## 4 Conclusions  
A new analytical technique combining the use of a molecularly imprinted polymer technique and direct FAPA-MS analysis for the determination of ibuprofen, naproxen, and diclofenac was proposed herein. Commercially available AFFINILUTETM MIP-NSAIDs columns containing an NSAID-selective \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Compound**} & \multicolumn{2}{c}{**Amount of Drugs**} & \multicolumn{2}{c}{**The Average Amount of**} & \multirow{2}{*}{**Measurement Error\%**} \\  & **in Sample [ug]** & & & \\ \hline \multirow{3}{*}{Naproxen} & 0.5 & 0.48 & 4 \\  & 1.0 & 1.05 & 5 \\  & 1.5 & 1.34 & 11 \\ \hline \multirow{3}{*}{Diclofenac} & 0.5 & 0.46 & 8 \\  & 1.0 & 0.98 & 2 \\  & 1.5 & 1.45 & 4 \\ \hline \multirow{3}{*}{Ibuprofen} & 0.5 & 0.47 & 6 \\  & 1.0 & 0.89 & 11 \\  & 1.5 & 1.43 & 5 \\ \hline \multirow{3}{*}{Naproxen/Diclofenac/Ibuprofen} & 0.5/1.0/1.5 & 0.44/1.12/1.38 & 12/12/8 \\  & 1.0/1.0/1.0 & 0.98/0.98/1.10 & 2/2/10 \\ \cline{1-1}  & 1.5/1.0/0.5 & 1.54/0.98/0.43 & 3/2/14 \\ \hline \end{tabular}
\end{table} 
Table 4: Analytical parameters for FAPA-MS in the analysis of drug solutions using AFFINILUTETM MIP-NSAIDs columns. Figure 12: FAPA-MS spectrum recorded in the last heating phase from 160 \({}^{\circ}\)C to 300 \({}^{\circ}\)C.  
polymer layer were used. Preconcentration of trace amounts of analytes was performed via the MISPE method. Two types of analyses were performed: the standard HPLC-MS and the new one, direct FAPA-MS. In the standard method, the analysis consisted of five stages. Sample feeding is preceded by conditioning the column, and the sample must be washed before analysis. Approximately 8 mL of various solvents is used in the whole process. In addition, the sample preparation process is time-consuming and the HPLC analysis time is 15 min. In the proposed method, a raw sample is dosed to the column. MIP with the analyte is washed with 1 ml of a solvent, which is the total amount of solvent used in this analytical process. Then, direct and quick FAPA-MS analysis is performed in about 2 min. The use of MISPE concentration only vaguely improved the analytical parameters determined by the HPLC-MS method. However, the combination of MISPE and FAPA-MS not only improved the detection limit of all analytes to 0.2 ug ibuprofen/naproxen/diclofenac applied once per spoon, but also allowed for shortened analysis time, reduced number of analytical steps, and reduced possibility of errors. An additional advantage was the reduction of the amount of solvent used, due to which the proposed method is not only analytically attractive, but also environmentally friendly and compliant with the principles of Green Chemistry. The presented new analytical method combining MISPE and FAPA-MS can be a successful alternative to MISPE in HPLC-MS. Besides this, the presented method allows us to quickly and easily determine low-molecular-weight organic compounds. By choosing MIPs selective for different particles, we can analyze different groups of compounds, e.g., drugs in wastewater, performance-enhancing drugs in the blood, unauthorized substances in legal highs, and many others. The main limitations of the method are the existence or possibility of the synthesis of relevant MIPs and the ability to detect ions obtained by FAPA by a mass spectrometer. The following are available online at [[http://www.mdpi.com/2076-3417/10/12/4217/s1](http://www.mdpi.com/2076-3417/10/12/4217/s1)]([http://www.mdpi.com/2076-3417/10/12/4217/s1](http://www.mdpi.com/2076-3417/10/12/4217/s1)), Figure S1: HPLC-MS full-range spectrum of naproxen, Figure S2: HPLC-MS full-range spectrum of diclofenac, Figure S3: HPLC-MS full-range spectrum of ibuprofen, Figure S4: Calibration curve (partial) of ibuprofen, naproxen, and diclofenac for FAPA-MS.  
Conceptualization, M.G. and G.S. ; methodology, M.G. ; software, M.G. ; validation, M.G. ; formal analysis, M.G. ; investigation, M.G. ; resources, M.G. ; data curation, M.G. ; writing--original draft preparation, M.G. ; writing--review and editing, G.S. ; visualization, M.G.