abhijit nag 01/08/2016 · 2016-11-29 · in acn (aprotic solvent) mass spectrometry co2 loss in...

Abhijit Nag01/08/2016

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Published in: Hanxue Xia; Athula B. Attygalle; Anal. Chem. 2016, 88, 6035-6043.DOI: 10.1021/acs.analchem.6b01230Copyright © 2016 American Chemical Society

Introduction

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In ACN (aprotic solvent) mass spectrometry CO2 loss

In MeOH/water mixture (protic solvent) no CO2 loss under the same condition.

From this they concluded that in aprotic solvent gas phase what is present is C-

and in protic solvent is P- .

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In ACN (aprotic solvent) Characteristic νCOOH and νCOH modes foundIn MeOH/water mixture (protic solvent) symmetric and asymmetric νCOO− .

From this they concluded that in aprotic solvent gas phase what is present is P- and in protic solvent is C- .

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Published in: Detlef Schröder; Miloš Buděšínský; Jana Roithová; J. Am. Chem. Soc. 2012, 134, 15897-15905.DOI: 10.1021/ja3060589Copyright © 2012 American Chemical Society

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In this paper

They found that the ESI ion-source conditions exert a dramatic effect

on the abundance ratio of the gaseous anions generated from p-

hydroxybenzoic acid.

They reported that the relative abundance of the two populations

depends not only on the solvent composition, but also on the ESI

probe spatial orientation, the capillary voltage, the source temperature,

the solvent flow rate, and the cone voltage.

They proposed that the observed ratio of the P− and C− forms indirectly

reflects the relative contribution of the charge-residue or ion-

evaporation process that occurs during the electrospray ion

generation process.

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Plot of the natural logarithm of average P–/C– peak intensity ratios against different Vernier-probe adjuster settings (N = 3). The m/z 137 ion generated by ESI at capillary voltage of 2.22 kV from a sample of p-hydroxybenzoic acid in water containing 0.1% NH4OH was subjected to ion-mobility separation. The sampling cone was set to 11 V, extraction cone to 1.5 V, sample infusion flow rate to 10 μL/min, and desolvation-gas flow rate to 370 L/h. The source and desolvation-gas temperatures were held at 80 and 100 °C, respectively. The arrival times of the m/z 137 anions were recorded at different probe position settings. Insets A and B show arrival-time profiles recorded at Vernier-probe adjuster position of 4.92 or 9.92 mm, respectively (the small peak at 4.26 ms represents the phenoxide ion, a product of decarboxylation of m/z 137).


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Result and discussion

Plot of the natural logarithm of average P–/C– peak intensity ratios against different desolvation-gas temperatures settings (N = 3). The m/z 137 ion generated by ESI at a capillary voltage of 2.22 kV from a sample of p-hydroxybenzoic acid in water containing 0.1% NH4OH was subjected to ion-mobility separation. The sampling cone was set to 11 V, extraction cone to 1.5 V, sample infusion flow rate to 10 μL/min, desolvation-gas flow rate to 370 L/h, and Vernier-probe adjuster position to 5.92 mm. The source-block temperature was held at 80 °C. The arrival times of the m/z 137 anion were recorded at different desolvation-gas temperatures. Insets A and B show arrival-time profiles recorded at desolvation-gas temperatures of 100 and 500 °C, respectively.


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Plot of the natural logarithm of average P–/C– peak intensity ratios against different capillary voltage settings (N = 3). The m/z 137 ion generated by ESI at a Vernier-probe adjuster setting of 5.92 mm from a sample of p-hydroxybenzoic acid in water containing 0.1% NH4OH was subjected to ion-mobility separation. The sampling cone was set to 11 V, extraction cone to 1.5 V, sample infusion flow rate to 10 μL/min, and desolvation-gas flow rate to 370 L/h. The source and desolvation-gas temperatures were held at 80 and 100 °C, respectively. The arrival times of the m/z 137 anion were recorded at different capillary voltage settings. Insets A and B show arrival-time profiles recorded at capillary voltage settings of 2 and 3.75 kV, respectively.


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Plots of the natural logarithm of average P–/C– peak intensity ratio vs capillary voltage (N = 3) prepared from ion-mobility separation data recorded for the m/z 137 ion in a closed source engulfed with oxygen at a flow rate of 400 L/h (red curve), or without oxygen (blue curve). For both experiments a sample of p-hydroxybenzoic acid in water containing 0.1% NH4OH was sprayed at a Vernier-probe adjuster setting of 5.92 mm. Insets A and B show arrival-time profiles recorded at a capillary voltage setting of 2.5 kV, whereas insets C and D depict profiles recorded at 4.5 kV. The peak at 4.26 ms represents the phenoxide ion. The sampling cone was set to 11 V, extraction cone to 1.5 V, sample infusion flow rate to 10 μL/min, and desolvation-gas flow rate to 370 L/h. The source and desolvation-gas temperatures were held at 80 and 100 °C, respectively.


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Plot of the natural logarithm of average P–/C– peak intensity ratios against different sample flow rate settings (N = 3). The m/z 137 ion generated by ESI at capillary voltage of 2.76 kV from a sample of p-hydroxybenzoic acid in water containing 0.1% NH4OH was subjected to ion-mobility separation. The sampling cone was set to 7 V, extraction cone to 1.3 V, desolvation-gas flow rate to 300 L/h, and Vernier-probe adjuster position to 5.92 mm. The source and desolvation-gas temperatures were held at 80 and 200 °C, respectively. The arrival times of the m/z 137 anion were recorded at different sample flow rate settings. Insets A and B show arrival-time profiles recorded at sample flow rate settings of 3 and 50 μL/min, respectively.


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Plot of the natural logarithm of average P–/C– peak intensity ratios against different sampling cone voltage settings (N = 3). The m/z 137 ion generated by ESI at capillary voltage of 2.22 kV from a sample of p-hydroxybenzoic acid in water containing 0.1% NH4OH was subjected to ion-mobility separation. The ESI extraction cone was 1.5 V, desolvation-gas flow rate was 370 L/h, sample infusion flow rate was 10 μL/min, and Vernier-probe adjuster position was 5.92 mm. The source and desolvation-gas temperatures were held at 80 and 100 °C, respectively. The arrival times of the m/z 137 anion were recorded at different sampling cone voltage settings. Insets A and B show arrival-time profiles recorded at sampling voltage settings of 5 and 45 V, respectively.


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Summary

Solvent effects are not the primary criteria that determine the

relative population distributions of tautomeric carboxylate (C−) and

phenoxide (P−) ions (m/z 137) generated by electrospray

ionization of p-hydroxybenzoic acid.

The population ratio depends on factors such as probe position,

capillary voltage, cone voltage, source temperature, flow rate,

ambient gases present in the source region, and concentration of

the sample.

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Future plan

We can spray Au25 through the one capillary and other cluster or compounds like (Cyclodextrin, Ag25, C60 etc) through the lock spray capillary to see the gas phase reaction.

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abhijit nag 01/08/2016 · 2016-11-29 · in acn (aprotic solvent) mass spectrometry co2 loss in...

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