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A method for concurrent diazomethane synthesis and substrate methylation in a 96-sample format

Nature Protocols volume 5, pages 1619–1626 (2010)Cite this article

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Abstract

In the emerging field of metabolomics, there is an increasing need for improving sample derivatization reactions for gas chromatographic–mass spectral analysis of metabolites with large numbers of samples. This protocol details the safe direct derivatization of organic acids using diazomethane in a 96-sample format. Diazomethane is a highly reactive gas that readily forms methyl esters with carboxylic functionalities, with minimal side products or nonvolatile reaction residues. However, diazomethane's reactivity and explosive potential make it hazardous to store and work with. In this procedure, diazomethane is generated in situ and used concurrently to methylate up to 96 samples simultaneously, thus reducing concerns about reagent stability and obviating the need for storage of solutions of the highly reactive gas. Once the diazomethane generator has been assembled, processing 96 samples takes 2–3 h using this procedure.

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Figure 1: Reaction scheme for the synthesis of diazomethane and the derivatization of organic acids.
Figure 2: View and schematic representation of a high-flow diazomethane generator.
Figure 3: A diagram of the complete 96-sample methylation and evaporation system.
Figure 4

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Acknowledgements

We thank J. Normanly, A.Culler, W.-P. Chen and Y. Mohammed for help in trials of the diazomethane generator, and M. Emerick for help with metal design and fabrication. This work was supported by grants from the US National Science Foundation (DBI 0077769, DBI 0606666, MCB 0725149 and IOS 0923960) and the US Department of Agriculture National Research Initiative (2005-35318-16197).

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Authors and Affiliations

  1. Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Saint Paul, Minnesota, USA

    Lana S Barkawi & Jerry D Cohen

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  1. Lana S Barkawi
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  2. Jerry D Cohen
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Contributions

J.D.C. and L.S.B. conceived the protocol. The protocol is based on a previous diazomethane generator design by J.D.C. that he redesigned for higher flows and volumes. L.S.B. conducted the experiments, tested the protocol and wrote the paper with assistance from J.D.C.

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Correspondence to Jerry D Cohen.

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The authors declare no competing financial interests.

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Barkawi, L., Cohen, J. A method for concurrent diazomethane synthesis and substrate methylation in a 96-sample format. Nat Protoc 5, 1619–1626 (2010). https://doi.org/10.1038/nprot.2010.119

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