Direct and fast determination of polychlorinated biphenyls in contaminated soils and sediments by thermal desorption-gas chromatography-tandem mass spectrometry

Abstract

A direct procedure based on thermal desorption-gas chromatography-tandem mass spectrometry (TD–GC–MS–MS) was developed for the fast extraction of seven polychlorinated biphenyls (PCBs) from sediments and soils. PCBs were directly extracted, from 20 to 75 mg of sample, without any chemical pre-treatment or use of organic solvents, after the addition of 10 µL internal standard (PCB 195) in acetone. Sample treatment was totally automated. PCBs were extracted at 250 °C for 20 min, using a helium flow and the PCBs were trapped in a cryogenic Tenax trap at −10 °C. After that, analytes were directly desorbed at 270 °C and introduced to the GC–MS–MS system. Recoveries were established using spiked soil and sediment from 2.5 to 50 ng g−1, obtaining values from 74 to 127%. The limits of quantification were from 1.0 to 1.7 ng g−1 for soil and from 0.3 to 0.4 ng g−1 for sediments, respectively. Precision, assessed as the relative standard deviation (RSD), was lower than 8 and 11% for sediment and soil analysis, respectively, except for PCB-28 in soil samples which provided a RSD of 18%. Certified reference material and field samples were analysed by the proposed TD–GC–MS–MS method. Results were compared by a paired samples Student's t-test with those obtained by a reference extraction procedure based on pressurized solvent extraction, followed by stir bar sorptive extraction, being statistically comparable (α = 0.05). A comprehensive greenmetric evaluation of the proposed method was carried out, having the TD extraction a negligible environmental impact as compared to conventional extraction procedures.