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ACD/Labs Blog

Arvin Moser
A calculated neutral loss spectrum is obtained from a mass spectrum by determining the mass differences between the precursor ion m/z and each of the other peaks in the spectrum and plotting the original intensity versus neutral mass. Neutral losses with small masses have limited possibilities for their composition and thus can facilitate the identification...

Arvin Moser
Without any structural information, we can estimate an upper limit on the number of carbons using the m/z for the molecular ion. For the molecular ion at m/z 386.4 Da (shown in the mass spectrum below), the upper limit on the number of carbons is calculated at 386.4 / 12 = 32.2. Rounding down, we...

Arvin Moser
MS data collected off an instrument is presented as either profile or centroid mode. Shown below are two mass spectra illustrating an ion cluster for profile data and a centroid mass spectrum created from the profile data. In profile mode, a peak is represented by a collection of signals over several scans. The advantage of...

Arvin Moser
On an MS dataset, the x-axis is a measure of the mass to charge (m/z) ratio. Although it is easy to classify a signal as belonging to a singly charged ion (+1 or -1), one needs to be capable of recognizing a multiply charged (+2, -2, +3, etc.) ion as not to misinterpret the MS...

Arvin Moser
As would-be elucidators dive into an elucidation for an organic unknown, narrowing down a single molecular formula (MF) becomes vital in simplifying the elucidation. However, one hurdle quickly leads into another. As the total atom count adds up, the number of possible isomers increases just as much (See Table and Graph below). I can’t imagine...

ACDLabs
Let me begin by stating my experiences with elucidations on organic molecules. I have led over 60 training sessions attended by chemists and Spectroscopists from Academia to industry around the world. Some more successful than others—this came down to expertise of the attendee. I have also conversed with dozens of chemists/Spectroscopists, experts and non-experts, at...