Topics in..
.
I
Chemical Instrumentation Edited by GALEN W. EWING, Seton Hall University, So. O r a n g e , N. J. 07079
Swiss owned company, markets three highperformance models: HX-60, HX-90, and HFX-90, each of which has multinuclear and wide-line capabilities. These models have an advanced transmitter system composed of three crystal-stabilized oscillators whose difference frequencies are phase locked fol. extra stability. The versat,ile "universal" probe used in all three models xllows change of frequency range by changing one console setling and some plug-in units. The saphistieated IIFX-00 (Fig. 5 ) has a. wide range sweep nystem which allows ohservrtt.ion of any nriclem without special modification.: and two frequency sweep units which furuish flexibilit,y for multiple resonance work.
These ariicles are intended to serve the readers O ~ T H I JOURNAL S by calling attention to new developments i n the theory, design, or availability oj chemical laboralory instrumentalion, or by presenting useful insights and ezplanations of lopics that are of practical imporlance to those who use, m leach lhe use of, modern instrumentation and instrumental techniques. The edilor invites correspondence from prospective contribulors.
LVII. Nuclear Magnetic Resonance Spectrometers-Part Two: Commercial Spectrometers DARRYL G. HOWERY, Deportment o f Chemistry, Brooklyn College of the City University of New York, Brooklyn, N. Y. 11210 INTRODUCTION I n Part, One of this two-part article we presented the main feat,ures of the instrumentation of current high-resolntion nmr spectrometerr. The main objec1,ive of Part Two is to summarize the desieu features of represent,ntive spectromet,ers cnrrenlly sold in t,he U. S. A brief discnssian of pulsed-wave, Fomier-transform and wide-he nmr spectroscopy will he inrluded. I n an eliort to keep the discussion as general R R pmsible, we deliberately avoided referrine ill P a r t One to narticular models. Now we shnll specify the performance and main foatnres of eneh current commercial spectrometer, The information cited is based upon the manufacturer's literature and opon consullations with company representatives. We makenovalue judgements since only long-term use of t,he varions models would justify evaluations. Ptxxpoctive porchasers of nmr spectrometers can acquire further informntion about performance, ease of operation .and upkeep (inchding extent of downtime and reliability of repair service) by contacting ot,her researchers who have used the model of inlerest,. ~
-
~
HIGH RESOLUTION MODELS Probably the most satisfsctory classificntiorr of high-resolntion nmr spectrornetors is based upon the field strength of the spectrometer's magnet. hlosl 60 MHz models are relatively inexpensive, easy-t,o-operate, routine, proton instruments which can be w e d for instruction and for most research. Speclrameters wibh greater field strengbhs are typically relatively expensive, less routinely operated units which are required only for more demanding or specialized research.
Flexibility is nn extlwnely imporbant factor which varies considernhly from model to model. A listing of represendetive nmr spectrometers grouped according to magnet strength nud overdl sophisticat,ion is given in Table 2. This compilation serves as the focal point of this article. The values of sensitivity, ~.esolntion, resolution stabilit,y, and spectral reproducibility arc useful far comparing instrument performance, while comparisons of nuclear and other capabilities indicate relative fl.exihiliby. Sbandnrds of performance and flexihilityhme risen steadily. T h e original Vrrrian A-60 had s sensitivity of 5 and n resolntion of 0.6, both below current minimum standards. Each spectrometer is described in grealer detail in brochures available from the manufactnrer upon request. The compauy literature is usually profosely illustrated with phot,ogr&phs,spectra, and diagrams. Recent, spectrometer design emphasizes comoactness with ~ e n e r e ltrends toward the use of modular construction, printed circuit boards, and solid-state componenbs. Modldar units are eonvenionl to sorvieo and can be readily altered to ,zccammodate new design features. The following models have entirely solid-state consoles: JNM-MH-60, It-12A, T-60, HX-GO, J N W MH-100, HX-90, JNM-PS-100, XL-100, snd HFX-90. The interfacing of highresolution spectrometers wit,h small computers is itnother significant trend. Since the main features are summarized in Tnhle 2, a detailed description of each model is unnecessary. I n the brief company-by-company survey which follows, uniqne advnuees and features not covered in Table 2 will he inclodod. Bmker-Scientific, Inc. (Cross Westchester Industrial Park, Elmsford, N. Y. 10523): Bntker-Scientific, a German-
Figure 5. Scientific).
Bruker HFX-PO.
lCourtery Bruker-
JEOLCO (USA.), Inc. (477 Riverside Ave., Rledford, hlass. 02155): JEOLCO, prodocers of nmr spectrometers since 1956, ranks second in the numher of units now in me in tho U. S. This Japanese owned company atiers two classes of high-resolution spectrometers: (a) compact, routine "miNi.\lnR" pmton units JNM-IMH-60 and JN.\I-IIH-100 (Fig. 6); and (b) high performance mullinuclear models JN.\I-C-6OHL (Fig. 7) and JNhI-PS-100. The 1111-60 :and the relatively inexpensive 1111-100 incorporate a lock sysbem whicll allow the spectrometer la be maintnined in exlemal lork when lhere is I I , sample in (he probe bnt aulomatic,zIly switches to i n t w t d lock upon inserl.ing n sample. All JEOLCO models circulate the~mostntted water through prohe heal-sink plates to minimize homogetmity rhnngos during
Figure 6. JEOLCO JNM-MH-100. JEOLCO 1U.S.A.)).
lCovrtesy
(Continued on page AA9O)
Volume 48, Number 6, June 1971
/
A389
Toble 2.
Varian EM-300
1970
30
P
3
2.0
JEOLCO JNM-MH-60-11
1969
60
E
18
0.4
0.4/16
I, E
0.2
Perkin-Elmer R-12A
1969
60
P
20
0.35
0.3/48
I
0.2
Varian T-60
1967
60
P
18
0.5
0.5/24
I, U
Varian A-60D
1968
60
E
18
0.3
0.3/16
Perkin-Elmer R-20B
1970
60
P
30
0.3
JEOLCO JNM-C-6OHL
1968
60
E
30
Bruker HX-60
1968
60
E
JEOLCO JNM-MH-100
1970
100
Vsrirtn HA-100D
1967
Bruker HX-90
Company and Model
Resolutiond
Spectral reproducibilityg -
Resolution stability' -
Introduced in USA
SensiStandard ireMagnet tivquency* type' ity
High Resolution NMR Spectrometers
Lock typef
U
Nuclear cap&Sweeph bilityy'
Variable T range, 'C
Additional capabilities!
Price*
H
None
H
-50/150
Ho
F
- 100/150
0.3
Ho
M
-100/100
I, E
0.4
Ho
H
-150/200
0.2/16
E
0.2
Y
M
- 120/200
het, trp, st8
0.3
0.4/16
I, E
0.2
Ho,
v
M
-150/200
bet, trp, st8, suto, wl
35
40
0.15
0.3/24
I
0.1
o , v
M
-150/200
bet, st15, wl
54
E
40
0.5
0.4/16
I, E
0.2
Ho,
v
H
-70/170
trp, auto
40
100
E
40
0.3
0.3/16
I
0.3
Ho,
v
M
-150/200
het, st8, auto
59
1968
90
E
50
0.2
0.3/24
I
0.1
Ha,
v
M
-150/200
het, st15, auto, wl
70
JEOLCO JNM-PS-100
1970
100
E
50
0.3
0.4/16
I, E
0.2
Ho,
v
M
- 150/200
het, trp, st12, auto, wl
70
Varian XGlOO
1969
100
E
50
0.3
0.3/24
I, E
0.1
M
-150/200
het, st15, auto
93
Bruker HFX-90
1968
90
E
50
0.15
0.3/24
I
0.1
Ho, v
M
-150/200
het, st15, auto, wl
82
Vssian HR-220
1968
220
S
55
1.1
-
I
0.2/hr
Ha,
v
M
-50/150
bet, trp
160
2 Varian HR-ROO
1970
300
S
65
1.5
-
I
02/hr
,
v
M
-50/150
bet, trp
220
z-
-
Ho
6
tT
24 29
het, trp
27 38 -36
Data furnished by the manufscturers. -,information lacking. a MHz for proton resonance; protons resonate at frequencies of 30 60, 90, 100, 220, and 300 MHz in magnetic fields of P = ermanent, E = electro-, S = superwnducting solenoid. signal-to-nke ratio minimum value; determined from the largest a 7046 14092, 21140, 23490,51700, and 70500 G, respectively. n -ethylbenzene. dHz; determined from the width at half height of specified peaks ip the spectrum of o,diohloropeak'in the methylene quartet in the spectrum of a. 1% (V/V in ~ ~ L P s o l u t i oof Hz; deternuned, unless otherwise noted, benzene. * Ha/hr; determined from the maximum increase of a. peek width during the specified time. 1 U = unlocked, I = internal, E = external. a from the average deviation of five 5-minute scans. * HHo= field, v = frequency. H = proton onl F = 1H and >OF,M = multinuclear. 1 auto = automatic !/-gradient control, het = heteronuclear spin decoupling (all models except the A-60D can simulate frequency-swept proton spin &coupling), st = larger sample tube with maximum o.d. in mm (all mod& use 5-mm tubes), are for the baslc spectrometer plus trp = triple resonance, wl = wide line; in many cases, accessory equipment must be purchased. L Nearest 81,000 including duty, November, 1970; p r j c ~ g varisble temperature unit, lock system and proton spin dewupler (except for the EM-300 which has no accessories); in many cases the price includes addhonill features.
'
-
Q
Chemical instrumentation
Figure 7. JEOLCO JEOLCO iU.S.A.)).
JNM-C-60HL.
(Courtesy
variable temperature or high power decoupling experiments. Perkin-Elmer Corporation (Main Ave., Norwalk, Conn. 06852): Perkin-Elmer, a U. S. company with an English subsidiary, ~ioneeredthe use of permanent magnets for cammercisl nmr spectrometers. The company produces two 60 MHz models, R-12A and R-20B, bath of which employ thermostatted permanent magnets. The easy-ta-operate R-12A (Fig. 8) has a. unique cross-coil probe design and s. variable temperature probe which ut,ilises the Joule-Thomsan effect for cooling the gas stream. The It-20B uses s widerange radio-frequency sweep and a novel ext,ernsl lock sysbem to facilitate the ~ l u d of y many nuclei. Varian Associates (Analytical Instrument Division, 611 Hansen Way, Palo Alto, Calif. 94303): Varian has been by far the leading producer of nmr spectrometers in the U. S. The company now markets a low sensitivity 30 MHz proton model: EM-300; two moderately high capability models: T-60 and A-60D; and four advanced models: HA-100, XL-100, HR-220, and HR-300. The development of the inexpensive EM-300 (Fig. 8) pl.omises to drnmntically increase ,
Figure 8. time
Perkin-Elmer R - 1 2 A rhowing digital to the top left, (courtery
Perkin-Elmer).
Figure9.
,,.
,
.
,
VorionEM-300.
(Covrteryvorianl.
(Conlinz,erl on pago A.XI4) - -. p p
A392
/
journal o f Chemical Education
Chemical Instrumentation
Other Modes of NMR Operotion There are four basic modes of nmr operation: (a) high-resolut,ion continnon8wave, (1,) pulsed-wnvo, (el Fooriertransform, pulsed-wave, and ( d ) wideline. Nuclear quadwpole resonance, which has some features in common with nmr. has heen diwnssed thorowhlv ~"., in TIns JOURNAI,in s four-part, article just proceding this orre (5). Pulsed-Wave NMR-In p~tlsed-wave nrnr the sample is irradiated with n short dwation rf n11Ise having R frea~tencv . . e q l d t.o t,he Gesonnnce fr&eney of t,he nucleus being observed. Annlysis of t,he rate of decay of the nrnr fiignal after termination of the pulse allom cnlcdation of characteristic rolaxnt,ion times. A modified proeedme cdled the method of spin echos nt,ilioes a carefully t,imed series of int,ense very short dnr;~(ion pulses. Applications of pulsed methods iuelude tho determination of self diffusion eoefficients iu liquids m d of kinetic parameters. Pulsed mdhods have seldom heen employed by rhemists. Cnrrenily marketed pulsed-wave nrnr spectrome1el.s are (a) JEOLCO .JSE40, ( b ) NMII Specidlies PS-Series: 60AW, GOIIW, and 100 AW, and (c) 13ntker n-KII series: 301s, 302s, 303s, 3218, 3225, nnd 323s. Pulsed models generally cost betwcon $20,000 a i d $30,000, x figure whirh would he considerably higher were i t not for the ~diltively undemanding requirements on the homogeneity of the magnetic field. The variable temperntrlre range wailable is -170 t o 200°C or hebter. Some of the Bruker models, e.g., the R-KR 321s shown in Figure 11, offer vxrinhle frequency operation. The development of multichannel sequence synihesizers represents a sig~~ifieant, ndv m r e in poked-wave instt~omentaiion. For additional information on pulsed nrnr the reader cnrr consdt the literature pot out, by Brrtker-Scientific a d NXlll Specialties (1410 Greenberg Rd., Now Kensington, PR.15068). Fourier-Transform NMR-The suceessful demonstraiion in 1!166 by Varisn of Foorier-transform, pulsed-wave (Ft) spectroscopy was a. major event in the development of rrmr. In F t nmr t h e sample is perturbed with a n intense, short duration pnlse having a frequency range encompassing the entire range of resonwee frequencies of t h e nucleus being studied. The free induction decay signal produced, ~~~
Figure 10.
Varian HR-220.
1Courfery Varian).
tho use of nmr industrinlly and nmdemienlly. A sample prehenter 2nd automsiic operating mode nre features of the T-60. Nearly all elremists who have done nrnr research are familiar with the A-60 serios which has easily been the best seller in the field. The XL-100 is all advanced instmment eomparahle to the Brrtker IIFX-90. All rf signals in the XL-100 are synchron i d with a, deulerinm master oscillntor; precise digital control of offsets and sweeps is handled by Lwo buil1.-in ireqnen?.y hynthesisers. At present the III
