Exponential multiplication

When processing NMR data a window function, or apodization, is often applied to the raw data before fourier transformation to enhance the appearance of the spectrum. For one dimensional spectra an exponential multiplication is often used. This window function reduces the noise at the expense of resolution.

Sensitivity in reduced diameter tubes

Sensitivity is the bane of NMR. Spectroscopists are always looking for ways of increasing it, particularly when sample is limited. One suggested method to increase sensitivity is to reduce the volume while keeping the amount of material constant, thereby increasing the concentration. This can be done by using a smaller diameter NMR tube, e.g a 3 mm or 1.7 mm tube. I have been skeptical of this method for a long time and finally decided to test how well it works.

Fill volume for 5 and 3 mm NMR tubes

While 5mm NMR tubes are the default size for solution NMR, several alternatives are available. For those with less sample 3mm, 1.7mm, and 1mm NMR tubes are available. The 1.7mm and 1mm NMR tubes really require a microprobe with reduced diameter coils, but 3mm tubes can be used in a 5mm probe. With our 1.7mm probe out of action I purchased a 3mm spinner and ran some spectra to compare the fill volumes of 5mm and 3mm tubes in our 5mm BBI probe.

How much sample do I need for a carbon?

Probably the most common question I get asked is "How much sample do I need for a carbon?" The answer is - it depends on the probe being used, the molecular weight of the compound, and how long you are prepared to run the experiment for. For most people, however, "it depends" is not a very satisfactory answer, so I've tried to find a way to get some numbers to answer the question.

The impact of poor tuning and matching

Tuning and matching is the process of optimising the frequency and resistance of the circuit that includes the detection coil. Every sample has a slightly different ionic content and so the probe should be tuned and matched for each sample. Modern NMR probes have automatic tuning and matching devices, but the Skaggs NMR Facility probes do not. Here, I look at the impact of poor tuning and matching on a 1D ¹H spectrum.

Altmetrics and citations

Publications arising from work at the SSPPS NMR Facility are tracked on the Facility's Publications webpage. Along with breakdowns of the list by year, lab and journal, this page also reports the Altmetric score for each publication. This is a measure of the attention the article has received, predominantly on social media. To see how the Altmetric score compares with citations I prepared a few graphs.

The acquisition time

In an NMR experiment the acquisition time is the period used to record the signal. Changing this value can affect the quality and appearance of your spectrum. Typically, larger acquisition times are used for one-dimensional spectra, with shorter values used in multidimensional spectra. The impact of using different acquisition times on 1D ¹H spectra are shown in this post.