APEOs, the reader is referred to other books and reviews. [24][25][26][27][28][29]
II. Analysis A. Sampling and StorageAnalytical results significantly depend on the homogeneity of the samples and accurate storage procedures which guarantee that no changes take place in the composition of the samples. The main problem of surfactants in general is their tendency to adsorb on all phase boundaries due to their amphiphilic nature. Consequently losses to surfaces or suspended solids from aqueous solutions are commonplace. Especially for matrices like sewage sludge, sediment, or soils, quantitative recovery of analytes turns out to be very difficult. Therefore, internal standards are added to the samples to correct for nonquantitative recovery during isolation and quantification of the analytes. Giger et al. used n-nonylbenzene 11,30 and 2,4,6-tribromophenol 8 in gas chromatographic determinations of APs/APEOs from sludge and water, respectively. 4-n-Nonylphenol, which is not included in technical NP, is applied to the quantification of NP in soils by GC. 31 For water analysis by HPLC 2,4,6-trimethylphenol is well suited. 32 This approach, however, is useless for nonspecific methods since they cannot discriminate analytes initially present from added internal standards.Environmental samples have to be preserved immediately upon collection with chemical biocides to minimize and prevent microbial degradation of the surfactant present. Water samples from sewage treatment plants, rivers, or seas are generally collected in glass bottles, preserved with 1% formaldehyde, and stored at 4 °C. [33][34][35][36][37] A less common preservation method for aqueous samples is the addition of methylene chloride and acidification to pH 2 with hydrochloric acid. 38 Kubeck et al. showed that refrigeration alone was sufficient to stabilize river water samples for up to 4 weeks. 35 Due to diurnal variations of APEO concentrations in the influents and effluents of sewage treatment plants, 24-h and 2-h composite samples should be collected, ideally, with automatic sampling devices. 39 Sewage sludges are dealt with in the same way as water samples, i.e. preservation with 1% formaldehyde and storage at 4 °C. 39,40 Jobst et al. preferred aluminium vessels to store the sludge samples. 41 Sediment samples are collected from the upper 2 cm using a grab sampler and frozen at -20 °C until analysis. 33,[42][43][44] In the laboratory, samples are freezedried 44 or air-dried at 21 °C43 .The application of sewage sludges to agricultural land has resulted in the need to monitor concentrations of detergents in sludge-amended soils. Soil samples are collected from the upper 5 cm with a stainless steel corer, dried at 60 °C, pulverized, and stored in the dark at 4 °C. 40 Biological matrices represent a difficult problem with regard to a representative sampling and a unchanged composition of the samples during storage. The Environmental Specimen Bank (ESB) of Germany has developed a method for collection and preparation of fresh biological materials. 45,46 ...
