2nd WL and few new groups of pharmaceuticals such as two antibiotics, which are often prescribed together to overcome antimicrobial resistance, an antidepressant pharmaceutical and its metabolite, and a group of three azole pharmaceuticals:
(3rd WL) amoxicillin, ciprofloxacin, sulfamethoxazole, trimethoprim, venlafaxine, O-desmethylvenlafaxine, clotrimazole, fluconazole, miconazole.
Moreover, there are already existing regulations regarding the Environmental Risk Assessment (ERA) pharmaceuticals such as the Committee for Medicinal Products for Human Use (CHMP, 2006 [21]) and the Committee for Medicinal Products for Veterinary Use (CVMP, 2000, 2004 [22]). According to these documents the ERA process is different for veterinary and human medicines; however, it usually starts with an initial exposure assessment (Phase I) that is based on a calculation of the predicted/measured environmental concentration (PEC or MEC respectively). A fate and effects analysis (phase II) is only required (with some exceptions) when the so-called action limits are exceeded in different environmental compartments. Hence, risk assessment (determined by the Risk Quotient (RQ)) is performed by calculating the ratio of the PEC (or MEC) and PNEC on non-target organisms. If RQ < 1, no risk is estimated, hence further testing is not recommended [23–25]. Moreover, the approaches for the ERA of pharmaceuticals are in some respect dissimilar in the U.S. and in the EU. For example, in the EU the introduced guideline excludes testing of pharmaceuticals whose PECsurface water is below the action limit of 0.01 µg L−1, whereas in the U.S. this threshold value is 0.1 µg L−1. It must also be highlighted that the current regulations refer mainly to the acute toxicity of only single compounds, while chronic and mixture toxicity is not obligatory. Finally, while assessing the risks posed by the residues of pharmaceuticals their TPs should also be accounted. This adds a further complexity to any chemical risk assessment. TPs may contribute significantly to the risk posed by the parent compound (a) if they are formed in a high proportion, (b) if they are more persistent/more mobile than the native forms or (c) if they are highly toxic. Current ERA guidelines refer to the issue of TPs only insofar as simulation-type degradation studies at higher tiers of the assessment, which usually include the identification of major TPs [11].
2.2 Sampling and Sample Preparation
The most commonly used method for the collection of environmental samples is grab sampling. Due to significant dilutions, the volume of samples, especially of drinking or marine water, should be sufficiently large due to the trace content of pharmaceuticals in this type of matrix. Water samples of 1000 mL are recommended for the determination of drug residues in drinking water, groundwater and treated wastewater (EPA Method 1694, December 2007, EPA-821-R-08-002). A different approach to monitoring the level of water pollution with pharmaceuticals is passive extraction, where the sampling process is carried out simultaneously with the extraction of analytes [26]. The use of passive extraction techniques has the advantage that the result obtained is a time-weighted concentration independent of the momentary and temporary variations in the concentration of the analytes. In the extraction of pharmaceuticals, the Polar Organic Chemical Integrative Sampler (POCIS) type sampler is most often used, in which the Oasis HLB sorbent is the acceptor phase (the same as in the case of SPE). In a paper by Bueno et al. [27] regarding the quantification of carbamazepine and its transformation products in French coastal waters using POCIS (Oasis HLB), the presence of 20 other compounds including β-blockers, lipid regulators, analgesics, antibiotics and antidepressants was revealed. In turn, Rimayi et al. [28] used the Chemcatcher passive sampler deployed in environmental waters over a period of 14 days. This resulted in the identification of over 200 compounds including pesticides, pharmaceuticals and personal care products, drugs of abuse and their metabolites in environmental waters. In recent years, the possibility of using other receiving phases in POCIS in order to increase the range of polarity of isolated compounds, namely Strata-X Strata XAW or Oasis WAX, Oasis MAX, molecularly imprinted polymers (MIP), carbon nanotubes and ionic liquids, has been described [29–32]. Although both standard POCIS design and prototype devices have great potential applications in water monitoring, there is still a gap between the determination of sampling frequency in the laboratory and its applicability in the field.
Extraction procedure is the second after sampling largest source of errors in determining the actual content of pollutants in the environmental samples. Thus it is important to select the proper procedure of extraction according to the selected analytes and the type of the studied matrix. The procedures used to extract pharmaceuticals depend mainly on the physical state of the matrix. Therefore the procedures can be divided into those targeting soil and sediment samples and those for water samples – mainly marine and fresh surface water, but also wastewater and drinking water.
2.2.1 Solid Samples
The determination of pharmaceuticals in soils/sediments is problematic due to the complexity of these matrices, the low concentration of targets and the lack of reference methods. These difficulties have been highlighted by numerous authors such as Białk-Bielińska [33], Brinkman [34], Pavlovic [35], Kemper [36], Buchberger [37], Tadeo [38], Babic and Mutavdzic [39] or Havens [40], who have presented reviews on the methods of determining of pharmaceuticals in soils available over the last decade. The developed methods are multi-steps with sample pre-treatment, solid-solvent extraction (assisted or not by ultrasounds or microwaves) and extract clean-up. A step-by-step summary of exemplary extraction techniques of pharmaceuticals from solid samples is presented in Table 2.2. Clean-up of extract by the solid-phase extraction (SPE) technique using HLB (hydrophilic-lipophilic adsorbent) columns is a common practice (Table 2.2). The most commonly used solvents are a mixture of acetonitrile and citric acid [41, 42], acetonitrile and EDTA-McIlvaine buffer [43, 44], and methanol with water [45–47]. In a nutshell, the extraction of pharmaceuticals from the soil can be carried out in various ways, depending on the chosen technique of quantification (GC or LC coupled with MS) and the properties of the analytes. For example, Aznar et al. [48] presented a method that allows the determination of pharmaceuticals belonging to three different therapeutic groups, in which they used ultrasound-assisted extraction (UAE). Kumirska et al. [49] used microwave-assisted extraction (MAE) to extract 13 NSAIDs and oestrogens from solid matrices such as sediment, sludge and soils. It may be concluded that both Aznar et al. and Kumirska et al. presented a rather standard approach to analysing pharmaceuticals in soil. The other methods used for this purpose are usually modifications or extensions of those mentioned above. A novel approach was characterized by the research conducted by Mijangos et al. [50], in which 11 endocrine-disrupting compounds were extracted from the soil using focused ultrasonic solid-liquid extraction (FUSLE), and the purification of the extract was performed using dispersive solid-phase extraction (dSPE). The use of FUSLE along with the simplified clean-up technique requires the use of only small samples, ranging from 0.01 to 1 g. The required amount of solvent ranges from 5 to 15 mL, and the extraction time can be several minutes or even seconds. So, it is an attractive method not only from the point of view of efficiency, but also of greenness and economy.
2.2.2 Water Samples
The high polarity of pharmaceuticals makes it unsuitable to use the standard liquid-liquid extraction technique. Furthermore, this technique is not environmentally friendly. Therefore, for the extraction of pharmaceuticals from aqueous samples the SPE technique is the most widely used. This technique allows for the simultaneous extraction of analytes from various groups and the clean-up of the sample with a high concentration factor and the low consumption of organic solvents. However, it should be mentioned that for SPE the water samples should be filtered, and it is recommended to adjust pH to accelerate the analytes adsorption. Filtration removes the fraction of target compounds adsorbed in suspended particles, and it is therefore recommended to wash the filters with methanol [51]. The extraction of pharmaceuticals from water requires a high volume of samples due to the low concentration of targets (at the level of a few ng/L of water) [33, 52] and a concentration factor higher than 1000. This means that with the extract volume equal to 1 mL, the volume of the tested
