Fluoxetine and norfluoxetine analysis by direct injection of human plasma in a column switching liquid chromatographic system

A column switching LC method is presented for the analysis of fluoxetine (FLU) and norfluoxetine (NFLU) by direct injection of human plasma using a lab-made restricted access media (RAM) column. A RAM-BSA-octadecyl silica (C-18) column (40 min x 4.6 mm, 10 mu m) is evaluated in both backflush and foreflush elution modes and coupled with a C-18 lab-made (50 mm x 4.6 mm, 3 pm) analytical column in order to perform online sample preparation. Direct injection of 100 mu L, of plasma samples is possible with the developed approach. In addition, reduction of sample handling is obtained when compared with traditional liquid-liquid extraction (LLE) and SPE. The total analysis time is around 20 min. A LOQ of 15 ng/mL is achieved in a concentration range of 15-500 ng/mL, allowing the therapeutic drug monitoring of clinical samples. The precision values achieved are lower than 15% for all the evaluated points with adequate recovery and accuracy. Furthermore, no matrix interferences are found in the analysis and the proposed method shows to be an adequate alternative for analysis of FLU in plasma.

Autoantibody response to chromatographic fractions from oxidized LDL in unstable angina patients and healthy controls

Levels of autoantibodies to oxidized low-density lipoprotein (oxLDL) have been correlated to atherosclerosis; however, contradictory results have been shown. To better understand the role of autoantibodies to oxLDL in atherogenesis, and their potential to predict risk of developing coronary artery disease we investigated the antibody response of unstable angina (UA) patients and healthy controls against chromatographic separated fractions of oxLDL. Five major peaks were detected after chromatographic separation of oxLDL and 10 fractions were collected. Surprisingly, when the response to high molecular weight fractions was analysed, we observed a significant increase in the levels of autoantibodies in controls compared to UA. In contrast, when the autoantibody response to intermediate and low molecular weight fractions was analysed, we observed that the UA group showed consistently higher levels compared with controls. Our data demonstrates that within oxLDL there are major fractions that can be recognized by autoantibodies from either UA patients or healthy individuals, and that the use of total oxLDL as an antigen pool may mask the presence of some antigenic molecules and their corresponding antibodies. Further studies are needed, but the analysis of antibody profiles may indeed open up a novel approach for evaluation and prevention against atherosclerosis.

Useful Strategies for Algal Volatile Analysis

The production of volatile organic compounds (VOC) by plants is well known. However, few scientific groups have studied VOC produced by green, brown and red algae. Headspace collection of volatiles and solid phase microextraction, as well as the traditional extraction by hydrodistillation combined with analytical chromatographic techniques (i.e., GC-MS), have significantly improved the investigation of VOC from plants and algae. The major volatile compounds found in seaweeds are hydrocarbons, terpenes, phenols, alcohols, aldehydes, ketones, esters, fatty acids and halogen or sulfur-containing compounds. This article presents an overview of VOC isolated from and identified in marine macro-algae. Focus is given to non-halogenated and non-sulfur volatile compounds, as well as strategies to analyze and identify algal VOC by GC-MS.

Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol

Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5 x 10(-7) to 3.5 x 10(-4) mol L-1, in 0.1 mol L-1 sulfuric acid electrolyte, as well as high sensitivity, 0.110 A mol(-1) L cm(-2) at the optimized flow rate. A detection limit of 7.6 x 10(-8) mol L-1 and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 mu L and a flow rate of 2.0 mL min(-1). The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0 x 10(-6) and 6.0 x 10(-5) mol L-1 ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis. (C) 2008 Elsevier B.V. All rights reserved.

Electroanalytical Method for the Analysis of Methyldopa In Pharmaceutical Tablets Using a Crude Extract of Laccase from Pycnoporus sanguineus as Oxidizing Agent

Several colorimetric and chromatographic methods have been used for the identification and quantification of methyldopa (MA) in pharmaceutical formulations and clinical samples. However, these methods are time- and reagent-consuming, which stimulated our efforts to develop a simple, fast, and low-cost alternative method. We carried out an electroanalytical method for the determination of MA in pharmaceutical formulations using the crude enzymatic extract of laccase from Pycnoporus sanguineus as oxidizing agent. This method is based on the biochemical oxidation of MA by laccase (LAC), both in solution, followed by electrochemical reduction on glassy carbon electrode surface. This method was employed for the determination of MA in pure and pharmaceutical formulations and compared with the results obtained using the official method. A wide linear curve from 23 x 10(-5) to 1 x 10(-4) mol L(-1) was found with a detection limit calculated from 43 x 10(-6) mol L(-1).