Detection limit

About: Detection limit is a research topic. Over the lifetime, 34379 publications have been published within this topic receiving 644817 citations. The topic is also known as: limit of detection & lower detection limit.

Indirect UV detection of carbohydrates in capillary zone electrophoresis

Abstract: A new system for the rapid and sensitive analysis of underivatized carbohydrates has been established using capillary zone electrophoresis with indirect UV detection. At an applied potential of 28 kV, sugars and sugar acids could be separated by the combined effects of electroendosmosis and electrophoresis within 20 minutes in a fused silica capillary of 50 μm internal diameter and an effective length of 100 cm using 6mM sorbic acid, pH 12.1, as both carrier electrolytie and chromophore. The alkaline pH ensured ionization of the sugars and, hence, their detection by means of charge displacement. Furthermore, the chosen concentration of sorbic acid allowed the smallest fractional change in the background signal to be measured. While the electrophoretic mobilities of the sugars were found to increase within a pH range of 11.9 to 12.3, those of the sugar acids were not affected. Due to the increasing competition of hydroxide ions in the displacement of the chromophore with rising pH, a significant loss of sensitivity is observed at pH values higher than 12.1 and this pH was found to provide sufficient resolution, optimum sensitivity, and a acceptably short analysis time. Under these conditions, a lower detection limit of 2 pmol was obtained for glucose.

Oxidation of Azide Anion at Boron-Doped Diamond Thin-Film Electrodes

Abstract: The oxidation of dissolved inorganic azide anion in aqueous media was investigated using high-quality, boron-doped diamond thin-film electrodes. Linear sweep and differential pulse voltammetry, along with flow injection analysis in the amperometric detection mode, were used to study the reaction at neutral pH as a function of the potential sweep rate, analyte concentration, and electrolyte composition. Comparison experiments were performed using polished glassy carbon. Azide undergoes an irreversible oxidation (1 e-/equiv) at both of these carbon electrodes, presumably with nitrogen as the primary product. A linear dynamic range of 3−4 orders of magnitude and a detection limit as low as 0.1 μM (4.3 ppb) at a S/N = 3 were observed for diamond in the voltammetric measurements. The flow injection analysis results for diamond indicated a linear dynamic range of 5 orders of magnitude and a detection limit of 8 nM (0.3 ppb) at a S/N = 3. The diamond response was generally reproducible from film to film, and the...