Balance between classical and instrumental methods desirable . . . . . . Automatic counting equipment described HE 12th Annual Louisiana State Tciiiversit,y Symposium on ~ n a ~ y t i cal Chemistry at Bat,on Ilouge, January 26 to 29, \vas rr-cll attended. I’hilip Kest, and his colleagues a t 1.SU rontinlie to maintain the fine tradition of these niret,ings combined with hospitalit,? whirl1 is already lexenilary. We h a r e had the honor of part,icipatin: in thc firct,, the fifth, and thii, thr i n r l f t h sympo4iim. For some years this event, ha. had an int,ernation:rl flavor. This year, Great Britain RRS represented by Ronald IMeher of Birminehnm and hy C r d IT’ilson of Rclfast, hv 1Ierhrrt Keisz of Vienna and TT‘ilhelm Freseniw of Wiesbadcn. The presenrc of FresTypical automatic windowless flow counting instrumentation for low level rniiis r z s a historical event,. FIe i s the beta counting grrat,-.randson of Rrmigiris Freseniiisthe contemporary of Liebig, Wnhler, tween tlie classical methork and the inthe actrial procrss of introdticing the and Beraeliui. The four grnerations of strumental approach. At the time, onc samples, startinq and stopping the this family encompass almost the entire could have wi?herl thnt tlie same rncounting, and rcroriling the elapscd history of nnslytical chemistry. Wit,h tional and ?ensihlc attitiirlr could hare timr or numher of corrnts is a procedrirr characterist,ic thou:ht,fiilness Vr.st nrprevailrd in our ar:i,lemic institutions. wliirh rrqiiirr? no skill at all. For weak ranged to have Frrcrniiis inducted into With a11 tlie information to be gleaned samples, it mny con.mme much of thr t,he Phi Lambda Upsilon honorary sofrom rlemcntnry nnalyiis, from gmvitotal timr. Whcn thi? time bccomes cicty and to deliver the first Freseniris tnetrir and volumetric methods, the rerrcessive, one is faced nith the need for Lecture. -4s all Phi Lambda’s will resiilt,s wrre sripplementrrl hy the techcluplicate eqiiipmrnt or additional trrhrnll, t,hc society’s padron “5aints” a r r niqiies of chromnto:raphy, electron nirinns. This is precisclv the timp at Frrsrniiis. Liehiq. and van’t TToff. If mierosropy, x-ray, infrared, speetrowhirh automatic sampling and autov e are not mistaken, t,he Frrsenius famphotometry, elect,ron diffraction, polarmatic coiint,ing should be considered. ily represents n unique rcrord in the ography, and other elecbroanalytical To quote lIcl\‘ult,y and Piranian: annals of srirnce. The triumvirate of techniques. TT’it,h surh perfect coorDecqirerels in France was another rxTwo important benefits thus accrue. dination of tcchniqrtes it was impossible ample. The grandson vas tlie disro\,The first is that laboratories which must go “overboard” in veneration of pret,o erer of radionctivit,y. meet definite work completion schedcipitatcs or to fall over the other rail The details of this meeting mere disiiles are alde t,o telescope their work in behalf of Ruck Rogers electronics. by utilizing time which formerly (for all missed earlier (ANAL. CHE\i., illarrh, The same philosophy is now being expractical purposes) did not exist. A page 38.4). One of the most, uiefiil pounded from the editorial chiir and .mend benefit is that it permit,s fuller I)y-products of Pitch mertingz is the oputilizat,ion of the radiation detection the Editor’s Column and it is one in portunity t o talk shop with analyst?. Pquipmcnt already avnilablc and often whirh all progressivc analysts will conT c wrre pleased to lrarn from our eood eliminatcs the need for duplieat,c scalers, CUT. frirnd Jay Inhr, now at Du Pont, that detectors, nnd other equipment. he has succeeded in int,roducing a hrond In addition to the economic hrnefitr Automatic Counting Equipment approach in the solution of analytical gained by t,he users of autotnat,ic sample problems. As he explained it, “some of From Paul McNnlt,y and Alex E . H. counting equipment, thcre arc other adLarry Hallett’s (Editor, A N A L Y T I C L Piranian, both of Tracerlab, ID01 Trarantagrs mhich arc worthy of con?iclerntion. >lost, import,nnt among tlicsc CHEXISTRY) broad philosophy had pelo Road, V d t h a m 54, Ilass., me learn is convenience; that is, the freedom brushed off on him,” and in his own of t,Iie seteral economies which can he from constant nttrntlance at, a camplr achieved hy tlir n‘c of :nitomntic m i n t rompet,ent hands, it is payinF off hanrli,hanoer. Thr marhine-printcd rcs,dti somely. in: equipmrnt. In any work rcqiiiring n-hicli are furni?hcd by the data printcr We, among ot,hers, were priviliged to the counting of radioisotopes, the skill provide permanent rcrords and grcatl>witness for some six or seven years whit, of nn analyit or radiochemist is conrcdnce the probability of error in rrHallet,t accomplished as director of f i n d to schemes of isolation, sample cording and t,ranscrihing resillis preparation. connting geomctry and nnalgsis and onalyt,irnl research a t GrnIn vim, of the advnnc,cs and mideera1 Aniline and Film Corp. Iahornsiicli effects as hnrkFcat,trring, sclf-ablories. It x v a y R nerfect halanre hesorption, rtc. Once these are settled,
VOL. 31, NO. 4. APRIL 1959
.
73 A
INSTRUMENTATION
5 : l O P.M.: Beginning of
it
diljicult, time-cons.t:nting a m l y s i s :
Ca ry Spect ro p hot0meters Record Spectra Around the Clock,. . unattended ...with the Program Control Accessory T h i s useful accessory enables CARY SPECTROPHOTOMETERS t o automatically repeat spectral scans at predetermined time intervals. Scans may be repeated at intervals ranging f r o m as little a s 10 minutes t o 24 hours, and may be spaced in a n y desired program. Some laboratories almost double t h e usefulness of their CARY SPECTROPHOTOMETERS by using them during t h e day on routine work, then setting them up with t h e Prclgram Control f o r automatic analysis d u r i n g the night. However, automatic programming i s j u s t one feature which d e m o n s t r a t e s t h e unmatched v e r s a t i l i t y of CARY SPECTROPHOTOMETERS. The wide wavelength range, high resolution, low s t r a y light, plus t h e availability of a number of useful accessories f o r other measurement techniques, enable Cary Instruments to serve a wide analytical field. Complete information on these versatile instruments is yours f o r t h e asking. Write f o r D a t a File A13-49.
A P P L I E D PHvSlCS C O R P O R A T l O N 2 7 Z S S O U T H P E C K Circle No. 33 on Readers' Service Card
74 A
ANALYTICAL CHEMISTRY
ROAD. MONRDVIA,CALIFORNIA
the last ten years, all users of radiochemical techniques should periodically review their operation to determine whether or not they too can enjoy its benefits. There are a number of interesting ways in which automatic sample counting equipment can be used, apart from the immediately obvious one of expediting routine sample counting. Laboratories studying the half lives of short-lived isotopes obtained from atomic piles, particle accelerator, or neutron activation, have found the automatic sample changer a convenient way to make half life measurements. -4single sample is inserted in an automatic changer and the unit is set to cycle continuously. Under these conditions, the sample is counted every 250 seconds. Several hours or days of counting generally provide sufficient data for an accurate determination of t'he half life. The scanning motor on a pulse heig!it analyzer is set to complete its scan 111, say, 10 minutes. A scaler-ratemeter with preset time feature is also set for 10 minutes and a st,rip-chart recorder is attached to the ratemeter. The recorder thus automatically provides a permanent pulse height spectrum record for all samples inserted. A less elaborate system incorporates a dual channel analyzer into t'he unit and analyzes samples of two separate energy peaks and reports its results separately. With regard 'to 'spectrometry, it is important t o remember that most spectrometry requirements can be incorporated into an automatic sample counting system with but minor moclifications t o the standard instrument setup. An impressive number of instruments ancl devices have been developed t o perform automatic sample counting. Typical of these are the standard automatic sample changer and the automatic windowless flow sample counter. The operat'ion of both units is simple and reliable. On the former up to 25 standard 1-inch samples are placed into slot's on the circumference of a large circular turntable. An arm with a 1-inch ring is lowered over the sample and slides it into the shielded detector unit. When fully inserted, a relay starts a scaler. When the scaler reaches either a preset time or a preset count, the scaler stops counting and relays this information t o a data recording printer. Simultaneously, the arm withdraws the sample, the turntable is advanced one position, and the next sample is inserted for counting. The 'entire operation (after loading) is performed without attention from working personnel. The unit can be set t o cycle once, twice, three times, or continuously. The detector shield used with this type of sample changer is particularly versatile and will accommodate standard Jeiger, proportional, scintillation, and Row-type Geiger detectors.
A new photoelectric instrument of high accuracy for the measurement of pale colors and faint turbidities. For all analytical colorimetric determinations i n which only a slight coloration can be developed. 0 For sanitary examination of drinkable water and for analysis of water for municipal and industrial purposes. 0 For color standardization of lightly colored liquids such as kerosenes, sugar solutions, solvents, varnishes, liquid waxes, vegetable. oils, beverages, cosmetics. Replaces visual color comparison i n Nessler tubes.
Circle Ne. 87-2 en
Readers' Senics Card
I
-Circle No. 87-3 on Readers' service Card VOL. 31, N3. 4, APRIL 1959
75 A
INSTRUMENTATION
N e w Eldorado S C 700 Decimal Scaler.with
better than I microsecond resolution Designed for general radiation counting, Eldolado's compact n e w SC700 Decimal Scaler provides high performance a t a budget price, $595. FEATURE S
0
-
Small Size 31/2" panel height, weighs only 16 pounds. 25 Millivolt Sensitivity Seven Decades of Count Storage Calibrated Input Amplifier See our exhibit at the Atom Fair,
Precision Iittegral Discriminator Building Block Construction Built-in le!,! Circuit Provision for External Timer
For complete technical infoi mation, please address Dept. A 4
lectronics
A Cleveland, nril5-10 Bboih 8 11
2621 TENTH ST.
BERKELEY 70, CALIF. Phone THornwall 1-4613
Circle No. 56 on Readers' Service Card
intensity microsource assures fastest exposure on large lattice materials or microsamples. No need for large, hard-to-grow crystals. Write for new catalog today.
ONLY MICRC3-FOCUS OFFERS:
0 0 0 0
Greater x-ray flux Less scattered radiation Superior resolution Shortest exposure
32 Farwell Street, Newtonville 60, Massachusetts Circle NO. 121 on Readers' Servicecard
76 A
o
ANALYTICAL CHEMISTRY
13
An automatic windowless sample counter is usually used when a large number of relatively weak samples must be counted with maximum efficiency. These counters may operate in either the Geiger or proportional region. Up t o fifty samples of any size up to 2 inches in diameter can be RCcommodated by this unit. The samples are placed on special planchet holders and loaded into a clear glass sample tower which is clamped onto the main unit. The sample changing mechanism takes a sample froin the bottom of t,hie tower and inserts it into the gas filled counting chamber. When the sample has been counted the information is fed to the data recording printer, the sample is removed from the detector and raised into a glass collecting tower. This operation is repeated until all samples have been counted. Geiger or proportional gas is fed first to the tletector and from the detector is split into two streams and vented after passing through the sample towers, thus keeping all samples in a sea!ed atmosphere of counting gas a t all times. The importance of a detector's ability t o accommodate extra large samples is one that cannot be overemphasized. If sufficient active material is available to prepare 2-inch samples a marked reduction can be made either in counting time or the lower limit of specific activity detectable. For example, 1inch samples of BaC03 (infinitely thick) with an absolute specific activity of approximately 1.0 d.p.m./mg. can be counted t o a 5% probable error in approximately 100 minutes on the SC-SOB. If 2-inch samples of the same material are prepared, only 22 minutes are required for similar results. In addition to the basic equipment described above, these automatic S R ~ I ple counting systems include a scaler and data recording printer. The scaler used contains special connectors and relay circuits, which are necessary to activate the changer itself and the dntx printer. It should also contain both preset count and preset time controls. Because it is usually desirable to count all samples to the same probable error, the preset count is .an essential feature. Since on occasions a very. weak sample is encountered, preset time is a desirable feature to cut short ally unprofitably long counting run. The data recording printer provides a permanent record of the sample number and the time required for a given nnmber of counts.
In our own nuclear researches, for lack of manpower, it has been found necessary t o embark on an extensive program of automation and the design of mechanisms using relays and pneumatic devices to perform routine manipulations. These enable one t o collect data overnight and leave regular hours for setting up new experiments and collating data.
