A Universal Low-Flow Secondary Electrospray Ionizer: High Sensitivity Volatile Analysis on

Pre-existing MS Instruments

Poster AS-103; Swiss Chemical Society Fall Meeting 2015 4th September, Lausanne (Switzerland)

C. Barrios-Collado1,2,3, D. García-Gómez1, R. Zenobi1, G. Vidal-de-Miguel1,2*, P. Martínez-Lozano Sinues1*

1 ETH Zürich, Switzerland; 2 SEADM S.L., Boecillo, Spain; 3 U. of Valladolid, Valladolid, Spain;*email: guillermo.vidal@seadm.com / guillermo.vidal@org.chem.ethz.ch / pablo.martinez@org.chem.ethz.ch

1. Overview

7. Conclusions

8. Acknowledgements

9. References

3. Drugs detection

2. Benchmarking

5. Real time breath analysis

We gratefully acknowledge Dr. Juan Zhang (Novartis AG) for the donation of the LTQ Orbitrap instrument used in this study and the European Community’s Seventh Framework Programme (FP7-2013-IAPP) for funding the project “Analytical Chemistry Instrumentation Development” (609691). We are indebted to Christoph Bärtschi (ETH workshop) for his assistance machining the ion source and Myriam Macía for assisting during the development phase.

• Secondary ElectroSpray Ionization (SESI) in tandem with Atmospheric Pressure ionization Mass Spectrometry (API MS) has achieved sensitivities in the sub-ppt range for polar vapors [1-7].

• Low-Flow SESI (LF-SESI), was developed in tandem with a Differential Mobility Analyzer, and in explosive detection applications reached sensitivities at the sub-ppq range [8-9].

• However, it is only available for dedicated applications.• We therefore developed an add-on Universal Low-Flow SESI which can be

coupled to a pre-existing MS [10].• This device consists basically on a heated asymmetric LFSESI chamber which

is coupled to the MS atmospheric pressure interface. A 2-axis micrometric positioning system provides fine mechanical alignment between the LFSESI and the MS inlet capillary. Also, the axial position of the electrospray tip can be optimized manually. Figure 1 shows the LFSESI coupled to an MS.

• SESI-MS has shown promise to investigate the in vivo pharmacokinetics of injected drugs in mice [11].

• LFSESI performance tested towards vapors of common drugs: Melatonin, Propofol, Acetaminophen, Pentobarbital and Midazolam.

• Sample flow set at an optimal value of 0.2 L/min.• Figure 4 shows that the system was able to detect these drugs from

concentrations of tenths of ppt in the gas phase, with a linear response across three orders of magnitude.

• Such low concentrations are deemed to be necessary to be detected in exhaled breath of small animals such as mice.

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y = 1313.4 x0.8566

R2 = 0.9701

y = 193.34 x1.2135

R2 = 0.9566

y = 368.34 x0.8078

R2 = 0.9757

y = 0.2012 x1.9375

R2 = 0.9963

y = 1084.7 x0.6707

R2 = 0.988

Figure 4 Detection of several compounds of interest ionized with the LFSESI [10]

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233.13

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Figure 5 Spectra of several compounds of interest:

a) Melatonin (m/z = 233);b) Propofol (m/z = 179);

c) Acetaminophen (m/z = 152);d) Pentobarbital (m/z = 227); e)Midazolam (m/z = 326) [10]

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Figure 1 Orbitrap Mass Spectrometer with LFSESI [10]:1. Mechanical alignment; 2. Thermal insulation surrounding the core; 3. High voltage electronics; 4. Electrospray vial holder; 5. Transfer line; 6. Electrospray positioning; 7. Temperature control connection for core and transfer line

• LFSESI performance benchmarked against a “standard” SESI source [10]• We delivered precise amounts of target vapor species and measured the

resulting mass spectral signal intensity. Figure 2 shows the set-up.• Electrosprayed solutions of the species of interest dissolved in H2O were

mixed with a controlled flow of clean nitrogen.• The vapor generator and the clean nitrogen line were heated up to 190°C.• The temperature of the ionization source was set to 85°C (PID controlled),

limited by the charging agent (H2O-formic acid 0.1%) boiling point.• Inlet capillary temperature was set to 200°C. Voltages, mechanical

alignment and electrospray tip axial position were optimized prior the experiments.

• The LFSESI ionizer, outperforms standard ionizers by a factor of 5 in terms of ionization efficiency.

• This add-on can be virtually interfaced with any commercial API-MS without any modification of the latter.

• As a result, pre-existing mass spectrometers can be deployed for the sensitive and real-time analysis of trace gases.

• We provide some examples of application for the universal LFSESI on the detection of drugs, suggesting that such system can be suitable for real-time pharmacokinetic studies, real time breath analysis or deciphering the language of plants by analyzing their released VOCs.

Figure 2 Experimental set-up for characterization

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Figure 7 Evolution of some VOCs of interest emitted by plants

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Figure 3 Experimental performance of the optimized (LFSESI) and standard (SESI) ionizers; DEA 23fg/s; electrospray of H2O-HCOOH (0.1%) [10]

• Figure 3 compares the performance of the optimized LFSESI against a standard SESI.

• For each sample flow rate (qs), 23 fg/s of DEA (diethylamine) were injected (in triplicate) during two minutes.

• Y-axis represents integrated signal minus the baseline level, from the beginning of the injection until the signal level returns to the baseline.

• LFSESI ionization efficiency improves at decreasing sample flow rates.• Standard SESI optimal performance is around qs = 0.9 L/min, dropping

abruptly for lower sample flows.• The LFSESI improves the standard SESI on a factor of five.

VS

4. Light-induced plant metabolism

• The LFSESI was used for real time breath analysis, a technique moresuitable for diagnosis purposes [14] than Exhaled Breath Condensate .

• High volatile aldehydes (less than six carbon atoms) were detected.• Figure 8 shows detection of aldehydes in exhaled breath with the LFSESI.

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• Plants release VOCs as part of their own metabolism or to send warning messages to other plants [12].

• SESI-MS can be used to decipher the language of plants [13].

• Experiments with begonia show more than 1000 different compounds detected.

• Figure 6 shows the set-up to analyze plant VOCs. Figure 7 shows the temporal evolution along two days of some basic plant VOCs related with photosynthesis.

Figure 6 Experimental set-up for analysis of VOCs emitted by plants

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Monoterpene alcohol C10H18O

Sesquiterpene C15H24

Sesquiterpene alcohol C15H26O

Figure 8 Real time analysis of aldehyde in Exhaled Breath Condensate [14]

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14. García-Gómez, D.; Martínez-Lozano, P.; Barrios-Collado, C.; Vidal-de-Miguel, G.; Gaugg, M.; Zenobi, R.Identification of 2-Alkenals, 4-Hydroxy-2-alkenals, and 4-Hydroxy-2,6-alkadienals in exhaled breath condensate by UHPLC-HRMS and in breath by real-time HRMS. Anal Chem. (2015).