Contaminant screening of wastewater with HPLC-IM-qTOF-MS and LC+LC-IM-qTOF-MS using a CCS database

Abstract

Non-target analysis has become an important tool in the field of water analysis since a broad variety of pollutants from different sources are released to the water cycle. For identification of compounds in such complex samples, liquid chromatography coupled to high resolution mass spectrometry are often used. The introduction of ion mobility spectrometry provides an additional separation dimension and allows determining collision cross sections (CCS) of the analytes as a further physicochemical constant supporting the identification. A CCS database with more than 500 standard substances including drug-like compounds and pesticides was used for CCS data base search in this work. A non-target analysis of a wastewater sample was initially performed with high performance liquid chromatography (HPLC) coupled to an ion mobility-quadrupole-time of flight mass spectrometer (IM-qTOF-MS). A database search including exact mass (±5 ppm) and CCS (±1 %) delivered 22 different compounds. Furthermore, the same sample was analyzed with a two-dimensional LC method, called LC+LC, developed in our group for the coupling to IM-qTOF-MS. This four dimensional separation platform revealed 53 different compounds, identified over exact mass and CCS, in the examined wastewater sample. It is demonstrated that the CCS database can also help to distinguish between isobaric structures exemplified for cyclophosphamide and ifosfamide. Graphical Abstract Scheme of sample analysis and database screening.

Coupling Front-End Separations, Ion Mobility Spectrometry, and Mass Spectrometry For Enhanced Multidimensional Biological and Environmental Analyses

“…Consequently, LC-DTIMS-MS and LC-TWIMS-MS have been used to separate metabolites (63, 64), lipids (65, 66), proteins (67), peptides (39, 60, 62, 68–71), and glycans (72) in complex biological and environmental samples. Furthermore, to add even more peak capacity, 2D LC applications, such as those with strong cation exchange and reversed-phase gradients or high- and low-pH reverse-phase gradients, have been combined with DTIMS-MS for four-dimensional measurements and even better coverage of complex mixtures (73, 74). Overall, the multidimensional LC and 2D LC-DTIMS-MS platforms have greatly improved the analytical sensitivity and specificity of LC-MS analyses.…”

Semi‐quantitative non‐target analysis of water with liquid chromatography/high‐resolution mass spectrometry: How far are we?

“…It is obvious that HRMS analysis can detect only the compounds that are retained during sample preparation, and this can lead to false‐negative results in non‐target analysis. In order to minimize the false‐negative rate, it is good practice to use SPE cartridges with mixed polarity or to combine extracts obtained with different SPE cartridges …”

“…The ion mobility data, similarly to MS/MS spectra, are strongly dependent on the instrumental conditions, which also makes the application of libraries complicated . However, distinguishing isobaric compounds with very similar retention times may become possible, if home‐built libraries are available . In both techniques, the comparison of the information obtained from the measurements with a plausible structure is computationally intensive and unavailable for most laboratories.…”

“…In order to minimize the false-negative rate, it is good practice to use SPE cartridges with mixed polarity 14 or to combine extracts obtained with different SPE cartridges. 25 Both surface water and groundwater samples also often contain a significant amount of particulate matter. These particles are known to absorb some of the compounds that may be present in the water sample; thus, it is not surprising that the filtration is known to influence the number of compounds detected and also the intensity of the peaks.…”

A Powerful Four-Dimensional Separation Method for Complex Samples

“…To overcome this and to simplify data evaluation with available software when IM as a further separation dimension is introduced, our group recently developed a method (here called LC ? LC) based on a continuous multiheart-cutting method with a long modulation time (4 min), realizing that peaks are mostly not-or for a few compounds only one time-modulated so that most of the compounds are only observed in a single second dimension chromatogram [17,18]. This allows us to view the data of a 2D-LC separation on a single time axis like in a simple 1D chromatogram.…”