Evaluation of horibe traps for cryogenic collection of hydrogen peroxide and methyl hydroperoxide

Efficiencies were measured for Horibe trap cryogenic collection of gas-phase hydrogen peroxide, (H₂O₂), and methyl hydroperoxide (MHP). The Horibe trap efficiency was compared to preconcentration using a standard vacuum trap with cryogenic sampling. Gas standard samples were collected in traps cooled to two temperatures, - 85°C and - 196°C. The interference of ozone, ethylene and sulfur dioxide in the cryogenic collection of H₂O₂ and MHP using Horibe traps was determined. Ozone was added at a concentration of 110 ppbv to a gas-phase peroxide standard consisting of 0.5 ppbv H₂O₂ plus 1.6 ppbv MHP. No statistically significant interferences in either hydroperoxide were observed. After addition of 110 ppbv ozone and 2.5 ppbv ethylene to a 2 ppbv MHP standard, a 180 pptv average increase in H₂O₂ was observed, with no affect on MHP levels. At the same concentrations, ozone added to ethylene in the absence of gas-phase peroxide produced the same amount of H₂O₂ on average, with no detectable MHP. Addition of 60 ppbv stone plus 13 ppbv SO₂ to the H₂O₂ standard produced a 65% loss of measured peroxide, and a 3 ppbv SO₂ addition gave a 20% H₂O₂ loss.