# Methacrylate Polymer Monoliths for Separation Applications
## 3 Applications of Methacrylate Polymer Monoliths in Separation Science
### Separation and Pre-Concentration of Chemical Species
#### 3.1.1 Solid Phase Extraction (SPE) and Pre-Concentration of Chemical Species  
This section discusses the use of methacrylate monolithic stationary phases as materials for the concentration and extraction of chemical species from a solution. Common species investigated using this type of SPE material include; pharma compounds [120; 121], PAHs [122; 123], chloro-phenols [122], dyes [41], herbicides [124], metal ions [54; 125] and basic compounds such as caffeine [126]. The implementation of methacrylate monoliths in microfluidic chips for on-chip SPE has also been investigated [127].  
A number of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) were extracted using a monolith composed of Alkyl-MethAcrylate-ester (AMA), Di-Vinyl Benzene (DVB) and Vinyl-Benzyl Tri-methyl-Ammonium chloride (VBTA) [121]. The composition of the monoliths component (AMA) was varied and the effect of such variations on the extraction performance was investigated. In addition, the ratio of AMA to DVB was varied. It was found that shorter carbon chains on the AMA lead to better extraction for some of the NSAIDs, butyl methacrylate showing particularly good extraction efficiency and reasonable levels of re-usability, exhibiting recoveries ranging between 80% and 95% over 50 uses.  
The application of methacrylate monoliths to the SPE of metal ions and herbicides would be of particular interest to environmental chemists. Three recent reports [54; 124; 125] show novel methods of applying acrylate monoliths in SPE. [PERSON] _et al._[54] utilized the increasingly popular additive manufacturing method of 3D Printing to fabricate a polyacrylate monolith within a microfluidic chip and demonstrated the effective extraction and pre-concentration of metal ions, such as Mn, Ni, Cu, Zn, Cd and Pb, from sea-water samples. The device was stable at flow rates up to 0.5 mL/min. Good extraction efficiencies were observed and the authors noted the potential of such a fabrication technique to produce SPE materials quickly and with well-defined morphologies, and the integration of such extraction phases within modular multi-component chips. The polyacrylate cube fabricated by the group is shown in Figure 8. This device can also be altered to give monoliths of varying lengths, a factor that can play a role in extraction efficiency. In addition, such commercial polymer resins are easier to prepare, with known curing times.  
[PERSON] _et al._[124] used a 1,6-hexanediol ethoxylate diacrylate (HEDA) monolith for the extraction of phenyl-urea herbicides from water samples. Extraction recovery values of >91% were found for the herbicides. Critically, the detection limits of such compounds were lower than the legal requirement (0.1 ng/mL), showing potential of the system for real world applications. The chemical structures of these herbicides (fluometuron, chlorotluron, buturon and chloroxuron) are shown in Figure 9.  
Figure 8: **(A,B)** Computer Aided Design (CAD) drawings of the (**A**) pre-concentrator and (**B**) a layer of ordered cuboids in the extraction channel; (**C**) Photograph of the printed device; two flat-bottom female connectors with a piece of Poly Tetra Fluoro-Ethylene (PTFE) tubing were fitted to allow connection to an Flow Injection Analysis (FIA) interface; (**D,E**) Photographs of the configuration of the ordered cuboids printed without the surrounding of the extraction channel. Reproduced with permission from [54], Copyright (2015) American Chemical Society.  
Figure 9: Chemical structures of herbicides ((**17**) fluometuron; (**18**) chlorotluron; (**19**) buturon and (**20**) chloroxuron), used by [PERSON] _et al._[124].