Abstract
A new method for the measurement of accurate masses using direct infusion in an electrospray-triple quadrupole mass spectrometer is presented and compared to the traditional method using high-resolution mass spectrometry. The proposed method uses internal calibrants and post-acquisition calibration of the mass spectrum signal using the MassWorks software to determine accurate masses. Then, based on parameters such as elemental composition, number of double bond equivalents, and type of ion (even- or odd-electron), etc., a list of potential molecular formula candidates are generated and ranked according to spectral accuracy, (i.e., similarity between the calibrated profile and theoretical isotopic patterns). Experiments using six diverse synthesis products showed that mass accuracy in the Quattro Premier triple quadrupole mass spectrometer (QqQMS) was ≤9.2 mDa and spectral accuracy was ≥90.6%. According to both mass accuracy tolerance (±10 mDa) and spectral accuracy, the correct molecular formula was ranked in the top seven compounds out of up to 32 potential candidates. When considering the context of the synthesis reaction, only one formula was possible. In summary, results showed that the measurement of spectral accuracy in a low-resolution instrument such as the triple quadrupole was strongly dependent on the signal intensity and the presence of interfering peaks in the profile mass range window. This study suggests that use of triple quadrupole mass spectrometry followed by post-acquisition calibration can be an economical and robust approach compared to the traditional method using high-resolution mass spectrometers for the measurement of accurate masses in routine applications using small organic molecules at microgram-per-litter concentrations in relatively clean matrices.
Highlights
The application of accurate mass measurements for the determination of molecular formulas of reaction products is a well-established technique in organic chemistry [1]
Mass accuracy improved up to 376 mDa. These results demonstrate that MassWorks software is able to correct large deviations in mass accuracy by using three-to-four internal calibrants
A new method for the determination of the mass accuracy (∆m) of small organic molecules using low-resolution mass spectrometry followed by post-acquisition calibration was compared to the traditional method based on high-resolution mass spectrometry
Summary
The application of accurate mass measurements for the determination of molecular formulas of reaction products is a well-established technique in organic chemistry [1] This technique was first proposed by Beynon [2], and is essential in the toolbox of routine techniques performed by modern organic chemists to verify the success of synthesis experiments. Such mass measurements are performed with high-resolution instruments like magnetic sectors or time-of-flight mass spectrometers that can measure masses with high accuracy, usually with a mass error lower than a few millidaltons. There have been previous works using liquid chromatography coupled to quadrupole mass analyzers for the accurate mass measurement of small organic molecules
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
