Adsorption of Pluronic Surfactants in Alkylene Carbonates on Silica.

Adsorption of triblock Pluronic surfactants bearing poly(ethylene oxide) (PEO) chains of different lengths, L-62 (5 EO groups on each end), L-64 (13 EO groups on each end), and F-68 (79 EO groups on each end), on silica has been characterized using atomic force microscopy (AFM). The solvent used herein was a mixture of ethylene carbonate (EC) and propylene carbonate (PC). The three Pluronic surfactants were dissolved in the mixed solvent, with the PEO chain acting as a solvophilic group and the poly(propylene oxide) (PPO) chain acting as a solvophobic group.

Pre-column dilution large volume injection ultra-high performance liquid chromatography-tandem mass spectrometry for the analysis of multi-class pesticides in cabbages.

Pre-column dilution large volume injection (PD-LVI), a novel sample injection technique for reverse phase ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), was developed in this study. The PD-LVI UHPLC-MS/MS system was designed by slightly modifying the commercial UHPLC-MS/MS equipment with a mixer chamber. During the procedure of PD-LVI, sample solution of 200μL was directly carried by the organic mobile phase to the mixer and diluted with the aqueous mobile phase.

Quantitative Analysis of Chloramphenicol in Royal Jelly by Column-switching LC-MS/MS Using a Pretreatment Column with a Higher-pressure Capability.

An on-line pretreatment liquid chromatography-tandem mass spectrometry (LC-MS/MS) system was developed for the analysis of chloramphenicol (CAP) in royal jelly. A novel methylcellulose-immobilized restricted access media column with a higher-pressure capability of 60 MPa (MC-ODS HP) was developed for the effective removal of proteins and other compounds in the sample matrix. CAP in a sample solution was extracted in 2 min by the column-switching LC-MS/MS system.

An automatic versatile system integrating solid-phase extraction with ultra-high performance liquid chromatography-tandem mass spectrometry using a dual-dilution strategy for direct analysis of auxins in plant extracts.

An automatic versatile system which integrated solid phase extraction (SPE) with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed. Diverse commercial SPE columns can be used under an ambient pressure in this online system realized by a dual-dilution strategy. The first dilution enabled the direct injection of complex samples with minimal pretreatment, and the second dilution realized direct introduction of large volume of strong eluent into the UHPLC column without causing peak broadening or distortion.

Analysis of impurities in streptomycin and dihydrostreptomycin by hydrophilic interaction chromatography/electrospray ionization quadrupole ion trap/time-of-flight mass spectrometry.

Impurities in streptomycin (STR) and dihydrostreptomycin (DHS) were investigated by hydrophilic interaction chromatography/electrospray ionization quadrupole ion trap/time-of-flight mass spectrometry (HILIC/ESI-QIT/TOFMS). Samples were separated on a fused-core silica column (100 mmx2.1 mm i.

On-line pretreatment using methylcellulose-immobilized cation-exchange restricted access media for direct liquid chromatography/mass spectrometric determination of basic drugs in plasma.

A novel methylcellulose-immobilized restricted access media column with strong cation-exchange groups on an internal surface (MC-SCX) was evaluated for the direct injection analysis of basic polar drugs in plasma by column-switching liquid chromatography/mass spectrometry (LC/MS). Analytical conditions, including an automated pretreatment step and MS detection, were optimized for a series of basic drugs (doxepin, desipramine, imipramine, nortriptyline, amitriptyline, clomipramine). On-line pretreatment with the MC-SCX column followed by fast gradient analysis using a C18 column resulted in a total analysis cycle time of 7 min for each spiked plasma sample.

Direct analysis of drugs in plasma by column-switching liquid chromatography-mass spectrometry using a methylcellulose-immobilized reversed-phase pretreatment column.

A novel methylcellulose-immobilized reversed-phase pretreatment column (MC-ODS) for column switching liquid chromatography-mass spectrometry (LC-MS) was investigated to improve recovery and durability. Pretreatment and analytical conditions were optimized so that high throughput and high selectivity was ensured during mass spectrometric analysis. Analytical runs, including deproteinization and gradient LC analysis, were conducted in a 6-min cycle.