###### Abstract
Many other applications of the simultaneous extraction of diverse analytes from complex biological matrices have been reported. Examples include extraction of benzodiazepines from plasma and PBS [14], 49 doping agents from saliva [15], a study of repaglinide metabolism [16], and obtaining fish tissue extracts [17]. C\({}_{18}\) coatings are also often subjected to comparisons with different coating chemistries in various applications. Selected publications on this subject from the last eight years compare four coatings with regard to the extraction of 110 doping agents from urine [18]; five coatings with regard to the extraction of phenolic compounds from wine, grapes, and berries [19]; seven coatings in metabolomic processes [20]; two coatings with regard to the extraction of abused drugs from plasma, blood, and urine [21]; two coatings with regard to the extraction of beta-blockers and bronchodilators from plasma and urine [11]; and eight chemistries with regard to the systemic evaluation of thin-film microextraction coatings [22]. The results of these studies often demonstrated that C\({}_{18}\) is the most suitable coating type for a given application. A common strategy used to increase the efficacy of TFME blades is an implementation of chemistries theoretically more suited for the use with aqueous samples than the conventional C\({}_{18}\). Most popular solutions include mixed-mode C\({}_{18}\) (octadecyl with strong cationic exchanger of benzenesulfic acid) [18; 19], polar enhanced (with unspecified weak anionic exchanger) polystyrene-divinylbenzene (PS-DVB) [18; 19; 20; 22; 23; 24], hydrophilic-lipophilic balance (HLB) [20; 21; 22; 11], and phenylboronic acid (PBA) [18; 19; 20; 22; 23] coatings. However, the selection of optimal chemistry is highly dependent on target analytes and their proprieties, with each coating characterised by its unique advantages and limitations. For example, PS-DVB coatings were more efficient than PBA coatings for extraction of diverse small molecules from plasma and PBS. In addition, they did not require preconditioning, unlike PBA coatings [23]. PS-DVB coatings were also superior to C\({}_{18}\), mixed-mode, or PBA coatings in terms of number of doping agents extracted from urine samples and their amounts, but also were characterized by greater carry-over, what prevented their use for anti-doping control purposes [18]. In another study, divinylbenzene (DVB) coatings were selected over the considered C\({}_{18}\) coatings for the extraction of six anti-inflammatory and antibacterial drugs from water samples. The reason stated by the authors was DVB's known suitability for extraction of small molecules from water [25]. Bearing structural similarity to DVB, the HLB particles comprised poly(divinylbenzene-co-N-vinylpyrrolidone) were purposely designed to exert both hydrophobic and hydrophilic type interactions [26] and thus, provide a universal stationary phase for simultaneous extraction of chemically diverse analytes. The benefits of HLB TFME coatings, such as an excellent wettability in aqueous conditions [21], even without preconditioning, were demonstrated for the extraction of nine quaternary ammonium compounds (with mixed hydrophobic-hydrophilic nature) from buffered water [27]. Evaluated by several authors, HLB coatings were superior to the compared alternatives for extraction of small molecules from aqueous media. The examples include better efficacy and lower carry-over than the C\({}_{18}\) and PS-DVB coatings for the extraction of 25 prohibited substances from plasma [28], greater efficacy than C\({}_{18}\) for extraction of eight drugs from plasma and urine [11], and greater efficacy than DVB for extraction of six chlorination by-products from hot tub water [26]. However, one fundamental aspect concerning silica-based C\({}_{18}\) particles has yet to be addressed by researchers.