Evaluation of nitrobenzenes and chlorobenzenes levels in samples of sediments from Italy: A rapid and simple method by automatic extractor and GC/MS ion trap

Abstract

Ninety-six marine sediment samples from an Italian harbour were analysed by GC/MS ion trap for the residues of nitrobenzenes and chlorobenzenes. The significance of these compounds in the investigated matrix was discussed. In order to determine the simultaneous presence of chlorobenzenes and nitrobenzenes in marine sediments, a simple extraction method by an automatic extraction system was developed. The use of an automatic extractor unit allows the extraction of the analytes of interest with no waste of volatile compounds, since small volumes of solvent are required. This also results in a reduction of the analysis time, compared with traditional extraction techniques such as extraction by Soxhlet. The samples under investigation were mixed with anhydrous sodium sulphate to obtain a free-flowing powder and quantitatively transferred into extraction thimbles. The thimbles were then introduced into the automatic extractor unit by solvent and extracted with 70 mL of acetone/hexane (1:1, v/v). The extract was analysed directly by GC/MS ion trap in EI mode. A VF5 ms low bleeding capillary column was used to separate the compounds of interest. Recovery rates were determined at two spiking levels, one ranging from 1.0 to 5.0 mg/kg, the other from 10 to 50 mg/kg. Six replicates were analysed for each fortification level. Mean recoveries proved to range from 60.6 to 125.1% in either case. The precision of the method was expressed as relative standard deviation (RSD%), which turned out to be in the range 5.2–15.0%. The determination limits ranged from 0.01 mg/kg to 1.0 mg/kg, when approximately 10 g (dry weight) samples were considered. The linearity (r² > 0.99) and the limit of detection were also studied.

Keywords:

• Contaminants
• nitrobenzenes
• chlorobenzenes
• sediments
• automatic extraction
• gas chromatography
• ion trap mass spectrometry

Acknowledgments

We would like to express our thanks to Dr. Lucilla Cataldi for the English grammar revision.

Notes

* Bo is the superficial layer (0.5 meters); A is the filling material (1–6.5 meters);

** B is the sediment layer (1.4–5.3 meters); C is the seabed (0.4–2.5 meters).