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Towards a Non-Biased Formaldehyde Quantification in Leather: New Derivatization Conditions before HPLC Analysis of 2,4-Dinitrophenylhydrazine Derivatives. | LitMetric

AI Article Synopsis

  • - The analysis of formaldehyde in leathers using the EN ISO 17226-1 standard is problematic due to resin hydrolysis that can artificially inflate formaldehyde readings.
  • - Traditional methods using strong acids during derivatization lead to inaccurate results when dealing with certain leathers, prompting a reevaluation of the derivatization process.
  • - A new method using acetonitrile for DNPH solubilization eliminates acid use, achieving complete formaldehyde derivatization in 3 hours while preventing unwanted resin hydrolysis, yielding stable and accurate results.

Article Abstract

In leathers, formaldehyde is currently analyzed according to EN ISO 17226-1 standard, by reversed phase liquid chromatography after off-line precolumn derivatization with 2,4 dinitrophenylhydrazine (DNPH) in strong acidic conditions. We first demonstrate that this standard is not adapted to leather retanned with resins likely to release formaldehyde by hydrolysis. Indeed, formaldehyde content may be largely overestimated due to concomitant resin hydrolysis (in harsh acidic conditions) that releases formaldehyde during the derivatization step and during the waiting time on autosampler before analysis. Therefore, we thoroughly studied the derivatization step in order to propose new derivatization conditions. Replacing orthophosphoric acid by less acidic buffer solutions is not enough to avoid hydrolysis. A derivatization without adding acid is realized by solubilizing DNPH in acetonitrile instead of orthophosphoric acid. These conditions lead to a complete derivatization of formaldehyde in 3 h at 50 °C (in a water bath) while avoiding the hydrolysis of co-extracted dicyandiamide and melamine resins. The as-obtained leather extracts are stable over time. Formaldehyde contents found with this method agree with the formaldehyde content measured immediately at the end of derivatization reaction in standard conditions or with formaldehyde content measured by a home-designed flow injection analysis with acetylacetone online derivatization and UV detection.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7729709PMC
http://dx.doi.org/10.3390/molecules25235765DOI Listing

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