Selective Measurement of Gaseous Hydrogen Peroxide with Light Emitting Diode-Based Liquid-Core Waveguide Absorbance Detector

Abstract

Atmospheric H₂O₂ is typically determined by enzymatically mediated fluorogenic reactions that do not discriminate between H₂O₂ and organic peroxides. Reactions of Ti(IV) with H₂O₂ has also been the basis of colorimetric measurements of H₂O₂ but is too insensitive. A more sensitive determination is possible with the Ti(IV)-4-(2-pyridylazo)resorcinol (PAR) complex, however, unreacted PAR must be chromatographically separated. A titanium(IV)-porphyrin complex, oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) [TiO(tpypH₄)⁴⁺], (TiTPyP) was introduced for the measurement of aqueous H₂O₂. In this paper, we show that TiTPyP can be used for measuring H₂O_2(g), it does not respond to CH₃HO₂. With a proper membrane collector, practically there is no interference from concurrently present gaseous SO₂ and O₃. The approach permits a S/N = 3 limit of detection (LOD) of 26 pptv with a 50 mm path liquid core waveguide (LCW) absorbance detector and a light emitting diode based light source. This is adequate for real atmospheric measurements.