1、Designation: E2977 14Standard Practice forMeasuring and Reporting Performance of Fourier-TransformNuclear Magnetic Resonance (FT-NMR) Spectrometers forLiquid Samples1This standard is issued under the fixed designation E2977; the number immediately following the designation indicates the year oforigi
2、nal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers procedures for measuring andreporting the p
3、erformance of Fourier-transform nuclear mag-netic resonance spectrometers (FT-NMRs) using liquidsamples.1.2 This practice is not directly applicable to FT-NMRspectrometers outfitted to measure gaseous, anisotropicallystructured liquid, semi-solid, or solid samples; those set up towork with flowing s
4、ample streams; or those used to makehyperpolarization measurements.1.3 This practice was expressly developed for FT-NMRspectrometers operating with proton resonance frequenciesbetween 200 and 1200 MHz.1.4 This practice is not directly applicable to continuouswave (scanning) NMR spectrometers.1.5 Thi
5、s practice is not directly applicable to instrumentsusing single-sideband detection.1.6 UnitsThe values stated in SI units are to be regardedas the standard. No other units of measurement are included inthis standard.1.7 This standard does not purport to address all of thesafety concerns, if any, as
6、sociated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E131 Terminology Relating to Molecular SpectroscopyE386
7、 Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance (NMR) Spec-troscopy2.2 ISO Standard:3ISO Guide 31 Reference MaterialsContents of Certificatesand Labels3. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, refer to Terminology E131, Practic
8、e E386, and Refs(1-4).4Chemical shifts are usually given in the dimensionlessquantity, , commonly expressed in parts per million. For agiven nucleus, the chemical shift scale is relative and iscommonly pegged to the resonance of an agreed upon refer-ence material as described by Eq 1.sample5 sample2
9、 reference! reference(1)3.1.1 Frequencies are given in Hertz. Because the numeratoris very small compared with the denominator, it is usuallyconvenient to express in parts per million.3.1.2 As the location of a resonance is determined in part bythe ratio of the magnetic field to the radio frequency
10、at whichit is observed, chemical shifts and spectral regions are oftendesignated as lower frequency (increased shielding) or higherfrequency (decreased shielding) relative to a reference point.Defined in this manner, chemical shifts are independent ofeither the magnetic field or the radio frequency
11、used. Couplingconstants, which are independent of the magnetic field or radiofrequency used, are expressed in Hertz.3.1.3 nuclear magnetic resonance (NMR) tube camber,nmaximum total deflection of any part of the outer wall ofthe tube held at the ends and rotated 360; a measure of thebow in the tube.
12、3.1.4 NMR tube concentricity, nmaximum variation inwall thickness of the tube; a measure of how centered the tubeinside diameter is relative to the tube outer diameter.1This test method is under the jurisdiction of ASTM Committee E13 onMolecular Spectroscopy and Separation Science and is the direct
13、responsibility ofSubcommittee E13.15 on Analytical Data.Current edition approved Aug. 1, 2014. Published September 2014. DOI:10.1520/E2977-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vol
14、ume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4The boldface numbers in parentheses refer to the list of references at the end ofthis stand
15、ard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 This practice permits an analyst to compare the perfor-mance of an NMR spectrometer for a particular test on anygiven day with the instruments prior perfor
16、mance for that test.The practice can also provide sufficient quantitative perfor-mance information for problem diagnosis and solving. Ifcomplete information about how a test is carried out is suppliedand sufficient replicates are collected to substantiate statisticalrelevance, the tests in this prac
17、tice can be used to establish thesetting and meeting of relevant performance specifications.This practice is not necessarily meant for the comparison ofdifferent instruments with each other, even if the instrumentsare of the same type and model. This practice is not meant forthe comparison of the pe
18、rformance of different instrumentsoperated under conditions differing from those specified for aparticular test.5. Test Samples5.1 In general, the test samples called for in this practice arecommercially available materials made explicitly for the test-ing of NMR spectrometer performance. The partic
19、ular sampleschosen are those that have been widely accepted by the NMRcommunity of users and vendors for these purposes. However,in certain instances, especially with higher field instruments,the commonly accepted samples may exhibit characteristicsthat render them less than ideal for such uses.5.2
20、Each sample shall be uniquely identifiable, and a cer-tificate containing information about the sample shall beavailable (ISO Guide 31). In addition to the informationrequired elsewhere in this practice, the certificate shall list themanufacturer of the sample, the date of manufacture, the nameof th
21、e sample, and a reference number (for example, sampleserial or lot number) (see Fig. 1).5.3 Sample TubesAlthough sample tubes with sizes rang-ing from about 1- to 25-mm outside diameter (OD) are used inmodern NMR spectrometers, the 5-mm OD tube remains themost common size. To avoid detailing test pr
22、ocedures for allpossible tube sizes, this practice specifies tests for use with5-mm OD sample tubes. Users requiring sample tubes ofdiffering size should scale the quantities, dimensions, andvolumes given here to the requirements of their spectrometerstaking into account any specific recommendations
23、 of theinstruments manufacturer.5.3.1 The inside diameter of the sample container shall bestated along with tolerances from the manufacturer.5.3.2 The quality of the tube in terms of its concentricity andcamber shall be stated. The concentricity and camber of thetube should be less than 60.025 mm an
24、d 60.013 mm,respectively.5.4 Analytes, Solvents, and Chemical Shift StandardsAnalyte concentration is defined as a volume percentage (v/v)at 25C, that is, the volume of the analyte divided by the totalvolume of the solution.5.4.1 Unless otherwise specified, the chemical purity ofeach component for s
25、tandard samples used to test sensitivityshall be 99.5 weight % and the purity of each component forall other standard samples shall be 99 weight %. Theresonances of impurities observed in the spectrum of thestandard sample should not interfere with the resonances ofinterest in the standard sample. T
26、his usually means that theimpurity peaks shall not appear within the region of thesatellite peaks, particularly for resolution standard samples.However, samples with higher water content may still beusable so long as the water signal does not interfere with thespectral test. Water content may be det
27、ermined by Karl Fischertitration or by1H NMR spectroscopy (protic water only). Thepurity of the analyte(s) shall be stated.5.4.2 Except as noted, the sample solvent should be deuter-ated to provide a field/frequency lock for the spectrometer, ofthe highest purity commonly obtainable, and have an ato
28、m-percent deuteration of at least 99 %. The solvents purity andlevel of deuteration shall be stated.5.4.3 When used, chemical shift standards should be of thehighest purity commonly available and added to the sample toachieve a concentration approximately one tenth that of theanalyte. The purity and
29、 concentration of the chemical shiftstandard shall be stated.5.5 Sample PreparationEither a m/m method or a v/vmethod may be used for sample preparation; however, careshall be taken to assure better than 1 % accuracy in themeasurements. If a v/v method is used, the densities used forthe liquid compo
30、nents shall be stated. Unless specifiedotherwise, any impurities in the final sample (including water)should be less than 10 mol % of the analyte concentration. Thefinal analyte concentration and its uncertainty shall be stated.5.5.1 The sample should be sealed under nitrogen or argontaking care tha
31、t the final sample is near atmospheric pressure.5.5.2 Each sample tube shall bear a label stating its contentand reference identifier.5.5.3 For long-term storage, samples should be maintainedin the dark to prevent photolysis. Except as noted, samples maybe stored at room temperature. For long-term s
32、torage, samplescontaining chloroform should be kept between 25 and 8Cunless the sample is known to have been deoxygenated.6. Preliminary Experimental Procedures6.1 To achieve consistent results, the following shall becompleted before the performance measurement:6.1.1 The sample temperature should be
33、 stabilized at ap-proximately 25C, controlled during the measurement (8.16),and specified in the report.6.1.2 The magnetic field homogeneity shall be adjusted tothe best achievable on the sample to be used (8.9 8.12).6.1.3 The observe radio frequency (rf) circuitry shall bewell-tuned and matched to
34、the sample to be used. If decouplingis used, the decoupling rf circuitry shall be tuned and matchedto the sample to be used.6.1.4 The 90 pulse for the probe to be used should bemeasured and reported. If decoupling is used, parameters, suchas peak power in Hertz, mean power level in Hertz, and thedec
35、oupling modulation pattern shall be measured and reported.The decoupling power is defined in Hertz as one divided by theduration of the decoupling channel 360 pulse in seconds at thepower level being used for decoupling.E2977 1426.1.5 The T1relaxation time of the specific sample reso-nance of intere
36、st should be measured on each sample to assurethat the equilibration period is adequate.As T1relaxation timesare dependent on the specific resonance observed, sampleconcentration, sample temperature, magnetic field strength,and the concentration of certain impurities (most notablydissolved oxygen),
37、basing the equilibration period on literatureT1values is insufficient. Unless experimental conditions suchas temperature or field strength are changed, the T1need onlybe determined once for a sealed sample.6.1.6 For sensitivity tests in which the signal-to-noise ratio(S/N) is insufficient, signal av
38、eraging may be used. If multipletransients are collected, the resulting sensitivity value shall beadjusted as described in 7.2.6.1.7 In cases in which the natural abundance of themeasured isotope is low, it may be necessary to correct the S/Nfor the actual abundance of the measured isotope in the sa
39、mpleitself. Examples of this are S/N determinations for13C,15N,and29Si.FIG. 1 Example of a Certificate of Analysis for an NMR Test SampleE2977 1436.1.8 For both sensitivity and resolution tests, decouplingshould not be used unless specified.7. Reporting Results7.1 General TestsResults may be reporte
40、d from determi-nations made by single procedures.7.2 Signal AveragingIf signal averaging is used, themeasured sensitivity value shall be adjusted by dividing by thesquare root of the number of transients.7.3 Tests for Establishing and Meeting SpecificationsSpecification-level test results shall be r
41、eported as the averagealong with the standard deviation of the results from tenreplications of the specified test made with no interveningadjustments. For specification results, actual analyte concen-trations and their uncertainties and tube dimensions(specifically, either the internal diameter or t
42、he external diam-eter and wall thickness) shall be reported.8. Specific Test Procedures8.11H SensitivityThis practice describes the determina-tion of the proton sensitivity of the NMR system.8.1.1 SampleThe sample is 0.1 % (vv) ethylbenzene indeuterochloroform (chloroform-d) containing 0.003 to 0.1
43、%(v/v) tetramethylsilane (TMS). The density of ethylbenzene is0.86702 g/cm3at 20C, 0.862 64 g/cm3at 25C, and 0.858 28g/cm3at 30C (5).The density of chloroform-d is 1.5007 g/cm3at 20C (6), 1.4999 g/cm3at 25C, and 1.4906 g/cm3at 30C(7). The density of TMS is 0.6386 g/cm3at 20C, 0.6329 g/cm3at 25C, and
44、 0.6274 g/cm3at 30C (8). The ethylbenzene shallbe 99.95 % pure and free from chlorinated by-products, such as(2-chloroethyl)benzene (9) and (1-chloroethyl)benzene (inchloroform-d5.12 and 1.88 ppm) (10), and care shall betaken to ensure that it has not reacted with air to produceoxygenated products (
45、11), such as the hydroperoxidechloroform-d8 to 9 ppm (s, 1H), 5.05 ppm (q, 1H), 1.45ppm (d, 3H) (12), sec-phenethyl alcohol (13), acetophenone(14), and benzaldehyde (15). The total contribution from allimpurities (excluding water) in the final sample shall be lessthan 1 mol % of the ethylbenzene con
46、centration. The peakheight of the signal from dissolved water in the sample shall besmaller than that of the methyl triplet. For very high-sensitivitysystems, a more dilute sample may be used. Sensitivity shallthen be converted to and clearly reported as “equivalent to0.1 % (v/v) ethylbenzene at 25C
47、.” The final concentration andits uncertainty shall be specified.8.1.2 Data AcquisitionThe following data acquisition pa-rameters shall be used:8.1.2.1 Spectral RegionThe larger of 30-ppm or 11-kHz(for proton frequencies below 400 MHz) width centered on themethylene resonance of ethylbenzene.8.1.2.2
48、 Equilibration DelayAt least five times the T1relaxation time of the ethylbenzene methylene resonancereduced by the acquisition time.8.1.2.3 Pulse Flip Angle90.8.1.2.4 Data Acquisition Time4to8s.8.1.2.5 Number of TransientsOne.8.1.2.6 Receiver GainOptimized to take advantage of thefull dynamic range
49、 of the receiver.8.1.2.7 Spinning RateThe measurement should be speci-fied as spinning or nonspinning. If the sample is spinning, itsrate shall be specified.8.1.3 Data ProcessingThe following data processing pa-rameters shall be used:8.1.3.1 Multiply the time domain data by an exponentiallydecaying function of the form e-LBtwhere LB (line broaden-ing)=1Hzandt = time value for each acquired data point.8.1.4 Zero fill to at least twice the size of the data table.Calculate the FT using sufficient data points to yield a di
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