Isocratic LC methods for the trace analysis of phthalates and 4-nonylphenol in varying types of landfill and adjacent run-offs

Abstract

To determine the levels of known endocrine disrupting chemicals such as phthalates and alkylphenols in environmental samples such as leachate water and sediment, suitable isocratic high performance liquid chromatographic (HPLC) methods utilising a narrow bore column were developed. The study was an analytical challenge in terms of developing a method, which would be sensitive enough to detect trace levels of these compounds, while still retaining the advantages of being suitable for relatively inexpensive instrumentation and featuring reasonable throughput. Generally speaking, when the internal diameter of the HPLC column is decreased by a factor of two, the signal of a sample component increases by a factor of four, the square of the change in diameter. However, combining a narrower bore column along with the isocratic method enabled us to see 20-fold increases in peak signal. The detection of these compounds was further improved by using pre-concentrating techniques known as solid-phase extraction (SPE) and accelerated solvent extraction (ASE). Limits of detection in the ng L−1 range were reached for target analytes. Maximum values (µg L−1) of 7.05 dibutyl phthalate (DBP), 7.37 diethylhexyl phthalate (DEHP), 5.56 diisononyl phthalate (DINP), 1.19 diisodecyl phthalate (DIDP) and 6.16 4-nonylphenol (NP) were found in sampled leachates, whilst maximum values (mg kg−1) of 42.3 DBP, 49.8 DEHP, 36.2 DINP, 20.0 DIDP and 1.14 NP were found in sediments. Concentrated leachate contained up to 226 µg L−1 DEHP. The highest levels of NP were found to leach from an unlined landfill, with concentrations of 10.6 µg L−1. The levels, which were quantified in the Irish midlands, are clearly linked to anthropogenic activity and were comparable to levels found in other pan-European studies.