99
by Pan et al. (2009) for the determination of Mws and PDI of the free polymers
generated in the surface-initiated RAFT polymerization of water-compatible MIP
microspheres.
The matrix-assisted laser desorption/ionization (MALDI) technique coupled to
time-of-flight (TOF) spectrometry allows a more precise mass determination of
organic macromolecules, as well as the structural elucidation from their mass spectra. MALDI is a soft ionization technique developed as an alternative to conventional ionization methods where these molecules are more fragile and, consequently,
fragmented (Saito and Kobayashi 2002).
The physicochemical characterization of the MIPs synthesized on the sensor surfaces has carried out through different electrochemical techniques such as cyclic
voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical
impedance spectroscopy (EIS). In CV and DPC, changes in anodic and cathodic
potential and peak current intensities of a redox couple (e.g. [Fe(CN) 6
4]/[Fe(CN) 6
3]) are observed when the electrode surface is coated (Lahcen et al. 2016; Xia et al.
2016). On the contrary, the template removal becomes a decrease in resistance due
to the formation of specific cavities that serve as an electron-transfer pathway (Yu
et al. 2012).
The swelling capacity in MIPs can be used as a relative measurement of the diffusion rate of solvent into the polymer (Rosengren et al. 2013; Prasad et al. 2014),
which is related to the degree of crosslinking. Conventionally, swelling is determined
as a volume change ratio calculated from the volume of the dry polymer and the
volume of the polymer after the addition of a solvent (Rosengren et al. 2013).
Higher accuracy can be obtained by measuring the volume change in a single bead
in the absence and presence of solvent by microscopic analysis (Spivak 2005).
The determination of the superparamagnetic properties of magnetic MIPs is
essential for the rapid magnetic separation of these NPs in the treatment of the
sample. NPs should not have magnetic hysteresis, which prevents NPs from aggregating and guarantees their dispersion when the magnetic field is removed (Gao
et al. 2011). Magnetic properties are usually measured by vibrating sample magnetometry (VSM) (Cheng et al. 2019).
X-ray diffraction (XRD) is particularly used to characterize crystalline materials.
When applied to MIP characterization, the XRD spectra may be suitable for checking if crystal structure of Fe 3 O 4 remains unchanged during the synthesis of magneticMIPs (Hassan et al. 2018).
The evaluation of thermal stability is usually carried out by thermogravimetric
analysis (TGA), where the mass loss of the sample is measured continuously as a
function of temperature or time. TGA allows to obtain not only characteristic
decomposition patterns and the upper use temperature of the polymer, but also to
determinate the polymer mass adhered to the solid surface (Gutierrez-Climente
et al. 2016). To a lesser extent, thermal stability studies have also been conducted to
investigate the chemical affinity of the polymer after heat treatment. Svenson and
Nicholls (2001) evaluated the thermal stability of the theophylline MIPs incubated
at more than 20–350 °C, determining the affinity of MIPs based on temperature
exposure.
5 Plastic Receptors Developed by Imprinting Technology as Smart Polymers Imitating…
by Pan et al. (2009) for the determination of Mws and PDI of the free polymers
generated in the surface-initiated RAFT polymerization of water-compatible MIP
microspheres.
The matrix-assisted laser desorption/ionization (MALDI) technique coupled to
time-of-flight (TOF) spectrometry allows a more precise mass determination of
organic macromolecules, as well as the structural elucidation from their mass spectra. MALDI is a soft ionization technique developed as an alternative to conventional ionization methods where these molecules are more fragile and, consequently,
fragmented (Saito and Kobayashi 2002).
The physicochemical characterization of the MIPs synthesized on the sensor surfaces has carried out through different electrochemical techniques such as cyclic
voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical
impedance spectroscopy (EIS). In CV and DPC, changes in anodic and cathodic
potential and peak current intensities of a redox couple (e.g. [Fe(CN) 6
4]/[Fe(CN) 6
3]) are observed when the electrode surface is coated (Lahcen et al. 2016; Xia et al.
2016). On the contrary, the template removal becomes a decrease in resistance due
to the formation of specific cavities that serve as an electron-transfer pathway (Yu
et al. 2012).
The swelling capacity in MIPs can be used as a relative measurement of the diffusion rate of solvent into the polymer (Rosengren et al. 2013; Prasad et al. 2014),
which is related to the degree of crosslinking. Conventionally, swelling is determined
as a volume change ratio calculated from the volume of the dry polymer and the
volume of the polymer after the addition of a solvent (Rosengren et al. 2013).
Higher accuracy can be obtained by measuring the volume change in a single bead
in the absence and presence of solvent by microscopic analysis (Spivak 2005).
The determination of the superparamagnetic properties of magnetic MIPs is
essential for the rapid magnetic separation of these NPs in the treatment of the
sample. NPs should not have magnetic hysteresis, which prevents NPs from aggregating and guarantees their dispersion when the magnetic field is removed (Gao
et al. 2011). Magnetic properties are usually measured by vibrating sample magnetometry (VSM) (Cheng et al. 2019).
X-ray diffraction (XRD) is particularly used to characterize crystalline materials.
When applied to MIP characterization, the XRD spectra may be suitable for checking if crystal structure of Fe 3 O 4 remains unchanged during the synthesis of magneticMIPs (Hassan et al. 2018).
The evaluation of thermal stability is usually carried out by thermogravimetric
analysis (TGA), where the mass loss of the sample is measured continuously as a
function of temperature or time. TGA allows to obtain not only characteristic
decomposition patterns and the upper use temperature of the polymer, but also to
determinate the polymer mass adhered to the solid surface (Gutierrez-Climente
et al. 2016). To a lesser extent, thermal stability studies have also been conducted to
investigate the chemical affinity of the polymer after heat treatment. Svenson and
Nicholls (2001) evaluated the thermal stability of the theophylline MIPs incubated
at more than 20–350 °C, determining the affinity of MIPs based on temperature
exposure.
5 Plastic Receptors Developed by Imprinting Technology as Smart Polymers Imitating…