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The separation of the structural isomers of OLED materials was carried out by using high performance liquid chromatography‐mass spectrometry (HPLC‐MS) and ion mobility‐mass spectrometry (IM‐MS). Almost all isomeric OLED materials were separated by using HPLC, however, some isomers were not distinguished with each other. On the other hand, by using IM, inseparable isomers by HPLC were separated and the structural information was obtained by MS/MS technique. [ABSTRACT FROM AUTHOR]

Recently, we have developed ultralow-temperature high-performance liquid chromatography (HPLC) at −196 °C using liquid nitrogen-based mobile phases. In this study, a retention model for ultralow-temperature HPLC, in which adsorption exchange and “pseudo partition” modes are combined, is proposed to describe the effect of the mobile phase composition on the retention of analytes. The experimental results agreed well with the equation of the proposed model. It was revealed that, in the low and high additive concentration regions, adsorption exchange and pseudo partition retention, respectively, dominate the analyte retention. The difference in the retention behavior between bare-silica and octadecylsilyl-modified silica (ODS) columns was also studied. Retention of alkanes in the ODS column was greater than that in the bare-silica one. Addition of both ethane and ethylene to the mobile phase in the ODS column afforded the elution of propylene, which was not eluted with the bare-silica column at −196 °C. [ABSTRACT FROM AUTHOR]

A method for evaluating the interactions between metal ions and nonionic surfactants in aqueous solutions containing high-concentration HCl, using gas pressure-driven low-pressure high-performance liquid chromatography (LP-HPLC) as a highly acid-resistant HPLC system, was developed. To construct the LP-HPLC for this purpose, poly(styrene- co-divinylbenzene)-based low-flow-resistance monolithic columns tolerant to highly acidic conditions were prepared using low-conversion thermal polymerization. Thermal polymerization at 65 °C for 1.5 h (monomer conversions, 33 % for styrene and 59 % for divinylbenzene) allowed preparation of a column with both high separation efficiency (around 60,000 plates m for alkylbenzenes) and a quite low back pressure of 0.14 MPa at a linear flow rate of 1 mm s (2.8 × 10 m in permeability). The base column prepared under the above conditions was coated with a nonionic surfactant, polyoxyethylene nonylphenyl ether (PONPE, average oxyethylene unit numbers ( n) = 3, 7.5, 15, and 20), and used for evaluation of the interactions between PONPEs and metal ions in 6 M HCl. The interactions between PONPEs and Au(III), Ga(III), Fe(III), Zn(II), and Cu(II) were successfully evaluated using both breakthrough and chromatographic methods. Furthermore, a study of the effect of the polyoxyethylene (POE) chain length revealed that the use of PONPE with the longer POE moiety enhanced the magnitude of the interaction together with the increase in the amount of oxyethylene (OE) units coated on the monolith. Moreover, the interactions of metal ions with a single OE unit were almost constant in the range of n = 7.5-20, whereas the suppression of the interaction between Au(III) with the shortest PONPE chain ( n = 3) was also observed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns. [ABSTRACT FROM AUTHOR]

A novel analytical pyrolysis device suitable for the measurements of the less volatile pyrolyzates was developed. This device is comprised of a pyrolysis unit based on the vertical microfurnace pyrolyzer and a movable pyrolysis tube made of stainless steel. The upper side of the pyrolysis tube is first set at the heated center of the pyrolysis unit. A polymer sample in a sample cup is introduced into the heated center and pyrolyzed under the flow of nitrogen carrier gas. The pyrolyzates are then transferred to the bottom side of the pyrolysis tube which is cooled down by air blow and the less volatile pyrolyzates are condensed. After that the pyrolysis tube is moved down out of the pyrolysis unit and blocked from the hot zone by moving the three port valve. Finally the trapped pyrolyzates are flushed by an appropriate solvent into a collection vial. The recovered pyrolyzates in the solution can be then subjected to the measurements suitable for less volatile products such as matrix-assisted laser desorption/ionization mass spectrometry. Moreover, this device is also on-line connected to the injection port of a high performance liquid chromatographic system, which is also appropriate for the measurements of oligomeric products. The basic performance of the developed device was tested by using some polymer samples forming less volatile pyrolyzates such as poly(butylene terephthalate) and poly(2,6-dimethyl-1,4-phenylene ether). In addition, the usefulness of this method was demonstrated through the characterization of the crosslinking sequences in a photocured resin combined with the thermally-assisted hydrolysis and methylation reaction. [ABSTRACT FROM AUTHOR]