Effect of Electrode Geometry on the Classification Performance of Rapid Evaporative Ionization Mass Spectrometric (REIMS) Bacterial Identification

Zsolt Bodai, Simon Cameron, Frances Bolt, Daniel Simon, Richard Schaffer, Tamas Karancsi, Julia Balog, Tony Rickards, Adam Burke, Kate Hardiman, Julia Abda, Monica Rebec, Zoltan Takats

Research output: Contribution to journalArticle

3 Citations (Scopus)
3 Downloads (Pure)

Abstract

The recently developed automated, high-throughput monopolar REIMS platform is suited for the identification of clinically important microorganisms. Although already comparable to the previously reported bipolar forceps method, optimization of the geometry of monopolar electrodes, at the heart of the system, holds the most scope for further improvements to be made. For this, sharp tip and round shaped electrodes were optimized to maximize species-level classification accuracy. Following optimization of the distance between the sample contact point and tube inlet with the sharp tip electrodes, the overall cross-validation accuracy improved from 77% to 93% in negative and from 33% to 63% in positive ion detection modes, compared with the original 4 mm distance electrode. As an alternative geometry, round tube shaped electrodes were developed. Geometry optimization of these included hole size, number, and position, which were also required to prevent plate pick-up due to vacuum formation. Additional features, namely a metal "X"-shaped insert and a pin in the middle were included to increase the contact surface with a microbial biomass to maximize aerosol production. Following optimization, cross-validation scores showed improvement in classification accuracy from 77% to 93% in negative and from 33% to 91% in positive ion detection modes. Supervised models were also built, and after the leave 20% out cross-validation, the overall classification accuracy was 98.5% in negative and 99% in positive ion detection modes. This suggests that the new generation of monopolar REIMS electrodes could provide substantially improved species level identification accuracies in both polarity detection modes. Graphical abstract.

Original languageEnglish
Pages (from-to)26-33
Number of pages8
JournalJournal of the American Society for Mass Spectrometry
Volume29
Issue number1
Early online date16 Oct 2017
DOIs
Publication statusPublished - 01 Jan 2018
Externally publishedYes

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Ionization
Electrodes
Geometry
Positive ions
Ions
Electron tubes
Point contacts
Vacuum
Aerosols
Surgical Instruments
Microorganisms
Biomass
Metals
Throughput

Cite this

Bodai, Zsolt ; Cameron, Simon ; Bolt, Frances ; Simon, Daniel ; Schaffer, Richard ; Karancsi, Tamas ; Balog, Julia ; Rickards, Tony ; Burke, Adam ; Hardiman, Kate ; Abda, Julia ; Rebec, Monica ; Takats, Zoltan. / Effect of Electrode Geometry on the Classification Performance of Rapid Evaporative Ionization Mass Spectrometric (REIMS) Bacterial Identification. In: Journal of the American Society for Mass Spectrometry. 2018 ; Vol. 29, No. 1. pp. 26-33.
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Effect of Electrode Geometry on the Classification Performance of Rapid Evaporative Ionization Mass Spectrometric (REIMS) Bacterial Identification. / Bodai, Zsolt; Cameron, Simon; Bolt, Frances; Simon, Daniel; Schaffer, Richard; Karancsi, Tamas; Balog, Julia; Rickards, Tony; Burke, Adam; Hardiman, Kate; Abda, Julia; Rebec, Monica; Takats, Zoltan.

In: Journal of the American Society for Mass Spectrometry, Vol. 29, No. 1, 01.01.2018, p. 26-33.

Research output: Contribution to journalArticle

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AU - Bodai, Zsolt

AU - Cameron, Simon

AU - Bolt, Frances

AU - Simon, Daniel

AU - Schaffer, Richard

AU - Karancsi, Tamas

AU - Balog, Julia

AU - Rickards, Tony

AU - Burke, Adam

AU - Hardiman, Kate

AU - Abda, Julia

AU - Rebec, Monica

AU - Takats, Zoltan

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N2 - The recently developed automated, high-throughput monopolar REIMS platform is suited for the identification of clinically important microorganisms. Although already comparable to the previously reported bipolar forceps method, optimization of the geometry of monopolar electrodes, at the heart of the system, holds the most scope for further improvements to be made. For this, sharp tip and round shaped electrodes were optimized to maximize species-level classification accuracy. Following optimization of the distance between the sample contact point and tube inlet with the sharp tip electrodes, the overall cross-validation accuracy improved from 77% to 93% in negative and from 33% to 63% in positive ion detection modes, compared with the original 4 mm distance electrode. As an alternative geometry, round tube shaped electrodes were developed. Geometry optimization of these included hole size, number, and position, which were also required to prevent plate pick-up due to vacuum formation. Additional features, namely a metal "X"-shaped insert and a pin in the middle were included to increase the contact surface with a microbial biomass to maximize aerosol production. Following optimization, cross-validation scores showed improvement in classification accuracy from 77% to 93% in negative and from 33% to 91% in positive ion detection modes. Supervised models were also built, and after the leave 20% out cross-validation, the overall classification accuracy was 98.5% in negative and 99% in positive ion detection modes. This suggests that the new generation of monopolar REIMS electrodes could provide substantially improved species level identification accuracies in both polarity detection modes. Graphical abstract.

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