C8-diol mixed phases for two-dimensional T.L.C. were prepared by mechanical mixing of silica-based bonded phases. Their properties in terms of retention and mechanisms developed were determined using polynuclear aromatic hydrocarbons as the compounds analyzed. Comparisons carried out with C18-cyano mixed phases revealed both similar behaviors and appreciably different behaviors, which we have explained.
Three major metabolites of rapamycin (M2, M3, and M5) were isolated from pooled plasma of orally dosed rats. Metabolites were extracted from the plasma with ethyl acetate/methanol prior to isolation by HPLC using a Supelcosil SPLC-18, 5 mu m, IO x 250 mm column. The mobile phase was a methanol/ammonium acetate linear gradient system. The isolated metabolites were characterized by negative ion FAB MS, ion-spray MS and ion-spray MS/MS. Metabolite M2 is oxygenated in the southern portion of rapamycin and the macrolide ring is opened. M3 is a structural isomer of rapamycin where the lactone ring is opened. M5 is O-demethylated on the C41 methoxy moiety and the macrolide ring is intact.
High Performance Liquid Chromatography(HPLC) and Capillary Electrophoresis (CE) are valuable analytical techniques for the determination of neuropeptides in biological fluids. A crucial aspect of HPLC and CE analyses is the preparation of samples. This review outlines sample preparation protocols for HPLC and CE methods that have been used for this determination, with a focus on enkephalins. Sample preparation protocols have ranged from simple techniques of extraction and centrifugation to solid phase extraction (SPE) and ultrafiltration. Additionally, this review also discusses the final determinant steps of HPLC and CE using various modes of detection. Detection modes for the HPLC methods included ultraviolet (UV), fluorometry, electrochemical and mass spectrometry (MS). Modes of detection when using CE for this determination have been more limited, focusing on UV and MS detection modes.
The HPLC determinations of cocaine and its main metabolites are critically reviewed with special attention to the matrices analysed. A comparison of the different extraction methods is given and the chromatography, internal standardization and detection modes are discussed.
9-Methylamino-methylanthracene (MAMA) is a secondary amine compound which can be used for derivatization and quantitation of isocyanate compounds by HPLC with detection by fluorescence and ultra-violet light absorbance The compound has potential as a chemical label for determination of airborne total reactive isocyanate group (TRIG) compounds arising from partially polymerized polyurethanes and thermal decomposition products of fully cured polyurethanes Six isocyanate oligomers and polyurethane precursors based on methylene-bis-(phenylisocyanate) (MDI), 1,6-hexamethylene-diisocyanate (HDI), and 2,4- and 2,6-toluenediiosocyanate (TDI) were assayed for isocyanate content using MAMA reagent After reaction of isocyanate with MAMA, the urea derivatives were analyzed by reversed phase HPLC using three detection / quantitation modes: fluorescence with excitation at 245 nm and emission at 414 nm, UV absorbance at 245 nm and UV absorbance at 370 nm. The ratio of absorbance at 245 nm and at 370 nm identified multiple peaks originating from isocyanate-containing compounds in each sample. The total amount of TRIG in each sample was then quantitated by absorbance of these peaks at both of the UV wavelengths. For the test samples, observed recoveries of TRIG by MAMA-HPLC assay ranged from 96 to 105%, in comparison to a reference titration assay. The technique was also evaluated for chemical interference from phosgene gas. A single compound was found after reaction of MAMA with phosgene which responded as two equivalents of TRIG.
