The Effect of Floor Vibrations on NMR Spectra

NMR spectra are very sensitive to floor vibrations. This can be a problem especially when the equipment is installed on the upper floors of a building. The proton spectra of chloroform in the figure below were acquired on our INOVA 500 in room 416 of D'Iorio Hall. The left hand spectrum was acquired with the vibration isolation mounts of the magnet pumped up with air. The spectrum on the right was acquired under identical conditions with the magnet sitting on the floor.

BLOG Index

University of Ottawa NMR Facility BLOG INDEX

March 2015

11B COSY

17O NMR of liquids

               H20 vs D2O

1D selective HOESY

               1H-19F

               1H-31P

1D selective NOESY measurements

               for exchanging roramers

1D TOCSY measurements

               as a function of mixing time

               for mixture analysis

1H NMR with X nucleus decoupling

               1H[11B]

               1H[13C]

               1H[19F]

               1H[27Al]

               1H[31P]

2D correlation spectroscopy (COSY)

               11B COSY

               COSY 90 vs COSY 45

               double quantum filtered

               ECOSY for measurement of coupling constants

               magnitude vs phase sensitive

               vs TOCSY

2D exchange spectroscopy (EXSY)

               and NOE (1)

               and NOE (2)

2D heteronuclear Overhauser measurement (HOESY)

2D NMR

               better data – more scans or more slices?

               data apodization

               phasing (video tutorial)

2D NOESY measurements

               19F NOESY

               and exchange (1)

               and exchange (2)

               choice of mixing time

               effect of viscosity

               phasing

               phasing (video tutorial)

               small vs large molecules

2D ROESY measurements

2D total correlation spectroscopy (TOCSY)

               HSQC - TOCSY

               TOCSY vs COSY

2H decoupling

2H NMR of liquids

               chemical shift referencing in

               on Bruker AVANCE spectrometers

Acoustic Ringing

               backward linear prediction to correct for

               pulse sequence to minimize

ASCII file generation

               in TOPSPIN (1)

               in TOPSPIN (2)

B1 Homogeneity

Background signals

               11B

               23Na

               from dirty NMR probe

Background suppression

               11B in liquids

               11B in solids

Baseline correction

               improving

               in 2D NMR spectra

               in solids MAS spectra of quadrupolar nuclides

Benchtop NMR

               (1)

               (2)

BIRD filter

Bloch decay vs Cross polarization

Chemical equivalence

Chemical exchange agents for spectral simplification

               D2O shake

               trifluorocaetic acid

Chemical shift referencing

               1H in aqueous solution

               external

               in 2H NMR

Chemical shift tensors

               and MAS sideband manifolds (1)

               and MAS sideband manifolds (2)

               effect of sample grinding on the measurement of

               from static CP spectra

               measurement from static solids spectra

Chemical shifts

               concentration dependent

               solvent effects – improving chemical shift resolution

               temperature dependent

Concentration gradients

               effect on spectral quality (1)

               effect on spectral quality (2)

Coupling

               13C – 14N

               13C-14N-31P

               13C – 19F

               13C – 2H (1)

               13C - 2H (2)

               13C – 2H (3)

               13C - 59Co

               coupling between magnetically equivalent nuclei

               signs of coupling constants vis ECOSY

               virtual

Cross polarization for solid and CPMAS

               CPMAS of household dust

               effect of contact time

               effect of MAS spinning speed

               effect of quadrupolar nuclides on spin I = ½ nuclides (1)

               effect of quadrupolar nuclides on spin I = ½ nuclides (2)

               field dependence of chemical shift resolution in

               importance of Hartman-Hahn match

               in relation to MAS and high power decoupling

               measurement of 13C 90 degree pulses with

               measurement of relaxation times with

               optimizing 1H decoupling in

               ramped contact pulses

               sensitivity improvement from

               to distinguish solid polymorphs

               vs Bloch decay

               with FSLG HETCOR

Cross polarization with dipolar dephasing for solids

               as an assignment tool

               effect of spinning speed

               with long dephasing delays (1)

               with long dephasing delays (2)

Decoupler pulse calibration

               in liquids

               in solids

Decoupling

               1H and 31P decoupling

               1H decoupling and 13C signal-to-noise ratio

               1H decoupling and 31P signal-to-noise ratio

               11B decoupling

               13C decoupling

               19F decoupling

               2H decoupling

               27Al decoupling

               31P decoupling

               high power 1H decoupling in solids

               homonuclear decoupling

               modes of heteronuclear decoupling in liquids

DEPT

               and quaternary alkyne carbon sites

               APT vs DEPT 135

               effect of 1H tuning on

               missing signals in

               of “acetone-d6”

               of “perdeuterated “ solvents

               vs DEPTQ

               with 29Si

DEPTQ

               vs DEPT

Diffusion and DOSY

               diffusion in CPMG measurements

               DOSY

Digital Filtering

Double presaturation

Dummy scans

Dynamic nuclear polarization (DNP)

Dynamic processes studied by 1D NMR

               exchange studied by saturation transfer

               exchanging rotamers

               the NMR time scale

Earth’s field NMR

Echoes

               CPMG

               Fourier transform of

               gradient spin echoes and selective excitation

               simple spin echo

               to remove 11B background in solids

Exponential line broadening

               tutorial video

EZ NMR

               tutorial video

Floor vibrations

               effect on NMR spectra

Food and drink

               candy cane

               coffee

               fruit cake

               popcorn

               rum and eggnog

               shortbread cookies

Free induction decay

               effects of truncation

Frequency shifted Lee-Goldberg CP-HETCOR for solids (CP-FSLG HETCOR)

Heat dissipation in Bruker spectrometers

Heteronuclear double quantum filter

HMBC experiments

               HMQC responses in HMBC spectra

               measuring  19F – 13C coupling in 1H - 13C HMBC

               missing signals in              

               Nyquist fold-backs in

HMQC, HSQC and edited HSQC experiments

               1H – 11B

               19F – 13C

               31P -109Ag

               31P – 13C

               doubled signals / poor decoupling

               HMQC vs HSQC

               HSQC - TOCSY

               HSQC vs edited HSQC

               isotope effects in 19F – 13C HMQC

               multiple bond or weak one-bond correlations in

               removing t1 noise in

Homonuclear 1H decoupling

               Bloch-Siegert shifts

               broadband 1H decoupled 1H spectra

HSQC-TOCSY

iPad / iPhone apps

               Bruker Almanac

               educational

               Stanford University course on Fourier transforms vis iTunes U

Isotope effects

               acetone

               chloroform

               complexed solvents

               ethane

               in 19F – 13C HMQC

               methylene chloride

               “perdeuterated” solvents

               triphenyl phosphate

               water    

Kinetic measurements

Lineshape specification

               erroneous

Linear prediction

               backward

               backward LP to correct for receiver overload

               forward

               forward LP for 2D data

Liquid crystalline samples

Lock

               consequence of locking on the wrong solvent

               how high should the lock signal be?

               paramagnetic samples

               spectra acquired with a sweeping field

               spectral distortion from weak lock signal

               Varian

Magic angle spinning for solids (MAS)

               1H MAS

               and available rf field

               effect on Hartman-Hahn match

               field dependence of chemical shift resolution

               how fast to spin

               how much sample

               increasing signal-to-noise ration in

               setting the magic angle (1)

               setting the magic angle (2)

               solution vs MAS spectra

               rotor crashes

Magnet

               accessing a used magnet

               measurement of field drift

               quench

Magnet cryogen fills and spectral quality

               helium fills

               helium one-way valve oscillation

               nitrogen fills

               nitrogen pressure in the magnet

Magnetic equivalence

Magnetic resonance imaging (MRI)

               gradient calibration / 1D MRI

               MRI photocopier

               Nyquist fold-backs in MRI images

               slice selection

               why MRI scanners are loud

Measurement of long range C-H coupling constants

NMR acronyms

NMR of more than one isotope

               23Na and 51V

NMR spectra without pulses

NMR spectrum frequency scale

NMR spectrum of dust (13C CPMAS)

NMR spectrum of hand cream (1H and 13C)

NMR spectrum of natural gas (1H)

NMR spectrum of TMS (1H)

NMR time scale

NMR tube thickness

NOE’s and decoupling

               negative NOE’s and decoupling

               positive NOE’s and decoupling

Nyquist fold-backs

               and digital filtering

               and mode of data acquisition

               in HMBC data

               in MRI

               used to enhance satellite transitions in quadrupolar nuclides

Paramagnetism

               13C spectra of paramagnetic compounds

               determination of paramagnetic susceptibility

               establishing the 2H lock for paramagnetic samples

               paramagnetic shifts

               the effect of paramagnetic oxygen

Phase of an NMR spectrum

               first order phase errors

               phasing a 1D spectrum (video tutorial)

               phasing a 2D spectrum (video tutorial)

Probes

               broadband vs inverse broadband

               coil geometry

               solids

               why so expensive

Probe arcing

Probe tuning and matching

               effect of 1H tuning on 13C spectra

               effect of cable length

               effect of sample spinning

               effect on 90 degree pulse

               probe electronics

               problems with salty samples

Pulse calibration

               effect of probe tuning

               fast determination

               for shaped pulses              

               for spin I = n/2 quadrupolar nuclei in solids

               measurement of 13C pulses using cross polarization in solids

Pulse power measurements

               expressed in dB Bruker vs Varian

               expressed in Hz  

               pulses

Pulsed field gradients

               calibration

               dephasing ability

               gradient spin echoes

               recovery times

Purge pulses

QCPMG measurements

               distortions in QCPMG spectra

               for solid state 2H NMR

Quadrature detection

Quadrature images

Quadrature spikes

               how to remove

Quantitative 1H NMR

Quantitative 13C NMR

               finding lost 13C signals

Radiation damping

Receiver gain

               and signal-to-noise ratio

               backward LP to correct for receiver saturation

               distortion from mis-setting

Relaxation

               effect of paramagnetic oxygen

               faster relaxation time measurements in solids

               relaxation differences used to resolve overlapping signals

               T1 anisotropy in solids

               T1 measurement

               T1r

               T2 CPMG filter to enhance sharp lines

               T2 measurements and diffusion

               T2 vs T2*

Residual 1H signals for benzene-d6 and chloroform-d

Resolution enhancement

               by using benzene as a solvent

Retrieving empty spinners from NMR magnets

Sample limitation

               making the best of

Saturation transfer measurements

Scans

               and signal-to-noise ratio

Shaped pulses and selective excitation or broadband inversion

               broadband 180 degree pulses

               calibration

               excitation profiles (1)

               excitation profiles (2)

               for selective excitation

Shimming

               effect of concentration gradients

               effect of sample depth

               effect of sample mixing

               effect of sample volume

               effect of variable temperature gas composition

               line shapes resulting from bad shimming

               without a lock signal

Sinc distortion

Slice selection

Software for data processing

Solid polymorphs

Solid state 1H NMR

               1H spin pairs

Solid state 2H NMR spectroscopy

               echoes and Fourier transforms

               increasing signal-to-noise ratio

               measuring spectral parameters

               QCPMG

               T1 anisotropy

               to determine molecular motions

Solid state NMR vs solution state NMR

Solid state NMR using a probe for liquids

Solid state NMR spectroscopy of quadrupolar nuclides with spin I = n/2

               90 degree pulse calibration

               baseline correction

               enhancement of satellite transitions via the Nyquist sampling theorem

               field dependence

               Fourier transform of a single rotational echo

               satellite transitions

Solution state NMR vs solid state NMR

Solvent effects

               improving resolution

Solvent suppression

               absolute water suppression

               double presaturation

               presaturation

               watergate

               watergate vs presaturation

Spin locking pulses

Spin simulations

               butane

               ethane

               isopropyl groups

               quadrupolar line shapes in solids (QUEST)

               virtual coupling

Spinning liquid samples

Spinning sideband suppression in MAS spectroscopy

Steady state scans

t1 noise removal in 2D spectra

               heteronuclear (tutorial video)        

               homonuclear (tutorial video)

Textbook recommendation

Thermal noise

TRAPDOR measurements

Triple resonance experiments

               13C [2H][1H]

               13C [31P][1H]

               31P -13C HMQC with 1H decoupling

Variable temperature measurements

               temperature calibration (1)

               temperature calibration (2)

               temperature dependent chemical shifts

               temperature gradients

               variable temperature gas composition and spectral quality

               variable temperature to improve resolution

Video lectures

Video commentary by NMR experts

Video tutorials

               1D spectrum phasing

               2D spectrum phasing

               exponential line broadening

               EZ NMR

               removing t1 noise from heteronuclear 2D spectra

               removing t1 noise from homonuclear 2D spectra

Virtual coupling

Zero Filling

               and throwing away noise