Journal of Chromatography A, 1216 (2009) 4787–4797 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma Combination of 1 H nuclear magnetic resonance spectroscopy and mass spectrometry as tools for investigation of the thermolytic and solvolytic effects Case of carbamates analysis Cédric Przybylski a,∗ , Véronique Bonnet b a Centre Technique de la Conservation des Produits Agricoles, Laboratoire de Recherche et Développement Analytique, 41 avenue Paul Claudel, 80480 Dury les Amiens, France b Laboratoire des Glucides, UMR CNRS 6219, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex, France article info Article history: Received 25 October 2008 Received in revised form 14 March 2009 Accepted 7 April 2009 Available online 15 April 2009 Keywords: Carbamates 1 H NMR GC–MS Solvolytic effect Thermolytic effect abstract The carbamate pesticides are a well known thermo-sensible compound class. Under unfavourable con- ditions, these compounds are highly prone to degradation via fragmentation and/or rearrangement mechanisms. Their transformation processes are observed in consequence of two factors: structure with fragile bonds on the one hand and a stressing environment on the other hand leading to a difficult direct gas chromatography (GC) analysis, i.e. without derivatisation. In this paper, we investigated an original methodology based on the complementarity of analysis by proton nuclear magnetic resonance spectroscopy ( 1 H NMR) and those provided by GC hyphenated with ion-trap mass selective detection (GC–ITMS) to investigate combined effects of temperature and solvent nature affecting the behaviour of 16 carbamates. Among tested solvents, toluene and acetonitrile with 0.1% acetic acid were considered as the best solvents for storage and GC analysis respectively. Carbaryl, chlorpropham, carbofuran and N-sulfenylated compounds began to be thermodegraded with a loss equal to 1–5% even at 50 ◦ C. An on- column injection validated as providing no degradation was used to analyse the identical solution that in 1 H NMR and it was emphasised that results of the measured degradation rates were identical at ±2%. It was highlighted that this methodology was extensible to study mechanisms and parameters with other (bio)molecules. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Pesticides are largely used around the world to protect farmlands. Numerous classes of these compounds such as organochlorines and organophosphorus are very persistent with high half-life and present a high toxicity for environment, ani- mals and final consumers. Considerable efforts have been made to substitute these pesticide classes with others that are more eas- ily degradable such as carbamates. This compound class has been used extensively since they have high effectiveness as insecticides, fungicides, herbicides, nematocides, acaricides, molluscicides but it induced dramatic toxicological effects in human beings, because they are inhibitors of acetylcholinesterase. Carbamates common structure is composed of the ester of carbamic acid, with vari- ous substituents. Generic formula is R 1 –O–CO–NR 2 R 3 where R n are usually hydrogen, methyl, phenyl or more complex groups. Their main physicochemical properties can be summarised as a ∗ Corresponding author. Present address: LAMBE, UMR CNRS 8587, Université d’Evry-Val d’Essonne, Boulevard Franc ¸ois Mitterrand, 91025 Evry Cedex, France. Tel.: +33 169477651; fax: +33 169477655. E-mail address: cedric.przybylski@univ-evry.fr (C. Przybylski). high polarity, a strong solubility in aqueous media and a thermo- instability. Their thermolability appears firstly as an advantage since natural degradation can be accelerated in environmental conditions but unfortunately they lead to problems of analysis in control laboratories and their metabolites are often active too. Different techniques have been employed for determining car- bamate pesticides. Liquid chromatography (LC) [1–5] and gas chromatography (GC) [6–9] coupled to a large number of detec- tors have been those generally preferred, but lability of carbamate lead to difficult direct GC analysis. In spite of some mass spectrom- etry (MS) technologic advances for sensitive molecules analysis with GC–MS coupling [10], some authors do not recommend the use of GC and consider that LC–MS seemed to be the most con- venient technique. Nevertheless, GC–MS is a powerful analytical tool for these analytes, as it provides good selectivity and sen- sitivity and apparatus is cheaper than LC–MS, leading to more widespread use in pesticide control laboratories around the world. To circumvent the problems of the thermal instability of carbamates particularly for N-methyl which are less stable than N-aryl ones, many solutions have been used to obtain thermally stable deriva- tives. Modification reaction is made by derivatisation with various chemical agents to block reactive NH moiety [11–15]. Neverthe- less, derivatisation methodology is time and reagent consuming, 0021-9673/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2009.04.016