Analysis of chloro- and nitroanilines and -benzenes in soils by headspace solid-phase microextraction

Quantitative analysis by headspace solid-phase microextraction (HS-SPME) of twenty chloro- and nitrobenzenes and anilines spiked into soil samples was possible when the calibration was performed with the same matrix. The SPME response increased with addition of water to the air dried soil samples, and by optimisation of extraction conditions such as temperature, extraction time and sample agitation. Distribution constants between the fibre coating materials and water were determined. They showed that polyacrylate, rather than polydimethylsiloxane, should be used in the analysis of polar compounds. Matrix effects, mainly depending on the organic carbon content of the soil, were so large that quantitative analyses of real soil samples would not be reliable with model matrix calibration. This problem would be overcome if a nearly exhaustive extraction could be achieved. Recovery studies showed that this was possible only in the case of extraction of the lightest non-polar analytes from a soil with a very low content of organic carbon. Instead quantification could be performed with calibration by standard addition. By this approach the non-linear calibration curves at concentrations near the detection limits would cause inaccurate results at trace level, whereas it could be applied successfully within the linear ranges. Hence, the potential of HS-SPME in soil analysis is primarily as a rapid screening technique.