Two-dimensional liquid chromatography coupled with mass spectrometry (2D-LC-MS) is a very powerful separation technique and extremely helpful for the analysis of complex samples. But also ion mobility spectrometry, such as drift tube ion mobility spectrometry, in combination with liquid chromatography and high resolution mass spectrometry provides great separation power. To investigate, if the combination of 2D-LC techniques such as LCxLC or LC+LC with ion mobility-mass spectrometry (IM-MS) show an advantage in comparison with 2D-LC methods without ion mobility spectrometry or one-dimensional LC with ion mobility spectrometry, the separation power of different one- and two-dimensional LC-techniques with and without an additional ion mobility spectrometry dimension was evaluated by the analysis of various herbal liqueur samples.

Two-dimensional liquid chromatography coupled with mass spectrometry (2D-LC-MS) is a very powerful separation technique and extremely helpful for the analysis of complex samples. But also ion mobility spectrometry, such as drift tube ion mobility spectrometry, in combination with liquid chromatography and high resolution mass spectrometry provides great separation power. To investigate, if the combination of 2D-LC techniques such as LCxLC or LC+LC with ion mobility-mass spectrometry (IM-MS) show an advantage in comparison with 2D-LC methods without ion mobility spectrometry or one-dimensional LC with ion mobility spectrometry, the separation power of different one- and two-dimensional LC-techniques with and without an additional ion mobility spectrometry dimension was evaluated by the analysis of various herbal liqueur samples.

Two-dimensional liquid chromatography coupled with mass spectrometry (2D-LC-MS) is a very powerful separation technique and extremely helpful for the analysis of complex samples. But also ion mobility spectrometry, such as drift tube ion mobility spectrometry, in combination with liquid chromatography and high resolution mass spectrometry provides great separation power. To investigate, if the combination of 2D-LC techniques such as LCxLC or LC+LC with ion mobility-mass spectrometry (IM-MS) show an advantage in comparison with 2D-LC methods without ion mobility spectrometry or one-dimensional LC with ion mobility spectrometry, the separation power of different one- and two-dimensional LC-techniques with and without an additional ion mobility spectrometry dimension was evaluated by the analysis of various herbal liqueur samples.

For more than a decade, many different ambient ionization methods for mass spectrometry have emerged. The term "ambient ionization" or “ambient mass spectrometry” not only means that ionization takes place at ambient temperature and pressure, but also that there is no or only very little sample preparation involved. Ambient ionization methods are either based on desorption of characteristic ions from the sample surface, on secondary ionization (usually in a solvent-only electrospray plume) of a gaseous or aerosolized sample, on plasma-based or Penning ionization, or on photoionization. This presentation will focus on recent technical developments and applications of two ion sources for ambient mass spectrometry: dielectric barrier discharge ionization (DBDI) [1] and secondary electrospray ionization (SESI) [2]. The operating principles, analytical figures of merit (detection limit, softness of ionization, upper mass limit, etc.) and the range of compounds that can be analyzed (polarity, volatility, molecular weight, etc.) will be discussed. DBDI is especially powerful for ionization of compounds with only moderate polarity that are difficult to ionize with ESI. SESI has recently been shown to be a viable alternative to proton transfer reaction-mass spectrometry (PTR-MS) and selected ion flow tube-mass spectrometry (SIFT-MS) for the ionization of trace volatiles. Finally, typical applications of DBDI-MS and SESI-MS will be presented, including ultrasensitive detection of perfluorinated compounds, pesticides, chemical warfare agents, and exhaled metabolites in human breath. [3]

For more than a decade, many different ambient ionization methods for mass spectrometry have emerged. The term "ambient ionization" or “ambient mass spectrometry” not only means that ionization takes place at ambient temperature and pressure, but also that there is no or only very little sample preparation involved. Ambient ionization methods are either based on desorption of characteristic ions from the sample surface, on secondary ionization (usually in a solvent-only electrospray plume) of a gaseous or aerosolized sample, on plasma-based or Penning ionization, or on photoionization. This presentation will focus on recent technical developments and applications of two ion sources for ambient mass spectrometry: dielectric barrier discharge ionization (DBDI) [1] and secondary electrospray ionization (SESI) [2]. The operating principles, analytical figures of merit (detection limit, softness of ionization, upper mass limit, etc.) and the range of compounds that can be analyzed (polarity, volatility, molecular weight, etc.) will be discussed. DBDI is especially powerful for ionization of compounds with only moderate polarity that are difficult to ionize with ESI. SESI has recently been shown to be a viable alternative to proton transfer reaction-mass spectrometry (PTR-MS) and selected ion flow tube-mass spectrometry (SIFT-MS) for the ionization of trace volatiles. Finally, typical applications of DBDI-MS and SESI-MS will be presented, including ultrasensitive detection of perfluorinated compounds, pesticides, chemical warfare agents, and exhaled metabolites in human breath. [3]

For more than a decade, many different ambient ionization methods for mass spectrometry have emerged. The term "ambient ionization" or “ambient mass spectrometry” not only means that ionization takes place at ambient temperature and pressure, but also that there is no or only very little sample preparation involved. Ambient ionization methods are either based on desorption of characteristic ions from the sample surface, on secondary ionization (usually in a solvent-only electrospray plume) of a gaseous or aerosolized sample, on plasma-based or Penning ionization, or on photoionization. This presentation will focus on recent technical developments and applications of two ion sources for ambient mass spectrometry: dielectric barrier discharge ionization (DBDI) [1] and secondary electrospray ionization (SESI) [2]. The operating principles, analytical figures of merit (detection limit, softness of ionization, upper mass limit, etc.) and the range of compounds that can be analyzed (polarity, volatility, molecular weight, etc.) will be discussed. DBDI is especially powerful for ionization of compounds with only moderate polarity that are difficult to ionize with ESI. SESI has recently been shown to be a viable alternative to proton transfer reaction-mass spectrometry (PTR-MS) and selected ion flow tube-mass spectrometry (SIFT-MS) for the ionization of trace volatiles. Finally, typical applications of DBDI-MS and SESI-MS will be presented, including ultrasensitive detection of perfluorinated compounds, pesticides, chemical warfare agents, and exhaled metabolites in human breath. [3]

Even today, a comprehensive congruent model for the electrospray ionization (ESI) process, explaining all experimental observations, is not established. This is due to the fact that the ESI process does not only include the ionization of a molecule but also the liquid-gas phase transfer including fluid dynamics and electrochemistry. The formation and evolution of charged droplets, the release of ions from charged droplets, the transport of ions/droplets into the vacuum system of a mass spectrometer, ion activation, transformation (i.e. chemistry), and means of preparing a defined ion beam in the ion transfer stage all potentially impact on the observed mass spectrum. A phenomenon coined in the literature as supercharging may yield new insights in the formation processes of multiply charged ions using ESI. Supercharging is used to generate highly charged ion species, which may then be subjected to selected fragmentation methods (e.g. ETD, ECD). There are two different approaches to achieve supercharging: The conventional way is to add supercharging agents (SCAs) to the sprayed analyte solution. In contrast, supercharging is also achieved by adding solvent vapor (e.g. acetonitrile) into the ion source. This presentation focuses on the systematic investigation of the impact of liquid and gas phase modifiers on the observed ion population and changes of the average charge state of the peptide Substance P (SP, sequence: RPKPQQFFGLM). SP is used as a model analyte since it is well characterized with regard to its structure and ionization behavior. In addition, proxies of individual motives of SP, e.g., 1,5-diaminopentane, ethylenediamine, n-butylamine, were also investigated. Results from experimental as well as theoretical work [1,2] are presented and discussed.

Even today, a comprehensive congruent model for the electrospray ionization (ESI) process, explaining all experimental observations, is not established. This is due to the fact that the ESI process does not only include the ionization of a molecule but also the liquid-gas phase transfer including fluid dynamics and electrochemistry. The formation and evolution of charged droplets, the release of ions from charged droplets, the transport of ions/droplets into the vacuum system of a mass spectrometer, ion activation, transformation (i.e. chemistry), and means of preparing a defined ion beam in the ion transfer stage all potentially impact on the observed mass spectrum. A phenomenon coined in the literature as supercharging may yield new insights in the formation processes of multiply charged ions using ESI. Supercharging is used to generate highly charged ion species, which may then be subjected to selected fragmentation methods (e.g. ETD, ECD). There are two different approaches to achieve supercharging: The conventional way is to add supercharging agents (SCAs) to the sprayed analyte solution. In contrast, supercharging is also achieved by adding solvent vapor (e.g. acetonitrile) into the ion source. This presentation focuses on the systematic investigation of the impact of liquid and gas phase modifiers on the observed ion population and changes of the average charge state of the peptide Substance P (SP, sequence: RPKPQQFFGLM). SP is used as a model analyte since it is well characterized with regard to its structure and ionization behavior. In addition, proxies of individual motives of SP, e.g., 1,5-diaminopentane, ethylenediamine, n-butylamine, were also investigated. Results from experimental as well as theoretical work [1,2] are presented and discussed.

Even today, a comprehensive congruent model for the electrospray ionization (ESI) process, explaining all experimental observations, is not established. This is due to the fact that the ESI process does not only include the ionization of a molecule but also the liquid-gas phase transfer including fluid dynamics and electrochemistry. The formation and evolution of charged droplets, the release of ions from charged droplets, the transport of ions/droplets into the vacuum system of a mass spectrometer, ion activation, transformation (i.e. chemistry), and means of preparing a defined ion beam in the ion transfer stage all potentially impact on the observed mass spectrum. A phenomenon coined in the literature as supercharging may yield new insights in the formation processes of multiply charged ions using ESI. Supercharging is used to generate highly charged ion species, which may then be subjected to selected fragmentation methods (e.g. ETD, ECD). There are two different approaches to achieve supercharging: The conventional way is to add supercharging agents (SCAs) to the sprayed analyte solution. In contrast, supercharging is also achieved by adding solvent vapor (e.g. acetonitrile) into the ion source. This presentation focuses on the systematic investigation of the impact of liquid and gas phase modifiers on the observed ion population and changes of the average charge state of the peptide Substance P (SP, sequence: RPKPQQFFGLM). SP is used as a model analyte since it is well characterized with regard to its structure and ionization behavior. In addition, proxies of individual motives of SP, e.g., 1,5-diaminopentane, ethylenediamine, n-butylamine, were also investigated. Results from experimental as well as theoretical work [1,2] are presented and discussed.

Chip-based high-performance liquid chromatography (chip-HPLC) has recently been the subject of intensive research because it offers benefits such as the parallelization of workflows, the minimization of solvent and sample consumption, as well as the reduction of overall operating costs. A key advantage of chip-HPLC over its conventional counterparts is the virtually dead-volume-free merging of injection, separation, and detection features on a single microfluidic chip, which enables fast separations with hardly any band broadening effects. [1] However, a challenge of miniaturized microfluidic devices is the detection of minute analyte fractions in the tiny microfluidic channels, unless they are combined with cost-intensive, complex, and bulky mass spectrometers (MS). A fast and highly-sensitive gas-phase detection device, which has gained renewed interest in analytical sciences, is ion mobility spectrometry (IMS). In contrast to MS, IMS is an ideal compact detector for chip-based separation techniques, as it operates at ambient pressures and is therefore not dependent on bulky and heavy vacuum pumping systems. [2] But IMS is not just a highly-sensitive detection technique, it moreover enables the separation of gas-phase ions in a split of a second based on their size, shape, and charge. Coupling chip-HPLC and IMS is therefore of particular interest, as it enables two-dimensional separations in the shortest possible time. Although both analytical techniques could ideally complement each other, the coupling of chip-based separation techniques with IMS is a challenge as the inlet of conventional IMS systems are usually at very high electrical potentials. This complicates a direct coupling of liquid- and gas-phase separation techniques via electrospray ionization (ESI). In this work, we present the first coupling of chip-HPLC with an IMS drift tube via a fully integrated ESI emitter. For this, a custom-built IMS with shifted potentials was devised, which enables the reliable coupling of chip-based HPLC with IMS under more moderate ESI potentials. To assess the general suitability of IMS as a new detection concept for chip-HPLC, a model mixture consisting of different fluorescent and ESI compatible compounds was chosen. Moreover, a test mixture consisting of three isobaric antidepressants demonstrated the performance of the newly developed chipHPLC/IMS setup in a two-dimensional separation.

Chip-based high-performance liquid chromatography (chip-HPLC) has recently been the subject of intensive research because it offers benefits such as the parallelization of workflows, the minimization of solvent and sample consumption, as well as the reduction of overall operating costs. A key advantage of chip-HPLC over its conventional counterparts is the virtually dead-volume-free merging of injection, separation, and detection features on a single microfluidic chip, which enables fast separations with hardly any band broadening effects. [1] However, a challenge of miniaturized microfluidic devices is the detection of minute analyte fractions in the tiny microfluidic channels, unless they are combined with cost-intensive, complex, and bulky mass spectrometers (MS). A fast and highly-sensitive gas-phase detection device, which has gained renewed interest in analytical sciences, is ion mobility spectrometry (IMS). In contrast to MS, IMS is an ideal compact detector for chip-based separation techniques, as it operates at ambient pressures and is therefore not dependent on bulky and heavy vacuum pumping systems. [2] But IMS is not just a highly-sensitive detection technique, it moreover enables the separation of gas-phase ions in a split of a second based on their size, shape, and charge. Coupling chip-HPLC and IMS is therefore of particular interest, as it enables two-dimensional separations in the shortest possible time. Although both analytical techniques could ideally complement each other, the coupling of chip-based separation techniques with IMS is a challenge as the inlet of conventional IMS systems are usually at very high electrical potentials. This complicates a direct coupling of liquid- and gas-phase separation techniques via electrospray ionization (ESI). In this work, we present the first coupling of chip-HPLC with an IMS drift tube via a fully integrated ESI emitter. For this, a custom-built IMS with shifted potentials was devised, which enables the reliable coupling of chip-based HPLC with IMS under more moderate ESI potentials. To assess the general suitability of IMS as a new detection concept for chip-HPLC, a model mixture consisting of different fluorescent and ESI compatible compounds was chosen. Moreover, a test mixture consisting of three isobaric antidepressants demonstrated the performance of the newly developed chipHPLC/IMS setup in a two-dimensional separation.

Chip-based high-performance liquid chromatography (chip-HPLC) has recently been the subject of intensive research because it offers benefits such as the parallelization of workflows, the minimization of solvent and sample consumption, as well as the reduction of overall operating costs. A key advantage of chip-HPLC over its conventional counterparts is the virtually dead-volume-free merging of injection, separation, and detection features on a single microfluidic chip, which enables fast separations with hardly any band broadening effects. [1] However, a challenge of miniaturized microfluidic devices is the detection of minute analyte fractions in the tiny microfluidic channels, unless they are combined with cost-intensive, complex, and bulky mass spectrometers (MS). A fast and highly-sensitive gas-phase detection device, which has gained renewed interest in analytical sciences, is ion mobility spectrometry (IMS). In contrast to MS, IMS is an ideal compact detector for chip-based separation techniques, as it operates at ambient pressures and is therefore not dependent on bulky and heavy vacuum pumping systems. [2] But IMS is not just a highly-sensitive detection technique, it moreover enables the separation of gas-phase ions in a split of a second based on their size, shape, and charge. Coupling chip-HPLC and IMS is therefore of particular interest, as it enables two-dimensional separations in the shortest possible time. Although both analytical techniques could ideally complement each other, the coupling of chip-based separation techniques with IMS is a challenge as the inlet of conventional IMS systems are usually at very high electrical potentials. This complicates a direct coupling of liquid- and gas-phase separation techniques via electrospray ionization (ESI). In this work, we present the first coupling of chip-HPLC with an IMS drift tube via a fully integrated ESI emitter. For this, a custom-built IMS with shifted potentials was devised, which enables the reliable coupling of chip-based HPLC with IMS under more moderate ESI potentials. To assess the general suitability of IMS as a new detection concept for chip-HPLC, a model mixture consisting of different fluorescent and ESI compatible compounds was chosen. Moreover, a test mixture consisting of three isobaric antidepressants demonstrated the performance of the newly developed chipHPLC/IMS setup in a two-dimensional separation.