Design, construction and evaluation of a simple pressurized solvent extraction system

this work describes the construction and testing of a simple pressurized solvent extraction (pse) system. a mixture of acetone:water (80:20), 80 oc and 103.5 bar, was used to extract two herbicides (diuron and bromacil) from a sample of polluted soil, followed by identification and quantification by high-performance liquid chromatography coupled with diode array detector (hplc-dad). the system was also used to extract soybean oil (70 oc and 69 bar) using pentane. the extracted oil was weighed and characterized through the fatty acid methyl ester analysis (myristic (< 0.3%), palmitic (16.3%), stearic (2.8%), oleic (24.5%), linoleic (46.3%), linolenic (9.6%), araquidic (0.3%), gadoleic (< 0.3%), and behenic (0.3%) acids) using high-resolution gas chromatography with flame ionization detection (hrgc-fid). pse results were compared with those obtained using classical procedures: soxhlet extraction for the soybean oil and solid-liquid extraction followed by solid-phase extraction (sle-spe) for the herbicides. the results showed: 21.25 ± 0.36% (m/m) of oil in the soybeans using the pse system and 21.55 ± 0.65% (m/m) using the soxhlet extraction system; extraction efficiency (recovery) of herbicides diuron and bromacil of 88.7 ± 4.5% and 106.6 ± 8.1%, respectively, using the pse system, and 96.8 ± 1.0% and 94.2 ± 3.9%, respectively, with the slp-spe system; limit of detection (lod) and limit of quantification (loq) for diuron of 0.012 mg kg-1 and 0.040 mg kg-1, respectively; lod and loq for bromacil of 0.025 mg kg-1 and 0.083 mg kg-1, respectively. the linearity used ranged from 0.04 to 1.50 mg l-1 for diuron and from 0.08 to 1.50 mg l-1 for bromacil. in conclusion, using the pse system, due to high pressure and temperature, it is possible to make efficient, fast extractions with reduced solvent consumption in an inert atmosphere, which prevents sample and analyte decomposition.