Sampling sediments is usually performed with grab corers The

Sampling sediments is usually performed with grab corers [16], [29]. The digested sludge analyzed by Ternes et al. [16] was taken directly from the digester and the activated sludge was obtained by thymidine phosphorylase inhibitor of the slurry of STPs [16]. Collected samples are transported under cooled conditions (+4 or −20°C) in the dark to avoid change in composition of the analytes of interest. Lyophilization is very often performed prior storage (−20°C) in order to preserve the samples [16], [29], [48], [49]. Storage of the wet sediment, as performed by Peck et al. [50], requires lower temperatures (−70°C). Apart from Petrovic et al. [48] and Céspedes et al. [49], who used a pressurized liquid extraction method, solvent extractions by ultrasonication using methanol and acetone [16], [29], ethyl acetate [41], [42] or water and dichloromethane [51] have been reported. Given the complexity of the samples and the low concentrations to be detected, the extraction step has to be as efficient and as selective as possible. According to some studies, this is a critical step in terms of loss of target analytes. Table 3 summarizes the recoveries calculated for only the extraction step and for the whole method in the works reviewed. Satisfactory extraction recoveries, in the range 85–96% [16], [41], [42], were obtained in most instances. However, Williams et al. [51] reported lower, varying percentages (42–80%) that depended on the properties of the sediment (Table 3). In the study performed by Ternes et al. [16], gel permeation chromatography (GPC), silica gel, SPE and HPLC clean-up procedures were characterized by recoveries close to 100%, while the extraction step yielded significantly lower recoveries (∼86%). After extraction, most of the reported analytical methods proceed directly with clean up by SPE. For this purpose, both octadecyl (C18) silica and polymeric materials (Oasis) have been employed as stationary phases. Further purification, when performed, has been carried out by HPLC [16], [50], [51] or using restricted access materials (RAMs) [48]. RAMs are bifunctional sorbents that combine size exclusion and reversed-phase retention mechanisms, tailored for the separation of macromolecular matrix components and the adsorption of low molecular target analytes, all in one step. Preparative HPLC fractioning, using reverse-phase C18 columns, has been included in some preparation procedures as a purification step preceding GC-MS analysis [16], [50], [51]. For analysis, both LC with different detectors (fluorescence, diode array, and MS) and, to a greater extent, GC-MSn have been used. However, LC-MS has the advantage of not requiring previous derivatization of the analytes, as in GC-MS, and its use for the analysis of water samples has grown considerably in recent years [43], [52], [53]. For analysis by GC-MS, derivatization to silyl derivatives has been performed using N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) [16], [50] and N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) [51]. To our knowledge, no method has been developed for quantification of estrogens and/or progestogens in soil samples. The values reported in these and other solid matrices in laboratory degradation and sorption studies are often calculated either indirectly (i.e. by the difference in the concentration determined experimentally in the aqueous phase) or by measuring estrogenicity by means of bioassays (e.g., yeast-based recombinant estrogen receptor-reporter assay (YES) [39], [40] and the estrogen receptor-mediated chemical activated luciferase gene expression assay (ER-CALUX) [47]).
Environmental levels Most research on estrogens and progestogens has been conducted on water samples, with solid samples largely being overlooked. Sediments and soils, in particular, have received very little attention, so data on these matrices are very scarce in the literature. Some studies have been conducted to profile endocrine-disruptive potency in solid samples using bioassays [47], [50]. Chemical analysis has focused on investigation of free estrogens, both natural (e.g., estradiol, estrone, estriol) and synthetic (e.g., ethynyl estradiol, mestranol, diethylstilbestrol). By contrast, estrogen conjugates [54], [55] and progestogens [56] have seldom been studied, probably because of their lower estrogenic potency.