A simple solvent selection procedure for accelerated solvent extraction (ASE ® ) of polymers is described using Hildebrand solubility parameters. A series of extractions with a solvent with a solubility parameter several Hildebrand units (MPa 1/2 ) different from the polymer are carried out at increasing temperatures until maximum extraction is reached. A second solvent with a solubility parameter close to that of the polymer is then added incrementally at the optimum temperature found from the initial experiments, until a maximum in the extraction rate is reached. This method is used to determine optimum conditions for ASE ® of additives from ground polypropylene (PP), poly(vinyl chloride) (PVC) and nylon. Complete extractions were possible of Irganox 1010 (pentaerythrityl tetrakis (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) from freeze ground PP in 18 min (propan-2-ol-cyclohexane (97.5+2.5) at 140 °C), and dioctyl phthalate (DOP) from PVC in 13 min (hexane-ethyl acetate (60+40) at 170 °C). ASE ® extraction from PVC pellets was possible in reasonable time (1 h) without grinding or cutting the polymer. The results were not significantly different from those obtained by conventional solvent extraction methods. From nylon, 96% extraction of the dimer in 19 min (hexane-ethanol (60+40) at 170 °C) was possible, compared to the total amount extracted by exhaustive ASE ® . The behaviour of poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) was observed with different solvents at high temperature to determine likely optimum extraction conditions. These were ethyl acetate at 190 °C for PET and hexane-ethyl acetate (70+30) at 150 °C for PMMA.

Harold Vandenburg graduated from Manchester Polytechnic where he studied Applied Chemistry parttime whilst working in quality control in the pharmaceutical/personal care sector. After working for a year in Australia and USA, he started six years of research on migration from polymers into foods at high temperatures at the Procter Department of Food Science at the University of Leeds. He obtained his PhD during this time. Still at the University of Leeds, but now at the School of Chemistry, he is undertaking research comparing the effectiveness of sample preparation methods for polymers and environmental samples.

Two groups of potential migrants were found in Nylon "microwave and roasting bags' (MRBs): volatile compounds were released at cooking temperatures and non-volatile compounds were extracted with methanol and/or water. A dynamic headspace system at 200 degrees C followed by gas chromatography (GC) coupled to mass spectrometry (MS) was used for determination of volatile compounds. Cyclopentanone (31.7 mg/bag), 2-cyclopentyl cyclopentanone (17.4 mg/bag), hexadecane (2.6 micrograms/bag), heptadecane (3.2 micrograms/bag), octadecane (3.0 micrograms/bag) and epsilon-caprolactam (5.0-35.5 mg/ bag) were the main volatile compounds present in the MRBs. High performance liquid chromatography (HPLC) and mass spectrometry were combined for identification and quantification of non-volatile compounds extracted with methanol (46.0 mg/bag). Nylon 6,6 cyclic monomer and cyclic oligomers up to the tetramer and Nylon 6 monomer and cyclic oligomers up to the octamer were identified and quantified, confirming that the plastic was made of Nylon 6,6 and Nylon 6 polymers. The same non-volatile compounds (except Nylon 6 heptamer and octamer) were found to migrate into olive oil at 175 degrees C for 1 h. A total of 0.916 mg/dm2 (19.2 mg/bag) of non-volatile compounds migrated into olive oil (41.8% of those quantified in the plastic material).

Irganox 1010 (pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)] propionate) is successfully extracted from polypropylene using solvents at high temperatures and pressures in a homemade accelerated solvent extraction system. For example, using freeze-ground polymer, 90% extraction is possible within 5 min with 2-propanol at 150 °C. Extraction curves for 2-propanol and acetone fit well to the "hot ball" model, previously developed for supercritical fluid extraction. Diffusion coefficients are determined for extractions with 2-propanol, acetone, and cyclohexane over a range of temperatures, and the activation energies for the diffusion are 134, 107, and 61 kJ mol(-)(1), respectively. The lower figure for acetone and cyclohexane indicates that these solvents swell the polymer more than does 2-propanol. The polymer dissolves in the solvent at too high a temperature, which causes blockage of the transfer lines. For maximum extraction rates, the highest temperature for each solvent that avoids dissolution of the polymer should be used. The use of mixed solvents is investigated and shows advantages in some cases, with the aim of producing a solvent that will swell the polymer but not dissolve it.

Analysis of extracts from two woad species (Isatis tinctoria and Isatis indigotica) and Polygonum tinctorium revealed that only one indigo precursor (indican) was present in Polygonum, but two precursors were found in Isatis spp. This was done using high performance liquid chromatography (HPLC), coupled to an evaporative light scattering detector (ELSD). In Isatis spp., the indigo precursors indican and a fraction representing isatan B were identified. The proportion of indican and isatan B was different between the two Isatis spp. tested. For the first time, it was possible to quantify the precursors in woad plant species, and the results were found to be in good agreement with those made from total indigo quantification using two different spectrophotometric methods or a derivatization technique.