Authors:Amar M. Ait, M. Idbenali, N. Selhaoui, K. Mahdouk, A. Aharoune, and L. Bouirden
available in the literature. In the present parameter optimization procedure, we first imposed the conditions d 2 G /d x 2 for modeling the liquid phase ( 0 L Ru,Y ) using the phase boundary data reported by Massalski [ 6 ] and thermodynamic data determined
Authors:Henryk Piekarski, Katarzyna Łudzik, and Michał Wasiak
concentration (c.m.c.), more pronounced visco-elastic properties, higher capacity to effectively reduce surface tension, etc. are determined by the structure of molecules and has been described in the literature, e.g. [ 3 , 10 ]. The micellisation processes in
Authors:Hariom Nagar, Jürgen Martens, and Ravi Bhushan
Enantioresolution of three active pharmaceutical ingredients (APIs), namely, atenolol, betaxolol, and orciprenaline, marketed as racemic mixture, has been achieved in a direct mode using (S)-glutamic acid as chiral additive in thin-layer chromatography. Two different approaches were adopted: (1) (S)-glutamic acid was mixed in the silica gel slurry for making thin-layer plates, or (2) it was added in the mobile phase and plain plates without any chiral additive were used. Both (1) and (2) were capable of separating enantiomers of all the three racemates, but different combinations and proportions of solvents were found successful in the two cases. Good resolution was achieved in both cases, and the results are compared for these two sets of studies among themselves and with other literature reports. Iodine was used to locate the spots of the corresponding enantiomers. The detection limits for each enantiomer were found in the range of 1.4–1.9 μg (per spot).
Authors:Łukasz Komsta, Urszula Dunin, and Robert Skibiński
During our previous studies, we discovered that reversed-phase thin-layer chromatography (RP-TLC) plates can behave in typical normal-phase manner, which is not widely known nor used in the literature. Therefore, we decided to investigate this behavior more comprehensively on RP-8 plates. We used 35 model compounds, and performed chemometric screening mixture design approach for 20 popular solvents. This gave us the possibility to estimate separate retention effect for each solvent being the measure of average solvent strength. The results were compared to the previous study done on silica gel. It can be concluded that RP-8 plates can be used in typical normal-phase systems and their behavior does not differ substantially from silica gel plates.
Authors:L. H. Blanco, O. M. Vargas, and A. F. Suárez
decrease with temperature and an increase with concentration, this is due to the nature of the solvent. These observations are in agreement with previous results found in literature [ 9 ].
The molar apparent and molar partial volumes at infinite
, according to the literature, the presence of the θ-Al 2 O 3 phase in these samples suggests a crystallite size smaller than 25 nm [ 12 ]. In the AlCr samples ( Fig. 3c ), the Cr 1.23 Al 0.77 O 3 phase was crystallized at 500 °C and remains stable for
Authors:Qasimullah, Ali Mohammad, and Mahfoozurrahman Khan
This review encapsulates the work which appeared in the literature during 1995–2015 on the use of microemulsion as the mobile phase in the analysis of inorganic anions and organic compounds by thin-layer chromatography (TLC). Among anionic, cationic, and non-ionic surfactants used as one of the components of oil-in-water (O/W) and water-in-oil (W/O) microemulsions, sodium dodecyl sulfate (SDS) (anionic surfactant) has been found the most effective for the analysis and separation of different compounds. Compared to the work performed with the use of W/O microemulsion, little work has been reported on use of O/W microemulsion in the TLC—high-performance thin-layer chromatography (HPTLC) analysis of organic compounds. In contrary to TLC, more work has been done on use of O/W microemulsion in high-performance liquid chromatography (HPLC). Out of the sorbent phases, silica gel in combination with microemulsion eluent has been favorable for realizing analytically useful separations. Classification of microemulsions and surfactants is also discussed in the present review.
Authors:Jarosław Pyzowski, Elżbieta Brzezińska, and Anna Weronika Sobańska
Chemical ultraviolet (UV) filters and preservatives used currently in sunscreen preparations are compounds of diverse structures, and the safety of their application depends on their inability to penetrate the skin and other barriers present in the human body. However, at least some of these chemicals meet the general requirements of the good blood—brain barrier (BBB) permeability described in the literature sources. The objective of this study was to examine the behavior of selected cosmetic raw materials (UV filters and preservatives) towards the BBB on the basis of the BBB permeability models developed in our earlier study, based on easily accessible RP-18 thin-layer chromatographic data and calculated molecular descriptors. The computed BBB permeability parameters B1 and B2 correlate with the chromatographic data (RF, RF/PSA) and calculated physicochemical descriptors usually associated with the BBB permeation (HA, Sa, DM, log D). The relationships between these values were developed by stepwise multiple regression analysis, validated, and found to explain 93–96% of the total variance. The models of the BBB permeation based on classification functions obtained previously from discriminant function analysis were used to assign the studied compounds to the groups of good (CNS+) or poor (CNS−) blood—brain barrier permeability, suggesting the inability of the majority of these compounds to cross the BBB. The universal character of BBB permeability models developed earlier was confirmed.
Authors:Alexander Zimmermann, Eliane Gandolpho Tótoli, Felipe Hugo Alencar Fernandes, and Hérida Regina Nunes Salgado
Cefazolin sodium (CFZ) is a semi-synthetic first-generation cephalosporin used for the treatment of infections caused by Gram-positive and Gram-negative microorganisms. Although it is a drug used worldwide, there are only a few green analytical methods described in the literature for its quantification. This work proposes an eco-friendly, low-cost, and rapid analytical method to analyze CFZ in lyophilized powder for injectable solution based on digital images, using thin-layer chromatography (TLC). For the TLC method, the mobile phase was comprised of ethanol and water, and the spots revelation was performed using iodine vapors. The TLC spots were analyzed through digital images, obtained by flatbed scanner, and evaluated using the free software “The Gimp” (GNU Image Manipulation Program), by quantification of pixels in pictures. This method was validated according to the International Conference on Harmonization (ICH) guidelines and presented adequate linearity, accuracy, precision, and robustness. It also showed its selectivity and stability-indicating capability (under acid, alkaline, aqueous, oxidative, and photolytic stress conditions). This is an innovative, easy, and low-cost method that can be used for the analysis of cefazolin sodium in lyophilized powder. Considering that this method does not use toxic organic solvents for the environment and operators, it contributes to the development of green chemistry.
Authors:Virginia Coman, Ștefan Kreibik, Miuța Filip, Mihaela Vlassa, and Ioana Perhaița
Thin-layer chromatography (TLC) is a frequently used technique for the separation of polar and non-polar compounds, with a rich literature in this field. The aim of this paper is to show the TLC adsorbent quality of the Nevşehir volcanic tuff from Turkey that is compared with the Mirșid volcanic tuff from Romania. Our experimental investigations have shown that it is possible to achieve TLC plates coated with Nevşehir volcanic tuff, in natural occurrence, excepting grinding and sieving processes, which can be used for the separation of polar compounds, such as amino acids or food dyes. In the present article, modern techniques for characterizing the volcanic tuff powders, namely, X-ray diffraction, inductively coupled plasma–optical emission spectrometry, scanning electron microscopy, specific surface area and porosity measurements, and infrared spectroscopy, were used in addition to the chromatographic testing. TLC plates coated with Nevşehir tuff were prepared and tested at the separation of some amino acids, obtaining good results. Also, the impregnation of Nevşehir tuff with NaOH and NaCl, respectively, allowed the separation of some hydrophilic dyes. The obtained results have contributed to understand the chromatographic properties of the Nevşehir volcanic tuff. The TLC capability of the Nevşehir tuff can enlarge the pallete of inexpensive adsorbents with possible applications in the field of layer chromatographic separations.