Related Experiment Video
Updated: Feb 6, 2026

Optical Detection of E. coli Bacteria by Mesoporous Silicon Biosensors
Published on: November 20, 2013
An Optical Dosimeter for the Selective Detection of Gaseous Phosgene with Ultralow Detection Limit
Alejandro P Vargas1, Francisco Gámez1, Javier Roales1
1Departament of Physical, Chemical and Natural Systems , Universidad Pablo de Olavide , Ctra. Utrera Km. 1 , 41013 Seville , Spain.
Abstract:
We present here a cheap, fast, and highly selective dosimeter for the colorimetric detection of gaseous phosgene with an ultralow detection limit. The disposable device is based on Harrison's reagent supported into a porous nanocrystalline TiO2 matrix film. We exposed the films to phosgene streams while the absorbance was monitored by an optic fiber in a gas chamber. The pronounced spectral changes were unaffected by humidity and oxygen and permitted us to use the response rate at 464 nm as a very stable calibration signal for quantitative analysis purposes. The use of a specific sensing reaction guaranteed a very high selectivity of the device even against saturated vapors of primary interferences like halide gases and other oxidizing and volatile agents. With this simple method, whose response is compatible with affordable and efficient miniature LED-photodiode devices, we reach an ultralow limit of detection well below the ppm level.
Related Concept Videos
Difference from Background: Limit of Detection
The LOD indicates the presence or absence...
Limits to Natural Selection
Homogeneous Equilibria for Gaseous Reactions
For gas-phase reactions, the equilibrium constant may be expressed in terms of either the molar concentrations (Kc) or partial pressures (Kp) of the reactants and products. A relation between these two K values may be simply derived from the ideal gas equation and the definition of molarity. According to the ideal gas equation:
Respiration and Gaseous Exchange
Respiration involves the exchange of gases, especially oxygen (O2) and carbon dioxide (CO2), between the alveoli and body cells, a process facilitated by blood circulation. As a result, the cardiovascular system, which involves...
Limiting Reactant
Detection of Gross Error: The Q Test

