1、Designation: E2977 14E2977 15Standard 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
2、 oforiginal 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 and report
3、ing the performance of Fourier-transform nuclear magneticresonance spectrometers (FT-NMRs) using liquid samples.1.2 This practice is not directly applicable to FT-NMR spectrometers outfitted to measure gaseous, anisotropically structuredliquid, semi-solid, or solid samples; those set up to work with
4、 flowing sample streams; or those used to make hyperpolarizationmeasurements.1.3 This practice was expressly developed for FT-NMR spectrometers operating with proton resonance frequencies between 200and 1200 MHz.1.4 This practice is not directly applicable to continuous wave (scanning) NMR spectrome
5、ters.1.5 This practice is not directly applicable to instruments using single-sideband detection.1.6 UnitsThe values stated in SI units are to be regarded as the standard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of the safety conce
6、rns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E131 Terminology Relating to Molecular Spec
7、troscopyE386 Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance (NMR) Spectroscopy2.2 ISO Standard:3ISO Guide 31 Reference MaterialsContents of Certificates and Labels3. Terminology3.1 DefinitionsFor definitions of terms used in this practice, refer to Terminology
8、E131, Practice E386, and Refs (1-4).4Chemical shifts are usually given in the dimensionless quantity, , commonly expressed in parts per million. For a given nucleus,the chemical shift scale is relative and is commonly pegged to the resonance of an agreed upon reference material as describedby Eq 1.s
9、ample5sample 2 reference!reference (1)3.1.1 Frequencies are given in Hertz. Because the numerator is very small compared with the denominator, it is usuallyconvenient to express in parts per million.1 This test method is under the jurisdiction of ASTM Committee E13 on Molecular Spectroscopy and Sepa
10、ration Science and is the direct responsibility of SubcommitteeE13.15 on Analytical Data.Current edition approved Aug. 1, 2014May 1, 2015. Published September 2014May 2015. Originally approved in 2014. Last previous edition approved in 2014 asE297714. DOI: 10.1520/E2977-14.10.1520/E2977-15.2 For ref
11、erencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 4
12、3rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.4 The boldface numbers in parentheses refer to the list of references at the end of this standard.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made
13、 to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyr
14、ight ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2 As the location of a resonance is determined in part by the ratio of the magnetic field to the radio frequency at which itis observed, chemical shifts and spectral regions are often des
15、ignated as lower frequency (increased shielding) or higher frequency(decreased shielding) relative to a reference point. Defined in this manner, chemical shifts are independent of either the magneticfield or the radio frequency used. Coupling constants, which are independent of the magnetic field or
16、 radio frequency used, areexpressed in Hertz.3.1.3 nuclear magnetic resonance (NMR) tube camber, nmaximum total deflection of any part of the outer wall of the tubeheld at the ends and rotated 360; a measure of the bow in the tube.3.1.4 NMR tube concentricity, nmaximum variation in wall thickness of
17、 the tube; a measure of how centered the tube insidediameter is relative to the tube outer diameter.4. Significance and Use4.1 This practice permits an analyst to compare the performance of an NMR spectrometer for a particular test on any given daywith the instruments prior performance for that test
18、. The practice can also provide sufficient quantitative performance informationfor problem diagnosis and solving. If complete information about how a test is carried out is supplied and sufficient replicates arecollected to substantiate statistical relevance, the tests in this practice can be used t
19、o establish the setting and meeting of relevantperformance specifications. This practice is not necessarily meant for the comparison of different instruments with each other, evenif the instruments are of the same type and model. This practice is not meant for the comparison of the performance of di
20、fferentinstruments operated under conditions differing from those specified for a particular test.5. Test Samples5.1 In general, the test samples called for in this practice are commercially available materials made explicitly for the testingof NMR spectrometer performance. The particular samples ch
21、osen 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, thecommonly accepted samples may exhibit characteristics that render them less than ideal for such uses.5.2 Each sample
22、shall be uniquely identifiable, and a certificate containing information about the sample shall be available (ISOGuide 31). In addition to the information required elsewhere in this practice, the certificate shall list the manufacturer of the sample,the date of manufacture, the name of the sample, a
23、nd a reference number (for example, sample serial or lot number) (see Fig. 1).5.3 Sample TubesAlthough sample tubes with sizes ranging from about 1- to 25-mm outside diameter (OD) are used inmodern NMR spectrometers, the 5-mm OD tube remains the most common size. To avoid detailing test procedures f
24、or all possibletube sizes, this practice specifies tests for use with 5-mm OD sample tubes. Users requiring sample tubes of differing size shouldscale the quantities, dimensions, and volumes given here to the requirements of their spectrometers taking into account any specificrecommendations of the
25、instruments manufacturer.5.3.1 The inside diameter of the sample container shall be stated along with tolerances from the manufacturer.5.3.2 The quality of the tube in terms of its concentricity and camber shall be stated. The concentricity and camber of the tubeshould be lesssmaller than 60.0250.02
26、5 mm and 60.0130.013 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 total volume of the solution.5.4.1 Unless otherwise specified, the chemical purity of each
27、component for standard samples used to test sensitivity shall be99.5 weight % and the purity of each component for all other standard samples shall be 99 weight %. The resonances ofimpurities observed in the spectrum of the standard sample should not interfere with the resonances of interest in the
28、standardsample. This usually means that the impurity peaks shall not appear within the region of the satellite peaks, particularly forresolution standard samples. However, samples with higher water content may still be usable so long as the water signal does notinterfere with the spectral test.Water
29、 content may be determined by Karl Fischer titration or by 1H NMR spectroscopy (protic wateronly). The purity of the analyte(s) shall be stated.5.4.2 Except as noted, the sample solvent should be deuterated to provide a field/frequency lock for the spectrometer, of thehighest purity commonly obtaina
30、ble, and have an atom-percent deuteration of at least 99 %. The solvents purity and level ofdeuteration shall be stated.5.4.3 When used, chemical shift standards should be of the highest purity commonly available and added to the sample toachieve a concentration approximately one tenth that of the a
31、nalyte. The purity and concentration of the chemical shift standardshall be stated.5.5 Sample PreparationEither a m/m method or a v/v method may be used for sample preparation; however, care shall betaken to assure better than 1 % accuracy in the measurements. If a v/v method is used, the densities
32、used for the liquid componentsshall be stated. Unless specified otherwise, any impurities in the final sample (including water) should be less than 10 mol % ofthe analyte concentration. The final analyte concentration and its uncertainty shall be stated.5.5.1 The sample should be sealed under nitrog
33、en or argon taking care that the final sample is near atmospheric pressure.5.5.2 Each sample tube shall bear a label stating its content and reference identifier.E2977 1525.5.3 For long-term storage, samples should be maintained in the dark to prevent photolysis. Except as noted, samples may bestore
34、d at room temperature. For long-term storage, samples containing chloroform should be kept between 25 and 8C unless thesample is known to have been deoxygenated.6. Preliminary Experimental Procedures6.1 To achieve consistent results, the following shall be completed before the performance measuremen
35、t:6.1.1 The sample temperature should be stabilized at approximately 25C, controlled during the measurement (8.16), andspecified in the report.6.1.2 The magnetic field homogeneity shall be adjusted to the best achievable on the sample to be used (8.9 8.12).6.1.3 The observe radio frequency (rf) circ
36、uitry shall be well-tuned and matched to the sample to be used. If decoupling is used,the decoupling rf circuitry shall be tuned and matched to the sample to be used.6.1.4 The 90 pulse for the probe to be used should be measured and reported. If decoupling is used, parameters, such as peakpower in H
37、ertz, mean power level in Hertz, and the decoupling modulation pattern shall be measured and reported. The decouplingpower is defined in Hertz as one divided by the duration of the decoupling channel 360 pulse in seconds at the power level beingused for decoupling.FIG. 1 Example of a Certificate of
38、Analysis for an NMR Test SampleE2977 1536.1.5 The T1 relaxation time of the specific sample resonance of interest should be measured on each sample to assure that theequilibration period is adequate. As T1 relaxation times are dependent on the specific resonance observed, sample concentration,sample
39、 temperature, magnetic field strength, and the concentration of certain impurities (most notably dissolved oxygen), basingthe equilibration period on literature T1 values is insufficient. Unless experimental conditions such as temperature or field strengthare changed, the T1 need only be determined
40、once for a sealed sample.6.1.6 For sensitivity tests in which the signal-to-noise ratio (S/N) is insufficient, signal averaging may be used. If multipletransients are collected, the resulting sensitivity value shall be adjusted as described in 7.2.6.1.7 In cases in which the natural abundance of the
41、 measured isotope is low, it may be necessary to correct the S/N for theactual abundance of the measured isotope in the sample itself. Examples of this are S/N determinations for 13C, 15N, and 29Si.6.1.8 For both sensitivity and resolution tests, decoupling should not be used unless specified.7. Rep
42、orting Results7.1 General TestsResults may be reported from determinations made by single procedures.7.2 Signal AveragingIf signal averaging is used, the measured sensitivity value shall be adjusted by dividing by the squareroot of the number of transients.7.3 Tests for Establishing and Meeting Spec
43、ificationsSpecification-level test results shall be reported as the average along withthe standard deviation of the results from ten replications of the specified test made with no intervening adjustments. Forspecification results, actual analyte concentrations and their uncertainties and tube dimen
44、sions (specifically, either the internaldiameter or the external diameter and wall thickness) shall be reported.8. Specific Test Procedures8.1 1H SensitivityThis practice describes the determination of the proton sensitivity of the NMR system.8.1.1 SampleThe sample is 0.1 % (vv) ethylbenzene in deut
45、erochloroform (chloroform-d) containing 0.003 to 0.1 % (v/v)tetramethylsilane (TMS). The density of ethylbenzene is 0.86702 g/cm3 at 20C, 0.862 64 g/cm3 at 25C, and 0.858 28 g/cm3 at30C (5). The density of chloroform-d is 1.5007 g/cm3 at 20C (6), 1.4999 g/cm3 at 25C, and 1.4906 g/cm3 at 30C (7). The
46、density of TMS is 0.6386 g/cm3 at 20C, 0.6329 g/cm3 at 25C, and 0.6274 g/cm3 at 30C (8). The ethylbenzene shall be 99.95 %pure and free from chlorinated by-products, such as (2-chloroethyl)benzene (9) and (1-chloroethyl)benzene (in chloroform-d5.12 and 1.88 ppm) (10), and care shall be taken to ensu
47、re that it has not reacted with air to produce oxygenated products (11),such as the hydroperoxide chloroform-d8 to 9 ppm (s, 1H), 5.05 ppm (q, 1H), 1.45 ppm (d, 3H) (12),sec-phenethyl alcohol(13), acetophenone (14), and benzaldehyde (15). The total contribution from all impurities (excluding water)
48、in the final sampleshall be less than 1 mol % of the ethylbenzene concentration. The peak height of the signal from dissolved water in the sampleshall be smaller than that of the methyl triplet. For very high-sensitivity systems, a more dilute sample may be used. Sensitivityshall then be converted t
49、o and clearly reported as “equivalent to 0.1 % (v/v) ethylbenzene at 25C.” The final concentration andits uncertainty shall be specified.8.1.2 Data AcquisitionThe following data acquisition parameters 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 Equilibration DelayAt least five times the T1 relaxation time of the ethylbenzene methylene resonance reduced by theacquisition time.8.1.2.3 Pulse Flip Angle
