Capillary electrochromatography of biologically relevant flavonoids.

Flavonoids were separated utilizing CEC technique. Baseline separation of biologically relevant flavonoids was obtained using a 100 microm ID fused-silica capillary filled with 3 microm Silica-C18 material and an optimized mobile phase comprising of 20 mM Tris-HCl (pH 6.5), ACN and water at a ratio of 10/40/50 v/v/v. Separations were carried out at 25 kV and a column temperature of 25 degrees C. The influence of relevant parameters for the CEC separation, such as buffer concentration, pH, separation voltage, and ACN concentration, was investigated and optimized. Dependencies of the electroendoosmotic flow (EOF) on these parameters and effects on the resolution of the analytes were studied. During analyses the solvents used for dissolving the samples turned out to have significant effects on the separation of flavonoids. The optimized system was then successfully used for the separation of the flavonoids epicatechin, myricetin, quercetin, naringenin, and hesperetin. CEC turned out to be a useful complementary tool for the economic analysis of flavonoids in addition to common HPLC, muHPLC, and CE methodologies. This method can be used for real applications in phytomics.

Sample pretreatment and determination of non steroidal anti-inflammatory drugs (NSAIDs) in pharmaceutical formulations and biological samples (blood, plasma, erythrocytes) by HPLC-UV-MS and micro-HPLC.

The article discusses the qualitative and quantitative determination of non-steroidal anti-inflammatory drugs like salicin, salicylic acid, tenoxicam, ketorolac, piroxicam, tolmetin, naproxen, flurbiprofen, diclofenac and ibuprofen by reversed phase high performance liquid chromatography (RP-HPLC) and micro-HPLC (micro-HPLC) hyphenated with UV-absorbance and mass spectrometric detection. Both detection methods delivered calibration plots with good linearity (r(2) > 0.9800), limits of detection in the low nanogram range and recovery rates between 94 and 104 %. For the analysis of biological samples such as blood, plasma and erythrocytes liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the basis of new synthesized glycidylmethacrylate/divinylbenzene copolymer (GMA/DVB) particles and commercially available material on the basis of poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer were investigated. Finally the use of a micro-HPLC system with separation columns in the range of 8 cm x 200 microm I.D. for the determination of non-steroidal anti-inflammatory drugs (NSAIDs) is presented, emphasizing on the type of column and sample amount needed.

Influence of the pore structure on the properties of silica based reversed phase packings for LC.

This paper describes the preparation and investigation of new, highly loaded, monomeric, silica based, reversed phase C18 and C30 packings. The influence of pore structure and endcapping on the properties of C18 and C30 packings is described. Using hydrothermal procedures, silicas with predictable pore size (9.3-25.5 nm) and surface area have been prepared. Silylation with long chain silanes substantially alters the pore structure of the silica: pore size and pore volume decrease. A new parameter, the volumetric surface coverage [mm3 x m(-2)] has been introduced. This parameter--calculated from on-column measured porosity data--indicates the pore volume portion occupied by the hydrocarbon chains. Endcapping does not significantly change the pore structure of the bonded phases. The reduced retentions (reduced with respect to unit area: [k/m2])--a good measure for comparing the retention behaviour of packings with different surface areas--are similar for most of the phases, demonstrating good accessibility of the pores for the solutes. Slightly lower retentions were found on the endcapped than on the non-endcapped phases for probes with dense pi-electron system (e.g. polyaromatic hydrocarbons) demonstrating the contribution of silanophilic interactions to the retention. The phases had been successfully used for various demanding separations, e.g. for the separation of flavonoids, carotenoids, resveratrol, and tocopherol isomers, fullerenes, and anions.