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Proteins are typically separated by an immune reaction, such as an enzyme-linked immunosorbent assay, and are detected by selective fluorescent labeling. This has potential for complicated procedures and the denaturation of proteins by labeling, and is cost consuming. In this study, we propose a technique for the selective separation and detection of a target protein using a molecularly imprinted hydrogel (PI gel) with fluorescent monomers. We focused on 8-anilino-1-naphthalenesulfonic acid (ANS), where the fluorescence intensity is easily changed by the interaction with proteins, and successfully synthesized the ANS monomer and a poly(ethylene glycol) (PEG) conjugated ANS monomer. The PI gel with the ANS monomers using bovine serum albumin (BSA) as a template showed the selective adsorption of BSA and the fluorescence intensity increased due to the adsorption of BSA.

Separation is an essential aspect in analytical chemistry or chemical measurement science. With the capability to separate components within a sample into individual bands or zones distributed spatially or/and temporally, separation makes the analysis or measurement more accurate through separating different components into individual fractions and reducing or even eliminating the interference from sample matrix species. Such a power also makes separation an important tool to purify components of interest from mixtures or natural products for further investigations. Meanwhile, separation can make a subsequent analytical method more sensitive through enriching or concentrating the components of interest in the samples to be tested. Modern separation science and techniques have been well established and are quite mature, making them widely employed in routine scientific research and practices. However, due to the increasing complexity and challenge of analytical tasks that we are facing, advanced separation science and techniques are still in high demand. This inspired us to organize this themed collection to reflect some trends and features of this practically useful, technically diverse and forever progressive area.

Cell collection based on deterministic lateral displacement (DLD) and cell circulation with a loop channel are two component technologies for stressless cell retention which have been developed with a view to working toward suspension culture in a microfluidic channel. DLD devices with low array angles collect floating S. cerevisiae through an array effectively. The DLD device with an array angle of 2.6° showed an efficiency of 91.7%. Two types of loop channels with a piezoelectrie pump make a stable two-phase laminar flow of a pre-filled fluid and supplied fluid. A loop channel with a connection between an inlet and outlet on the opposite side replaces a filled fluid in the channel with a supplied fluid, which is essential for supplying nutrient rich medium to cells in microfluidic channels as well as retaining cells in a microenvironment without external stresses.

We report problems and improvements of a regulated analytical GC method supported by ISO/DIS 24293 for nonyl phenol isomers (NPs). The variations of peak area and recovery of NPs were found on a regulated GC method which 4-n-nonyl phenol-2,3,5,6-d4 (4-np-d) and phenanthrene-d10 (fnt-d) were utilized as surrogate compounds with syringe spiking. Furthermore, we investigated the relative recovery by the continuous injection of NPs, 4-np-d, and fnt-d, then the decrease rate of peak area of each compound was different although all peaks were gradually decreased. Consequently, the decrease rates of NPs and 4-np-d were higher, and the relative recovery of NPs were also decreased. After cutting off the GC column (about 50 cm) and replacement of an injection insert, the peak areas of compounds were completely recovered. Therefore, we anticipate that the problem was caused by adsorption or degradation of NPs in the inlet area. Additionally, a similar decrease of peak area was observed on the pretreated real samples by the effect of matrix.

Spontaneous cleanup processes based on capillary action for natural water containing humic acids were carried out using an epoxy-based polymer monolith. We were able to control the microstructures of monoliths by changing the polymerization conditions, including the curing agent/monomer/porogenic solvent ratio and the polymerization temperature. Furthermore, we confirmed that updrawing of water based on capillary action was highly dependent on the microstructures of the monolith, i.e., whether they are structures of particle aggregates, non-porous structures, or three-dimensional monolithic structures. The epoxy-based monoliths have a unique ability to adsorb hydrophobic and anionic compounds because the monoliths are prepared using epoxy monomers and curing agents with amines, and therefore, the monoliths can be used for the selective adsorption of polyphenols such as humic acids. In fact, we used a siphonic system to completely remove the humic acids in water samples and for the spontaneous cleanup of real pond water via spontaneous updrawing of water by “J”-shaped monoliths.