# Contamination with Pharmaceuticals in Aquatic Environment: Focus on Analytical Methodologies
## 3 Determination of Pharmaceuticals in Environmental Samples
### Sample Preparation Techniques
#### 3.1.3 Microextraction Techniques
The extraction of pharmaceuticals by BA\(\upmu\)E--diclofenac, ketoprofen, gemfibrozil, and mefenamic acid with multi-walled carbon nanotubes (5-20 \(\upmu\)m length, 30 \(\pm\) 15 nm film layer, 95% purity) used as the sorption material was proposed, and LOQs lower than 0.35 \(\upmu\)g/L were achieved [64]. [PERSON] et al. [62] selected the dispersive-micro-solid-phase extraction (d-\(\upmu\)-SPE) technique for the extraction of pharmaceuticals from the NSAID group (ketoprofen, diclofenac, ibuprofen, and mefenamic acid). Surface water and drinking water samples were filtered and acidified (HCI; 0.1 M) after collection. For d-\(\upmu\)-SPE extraction, an amount of 40 mg of derivatized sporopolenin sorbent and 15 mL of a water sample (vortex, 5 min) were applied. After separating the sample solution and modified sporopolenin, 250 \(\upmu\)L of isopropanol was used for the desorption of the analytes from the sorbent (ultrasound, 5 min). This technique, in combination with LC-MS/MS, achieved LODs in the range of 220-510 ng/L [62]. Stir bar sorptive extraction (SBSE) represents a type of microextraction technique based on the sorption of analytes, most often on a layer of polydimethylsiloxane (PDMS) applied to a magnetic stirrer. [PERSON] et al. [70] used the SBSE technique with a commercially available type of PDMS sorbent to analyze NSAIDs in surface water samples. PDMS is suitable for the extraction of non-polar and semi-polar substances from various matrices and is a relatively widespread and used type of sorbent for SBSE [67; 71]. SBSE sorbents such as polyacrylate (PA), polyethylene glycol (EG), or polyethylene glycol-modified silicone (EG-SIL) are suite for the extraction of polar analytes, and they find application in the extraction of pharmaceutical substances, e.g., in wastewater [71]. The resulting extraction conditions--40 mL of the sample, pH 2, extraction time of 3 h (500 rpm), desorption time, and elution solvent volume of acetonitrile being 800 \(\upmu\)L (ultrasound 40 min)--provided satisfactory LOD values for diclofenac 11 ng/L, mefenamic acid 7.5 ng/L, and ibuprofen 8 \(\upmu\)g/L, as well as for ketoprofen 60 ng/L and naproxen 71 ng/L using the EG-SIL sorbent, which was more suitable for the monitored analytes with a polar character [71]. [PERSON] et al. [72] compared the use of SBSE sorbents--EG-SIL and PDMS--for the extraction of pharmaceuticals (diclofenac, bezafibrate, ethinylestradiol, estrone, ibuprofen, ketoprofen, gemfibrozil, etc.) in surface waters. Compared to the PDMS sorbent, the highest recoveries were achieved with the EG-SIL type sorbent, which was more favorable for analytes with both polar and non-polar character. The LOD values ranged from 5.6 to 23 ng/L for pharmaceuticals in surface waters [72]. [PERSON] et al. [73] used sorption microextraction with the MIP phase immobilized on rotating disks (RDSE) to isolate pharmaceuticals (diclofenac and mefenamic acid) from wastewater. The methods developed for the synthesis of the MIP fibers for solid-phase microextractions or MIP stir rods for SBSE are relatively simple and robust, and therefore, their use and applications in analytical laboratories can be foreseen in the coming years. RDSE represents an alternative to microextractions or purification techniques. RDSE offers a large extraction surface, and rotating disks can be stirred at higher speeds than stirring bars in SBSE extraction, during which they can be damaged [73]. Higher rotational speeds in RDSE help and facilitate mass transfer to the sorption surface. [PERSON] et al. used Teflon rotating disks (diameter 1.5 cm) that were inserted into vials with the prepared MIP phase (3000 rpm, 60 min, laboratory temperature). After extraction, the disk was transferred to a vial with 10 mL of methanol, where the target analytes were desorbed (2000 rpm, 5 min), and the extract was evaporated to dryness under a stream of nitrogen and reconstituted with ethyl acetate to a volume of 0.5 mL.