Interrogating Proton Affinities of Organophosphonate Species Via Atmospheric Flow Tube Mass Spectrometry and Computational Methods

Morrison, Kelsey A.; Bythell, Benjamin J.; Clowers, Brian H.

doi:10.1007/s13361-019-02202-w

Cited by 3 publications

(1 citation statement)

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“…Frequency calculations from the optimized structures enabled the standard enthalpy at 298 K to be calculated. Our computational estimates of the proton affinities of the neutral analytes were determined as the difference between the lowest standard enthalpy at 298 K values of the protonated analyte and the sum of the neutral analyte plus the 6.2 kJ mol −1 correction for the thermal energy of a proton at 298 K. 33 ■ RESULTS AND DISCUSSION System Optimization. The nSF-MS system was used to evaluate the signal response for analytes of different proton affinities and hydrophobicities (Figure 1).…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Supercritical Fluid Nanospray Mass Spectrometry: II. Effects on Ionization

Mostafa

Hayes

Grinias

et al. 2023

J. Am. Soc. Mass Spectrom.

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Nanospraying supercritical fluids coupled to a mass spectrometer (nSF-MS) using a 90% supercritical fluid CO2 carrier (sCO2) has shown an enhanced desolvation compared to traditional liquid eluents. Capillaries of 25, 50, and 75 μm internal diameter (i.d.) with pulled emitter tips provided high MS detection sensitivity. Presented here is an evaluation of the effect of proton affinity, hydrophobicity, and nanoemitter tip size on the nSF-MS signal. This was done using a set of primary, secondary, tertiary, and quaternary amines with butyl, hexyl, octyl, and decyl chains as analytes. Each amine class was analyzed individually to evaluate hydrophobicity and proton affinity effects on signal intensity. The system has shown a mass sensitive detection on a linear dynamic range of 0.1–100 μM. Results indicate that hydrophobicity has a larger effect on the signal response than proton affinity. Nanospraying a mixture of all amine classes using the 75 μm emitter has shown a quaternary amine signal not suppressed by competing analytes. Competing ionization was observed for primary, secondary, and tertiary amines. The 75 and 50 μm emitters demonstrated increased signal with increasing hydrophobicity. Surprisingly, the 25 μm i.d. emitter yielded a signal decrease as the alkyl chain length increased, contrary to conventional understanding. Nanospraying the evaporative fluid in a sub-500 nm emitter likely resulted in differences in the ionization mechanism. Results suggest that 90% sCO2 with 9.99% methanol and 0.01% formic acid yielded fast desolvation, high ionization efficiency, and low matrix effect, which could benefit complex biological matrix analysis.

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Section: ■ Materials and Methodsmentioning

confidence: 99%