Analysis of mono- and diesters of o-phthalic acid by solid-phase extractions with polystyrene–divinylbenzene-based polymers

Retention mechanisms of an unmodified and a hydroxylated polystyrene–divinylbenzene polymer were studied by solid-phase extraction of o-phthalic acid and some of its mono- and diesters from purified water and then analysing by GC–MS. The monoesters and phthalic acid were retained only when protonated (i.e. acidified with HCl to pH 0.9). Of all elution solvents tested, ethyl acetate gave the best overall recoveries (61–89%) with both polymers. Applicability to complex matrixes (e.g. acidogenic landfill leachates) was examined by introducing a washing step with acetone in acidified water (pH 0.9) to eliminate volatile fatty acids (C2–C6) from the cartridge. Finally, the method was tested on real samples.