Performance Benchmarks

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On this page we show a series of spectra, making a change to one parameter each time and presenting them together for easy comparison.

Sample Concentration Number of Scans Repetition Time Resolution Enhancement
Ibuprofen Click Here Click Here Click Here Click Here
Ethyl Crotonate Click Here Click Here Click Here Click Here
Ethyl Benzene Click Here Click Here Click Here

Ibuprofen

The reference spectrum for ibuprofen is a 200 mM sample in deuterated chloroform, acquired with 16 scans. A concentration of 200 mM is 20 mg of ibuprofen dissolved in 0.5 mL of solvent. For each parameter change, we will compare the new spectrum to this reference spectrum.

Reference spectrum

Reference spectrum of ibuprofen

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Concentration

Here we reduce the concentration from 200 mM to 20 mM. 20 mM is 2 mg of Ibuprofen dissolved in 0.5 mL of solvent. There is a big change in the chemical shift of the hydroxyl peak from 9.5 ppm to 4.7 ppm and you can clearly see the residual protonated chloroform in the solvent. Even though there is a reduction of signal to noise by factor of ten, at 20 mM the peaks are all still clearly visible.

200 mM vs 20 mM ibuprofen

200 mM vs 20 mM ibuprofen

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Number of Scans

Reducing the number of scans from 16 to 1 results in four times less signal to noise. However, even with one scan, all of the peaks are clearly resolved and you can still make out the carbon satellites.

16 v s 1 scan

16 v s 1 scan for ibuprofen

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Repetition Time

Running the experiment with a short delay between scans means that protons with longer relaxation times, such as aromatic protons, don’t have time to fully relax. This means the integrals are no longer accurate and are underestimated for protons with long relaxation times. In the spectra below there is a significant reduction in the aromatic proton integral such that it appears that the aromatic region accounts for three protons rather than four.

10 s vs 4 s repetition time

10 s vs 4 s repetition time for ibuprofen

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Resolution Enhancement

Resolution enhancement (in this case we are doing reference deconvolution) makes the peaks appear sharper and narrower. Resolution enhancement can reveal more useful fine structure in peaks, such as the base of the aromatic peaks in ibuprofen below. However, resolution enhancement like this comes at a cost: signal to noise. For a concentrated sample such as this, the decrease in signal to noise is not very significant compared to the resolution gained.

Resolution enhancement on and off

Resolution enhancement on and off for ibuprofen

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Ethyl Crotonate

The reference spectrum for ethyl crotonate is a 150 mM sample in deuterated chloroform, acquired with 64 scans. For ethyl crotonate, 150 mM is 8.5 mg of sample in 0.5 mL of solvent. For each parameter change, we will compare the new spectrum to this reference spectrum.

Reference spectrum of ethyl crotonate

Reference spectrum of ethyl crotonate

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Concentration

Decreasing the concentration from 150 mM to 15 mM reduces the signal to noise by a factor of 10. There is significantly more noise in the spectrum of the 15 mM sample, however the peaks are still clearly visible. Note that going to 15 mM we are only measuring 0.85 mg of ethyl crotonate!

150 mM vs 15 mM ethyl crotonate

150 mM vs 15 mM ethyl crotonate

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Number of Scans

Reducing the number of scans from 64 to 4 results in four times less signal to noise. However, even with four scans, all of the peaks are clearly resolved.

64 vs 4 scans ethyl crotonate

64 vs 4 scans ethyl crotonate

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Repetition Time

Running the experiment with a short delay between scans means that protons with longer relaxation times, such as the alkene protons in ethyl crotonate, don’t have time to fully relax. This means the integrals are no longer accurate. In the spectra below, the integrals are normalized to the six methyl protons at 1.3 and 1.9 ppm. The spectrum acquired with the short repetition time underestimates the integrals of the alkene proton at 5.8 ppm which account for 1 protons, as shown in the top spectrum acquired with a longer repetition time of 15 seconds. Note that the integral of the alkene proton at 6.9 ppm was not calculated as it overlaps with the solvent peak.

15 s vs 4 s repetition time

15 s vs 4 s repetition time

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Resolution Enhancement

Resolution enhancement (in this case we are doing reference deconvolution) makes the peaks appear sharper and narrower. Resolution enhancement can reveal more useful fine structure in peaks, such as the small quartet splitting of the doublet of quartets at 6 ppm. However, resolution enhancement like this comes at a cost: signal to noise. For a concentrated sample such as this, the decrease in signal to noise is not very significant compared to the resolution gained.

Resolution enhancement on and off ethyl crotonate

Resolution enhancement on and off ethyl crotonate

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Ethyl Benzene

The reference spectrum for ethyl benzene is a 20% v/v sample in deuterated chloroform, acquired with 8 scans. For each parameter change, we will compare the new spectrum to this reference spectrum.

Reference spectrum

Reference spectrum for ethyl benzene

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Concentration

There is a factor of 20 decrease in the signal going from the 20% sample to a 1% concentration sample. Note that the peaks are still clearly visible.

20% vs 1% Ethyl Benzene

20% vs 1% for ethyl benzene

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Number of Scans

Decreasing the number of scans from 8 to 1 scans results in just under 3 times less signal to noise.

8 scans vs 1 scan

8 scans vs 1 scan for ethyl benzene

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Resolution Enhancement

Resolution enhancement (in this case we are doing reference deconvolution) makes the peaks appear sharper and narrower. Resolution enhancement can reveal more useful fine structure in peaks. However, resolution enhancement like this comes at a cost: signal to noise. For a concentrated sample such as this, the decrease in signal to noise is not very significant compared to the resolution gained.

Resolution enhancement on and off

Resolution enhancement on and off for ethyl benzene

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