Differential sensing techniques are becoming nowadays an attractive alternative to classical selective recognition methods due to the “fingerprinting” possibility allowing identifying various analytes without the need to fabricate highly selective binding recognition sites. This work shows for the first time that surfactant-based ion-sensitive microspheres as optodes in the microscale can be designed as cross-sensitive materials; thus, they are perfect candidates as sensing elements for differential sensing. Four types of the newly developed chemosensory microspheres—anion- and cation-selective, sensitive toward amine- and hydroxyl moiety—exhibited a wide range of linear response (two to five orders of magnitude) in absorbance and/or fluorescence mode, great time stability (at least 2 months), as well as good fabrication repeatability. The array of four types of chemosensitive microspheres was capable of perfect pattern-based identification of eight neurotransmitters: dopamine, epinephrine, norepinephrine, γ-aminobutyric acid (GABA), acetylcholine, histamine, taurine, and phenylethylamine. Moreover, it allowed the quantification of neurotransmitters, also in mixtures. Its selectivity toward neurotransmitters was studied using α- and β-amino acids (Ala, Asp, Pro, Tyr, taurine) in simulated blood plasma solution. It was revealed that the chemosensory optode set could recognize subtle differences in the chemical structure based on the differential interaction of microspheres with various moieties present in the molecule. The presented method is simple, versatile, and convenient, and it could be adopted to various quantitative and qualitative analytical tasks due to the simple adjusting of microspheres components and measurement conditions.

The essential oils from needles, twigs, bark, wood, and cones of Pinus cembra were analyzed by GC-FID, GC/MS, and H-NMR spectroscopy. More than 130 compounds were identified. The oils differed in the quantitative composition. The principal components of the oil from twigs with needles were α-pinene (36.3%), limonene (22.7%) and β-phellandrene (12.0%). The needle oil was dominated by α-pinene (48.4%), whereas in the oil from bark and in the oil from twigs without needles there were limonene (36.2% and 33.6%, resp.) and β-phellandrene (18.8% and 17.1%, resp.). The main constituents of the wood oil as well as cone oil were α-pinene (35.2% and 39.0%, resp.) and β-pinene (10.4% and 18.9%, resp.). The wood oil and the cone oil contained large amounts of oxygenated diterpenes in comparison with needle, twig, and bark oils.

In many fields, the goal is to obtain structures with small dimensions in the order of micro/nanometers. Small-sized systems can have countless applications in various industries such as cosmetology, medicine, and nutrition technology. Many techniques are used to obtain the most miniature possible spheres, such as interference with the composition, use of surfactants, or mechanical interference: rapid mixing, increased pressure, and ultrasound. The use of ultrasound in the development of colloidal systems can be an effective method of reducing the size of particles of dispersed phase and influencing the functions they represent. An important aspect here is the time during which the ultrasound is used. In this work, the influence of ultrasound on the chemosensory properties and size of produced ion-sensitive microspheres was investigated and compared. The chemosensory response of the developed microspheres was studied using spectrophotometry and spectrofluorimetry, while the size of the microsphere optodes was estimated by confocal microscopy.

Working parameters of chemical sensors, such as selectivity and sensitivity, can be adjusted by optimizing components of chemosensitive layers, including type and amount of plasticizer in the case of PVC membranes in optodes. Plasticizers are also used in the process of creating micro/nanospheres that are incorporated with chemical indicators to form micro/nano-scale optodes. This study investigated the influence of the type of plasticizer (polar o-NPOE and non-polar DOS) on the optical response of microspheres that are sensitive to lipophilic ions. Moreover, the amount of plasticizer was also adjusted in order to obtain satisfactory sensitivity in the widest linear range. The chemosensory response of the developed microspheres was studied with the use of spectrophotometry and spectrofluorimetry, while size of the optodes was estimated by confocal microscopy.

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