The Puzzling Presentation of Pyrethrin Pesticides: Exploring Isomerization in Comprehensive Two-Dimensional Gas Chromatography

Neil Byrnes; Philip Marriott

Abstract

Comprehensive two-dimensional gas chromatography (GC×GC) imparts an additional degree of separation and enhanced resolution when compared to traditional one-dimensional gas chromatography (1DGC). The visual presentation of results in the form of a contour plot aids in analyte identification but can also yield interesting patterns which provide insight into chemical processes, not immediately apparent by 1DGC. Chemical isomerization has been reported in GC×GC literature, yet the influence of heat on this process and its visual presentation has not been fully explored. The six natural pyrethrin pesticides are produced by pyrethrum daisies (Chrysanthemum cinerariifolium); two of them, pyrethrin I and pyrethrin II, are susceptible to irreversible thermal isomerization.[1,2] These pyrethrins convert to isopyrethrin I and II, respectively, when exposed to temperatures above 200 °C.[3] Using natural pyrethrins as a case study, this work aims to investigate how GC×GC method parameters affect thermal isomerization occurring during GC×GC analysis, and how these changes are visually represented in the 2D plot. The utility of GC×GC will be highlighted through comparison to the 1DGC results. The effect of inlet temperature, oven temperature, and oven temperature program (isothermal vs. gradient) will be examined with a focus on the qualitative interpretation of results. Through the unconventional approach of using GC×GC columns comprising the same stationary phase in both dimensions, the thermal isomerization of pyrethrins will be presented.

Keywords: isomerization, peak bridging, pyrethrin, isopyrethrin, GC×GC

References:
[1] Goldberg AA, Head S, Johnston P. Action of heat on pyrethrum extract: the isomerisation of pyrethrins to isopyrethrins. J Sci Food Agric. 1965;16(1):43-51.
[2] Wenclawiak BW, Krappe M, Otterbach A. In situ transesterification of the natural pyrethrins to methyl esters by heterogeneous catalysis using a supercritical fluid extraction system and detection by gas chromatography-mass spectrometry. J Chromatogr A. 1997;785(1-2):263-7.
[3] Brown NC, Hollinshead DT, Phipers RF, Wood MC. New isomers of the pyrethrins formed by the action of

Original language	English
Pages	22
Number of pages	1
Publication status	Published - 5 Dec 2022
Event	28th Annual RACI R&D Topics 2022 - RMIT University, Melbourne, Australia Duration: 4 Dec 2022 → 7 Dec 2022

Conference

Conference	28th Annual RACI R&D Topics 2022
Country/Territory	Australia
City	Melbourne
Period	4/12/22 → 7/12/22

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 3 Good Health and Well-being

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Cite this

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title = "The Puzzling Presentation of Pyrethrin Pesticides: Exploring Isomerization in Comprehensive Two-Dimensional Gas Chromatography",

abstract = "Comprehensive two-dimensional gas chromatography (GC×GC) imparts an additional degree of separation and enhanced resolution when compared to traditional one-dimensional gas chromatography (1DGC). The visual presentation of results in the form of a contour plot aids in analyte identification but can also yield interesting patterns which provide insight into chemical processes, not immediately apparent by 1DGC. Chemical isomerization has been reported in GC×GC literature, yet the influence of heat on this process and its visual presentation has not been fully explored. The six natural pyrethrin pesticides are produced by pyrethrum daisies (Chrysanthemum cinerariifolium); two of them, pyrethrin I and pyrethrin II, are susceptible to irreversible thermal isomerization.[1,2] These pyrethrins convert to isopyrethrin I and II, respectively, when exposed to temperatures above 200 °C.[3] Using natural pyrethrins as a case study, this work aims to investigate how GC×GC method parameters affect thermal isomerization occurring during GC×GC analysis, and how these changes are visually represented in the 2D plot. The utility of GC×GC will be highlighted through comparison to the 1DGC results. The effect of inlet temperature, oven temperature, and oven temperature program (isothermal vs. gradient) will be examined with a focus on the qualitative interpretation of results. Through the unconventional approach of using GC×GC columns comprising the same stationary phase in both dimensions, the thermal isomerization of pyrethrins will be presented. Keywords: isomerization, peak bridging, pyrethrin, isopyrethrin, GC×GC References: [1] Goldberg AA, Head S, Johnston P. Action of heat on pyrethrum extract: the isomerisation of pyrethrins to isopyrethrins. J Sci Food Agric. 1965;16(1):43-51. [2] Wenclawiak BW, Krappe M, Otterbach A. In situ transesterification of the natural pyrethrins to methyl esters by heterogeneous catalysis using a supercritical fluid extraction system and detection by gas chromatography-mass spectrometry. J Chromatogr A. 1997;785(1-2):263-7. [3] Brown NC, Hollinshead DT, Phipers RF, Wood MC. New isomers of the pyrethrins formed by the action of",

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AB - Comprehensive two-dimensional gas chromatography (GC×GC) imparts an additional degree of separation and enhanced resolution when compared to traditional one-dimensional gas chromatography (1DGC). The visual presentation of results in the form of a contour plot aids in analyte identification but can also yield interesting patterns which provide insight into chemical processes, not immediately apparent by 1DGC. Chemical isomerization has been reported in GC×GC literature, yet the influence of heat on this process and its visual presentation has not been fully explored. The six natural pyrethrin pesticides are produced by pyrethrum daisies (Chrysanthemum cinerariifolium); two of them, pyrethrin I and pyrethrin II, are susceptible to irreversible thermal isomerization.[1,2] These pyrethrins convert to isopyrethrin I and II, respectively, when exposed to temperatures above 200 °C.[3] Using natural pyrethrins as a case study, this work aims to investigate how GC×GC method parameters affect thermal isomerization occurring during GC×GC analysis, and how these changes are visually represented in the 2D plot. The utility of GC×GC will be highlighted through comparison to the 1DGC results. The effect of inlet temperature, oven temperature, and oven temperature program (isothermal vs. gradient) will be examined with a focus on the qualitative interpretation of results. Through the unconventional approach of using GC×GC columns comprising the same stationary phase in both dimensions, the thermal isomerization of pyrethrins will be presented. Keywords: isomerization, peak bridging, pyrethrin, isopyrethrin, GC×GC References: [1] Goldberg AA, Head S, Johnston P. Action of heat on pyrethrum extract: the isomerisation of pyrethrins to isopyrethrins. J Sci Food Agric. 1965;16(1):43-51. [2] Wenclawiak BW, Krappe M, Otterbach A. In situ transesterification of the natural pyrethrins to methyl esters by heterogeneous catalysis using a supercritical fluid extraction system and detection by gas chromatography-mass spectrometry. J Chromatogr A. 1997;785(1-2):263-7. [3] Brown NC, Hollinshead DT, Phipers RF, Wood MC. New isomers of the pyrethrins formed by the action of

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Y2 - 4 December 2022 through 7 December 2022

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