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

Caroline Bourgeois,Claire Demesmay,Nicolas Blanc,Jean-Claude Cannot

doi:10.3390/molecules25235765

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.

Highlights

The European commission regulation No 605/2014 classifies formaldehyde as a class 1B carcinogen.formaldehyde is dangerous: it is flammable, irritating for the respiratory tract, skin, eyes [1], and may cause an allergic skin reaction [2]
In order to study the influence of this time frame, formaldehyde was analyzed in leather samples immediately after preparation of the derivatization flask, and repeatedly during the time-frame allowed by the standard (1 to 3 h) and after a longer period of time
We have demonstrated that the EN ISO 17226-1 standard is not adapted to leather samples retanned with resins likely to release formaldehyde by hydrolysis

Summary

Introduction

The European commission regulation No 605/2014 classifies formaldehyde as a class 1B carcinogen.formaldehyde is dangerous: it is flammable, irritating for the respiratory tract, skin, eyes [1], and may cause an allergic skin reaction [2]. Formaldehyde is used in various industrial fields such as the wood [3], cosmetic [2], textile [4], and leather industries [5,6,7]. Formaldehyde was previously used for tanning or finishing because of its crosslinking properties [8]. It is mainly used to synthetize quick and easy to use tanning agents (such as dicyandiamide and melamine resins) that give suitable properties to leather [9]. Such dicyandiamide and melamine resins are synthetized by C-N bond formation during polycondensation of dicyandiamide and melamine with formaldehyde. This reaction is known to be reversible: hydrolysis

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