 7 vials, followed b y an adjustable p u m p for sample u p t a k e and dilution factor and, to t h e right of this component, a pipetter swings through a n arc to dispense a diluted sample t o the sample cup of preconcentrator. Second from t h e left is t h e preconcentrator which dries the sample and aerosol is carried b y a long plastic tube t o t h e flame. The center unit in this a r r a y contains, on the left, the hollow cathode tubes and fore optics. Next is the flame unit, followed by the atomic absorption and flame emission system with twin ' 0.5 meter monoehromators. The next to the last component is the " a n a c o m p " computer with two controls for signals from each monochromator plus a digi-
tal voltmeter. T h e last component on the right is a teletype printer with print-out in concentration units a n d which also cuts code-punched paper tape. T h e apparatus employs two monoehromators that space share hollow cathode light t h a t passes through the flame. I n addition, each of t h e two monoehromators also space shares light t h a t by-passes the flame and subsequent electronic circuits correct light variations. This is of importance when two hollow cathode light sources are used a t t h e same time. Each monochromator may be turned t o any wavelength and, for example, selected wavelengths may be those for two separate elements when no correction is necessary, and this is frequently t h e case with aqueous solutions. Some other matrices, however, cause hollow cathode light to be lost by scattering or b y molecular absorption a n d compensation for such phenomena is necessary. To achieve this, one monochromator is timed t o a resonant wavelength of the element being analyzed a n d the other monochromator t o a nearby b u t nonresonant wavelength which, a s such, is not selectively absorbed b y atoms of the element under analysis. T h e first monochromator responds t o all causes for light loss, including t h e selective
atomic absorption. Electronic means embodying loop amplifiers are employed to effect t h e corrections so t h a t a n accurate determination of the element m a y be made. The resulting improvement is shown in Figure 2. The curve for Cu 3274 is that of a single channel information for Cu concentration in a N I B K matrix. The working curve is classed as unsatisfactory and exhibits the shape characteristic of light losses from causes in addition to t h a t of atomic absorption. Variations in flame and aspiration conditions cause the calibration curve t o change in slope and shape and, consequently, reproducibility of data is highly dependent on exactness of all experimental conditions. T h e nonabsorbing line chosen for correction was t h a t of Ag, which element was not present in t h e sample. T h e Ag radiation a t 3281 cannot be selectively absorbed b y C u atoms and, therefore, the magnitude of the signal should remain at a pre-set level. When this is n o t so, automatic gain is a p plied to the measuring circuit to restore the signal to the correct level and the same gain factor is automatically a p plied to the Cu channel. A neat method of flame-noise suppression is achieved b y the Curry twoline method, in which two absorbing lines for the element are measured si-
Figure 1 . Jarrell-Ash fully compensated a t o m i c a b s o r p t i o n / f l a m e emission unit VOL. 40, NO. 1 0, AUGUST 1 968
·
85 A
INSTRUMENTATION
Harleco
100
®
INDUSTRIAL REAGENTS 2106 BUFFER REFER-32 oz. 2.5 gal. ENCE SOLU TION—pH 4.01 ± .01 @ 25°C 4.95 17.60 Potassium hydrogen phthalate solution. Includes N.B.S. temperature coefficient 0° t o 6 0 ° C 21131 BUFFER REFER- 32 oz. 2.5 sal. ENCE SOLU TION—pH 7.00 ± .01 @ 25°C 4.95 17.60 Potassium and sodium phosphate solution. 2119 BUFFER REFER- 32 oz. 2.5 sal. ENCE SOLU TION—PH 10.00 ± .01 @ 25°C 4.95 17.60 Boric acid-potassium hydroxide solution. 1306c S O D I U M ΗΎ- 32 oz. 2.5 gal. DROXIDE— N / 1 0 Solution.. 2.45 13.20 1306d S O D I U M HY32 oz. 2.5 sal. DROXIDE— Normal Solution. 2.45 13.20 *3786 KARL FISCHER 16 oz. 32 oz. REAGENT— Stabilized Single
5 gal.
1248a
1248d
*2038 *1258
*1256
2830
2832 2005
20052
*1895
*64094
*U.S. Postal Ruling.
Cu
5 gal.
22.00
5 gal. 19.25 5 gal. 19.25 gallon
Not permitted in mails.
ANALYTICAL CHEMISTRY
5
22.00
/fet/le»®
·
10
3
60TH & WOODLAND AVENUE PHILADELPHIA, PENNSYLVANIA 19143
86 A
%A
3274/ / A g 3281
5 sal.
For a complete listing of Harleco Industrial Reagents, please write for publication number 6 2 3 .
Circle No. 115 on Readers' Service Card
30
22.00
29.10 Case-4 X 1 gal. bottles 98.00 107.80 KARL FISCHER 32 oz. 2.5 gal. 5 sal. REAGENT WATER STAN DARD—Meth anol 3.65 15.95 28.35 1 ml. => 1 mg. H2O ± 0.01 π s. HYDRO32 oz. 2.5 gal. 5 sal. CHLORIC ACID—N/10 Solution 2.45 13.20 19.25 HYDRO32 oz. 2.5 gal. 5 gal. CHLORIC ACID—Normal Solution 2.45 13.20 19.25 DICHROMATE gallon 2.5 gal. 5 gal. CLEANING SOLUTION 6.40 10.75 21.75 IODINE16 oz. 32 oz. gallon MONOCHLORIDE—Wijs 26.65 IODINE16 oz. 32 oz. gallon BROMINE— Hanus SolutionA.O.A.C 5.05 8.65 31.30 SILVER NI32 oz. 2.5 sal. 5 gal. TRATE—1 ml. = 1 mg. NaCI 2.65 14.30 21.45 SILVER Nl32 oz. 2.5 sal. 5 gal. TRATE—1 ml. = 1 mg. CI 2.65 15.15 27.50 EDTA—Dl. 32 oz. 2.5 gal. 5 sal. SODIUM SOLUTION— 1 ml. = 1 mg. CaCOî 2 40 9.35 16.50 Contains magnesium. Diehl, Goetz and Hach. EDTA—Dl32 oz. 2.5 sal. 5 sal. SODIUM SOLUTION— 1 ml. = 1 mg. CaCOs 2.90 12.65 21.75 Without masnesium. Betz and Noll. NESSLER RE32 oz. 2.5 sal. 5 gal. AGENT— A . P . H . A . Speci97.35 NESSLER unit COMPOUND— (Dry) A . P . H . A 5.80 Sufficient for 1000 ml. solution Compound contains required alkali.
*1849
Cu 3274
50
I 3
5
10
30
50
100
300
ppm Cu
Figure 2. Correction necessitated by matrix influences is shown above. Upper curve is that of a single channel for Cu; lower curve represents improvement in curve by use of Ag nonabsorbing line for correction
multaneously in each channel. Perturbations in the flame cause exactly similar variations of absorption signals both in time and magnitude for both resonance lines of the same element. Accordingly, a ratio of the measurements provides correction for flame noise. In Figure 3, for the purpose of demonstration, flame noise was purposely magnified by reducing the sample aspiration rate from 6 ml per minute to 0.3 ml/min thus reducing sensitivity 20-fold but simultaneously increasing the sensitivity by a 20-fold scale expansion. The signal at the left is for single channel recording. On the right, the recording is the ratio of absorbance by the two Ou lines. There are six ways to use the JarrellAsh fully compensated atomic absorption unit. 1. As two independent channels for atomic absorption with each set for the analysis of a different element. The operator may choose to read the two channels sequentially on a recorder or print-out system by punching a single button, or may elect to read both channels separately on command. When a twin-channel recorder is available, the signals may be displayed simultaneously. 2. As a unit with one channel operated in atomic absorption and the other channel, simultaneously, in flame emission. 3. As an analytical system compensating for interferences caused by the matrix. One channel is tuned to the absorbing wavelength for the element and the other channel to a nearby wavelength which is not capable of being selectively absorbed by atoms of the
Cu
3247-
Cu 3 2 7 4
( 3ppml
0.3 ml/ min (20 X S E ) Single Chonnel Cu
3247
Rotlo Cu 3 2 4 7 / Cu 3274
J»
Figure 3. Flame noise suppression is achieved by the Curry two-line method. A ratio of measurements provides correction as shown above
element being analyzed. The normal mode of readout is the ratio of the two signals and actuation of a button displays the value. The operator may also elect as an alternative to observe the independent signal in each channel. 4. As an analytical system correcting for noise produced in the flame, by the Curry two-line method. Each of the two channels is tuned to a differing absorbing line of the same element. The same flame noise occurs in each channel and the noise values cancel each other when the ratio of the signals is displayed. This operation permits a determination to be made with as little as 20 microliters of sample soultion. 5. The instrument may be used to give the ratio signal for two separate elements when one is present in a known concentration and is employed as an internal standard for the other.
INSTRUMENTATION
COLEMAN 40 R-F REACTOR will prepare samples for microscopy, elemental analysis, radio chemistry, and reaction chemistry
6. The instrument may be operated on manual command by the operator. In addition, however, the instrument includes the basic circuit logic that al lows operational command from auto mated sample presentation and readout systems. Jacks are available to permit direct connection to a choice of millivolt strip-chart recorder, digital display and print unit, meter readout, computer, and teletype system. Although the Jarrell-Ash unit has wide research capabilities, its most dis tinctive feature is the automation and data assimilation capabilities and its unique ability to recognize and com pensate for extraneous behavior of the matrix. In the New York City ap plication, the Department of Air Pollu tion Control has set up 38 stations dis tributed in carefully planned locations over Manhattan both at ground level and selected elevations. At each, an electrically driven blower system forces air at 40 cubic feet per hour through a cellulose type filter. Each filter is submitted daily to the Department's laboratories and is dissolved in nitric acid and aqua regia. The sample solu tions, in 8 vials, one for each day of the week and one containing highly purified water for washing purposes are held in racks. The program calls for 38 such racks making a total of 266 samples. Each is analyzed for 12 metallic ele ments, requiring a total of 3192 de terminations. At present, the follow ing elements are of interest in this pro gram, with their sensitivity for atomic absorption analysis given in parenthe ses (ppm) : As (0.05), Be (0.005), Pb (0.02), V (0.20), Mn (0.01), Co (0.02), Cd (0.005), Cr (0.02), Zn (0.002), Fe (0.02), Ni (0.02), Cu (0.015). For an ambitious program of this sort, one can easily appreciate the need for elegant, reliable equipment and the full resources of automation and data R-F ashing at low temperature with the Coleman Model 40 Reactor is collection. I t is obvious that in this the ideal way to prepare samples for analysis. It's simple, clean and short report we have not been able to safe. Molecular oxygen is the only reagent required. Organic content cover all the important and distinctive is removed without loss of volatile elements, without reagent con developments. Presumably, Dr. Brech tamination and without danger of fire or explosion. The low tempera will describe these in great detail in ture preserves mineral patterns and cell structures. company bulletins or elsewhere. Many R-F ashing is the most practical method of preparing samples for chemists are annoyed with the trace microscopy. Organic matter is removed from skeletal substructures analyst's preference for parts per mil revealing inorganic details which cannot be observed by other pre lion or per billion. We keep conversion paratory systems. The R-F Reactor has been used successfully to graphs on our desk for quick conver improve analyses based on mass spectrometry, atomic absorption, sion to more conventional units of con emission spectroscopy, neutron activation, UV and IR spectrophotom centration. I n a press release, Fred etry and conventional "wet" methods. Brech has given a few useful "bench marks" for reference. For example, 1 For complete information or a demonstration, write . . . W. H. Curtin drop of vermouth in 54 quarts of gin & Company, P.O. Box 1546, Houston, Texas 77001. = 1 part per million (bone dry mar tini) ; 0.01 ppm = 10 ppb is 1 drop in 5,400 quarts or 1 drop per 20 χ 20 χ 2.5 foot wading pool. These scientific con SCIENTIFIC A P P A R A T U S • CHEMICALS . LABORATORY FURNITURE stants may be of passing interest even H O U S T O N . T U L S A · LOS ANGELES . N E W ORLEANS · A T L A N T A · S A N FRANCISCO D A L L A S . J A C K S O N V I L L E « W A S H I N G T O N « W A Y N E , N . J . "MEXICO CITY · MONTERREY in the more arid areas of the country.
...all by itself!
W. H. CURTIN & COMPANY
253
Circle No. 101 on Readers' Service Card VOL. 4 0 , NO. 10, AUGUST 1968 ·
87 A
