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Abstract
Characterisation and selectivity of planar crossflow filtration membranes of 47 mm diameter for sampling and sample clean-up of environmental waters containing triazines and high levels of humic substances were investigated. The filtrate is collected in a sample loop, introduced to a column liquid chromatographic (CLC) separation system and quantified by UV-absorbance at 220 nm. Seven membranes, both cellulosic- and polymer types were investigated using samples with 10–80 mg/l of commercial humic acid. Triazine herbicides were chosen as model compounds together with other compounds of environmental concern such as p-nitrophenol and p-chlorophenol. The investigated membranes were found to interact in the filtration process. This led to large differences in terms of selectivity due to differences in pore size, hydrophobicity, porosity, and chemical structure of the membrane. The size and shape of the characteristic matrix front present in the obtained chromato-grams were depending on the type of membrane used. In addition to these matrix effects, some of the membranes resulted in analyte recovery values of less than 100%. Repeatability and stability using nylon and PVDF membranes were evaluated as well as flux variances. An application with the optimised conditions in the CFF-LC-UV system for real surface water from a local creek was carried out with a resulting LOD of 1–5 μ.g/l (S/N = 3) using a 100 μl injection volume.