Jeff Goshawk (Presenter)
Waters Corporation
Authorship: Nayan S Mistry, Nick Tomczyk, Martin Palmer, Jeff Goshawk and Michelle Wood
Waters Corporation, Wilmslow, UK
| Short Abstract The utility and potential benefit of collision cross-section (CCS) data, as generated through use of ion mobility separation (IMS) techniques, was evaluated for >50 toxicologically-relevant substances. Solvent standards were analysed using an established UPLC-method in combination with an IMS-QTof (Waters). Reference CCS values were measured and then incorporated into an existing toxicology library comprising retention time and exact mass data. Collision cross-section measurements were shown to be highly reproducible (within 2% of reference), both in the presence or absence of biological matrix. Use of IMS led to cleaner, low and elevated energy spectra due to the alignment of ions in drift time. CCS values provide an additional dimension of specificity which proves valuable in systematic toxicological analysis. |
Long Abstract
Introduction
Laboratories are frequently required to perform broad screening techniques to identify toxicologically-relevant analytes in complex biological samples. A number of analytical techniques are available for comprehensive screening but more recently, time-of-flight (Tof) mass spectrometry has gained popularity due to the ability to perform both targeted and non-targeted analysis. In addition to mass accuracy, substances can be identified using supporting information such as retention time (RT) and fragment ions generated by MSE (Rosano et al., 2013). The combination of such measurements can reduce false positive assignments in screening assays. However for some substances, identification can remain challenging due to the presence of co-extracted matrix interferences or structural isomers.
The incorporation of collision cross-section (CCS) data, generated through ion mobility separation (IMS) techniques, has been demonstrated to improve the accuracy of screening for pesticides in food (McCullagh et al., 2014). Thus the potential value of CCS data for toxicological analysis is of interest.
Objective
To evaluate the feasibility and potential benefits of CCS data for systematic toxicological analysis.
Methods
Solvent standards for more than 50 molecules including opiates, amphetamines and benzodiazepines were analysed using UPLC interfaced with a novel IMS QTof mass spectrometer (Waters).
An established 15 min chromatographic method was used and the IMS QTof was operated in high-definition MSE (HDMSE) mode. This involves sequential ion mobility separation, where molecules can be distinguished on the basis of their 3D conformation, followed by MSE analysis. MSE comprises a rapid alternation between two collision energy functions: the low energy provides the accurate mass of the drift time-separated precursor ions whereas the elevated energy function provides the accurate mass of the fragment ions, for additional confirmatory purposes. IMS led to simplified elevated energy spectra during HDMSE analysis due to drift time alignment of fragment ions with their respective precursors. Reference CCS values were measured and subsequently added into an existing library (UNIFI Toxicology Screening Library; Waters) containing more than 1300 substances.
Preliminary Data
To assess the validity and reproducibility of the reference CCS values, blank urine and plasma samples enriched with the same drug standards, were analysed using UPLC-HDMSE. In addition, a series of authentic biological samples were analysed. Data were processed and screened against the updated toxicology library. For all molecules investigated, observed CCS values were within 2% of reference values. The feasibility of using CCS as a potential substitute for RT was demonstrated by the successful application of an alternative chromatographic method with a shorter analytical run time.
Conclusions
Collision cross-section values were shown to be highly reproducible both in the presence or absence of complex biological specimens. IMS led to simplified low and elevated energy spectra during MSE analysis due to the alignment of ions in drift time. CCS values provide an additional dimension of specificity which proves valuable in systematic toxicological analysis.
References & Acknowledgements:
TG Rosano, M Wood, K Ihenetu and TA Swift. Drug Screening in Medical Examiner Casework by High-Resolution Mass Spectrometry (UPLC–MSE-TOF). J. Anal. Toxicol. (2013).
M.McCullagh, V. Hanot, and S. Goscinny, Use of Ion Mobility Spectral Cleanup and Collision Cross Section Values to Increase Confidence and Efficiency in Pesticide Residues Screening Strategies. Waters Application Note Library-720005080EN.
| Description | Y/N | Source |
| Grants | no | |
| Salary | yes | Waters Corporation, salaried employee |
| Board Member | no | |
| Stock | no | |
| Expenses | no |
IP Royalty: no
| Planning to mention or discuss specific products or technology of the company(ies) listed above: | yes |