Mercury(II) and methylmercury determination in water by liquid chromatography hyphenated to cold vapour atomic fluorescence spectrometry after online short-column preconcentration

This paper reports a method developed for the simultaneous determination of methylmercury (MeHg+) and mercury(II) (Hg2+) species in water by liquid chromatography coupled to online UV irradiation and cold vapour atomic fluorescence spectrometry (LC-UV-CV-AFS) after online short-column preconcentration. This work focused on systematic studies of several variables to establish the maximum species recoveries, preconcentration factors and good reproducibility. The optimum results obtained were the following: 0.07 mmol L-1 2-mercaptoethanol as a complexing agent, precolumn conditioning with the mobile phase: a mixture of 80% of methanol (MeOH) and 20% of the following buffer: 0.0015 mol L-1 ammonium pyrrolidine dithiocarbamate (APDC) and 0.01 mol L-1 ammonium acetate (NH4CH3COO) at pH 5.5, 2 cm precolumn length and 2 mL min(-1) sample flow. This method was applied to three water samples with different mineralisation contents. Various tests, based on spikes, were performed on each sample. A breakthrough volume of 4 mL was found. The recovery values of 72 +/- 3% and 81 +/- 5% for MeHg+ and Hg2+, respectively, were obtained regardless of the matrix composition, and the PF values were 30 and 32 for MeHg+ and Hg2+, respectively. The accuracy of the preconcentration method was verified by analysing a certified reference material. The detection limits (LDs) obtained were 15 ng L-1 for MeHg+ and 2 ng L-1 for Hg2+. The quantification limits (LQs) were 50 ng L-1 for both species. The established analytical online preconcentration method is suitable for the quantification of mercury species in a wide range of environmental waters

Stress neuropeptide levels in adults with chest pain due to coronary artery disease: potential implications for clinical assessment

: Substance P (SP) and neuropeptide Y (NPY) are neuropeptides involved in nociception. The study of biochemical markers of pain in communicating critically ill coronary patients may provide insight for pain assessment and management in critical care. Purpose of the study was to to explore potential associations between plasma neuropeptide levels and reported pain intensity in coronary critical care adults, in order to test the reliability of SP measurements for objective pain assessment in critical care