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ACD/Labs Blog

Arvin Moser
On the surface, both good data and poor data offer information about an unknown compound. The challenge is to differentiate between what is good data and what is poor data. The purpose of this puzzle is to examine some poor data. From an LC-MS+ TOF dataset, an unknown compound elutes at 2.86 minutes and spans...

Arvin Moser
To identify co-eluting components on a chromatogram, one searches for any distinct differences between the components. There are basically three criteria to check the XICs (extracted ion chromatograms) for to confirm whether the m/z signals pertain to the same component: line shape, signal apex and retention time range. The XICs for m/z 188.1 and 205.1...

Arvin Moser
Sorting out what compounds are present in a mixture is a difficult task. The process is further complicated when the compounds co-elute on a chromatographic run. An LC/MS (ESI+) was collected for an unknown sample comprising of small organic molecules. The total ion chromatogram (TIC shown in black) shows a signal at 2.86 minutes. The...

Arvin Moser
The results for calculating the empirical formula for an unknown compound using data from elemental analysis are presented. An elemental analysis was collected for an unknown organic compound. A 0.30 g sample of the unknown was burned to completion and it gave 59.6 % C, 6.9 % H and 8.7 % N. The results are...

Arvin Moser
Elemental analysis is an experiment used to determine the elemental composition of an unknown compound. The purpose of this puzzle is to use the percentage composition data from elemental analysis to deduce an empirical formula. An elemental analysis was collected for an unknown organic compound. A 0.30 g sample of the unknown was burned to...

Arvin Moser
The explanation offered herein covers one possible scenario to a complicated situation. Please note that other explanations are possible. The LC/MS data shows an unknown at 1.8 minutes exhibiting an [M+H]+ at m/z 260 and an [M-H]- at m/z 256. The difference of 4 mass units lends itself into a scenario of conflicting data. One...

Arvin Moser
The purpose of this puzzle is to examine data collected from multiple detectors with the hopes of sorting out the conflicting data surrounding the unknown. In an attempt to identify the structure for an unknown, UPLC data was collected using a C18 column with a run time of 2.2 minutes. The UV, ESI- and ESI+...

Arvin Moser
As more information is needed to solve an unknown, it becomes useful to understand what information is available, make a hypothesis and then get to the grunt work of eliminating the unlikely candidates. Below is a summary explaining some of the information that can be extracted from the problem set. Given an unknown compound as...

Arvin Moser
It is fairly route for an elucidator investigating an unknown compound to relate data from multiple spectroscopies. This puzzle aims at establishing a molecular formula from a set of spectroscopic data. For an unknown organic, a ESI(neg.)-ToF mass spectrum for a singly-charged species and a 13C NMR spectrum are supplied below. In addition, the 1H...