1 Solid-phase micro-extraction (SPME) in the early detection of potentially active volatile compounds from organic wastes used for the management of soil-borne pathogens ESTHER DE LA FUENTE 1 , ANA C. SORIA 1 , MIGUEL A. DÍEZ-ROJO 2 , ANA PIEDRA BUENA 2 , AVELINO GARCÍA-ÁLVAREZ 3 , GONZALO ALMENDROS 12* and ANTONIO BELLO 2 1 Instituto de Química Orgánica General (CSIC), Madrid, Spain. 2 Centro de Ciencias Medioambientales (CSIC), Madrid, Spain. 3 Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Madrid, Spain. ABSTRACT The complex molecular assemblages were analysed in the soil gas phase after applying pine forest wastes (PFW) or sugarbeet vinasses (SBV) for soil-borne crop pests management. For this purpose, solid-phase micro-extraction (SPME) and gas chromatography (GC) were used coupled with mass spectrometry (MS). The organic wastes were applied either to Calcic Entisol or Haplic Arenosol moistened at field capacity and soil was covered with polyethylene sheet for 28-30 days to retain the volatiles. The PFW-treated soil mainly released volatile terpene hydrocarbons (trans-caryophyllene, β-myrcene and p-cymene), with α-humulene and ethylbenzotriazole prevailing in the untreated soil. After SBV application mainly alkyl compounds and alkylbenzenes were released, whereas cyclohexanone, limonene, butanone, acetic acid, camphor and benzaldehyde occurred in the untreated soil. Compound assemblages also depended on the increasing water saturation in terms of soil depth, with sulphur compounds prevailing in deep horizons. Our results showed that SPME can be directly applied to soils to provide valuable information on volatile products from organic amendments. Keywords: Biodisinfestation, biofumigation, compost, forest waste, gas phase, pine litter, sugarbeet vinasses. INTRODUCTION Gas chromatography coupled with mass spectrometry (GC-MS) is the most frequently used technique in the analysis of complex mixtures of organic volatile compounds. However, this requires their previous isolation from the non-volatile components of the sample. On the other hand, solid phase microextraction (SPME) is a simple, rapid and non-expensive technique which allows the fractionation of the volatiles released from liquid and solid samples. [1] Such a technique, which has been mainly used in the analysis of food and in the monitoring of environmental pollution, [2,3] could also be useful in other areas, such as agricultural chemistry. However, to date, its application in the analysis of natural volatile products in the soil gas phase has been very scarce, and usually directed towards the determination of pollutants. [4] Volatile organic compounds have recently been analyzed by SPME in marine sediments [5] and in waste disposal landfills. [6] *Address correspondence to Gonzalo Almendros, Soils Dept., Centro de Ciencias Medioambientales (CSIC), Serrano 115B, 28006 Madrid, Spain. Phone: +34-917452500 ext. 220; Fax: +34-915640800; E-mail: humus@ccma.csic.es or a.piedrabuena@ccma.csic.es Received December 30, 2008. Accepted March 25, 2009.